MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes

TOPIC OUTLINE → These are the species that belong to each type of
REFERENCES: fluke.
• Medical Parasitology in the Philippines, Blood trematodes Schistosoma – For
Belizario Jr., De Leon example, Schistosoma
• VOPPT – Prof. Carmona haematobium reside in
I. Classification the vesicle venous
II. General Characteristics plexus, which is a part of
III. Blood Flukes the circulatory system.
A. Schistosoma spp. Hepatic trematodes Fasciola hepatica – and
IV. Lung Fluke Fasciola gigantica reside
A. Paragonimus westermani in the liver.

CLASSIFICATION Clonorchis spp. – reside

TREMATODES in the bile duct (liver).
Phylum Platyhelminthes
Opisthorchis spp. –
*Under Platyhelminthes reside in the bile duct
are Cestoda (liver).
(tapeworms) and Intestinal trematodes Fasciolopsis buski –
Trematoda (flukes) reside in the small
Common name of Flukes intestine.
Trematodes
Types of Flukes 1. Intestinal - flat and Heterophyes spp. -
leaf-shaped reside in the small
(Fasciolopsis, Fasciola, intestine.
Paragonimus, etc.)
2. Liver - flat and leaf- Metagonimus spp. -
shaped (Fasciolopsis, reside in the small
Fasciola, Paragonimus, intestine.
etc.)
3. Lung - flat and leaf- Watsonius spp. - reside
shaped (Fasciolopsis, in the small intestine.
Fasciola, Paragonimus,
etc.) Gastrodiscoides spp. –
4. Blood - cylindrical reside in the large
body shape (Schistosoma intestine.
sp.) Lung trematodes Paragonimus
NOTES westermani – reside in
→ You can see the difference wherein Schistosoma sp. the lungs.
Is cyclindrical in body shape while other types of flukes
are flat and leaf shaped. GENERAL CHARACTERISTICS
→ Many intestinal, lung, and liver trematodes species TREMATODES
are pathogenic for humans. The severity of the disease Shape Leaf like and
depends on the original infective dose of the unsegmented
Metacercariae. Size Up to 75mm; smallest is
→ Some cases caused by trematodes may be under 2mm (about 1 mm
asymptomatic. in size)
→ Depending on the type of fluke, it can cause mild,
severe, or asymptomatic diseases. - In other books they only
→ All Schistosoma sp. are pathogenic for humans. measure up to 60mm.
However, the largest
FLUKES human parasite
→ Hermaphroditic organisms that are capable of cell belonging to this group is
fertilization, except for Schistosoma spp. (a type of blood the Fasciolopsis which
fluke) can attain a length up to
75mm.

CLASSIFICATION

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes
- The smallest are only need two hosts. The
Heterophyes definitive host is man,
heterophyes, which are and the intermediate
under 2 mm. host can be snail.
Head end Suckers present (oral and Development Oviparous – lay eggs, and
ventral); No hooklets the eggs are
operculated.
- Located in the anterior
end of the trematode EXCEPT FOR
(Uppermost; see picture SCHISTOSOMES
on the next page) Mode of transmission Eating aquatic plants,
- Anterior (oral) sucker fishes or crabs harboring
surrounds the mouth infective form
- The posterior sucker is (metacercariae) or by the
the acetabulum or the penetration of free living
ventral sucker. cercariae
Alimentary canal Present but incomplete (schistosomes).

-Digestion system is - For the host to be

incomplete as compared infected, they need to
to the nematodes which ingest the aquatic plants,
have a well-developed fish, or crabs, which
digestive system. contains the infective
-Consists of a anterior form (metacercariae) or
mouth and the pharynx by the penetration of
which continues as the free living cercariae
esophagus (schistosomes).
-The esophagus NOTES
bifurcates in front of the → Anus is absent.
ventral sucker into a pair → Schistosomes usually differ.
of intestinal pouches → Larval forms are usually called cercaria, metacercaria,
which becomes the redia, miracidium, or sporocyst
cecum.
Body Covered with a resistant
cuticle, which may be
smooth or spiny
Body Cavity Absent

- Body is covered with a

resistant cuticle which
can be smooth or spiny.
Sex Monoecious (except
schistosomes)

- Nematodes are
diecious
Life Cycle Requires three hosts
(except Schistosoma)

- Example of hosts that

trematodes can infect:
*1 definitive host (man)
*2 intermediate hosts → The oral cavity leads to the esophagus, wherein it will
(first - snail; second – first transcend the pharynx, then the esophagus, and
aphotic plant/fish) branch into two intestinal ceca that run parallel to each
other and end up right at the posterior end of the worm.
EXCEPT FOR Most of the rest of the body are taken up with the
SCHISTOSOMES, which reproductive organs. There are usually two testes leading to

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes
the genital core and single ovary. A series of glandular 9. Schistosomulae migrates to the portal blood in the
structures called the vitellaria or the vitelline. liver and becomes developed into adults
→ The vitelline duct usually leads inward to the uterine of 10. Once they copulate, the paired adults migrate to:
the ovary where the shell is formed over the ovum. (A and B) – mesenteric venules of bowel/rectum (laying
→ The uterus winds forward to the genital pores. This is eggs that circulate to the liver and shed in stools)
where thousand of eggs are contained and is considered the **depends sa species kung saan madalas, although
largest organ in the body. capable to migrate in both locations – S. japonicum
species are more frequently found in the superior
mesenteric veins, which drain the small intestine.
BLOOD FLUKE Meanwhile, S. mansoni species are more often found in
SCHISTOSOMA SPP. the inferior mesenteric veins, which drain the large
Intermediate Host Snail intestine**
Infective Stage Cercariae (C) – vesicular and pelvic venous plexus of bladder or
Mode of Transmission Skin penetration rectal venules; eggs shed in urine
Definitive host Man (but also infects Cycle perpetuates
birds and mammals)
Diagnostic stage Eggs S. mansoni S. S. haematobium
japonicum
GENERAL LIFE CYCLE Manson’s Oriental Bladder fluke

Common
blood fluke blood fluke

Name
(smallest of
the three
species)
Inferior Superior Vesicular and
mesenteric mesenteric pelvic venous
Habitat
veins draining veins draining plexus of the
the large the small bladder; also in the
intestine intestine rectal venules

Feces Feces Urine

Laboratory
Specimen

• 112-182 • 50-85 μm x • 110-170 μm x

Morphology of Eggs

1. Embryonated eggs being shed from infected humans μm x 40-75 38-60 μm 38-70 μm
by feces or by urine, depending on the species—S. μm • Roundish • Oblong
mansoni (A) and S. japonicum (B) are being shed • Oblong • Small • Prominent
through feces while S. haematobium (C) is shed through • Prominent lateral terminal spine
urine lateral spine
spine
2. Under appropriate conditions, they are hatched
within 2 to 4 hours into free-swimming miracidia.
3. Miracidia swim and penetrate immediate hosts’
tissues (snails - Oncomelania hupensis quadrasi)
4. Sporocysts develop in snail and reproduce asexually
(successive generations) and can later give rise to free-
swimming cercariae after 60-70 days.
5. Free-swimming cercariae is released from the snail
into the water. (infective stage; morphology: fork-like
tail) S. mansoni S. japonicum
6. Cercariae penetrates the skin of its host (man) when
the host comes into contact with infested fresh water
7. The cercariae lose their tails during penetration and
become/develop into schistosomulae.
8. Schistosomulae then migrate to the lungs via
superficial lymphatic vessels or subcutaneous
veins, then to the venous portal circulation and to the
heart. S. haematobium

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SCHISTOSOMIASIS
ADDITIONAL INFO FROM THE BOOK →Disease upon getting infected by the Schistosoma spp.
→ S. japonicum is the predominant species in the →Schistosome eggs, and not adult worms, induce the
Philippines. morbidity caused by schistosome infections. (explanation:
→ Schistosomes have an incomplete digestive system and yung eggs kasi parang nattrap or naeencyst or naiiwan sila
an excretory system made up of flame cells. These internal sa mga organs; they are lodged in the intestine, liver, or
structures are surrounded by circular and longitudinal bladder)
muscles. →Eggs not excreted become permanently lodged in the
Symptoms: intestines or liver (for S. mansoni and S. japonicum) or in the
→ Cercarial penetration of skin
bladder and urogenital system (for S. haematobium) →
• dermatitis with pruritus and localized reaction
granuloma formation → chronic inflammation, wherein
known as “swimmer’s itch.”
dito nagmamanifest yung symptoms and causes the
→ Schistosomule migration
schistosomiasis.
• “snail fever,” Katayama fever, or Katayama
syndrome characterized by easy fatigability,
respiratory symptoms, arthralgias, myalgias,
malaise, eosinophilia, fever, and abdominal pain
• Hepatosplenomegaly is not uncommon and can
be quite debilitating during this period of
infection, and in rare cases may lead to severe
hepatic dysfunction and death.
→ Migration through the pulmonary circulation
• wheezing and coughing.
→ Aberrant migration of maturing schistosomules
• may occlude the circulation of the brain and the
spinal cord precipitating seizures, paresthesias,
transient ischemic attacks, and strokes. Schistosoma mansoni egg-induced granulomas in the liver
Treatment:
of an infected mouse. Source: doi:
→ Praziquantel, a heterocyclic prazinoisoquinoline
10.1016/S0140-6736(13)61949-2
compound
Prevention: SCHISTOSOMIASIS
→ health education, attention to the water supply and
1. Katayama Syndrome
sanitation, strong community participation, environmental
management, and appropriate snail control. • Acute schistosomiasis
• Early clinical manifestation of Schistosoma
ADULT FORMS OF SCHISTOSOMA SPP. spp. infection
• Most common in in travelers and children
→the only trematodes
that have separate sexes • Systemic hypersensitivity reaction to
(dioecious) schistosome antigens and circulating immune
complexes which coincides with beginning of
→rounder in egg production (1st cycle of egg deposition)
appearance and rapid increase in antigen burden (3-8
weeks post exposure)
→female: 2 cm long; • Sudden onset of fever, malaise, myalgia,
male: 1.5 cm long headache, eosinophilia, fatigue, and
→male surrounds the abdominal pain lasting 2–10 weeks
female almost Clinical manifestation: Credit to Dr. Gerald Diaz; retrieved
from: https://www.grepmed.com/images/10892/diagnosis-
completely, facilitating clinical-photo-katayama-schistosomiasis. Accessed: May 19 2022.
copulation

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes

(a) Yellowish rectal mucosa. (b) Yellow miliary Schistosoma egg

deposits in the sigmoid colon. (c) Yellow-white mucosal patch of
the rectal mucosa. (d) Magnifying endoscopy shows yellow
granular material with thickened, disordered, borderless
submucosal vessels. (e) Many Schistosoma japonicum eggs were
deposited in the diseased intestinal mucosa.
Retrieved from: https://doi.org/10.1186/s12876-020-01591-7.
Accessed: May 19 2022.

3. Urogenital schistosomiasis
• Hematuria
• Caused by egg-laying Schistosoma spp.
(usually S. haematobium) worms dwelling
within the veins draining the main pelvic
organs, including the bladder, uterus, and
2. Chronic intestinal form cervix.
• Non-specific intermittent abdominal pain, • Urinary frequency, burning micturition, and
diarrhea, and rectal bleeding suprapubic discomfort
• Some people develop extensive fibrosis and • Squamous-cell carcinoma of the bladder
hepatosplenic disease with periportal fibrosis
• Upper abdominal discomfort with palpable
nodular and hard hepatomegaly, often with
splenomegaly
• Pulmonary hypertension caused by
granulomatous pulmonary arteritis can also
occur in patients with advanced hepatic
fibrosis disease
Colonoscopy of patients with Chronic Intestinal
Schistosomiasis

Retrieved from: https://doi.org/10.3390/jcm10020205. Accessed:

May 19 2022.

4. Female genital schistosomiasis

• S. haematobium eggs in the vesical plexus
migrate to the genital tract causing
inflammatory lesions in the ovaries, fallopian
tubes, cervix, vagina, and vulva
• Pain, stress incontinence, infertility, and
increased risk of abortion
• Lesions can increase transmission of HIV

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes

Manifestations of female genital schistosomiasis on the cervix

uteri. (A) Rubbery papules are smooth, firm, like a rubber ball, they a) Photomicrograph showing nodular granulomas within the
constitute viable ova and a rich eosinophilic reaction. (B) Grainy parenchyma of the brain containing deposits of S. haematobium
sandy patches constitute calcified and occasional viable ova. (C) ova in the center of the granulomas (hematoxylin-eosin stained;
Homogenous sandy patch. (D) Abnormal blood vessels. magnification, ×100). (b) Ova of S. haematobium with a
Gynecological Manifestations, Histopathological Findings, and characteristic prominent terminal spine (hematoxylin-eosin
Schistosoma-Specific Polymerase Chain Reaction Results Among stained; magnification, ×400). Source: DOI: 10.1128/JCM.01073-11
Women With Schistosoma haematobium Infection: A Cross-
sectional Study in Madagascar. Retrieved from: doi: LUNG FLUKE
10.1093/infdis/jiv035. Accessed: May 19 2022.
PARAGONIMUS WESTERMANI
5. Male urogenital schistosomiasis Common Name Oriental Lung Fluke
• Hematospermia, orchitis, prostatitis, 1st Intermediate Host Snail
dyspareunia, and oligospermia 2nd Intermediate Host Crustaceans
• Resolve more readily after anti-schistosomal Infective stage Metacercariae
treatment than female genital Mode of transmission Ingestion of infected
schistosomiasis crustacean
6. Cerebral schistosomiasis Definitive host Man
• Most common with S. japonicum Habitat of adults in Cystic cavities in lungs
• Includes symptoms of meningoencephalitis man
with pyrexia, headache, vomiting, blurred Diagnostic Stage Unembryonated eggs
vision, and altered sensorium or Jacksonian There are 40 known species of Paragonimus, and six
epilepsy are reported to cause infections in humans
• Spinal cord involvement can present as acute Causes 90% of paragonimiasis in Asia
transverse myelitis or subacute In the Philippines, P. westermani is also the major
myeloradiculopathy paralysis or lumbar and species that causes paragonimiasis in humans. The
leg pain, with muscle weakness, sensory loss, other species in the Philippines is P. siamensis, which
and bladder incontinence has only been identified in cats

LIFE CYCLE

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes
The immature egg embryonates in water, moist soil, or EGGS
leached feces → 80 to 120 um long by
A miracidium develops within 2 to 7 weeks 45-70 um wide
It subsequently pushes open the operculum and swims → Yellow-brown, ovoid or
freely in search of its appropriate snail host elongate, with a thick
In the Philippines, the 1st intermediate hosts are shell
Antemelania asperata and Antelemania dactylus, the → Often asymmetrical
former previously known as Brotia asperata. with one end slightly
Inside the snail, the miracidium passes one sporocyst flattened
and two redial stages of development. → At the large end, the
Leaf-like operculum is clearly
Cercariae subsequently emerge from the snail to seek
and infect the second intermediate host, the mountain visible
crab Sundathelphusa philippina, formerly known as → Opposite (abopercular)
Parathelphusa grapsoides end is thickened
The cercariae penetrates the soft parts of the → Immature egg
crustacean and encysts as a metacercaria in the gills, embryonates in water,
body muscles, viscera or legs moist soil, or leached
The definitive host acquires the infection by ingesting feces
raw or insufficiently cooked crabs harboring ADULT
metacercariae → Large, robust, ovoid
Metacercariae excyst in the duodenum of the host flukes
Immature worm then traverses through the intestinal → Hermaphroditic
wall into the peritoneal cavity, where it wanders about → Lobed ovary anterior
for several days and embeds itself in the abdominal to the two branching
wall testes
The parasite then returns to the coelom and migrates → Possess oral and
through the diaphragm into the pleural cavity ventral suckers
→ Cuticle possesses
LIFE CYCLE EXPLAINED IN VOPPT spines, similar to the
Eggs are excreted as an unembryonated eggs from other adult trematodes
sputum or passed in stool → Measures 7 to 12 mm
In the external environment, eggs develop into further in length, 4 to 6 mm in
stages width, 3.5 to 5 mm in
• Unembryonated → embryonated thickness, and resembles
Miracidia hatch into the water and looks for its host a coffee bean
• Snail – first intermediate host
• Penetrates the smooth tissue and goes PARAGONIMIASIS
through several developmental stages Prevalent in Asia, Africa, and Central and South America
Becomes:
• 4A – Sporocysts
• 4B – Rediae
• 4C – Cercariae – infective stage
Cercariae is then ingested by the host
• Man – definitive host
Cercariae invade the crustacean and encyst into
metacercariae
Once encysted, pwede na makain which will then infect
the tao
• Crustaceans – 2nd intermediate host
They then excyst in duodenum and penetrate the
intestinal wall, the peritoneal cavity, through the
abdominal wall and diaphragm, into the lungs.
They become encapsulated and develop into adults Normal lungs will not have any opacity present in x-rays
• Worms can reach into other organs, tissues, There is an increased opacity in the middle lobe and
brain, muscle tissues and other types of upper lobe of the lungs which is a
tissues symptom/manifestation of Paragonimiasis

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MEDICAL PARASITOLOGY-LECTURE: Trematodes: Lung and Blood Flukes
Hazy and according to the definition of lung opacity, if Stool examination → Demonstration of eggs;
may ganyan sa x-ray, there is a but these are not present
decreased/exchange/flow of gas to the tissues until 2 to 3 months after
Acute stage → Corresponds to invasion and infection
migration of young flukes Effusion fluid or biopsy → Eggs may also be
Chronic stage → Pulmonary infection material encountered
→ Corresponds to the adult flukes Concentration
residing in a cyst in the lung techniques
parenchyma Biopsy → Adult or developing
→ Chronic cough with gelatinous, fluke may be recovered;
tenacious diagnostic confirmation
→ Rusty-brown sputum and species identification
Pleural involvement is common and should be Serologic tests → Antibody detection
differentiated from pulmonary tuberculosis, especially Microscopy → Most basic and most
when it presents with hemoptysis (have similarities in readily available
tuberculosis) diagnostic tool for
Presence of blood paragonimiasis
Cerebral → Most important form of Chest radiographs → Aid in the diagnosis of
involvement extrapulmonary paragonimiasis pulmonary paragonimiasis
→ Can be diagnosed by finding eggs when combined with a
in the sputum, stool, pleural fluid and high index of suspicion
even the cerebrospinal fluid Peripheral blood count → Reveals eosinophilia
→ Can be diagnosed through ELISA and elevated levels of IgE,
which is typical for
PATHOGENESIS AND CLINICAL MANIFESTATION parasitic infections.
In the lungs, Paragonimus worms provoke a
granulomatous reaction that gradually gives rise to the TREATMENT
development of a fibrotic cyst containing blood-tinged Praziquantel is the medication of choice
purulent material, adult worms, and eggs Triclabendazole – demonstrated to be an effective drug
Early stages of the infection are usually asymptomatic as it probably binds to B-tubulins of trematodes,
The circuitous route of migration allows the worms to leading to depolymerization and disruption of
lodge and mature in different ectopic locations microtubule-based processes
Cutaneous and cerebral paragonimiasis are the classic Alternative drug – bithionol
known forms of ectopic infection
Cerebral involvement is the most serious complication PREVENTION AND CONTROL
of human paragonimiasis Avoiding human ingestion of undercooked crayfish and
crabs
LABORATORY DIAGNOSIS Exercising proper disposal of human waste products
(feces/urine)
Defecate and proper hygiene
Safe food preparation
Changing the risky dietary habits of the population,
through health education and promotion
Capacity building of local health staff on the diagnosis
and treatment

Hematoxylin and eosin stain

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➔ Released from the worm immature, containing

LIVER FLUKES a large unsegmented mass of vitelline cells.
➔ The F. gigantica egg is slightly larger than F.
TOPIC OUTLINE hepatica egg (160-190 um by 70-90 um)
1 Fasciola hepatica
2 Fasciola gigantica
3 Clonorchis sinensis
4 Opisthorchis felineus
5 Opisthorchis viverrini

Fasciola hepatica

General Characteristics: Fasciola gigantica

Common ➔ Sheep liver fluk/temperate liver
name fluke
1st ➔ Snail (Lymnea spp.)
Intermediate
Host
2nd ➔ Plant / vegetation (water
Intermediate spinach)
Host
Definitive ➔ Sheep, domestic and wild
host ruminants
Mode of ➔ ingestion of metacercariae
transmission encysted on edible aquatic
plants or by drinking
contaminated water.
Habitat ➔ Biliary duct/passages of liver
Infective ➔ Metacercariae
stage
Diagnostic ➔ Unembryonated eggs
Stage

Fasciola hepatica egg

Adult: Fasciola hepatica

➔ large, broad, oval, flat
➔ 18 to 51 mm in length and 4 to 13 in width
(near the body).
➔ cephalic cone which has a marked widening at
the base of the cone (“shoulder”)
Life Cycle of Fasciola hepatica ➔ testes are highly-branched and ovary is
dendritic.
➔ Resembles hen’s eggs.
Egg: Fasciola hepatica
➔ large, ovoidal, operculated, and yellowish to
brownish.
➔ 140 to 180 um by 63 to 90 um in size.

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in the biliary epithelium leading to

fibrosis.
◆ Symptoms of late stages: biliary
obstruction and cholangitis.
◆ It’s found in extrahepatic biliary
ducts - mimic cholelithiasis.
◆ Rare complication: acute
pancreatitis.
◆ Halzoun (Lebanon syndrome),
Marrara in Sudan - adult worms
may attach to the pharyngeal
mucosa, causing suffocation
(after ingestion of uncooked
goat/ sheep liver).
Laboratory Diagnosis
➔ Stool exam and ELISA
◆ Eggs of F. hepatica can resemble
those F. gigantica (liver fluke)
Fasciola hepatica adult female worm (left) while and Fasciolopsis buki (intestinal
adult male is in the right. fluke).
➔ If available, antigen or antibody detection
Fascioliasis may be helpful in confirming the infection.
➔ acute phase; also, the migratory, invasive, ➔ Tests for confirmation and follow-up:
hepatic, parenchymal, or larval phase) radiographic techniques and magnetic resonance
◆ the period when the larval fluke imaging.
is migrating from the intestines ➔ Spurious infection - presence of eggs after
and through the liver ingesting infected liver.
parenchyma. ➔ Liver biopsy - asymptomatic disease.
◆ larval migration can be Prevention and Control
associated with inflammation, ➔ Prevention may be accomplished by puvlic
tissue destruction, and health education in areas where infections are
toxic/allergic reactions. endemic, stressing the dangers of eating
Nonspecific symptoms/signs watercress grown in the wild where animals
(e.g. abdominal pain, nausea, and snails are abundant,
vomiting, hepatomegaly, malaise, ➔ Other measures have included killing snails,
fever, cough) and laboratory treating infected animals, and draining pasture
abnormalities (e.g., peripheral lands.
eosinophilia, elevated
transaminase levels) may
develop. Fasciola gigantica
◆ Occasionally, larval flukes
migrate to ectopic sites, such as General Characteristics: Fasciola gigantica
the lungs, subcutaneous tissue, Common ➔ Giant liver fluke
pancreas, genitourinary tract, name ➔ Tropical liver fluke
eyes, or brain. 1st ➔ Snail (Lymnea spp.)
◆ Can be asymptomatic. Intermediate
◆ Triad of diagnostic significance: Host
sudden onset of high fever,
2nd ➔ Plant / vegetation (water
hepatomegaly, marked
Intermediate spinach)
eosinophilia.
Host
➔ During the chronic phase of the infection
(also referred to as the biliary or adult phase. Definitive ➔ cattle
◆ Clinical manifestations, if any, host
may develop months to years Mode of ➔ ingestion of infected aquatic
postexposure and include transmission plants
inflammation or blockage of bile Habitat ➔ biliary passages of liver
ducts or the gallbladder (e.g. Infective ➔ Metacercariae
cholangitis, cholecystitis), which stage
can be intermittent. Inflammation Diagnostic ➔ Unembryonated eggs
Stage

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SIDE NOTE
NI MAAM NOTE
● endemic in the African
regions
● Fascioliasis is not endemic in
the Philippines but it is in
other parts of the world
● if ever may cases in the
Philippines, it probably came
from foreigners because it is
not endemic in the
Philippines
● in the Philippines, it can
infect water buffalo (kalabaw)
buti na lang umuulan na raw
sakanila kasi sobrang init daw

Fasciola gigantica adult worm (left) and egg (right)

Clinical: Fasciola gigantica
➔ similar to those of F. hepatica infection and
depend on the worm burden
➔ patients may experience fever, nausea,
vomiting, abdominal pain, hepatomegaly,
hepatic tenderness, and eosinophilia
➔ abscess or tumorlike reactions have also been
reported to occur in subcutaneous tissues or
the liver
◆ it can migrate from ex: intestinal wall to
liver parenchyma so possible syang
mapunta sa mga subcutaneous tissues
during migration (pero rare occasions lang
naman)
◆ merong tumor like reaction dahil sa mga
Life Cycle of Fasciola gigantica inflammation
◆ kaya important yung pag check for lesion
Adult and Egg: Fasciola gigantica sa mga internal organs via MRI
➔ the operculum can be difficult to see; this egg Laboratory DIagnosis: Fasciola gigantica
resembles that of F. buski (intestinal ➔ similar to those methods of F. hepatica
trematodes) and F. hepatica (liver trematodes) infection
➔ egg of F. gigantica is larger (160 to 190 um to ➔ eggs are more absent than in infections with F.
90 um) than F. hepatica hepatica, multiple stool samples are
➔ F. gigantica adult worm is 25 to 75 mm long by recommended
12 mm wide ➔ recovery of adult flukes at surgery would
confirm the diagnosis
◆ stool samples: use of sedimentation
concentration techniques = recommended
for observing the F. gigantica
Treatment: Fasciola gigantica
➔ Praziquantel is sometimes effective at a dose
of 25 mg/kg taken after each meal for 2 days
➔ biothonol at 30 to 50mg/kg on alternate days
for 10 to 15 doses is recommended
➔ Triclabendazole - drug of choice
◆ 10mg/kg as a single dose is also
recommended, but this drug may not be
as easily obtained
◆ if a single dose has failed, the use of
triclabendazole at 20mg/kg is
recommended

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Clonorchis sinensis
General Characteristics: Clonorchis sinensis
Common ➔ Chinese or oriental liver fluke
name
1st ➔ Snail (Parafossarulus spp.
Intermediate Bulinus spp. Etc)
Host
2nd ➔ Freshwater fish
Intermediate
Host
Definitive ➔ Man
host
Reservoir ➔ Dogs, cats, pigs, rats, other
hosts fish-eating mammals
Mode of ➔ ingestion of infected raw or
transmission undercooked fish
Habitat ➔ biliary ducts/liver
Infective ➔ Metacercaria
stage
Diagnostic ➔ Embryonated eggs
Stage

Clonorchis sinensis egg

Clonorchis sinensis Adult
➔ Flattened, lance shaped
➔ Each end of the adult worm is narrower that
the midportion of the body.
➔ 10 to 25 mm long by 3 to 5 mm wide
➔ The two testes are located posterior to the
ovary and are highly branched - a feature
which separates it from the related
Opisthorchis spp. (rounded testes).

Life Cycle of Clonorchis sinensis

Clonorchis sinensis Egg

➔ Operculated, mature (containing miracidium)
➔ Eggs like an old-fashioned electric light bulb.
➔ Pitcher-like appearance
➔ Dinstinct opercular shoulders surrounding the
operculum
➔ Contain a comma-shaped appendage (small
knob) at the abopercular end.

Cabales, Cabaltea, Calderon, Manaog, Marquez

MEDICAL PARASITOLOGY LEC (BMD4203-3)
LECTURE 5 / SOURCES: PPT NI MAAM

Prevention and Control

➔ Infection can be prevented in humans by
thorough cooking of all freshwater fish.
➔ Public health education.
➔ Night soil used without disinfection for fertilizer
should not be applied in lakes or ponds
containing susceptible snails.
➔ It has been suggested that night soil should be
stored prior to use; eggs of C. sinensis die
within 2 days when stored at 26C.
➔ In chronic infections, cholangitis, cholelithiasis,
cholecystitis, and cholangiocarcinoma,
pancreatitis, and lived abscesses may develop
and can lead to death.
➔ Most common liver fluke due to association
with cholangocarcinoma.

Laboratory Diagnosis
➔ Stool exam
Clonorchis sinensis adult ● However, the eggs of Clonorchis
Clonorchiasis are practically indistinguishable
➔ Biliary obstruction. from those of Opisthorchis.
➔ Light infections - generally no symptoms. ➔ Adult flukes have been recovered at surgery or
➔ Heavy infections - dull pain and abdominal may be spontaneously passsed after
discomfort. anthelmic treatment.
➔ With infections of longer duration, the ➔ Morphologic examination of the intact adult
symptoms can be more severe, and fluke allows definitive species identification.
hepatomegaly and malnutrition may be
present associated with fever, chills, diarrhea.
➔ In chronic infections, cholangitis, cholelithiasis,
cholecystitis, and cholangiocarcinoma,
Opisthorchis felineus
pancreatitis, and lived abscesses may develop
and can lead to death. General Characteristics: Opisthorchis felineus
➔ Most common liver fluke due to association Common ➔ Cat Liver Fluke/Siberia Liver
with cholangocarcinoma. name Fluke (common in Russia,
Germany, Siberia,
Kazakhstan)
1st ➔ Snail (Bythinia spp.)
Intermediate
Host
2nd ➔ Freshwater fish
Intermediate
Host
Definitive ➔ Man, cats
host

Cabales, Cabaltea, Calderon, Manaog, Marquez

MEDICAL PARASITOLOGY LEC (BMD4203-3)
LECTURE 5 / SOURCES: PPT NI MAAM

Reservoir ➔ Dogs, cats, other fish-eating

hosts mammals
Mode of ➔ ingestion of infected raw or
transmission undercooked fish
Habitat ➔ biliary ducts/liver
Infective ➔ Metacercaria
stage
Diagnostic ➔ Embryonated eggs
Stage

Opisthorchis felineus adult

Opisthorchiasis (felineus)
➔ With a low worm burden (up to 50 or 60
worms), there may be localized damage in the
distal bile ducts but the liver function remains
normal.
➔ With a worm count up to 1,000, there may be
hepatomegaly and jaundice; the pancreas may
also be involved (because of the passages
that are connected as well to the biliary
Life Cycle of Opisthorchis felineus ducts), which can result in digestive problems.
➔ Chronic infection will lead to
Opisthorchis felineus Egg cholangiocarcinoma (almost the same with
➔ Elongate and ovoid, with an operculum that fascioliasis, clonorchiasis).
resembles that seen in O. viverrini ➔ Overall, the symptoms and clinical sequelae
➔ Light yellowish brown and measure are similar to those seen with O. viverrini
approximately 30 by 11 μm infection.
➔ Like the eggs of some strains of C. sinensis ➔ Acute symptoms can include abdominal pain,
and O. viverrini, some eggs have a small urticaria, dizziness, and fever, may resemble
tubercular thickening (“comma”) at the Katayama fever (schistosomiasis), facial
abopercular end. edema, lymphadenopathy, arthralgias, rash,
➔ It’s hard to differentiate the eggs of O. felineus and eosinophilia
and C. sinensis. Laboratory Diagnosis
➔ Similar diagnostic methods with C. sinensis
and O. viverrini
➔ Testes:
● C. sinensis - branched testes
● O. felineus - slightly lobulated testes
● O. viverrini - deeply lobulated testes

Opisthorchis viverrini
General Characteristics: Opisthorchis viverrini
Opisthorchis felineus egg Common ➔ Southeast Asian Liver Fluke
name (common in parts of Thailand,
Opisthorchis felineus Adult
Cambodia, Laos, Vietnam)
➔ Lancet-shaped and measures 7 to 12 mm in
1st ➔ Snail (Bythinia spp.)
length, which is larger than the adult worms of
Intermediate
O. viverrini
Host
➔ Attached in the biliary and pancreatic ducts of
host
➔ Lobulated, just like the O. viverrini

Cabales, Cabaltea, Calderon, Manaog, Marquez

MEDICAL PARASITOLOGY LEC (BMD4203-3)
LECTURE 5 / SOURCES: PPT NI MAAM

2nd ➔ Freshwater fish ➔ have distinct shoulders or opercular shoulders

Intermediate (same as Clonorchis sinensis) and may have
Host a comma-shaped appendage ar the
Definitive ➔ Man abopercular end.
host ➔ Its almost the same as Clonorchis sinensis
Reservoir ➔ Dogs, cats, other fish-eating ➔ The egg size averages 27 by 15 um
hosts mammals
Mode of ➔ ingestion of infected raw or
transmission undercooked fish
Habitat ➔ biliary ducts/gallbladder
Infective ➔ Metacercaria
stage
Diagnostic ➔ Embryonated eggs
Stage

Opisthorchis viverrini egg

Adult: Opisthorchis viverrini
➔ slightly shorter than C. sinensis adults being 8
to 12 mm long and 1.5 to 3 mm wide.
➔ The main similarity between C. sinensis and
Opistorchis spp. is the location of the vitellaria,
which are found in the middle third of the body
at the level of the uterus;
➔ Whereas the main difference are in the
morphology and arrangement of their testes:
lobate testes, which are arranged obliquely to
the sides.
➔ The testes of O. viverrini as compared to O.
felineus, are positioned close to each other,
are more deeply lobulated.

Life Cycle of Opisthorchis viverrini

LIFE CYCLE
(almost the same for all flukes)
1 🡪 Starting from the embryonated eggs which
& are passed into the feces coming from the
2 host, the eggs are ingested by the first Opisthorchis viverrini adult
intermediate host which is the snail (Bythinia
spp.).
🡪 From there, development of miracidia to
cercariae happens.
3 🡪 Cercariae is released from the snails then it
is ingested by the fish.
🡪 Free-swimming cercariae encyst in the skin
or flesh of fresh water fish.
4 🡪 Metacercariae that are inside the flesh or
skin of freshwater fish will be ingested by the
definitive host or the human host.
5 🡪 Excystation happens in the duodenum.
6 🡪 Adults develop in the biliary duct.
Opisthorchis viverrini adult
CHARACTERISTICS
Egg: Opisthorchis viverrini NOTE: based on the image above
➔ brownish yellow, oval, and operculated; ➔ Vitellaria (VT)- midbody of the worm
➔ Mature when laid (It carries the miracidia)

Cabales, Cabaltea, Calderon, Manaog, Marquez

MEDICAL PARASITOLOGY LEC (BMD4203-3)
LECTURE 5 / SOURCES: PPT NI MAAM

➔ Testes (TE)- If the testes of the Clonorchis

sinensis is highloy branched, the testes of
O. viverrini is lobate and more chunky.
➔ Oral sucker (OS)- in the anterior portion
➔ Ceca (CE)
➔ Acetabulum (AC)- or the ventral sucker
➔ Uterus (UT)
➔ Ovaries (OV)

OPISTHORCHIASIS
➔ most infections are asymptomatic.
➔ most pathologic manifestations result from
inflammation and intermittent obstruction of the
biliary ducts
➔ In mild cases, manifestations include
dyspepsia, abdominal pain, diarrhea, or
constipation.
➔ With infections of longer duration, the
symptoms can be more severe, and
hepatomegaly and malnutrition may be
present.
➔ Patients with heavy worm burdens may have
severe cirrhosis, ascites, pedal edema, and
acute abdominal pain.
Laboratory DIagnosis: Opisthorchis viverrini
➔ Same diagnostic methods with Clonorchis
spp.
➔ If the two will be differentiated, they are
different in terms of the form of the adult
worms and patient history (anong lugar)
◆ For example: The patient was
from South-East Asia, so its
Opistorchis viverrini
◆ You have at least an idea of what
is endemic in those areas
Treatment: Opisthorchis viverrini
➔ Praziquantel
◆ 75 mg/kg/day orally, three doses
per day for 2 days
➔ Albendazole
◆ alternative drug; the dosage is 10
mg/kg/day for 7 days
Prevention and Control: Opisthorchis viverrini
➔ Public health education
◆ It includes awareness, personal
hygiene, proper food safety
protocols like cooking the
freshwater fish/food up to its safe
temperature
◆ Safe temperature for fish is 63°C
as well as for pork
◆ For chicken, safe temperature
70+°C
➔ defecation in or near ponds or lakes
should be prevented, as should the
application of night soil the intermediate
hosts are abundant

Cabales, Cabaltea, Calderon, Manaog, Marquez

 Medical Parasitology Lec
INTESTINAL FLUKES

7 The mammalian hosts become infected by ingesting

INTESTINAL FLUKES metacercariae on the aquatic plants. After ingestion, the
metacercariae excyst in the duodenum and attach to the
● Fasciolopsis buski intestinal wall.
● Echinostoma ilocanum 8 There they develop into adult flukes (20 to 75 mm by 8
● Heterophyes heterophyes to 20 mm) in approximately 3 months, attached to the
intestinal wall of the mammalian hosts (humans and
pigs)
*The adults have a life span of about one year.
Fasciolopsis buski
Common name Large intestinal fluke
Egg
Intermediate snail ➔ Elongated, oval in shape
host ➔ Yellowish brown
Definitive host Humans & pigs ➔ Clear, thin shell w/ a small operculum but no opercular
Mode of Ingestion of infected aquatic plants shoulders
transmission ➔ Operculated, unembryonated
Habitat Small intestine ➔ 130 to 140 μm by 80 to 85 μm
Infective stage metacercariae
Diagnostic stage Unembryonated eggs

Adult
LIFE CYCLE (CDC) ➔ Fleshy, dark red, and elongate-ovoid
1

2
stool🔬
Immature eggs are discharged into the intestine and

Eggs become embryonated in water.

➔

➔
20 to 75 mm in length, 8 to 20mm in width, and 0.5 to 3
mm in thickness
Does not have a cephalic cone and its intestinal ceca are
3 eggs release miracidia… unbranched and reach up to the posterior end
4 …which invade a suitable snail intermediate host.
In the snail the parasites undergo several
developmental stages:
1. sporocysts (4a)
2. Rediae (4b)
3. cercariae (4c)
5
6
The cercariae are released from the snail…
…and encyst as metacercariae on aquatic plants ☣️
1
 Echinostoma ilocanum
Common name Garrison fluke
Intermediate ➔ 1st: snail (Gyraulus convexiusculus
host & Hippetus umbilicalis - common
snails found in Philippines)
➔ 2nd: snails (Gyraulus
convexiusculus & Hippetus
umbilicalis) “so ganun parin parang
twice - maam”
Definitive host Humans, dogs, cats, rats, & pigs
Diagnostic stage Unembryonated eggs
Infective stage Metacercariae
Habitat Small intestines
Mode of Ingestion of infected host
transmission

Fasciolopsiasis
➔ The attachment of worms to the mucosal wall - local
inflammation w. Hypersecretion of mucus, hemorrhage,
ulceration, & possible abscess formation (minor
symptoms sabi ni maam)
➔ In heavy infections - bowel obstruction, acute ileus,
general edema and ascites, abdominal pain, diarrhea
➔ Malabsorption (if doon daw tumira si F. buski) - low vit.
B12 levels,
➔ Marked eosinophilia, leukocytosis
➔ Depending on the worm burden - the infection can be
associated. w/ severe cachexia & prosteation and can
lead to death

Laboratory Diagnosis
➔ Eggs in stool
➔ Rarely, adult worms are found during heavy infections
➔ Recommended technique: Formalin-ethyl acetate
sedimentation concentration

Treatment
Praziquantel ➔ Isoquinolone derivative
➔ Side effects: abdominal pain,
headache, dizziness, nausea, LIFE CYCLE (CDC)
drowsiness, pruritus, & myalgia 1 Like many trematodes, echinostomid flukes undergo a
➔ Disappear within 48 hrs but may be multi-host (indirect) life cycle
more pronounced in heavily infected

Niclosamide
indivs
Salicylamide derivative
2
definitive hosts…. 🔬
Unembryonated eggs are passed in feces of infected

…and develop in water.

Prevention and Control 3 Miracidia usually take about 3 weeks to mature before
➔ Plants should be cooked/ immersed in boiling water for hatching ….
a few secs before eaten or peeled 4 after which they swim freely and penetrate the first
➔ Use of unsterilized night soil for fertilizer should be intermediate host, a snail. The intramolluscan stages:
prohibited 1. sporocyst (4a)
2. one or two generations of rediae (4b)
3. cercariae (4c)
5 The cercariae may encyst as metacercariae within the
same first intermediate host or leave the host and
penetrate a new second intermediate host.
6

7
The definitive host becomes infected after eating
metacercariae in infected second intermediate hosts
Metacercariae excyst in the duodenum….
☣️
2
8 ….and adults reside in the small intestine (for some
species, occasionally in the bile ducts or large intestine)

Egg
➔ Immature, ellipsoidal/ovoid, yellow brown &
operculated
➔ 86 to 116 μm by 58 to 69 μm
➔ Inconspicuous operculum & thickened abopercular end

Echinostomiasis
➔ Light infections: patient may be asymptomatic & adult
worms cause only minor problems other than localized
Adult inflammation
➔ Reddish-gray; tapered at posterior end ➔ Heavy infection: worms can produce catarrhal
➔ Anterior end of adult worm has circumoral disk w/ a inflammation & mild ulceration and patient may
crown of spines (49 to 51 coral spines) surrounding the experience diarrhea & abdominal pain
small oral sucker (ventral portion)
Laboratory diagnosis
➔ Similar w/ F. buski
➔ Eggs in stool (Formalin-ethyl acetate sedimentation
concentration)
➔ Eggs of E. ilocanum, G. hominis, F. buski, F. hepatica & F.
gigantica appear almost identical and are very difficult
to differentiate from one another

Treatment
➔ Praziquantel
➔ Albendazole

Prevention and Control

➔ Infection can be prevented in areas of endemicity by
restricting use of night soil for fertilizer & eating cooked
rather than raw mollusks

Heterophyes heterophyes
Common name Von Siebold’s fluke
Intermediate ➔ 1st: snail (Cerithidia, Pironella)
host ➔ 2nd: fresh/brackish water fish
Definitive host Human
Diagnostic stage Embryonated eggs
Infective stage Metacercariae
3
Habitat Small intestines
Mode of ➔ Ingestion of infected
transmission raw/undercooked fish

Adult
➔ Elongated, oval or piriform, gray and have abroadly
rounded posterior end
➔ 1.0 to 1.7 mm length x 0.3 to 0.4 mm in width
➔ surface/tegument has finescale-like spines
➔ Contains a third sucker or a genital sucker thats located
near the left posterior border of the ventral sucker
LIFE CYCLE (CDC) ➔ tested variously arranged are in the posterior end of
1 Adults release embryonated eggs each with a body

2
host’s feces🔬
fully-developed miracidium, and eggs are passed in the

After ingestion by a suitable snail (first intermediate

➔ Ovary globular or slightly lobed is located in the
submedian, pre- or post- testicular area

host), the eggs hatch and release miracidia which

penetrate the snail’s intestine. Heterophyiasis
➔ Diarrhea & colicky abdominal pain
The miracidia undergo several developmental stages in ➔ Heavy infections: abdominal pain mucous diarrhea,
the snail: ulceration at intestinal wall, consistent w/ peptic ulcer
1. sporocyst (2a) disease & acid peptic disease
2. rediae (2b) ➔ Eggs of degenerating worms may be filtered through
3. cercariae (2c) the intestinal lymphatics & blood vessels and may be
3 Many cercariae are produced from each redia. The deposited in various tissues (pathological lesions) “kasi
cercariae are released from the snail… nga maliliit sila so they can really encyst and be
4 …and encyst as metacercariae in the tissues of a deposited in diff tissues -mam”
suitable fresh/brackish water fish (second intermediate ➔ Eggs + adults of heterophyids have been observed in
host). the heart & brain of Filipino patients who died of heart
5 The definitive host becomes infected by ingesting failure & intracerebral hemorrhage

6
undercooked
metacercariae.☣️ or salted fish containing

After ingestion, the metacercariae excyst, attach to the

➔ Eggs lodges in the spinal cord may result in sensory &
motor losses at the level of the lesion

mucosa of the small intestine…. Laboratory diagnosis

7 ….and mature into adults. ➔ Definitive diagnosis is y detection of eggs in stool via
8 In addition to humans, various fish-eating mammals Kato thick method, which has higher sensitivity
(e.g.,cats and dogs) and birds can be infected by compared to formalin-ether/ethyl acetate conc
Heterophyes heterophyes. technique
➔ PCR may be useful as sensitive diagnostic tool,
Egg particularly for low-intensity heterophyid infections
➔ Small, brownish, yellow, and operculated, mature when ➔ Eggs are similar to C. sinensis & can be differentiated
laid based on patient history or recovery of adult worms in
➔ Possess very subtle opercular shoulders stool
➔ 27 to 30 μm by 15 to 17 μm
Treatment
➔ Praziquantel (drug of choice & cna be given in a single
dose of 15-25 mg/kg at bedtime)
➔ Tetrachloroethylene (alternative)

4
 Prevention and Control
➔ Improving sanitary conditions & educational info abt.
Proper sewage disposal away from ponds/lakes where
the intermediate hosts reside
➔ Avoiding ingestion of raw or improperly cooked fish

5
 Medical Parasitology Lec
CESTODES
(4)Dipylidium spp.
TOPIC OUTLINE Somatic/Tissue (1)Taenia solium
1. Pseudophyllidea Cestodes (2)Taenia multiceps
a. Diphyllobothrium latum (Dibothriocephalus (3)Echinococcus spp.
latus) (4)Spirometra spp.

2. Cyclophyllidea Body Structure of Cestodes

a. Dipylidium caninum Head or ➔ Organ of attachment
b. Hymenolepis nana Scolex ➔ Cyclophyllidean cestodes - four cup like
c. H. diminuta muscular suckers (acetabula)
d. Echinococcus granulosus ➔ T. solium and H. nana - has a beak like
e. Taenia saginata apical protrusion called as rostellum,
f. T. solium which may be armed with hooklets (armed
g. Minor Taenia species tapeworms)
➔ Pseudophyllidean cestodes - a pair of
longitudinal groove called as bothria by
Cestodes which it attaches to small intestine
➔ Suckers (grooves or acetabula)
General Characteristics ◆ majority with 4 cup-like structures
Shape ➔ Long, segmented, flattened ◆ Diphyllobothrium latum - 2 slit-like
dorsoventrally, tape-like and suckers
segmented
Size ➔ Few millimeters up to meters
➔ Hymenolepsis nana - smallest
➔ Dyphyllobotrium - longest
Head end ➔ Suckers present
➔ Some have attached hooklets
Circulatory ➔ Absent
system or
alimentary
canal
Body ➔ Consist of head/scolex, neck, strobila
Body wall ➔ Made up of three layers
1. Outer microvillus like structure called as
microthrix
2. Middle basal plasma membrane
3. Inner muscular layer (outer circular and
inner longitudinal muscle coats)
Body cavity ➔ Absent
Sex ➔ Monoecious; with well-developed Neck ➔ Portion from which the segments
reproductive system (proglottids) arise
Life cycle ➔ Requires two hosts (except Strobila ➔ Body or trunk which is surrounded by a
Hymenolepsis and Diphyllobothrium) body wall called as tegument
➔ They are oviparous ➔ Proglottids:
Habitat ➔ Small Intestine ◆ Immature segments- Male and
Mode of ➔ Ingestion female reproductive organs are not
transmission differentiated
◆ Mature segments - Contain male and
Classification female organs in the same segment,
Pseudophyllidea (1)Diphyllobothrium male organ appear first
(2)Spirometra ◆ Gravid segments or fertilized
segments - the uterus gets filled with
eggs.
Cyclophyllidea (1)Echinococcus
(2)Hymenolepididae
(3)Hymenolepsis
(4)Dipylidiidae

Intestinal Cestodes (1)Diphyllobothrium spp.

(2)Taenia solium and Taeina saginata
(3)Hymenolepsis spp.
 ➔ They release their secretion through
their ducts into the ootype.

Male Reproductive Organs

(Present on the dorsal side)
Testes ➔ Exist as multiple follicles (except in
Hymenolepsis which are three in
number).
➔ Sperms are released to vasa
efferentia which join together to form
vas deferens
Vas deferens ➔ It is a convoluted tube, opens in the
common genital pore.
➔ It bears a seminal vesicle and ends in
the common genital pore as a
swollen muscular and protrusible
organ called cirrus (equivalent of
penis) surrounded by a cirrus sac.

Female Reproductive Organs

(Present on the Ventral Side)
Bilobed Ovary ➔ Present in the middle and posteriorly
Oviduct ➔ Arises from ovary, joins with
spermatic duct and opens into the
ootype
Ootype ➔ It is the chamber where fertilization
takes place.
➔ There may be self fertilization or
cross fertilization between the
segments.
Vagina ➔ A tube that connects genital pore to
the ootype through which the sperm
enters.
➔ At its inner end, it contains seminal
receptacle (for storage of sperm) and
spermatic duct
Uterus ➔ Straight tube arises from the ootype
where the eggs are stored after
fertilization in the gravid females. Nervous System
➔ Its end may be opened (in ➔ Rudimentary
pseudophyllideans) or closed as blind ➔ Consists of brain like structure (central ganglion, lateral
sac (in cyclophyllideans) and rostellar ganglia connected by central nerve ring)
Vitelline gland ➔ Present near the ootype present in the scolex from which the longitudinal nerve
(vitellaria) ➔ They occur as single mass (in trucks arise and pass through all the segments and
and Mehlis’ cyclophyllideans) or scattered mass joined by transverse nerves in each segment.
gland (in pseudophyllideans).
 Excretory System
➔ It is also rudimentary and present in each segment.
➔ It consists of two lateral canals (dorsal and ventral)
connected by transverse canals in each segment.
➔ The excretory canals are built up of flame cells
(terminal cells) and canal cells.

Pseudophyllidean Cyclophyllidean
cestodes cestodes
Scolex ➔ Bears two grooves ➔ Bears four suckers
(bothria) (Some species bear
rostellum with
hooklets)
Uterus ➔ Convoluted ➔ Branched and
(rosette shaped), closed as a blind
unbranched, sac
opens at the ➔ No uterine pole
uterine pole
Genital ➔ Situated ventrally ➔ Situated laterally
pore in the midline
Vitelline ➔ Scattered ➔ Single mass behind
gland throughout the ovary
segment
Eggs ➔ Covered by one ➔ Covered by two
layer - egg shell layer - egg shell and LIFE CYCLE
➔ Freshly passed embryophore
eggs in feces are ➔ Embryonated from
unembryonated the beginning
1

2
🔬
Unembryonated eggs passed in feces of definitive host.

Eggs emryonate in water.

➔ Eggs are ➔ Eggs are not 3 Coracidia hatch from eggs and are ingested by the first
operculated and operculated and intermediate host, crustaceans.
the embryo is the embryo is not 4 Procercoid larvae develop in body cavity of
ciliated ciliated crustaceans.
Larval ➔ Solid ➔ Contains bladder 5 Infected crustacean ingested by the second
form like sac intermediate host, usually small fish.
● Procercoid larva released from crustacean
Oncosphere ➔ Protects the embryo develops into plerocercoid larva.

☣️
➔ Contains 6 hooklets 6 Predator fish (paratenic host) eats small fish;
Hexacanth ➔ Embryo with 6 hooklets plerocercoid invades tissue.
embryo 7 Definitive host ingests plerocercoids in infected fish.
Adults ➔ Found in the intestines of definitive 8 Adults in small intestine.
host ● Many fish-eating mammals and birds are definitive hosts.
Larva ➔ Encysted tissues of the intermediate
host Dyphyllobotrium latum (Egg)
➔ Operculated, immature
Pseudophyllidea ➔ Confused with eggs of P. westermani
Diphyllobothrium latum ➔ May also resemble eggs of Nanophyetus salmincola
(Dibothriocephalus latus) ➔ Opposite the operculum is a knob like thickening
(abopercular knob)
Common name ➔ Fish tapeworm/human broad ➔ Appear 5-6 weeks after infection
tapeworm
1st Intermediate ➔ Fresh water copepods (Cyclops
host and Diaptomus)
2nd Intermediate ➔ Fresh water fishes (pike, salmon,
host perch and trout)
Definitive host ➔ Man
Reservoir host ➔ Dogs, cats, rats and other fish
eating mammals
Diagnostic Stage ➔ Unembryonated eggs
Infective Stage ➔ Third stage plerocercoid larvae
Mode of ➔ Ingestion of undercooked (larger)
Transmission fresh water fish containing third
stage plerocercoid larva
 Dyphyllobotrium latum (Adult)
➔ Scolex is spatulate/spoon shaped/ diamond shaped
with sucking organ called bothrium
➔ Uterus with characteristic rosette formation (highly
coiled uterus)
➔ Mature and gravid proglottids are wider than they are
long, with the main reproductive structures (mainly the
uterus) located in the center of the gravid proglottid

Diphyllobothrium latum scolex

Diphillynothriasis
➔ Most of D. latum infections are asymptomatic.
➔ Minor manifestations may include abdominal
discomfort, diarrhea, vomiting, weakness and weight
loss or rarely acute abdominal pain and intestinal
obstruction, cholangitis or cholecystitis (may be
produced by migrating proglottids)
➔ Vitamin B12 deficiency
◆ The adult worm absorbs large quantities of vitamin
B12 and interferes with ileal B12 absorption
◆ leads to development of megaloblastic anemia
and some people may exhibit neurologic
sequelae like paresthesia.
◆ This effect has been noted only in Scandinavia,
where up to 2% of infected patients, especially the
elderly, have megaloblastic anemia
➔ Larger worms with close proximity to stomach can
➔ In freshly passed or formalin preserved segments, one absorb more vitamin B12
frequently observes a pronounced central elevation,
which marks the site of the egg filled uterus Laboratory Diagnosis
➔ May reach more than 10m in length with 3000 Stool ➔ Recovery and identification of eggs
proglottids Examination and proglottids (passed in chains
➔ Confused with adults of Spirometra spp. few inches to several feet)
➔ scolex is spatulate and measures 2 to 3 mm in length by ➔ Kato technique
1 mm in diameter ◆ useful in demonstrating eggs
➔ has two bothria or sucking grooves, which are located Examination of ➔ Presence of free hydrochloric acid
dorsally and ventrally. gastric juice ➔ Pernicious anemia is associated with
➔ neck is long and attenuated, and is followed by achlorhydria
immature proglottids. ➔ To differentiate anemia due to
➔ terminal four-fifths of the worm is composed of mature diphyllobothriasis from pernicious
and gravid proglottids. anemia
➔ mature proglottid
➔ Residence in or travel to an endemic area, a raw-fish
◆ has a longer width than its length
diet, and a pernicious type of anemia may be suggestive
◆ measures 2 to 4 mm in length by 10 to 12
of diphyllobothriasis
mm in width
➔ Sometimes, proglottids may be vomited.
◆ contains one set of reproductive organs
➔ The testes are located in the dorsolateral part of the
proglottid. Treatment
➔ The vas efferens converge to form a vas deferens and Praziquantel ➔ (5-10 mg/kg once)
this enlarges into a seminal vesicle and terminates in a ➔ highly effective (drug of choice)
muscular cirrus found at the midventral common genital Niclosamide ➔ is given alternatively
pore. Parenteral ➔ should be given if B12 deficiency is
➔ The dark, rosette-like, coiled uterus located in the vitamin B12 manifested.
middle of the gravid proglottid extends from the ootype ➔ The criterion for cure is recovery of the scolex in feces
and opens through a uterine pore in the midventral line after treatment.
behind the common genital pore. ➔ If the scolex is not recovered, a repeat stool examination
➔ A symmetrical bilobed ovary is present at the posterior is done after 3 months to be certain that the patient is
third of the proglottid immediately above the Mehlis’ no longer infected.
gland.
➔ From the common genital pore, the vagina extends up
to join the oviduct and the vitelline duct. Prevention and Control
➔ the proglottids of D. latum disintegrate only when the ➔ Proper cooking of fish (10 minutes at 50 C)
segment has completed its reproductive function. ➔ Deep freezing (10 C for 24 hours) for the people who eat
raw fish.
 Cyclophyllidea
Dipylidium caninum

Common name ➔ Double pored tapeworm

Intermediate ➔ Insects (fleas)
host
Definitive host ➔ Dogs (Ctenocephalides canis) and
cats (Ctenocephalides felis) Dipylidium caninum egg capsule.
Accidental host ➔ Man (Pulex irritans) (observed to
be more common in children than Dipylidium caninum (Adult)
in adults) ➔ Relatively small, averaging about 15 cm in length, they
Infective stage ➔ Cysticercoid larva may reach a length of 80cm
Diagnostic stage ➔ Gravid proglottids ➔ Scolex: small and globular, with four deeply cupped
Mode of ➔ Ingestion of flea containing suckers and protrusible rostellum, which is armed with
transmission cysticercoid larva 1-7 rows/several rings of rose thorn shaped hooklets
➔ Proglottids: narrow with two sets of male and female
reproductive organs and bilateral genital pores (double
pored). Hence, the name Dipylidium (dipylos-two
entrances).
➔ Mature and gravid proglottids are typically shaped
like melon seeds/pumpkin seeds/rice grains/cucumber
seeds when moist and rice grains when dry
➔ Filled with capsules or packets of about 8 to 15 eggs
enclosed in an embryonic membrane.
➔ Gravid proglottids are passed out of the anus of the
host singly or in groups.
➔ The ova are released by contraction of the proglottid or
by its disintegration outside the host.
➔ Following self fertilization, the resulting gravid
proglottid is full of eggs enclosed in an embryonic
membrane

LIFE CYCLE
1 Gravid proglottids are passed intact in the feces or

🔬
emerge from perianal region of either animal or human
hosts.
2

3
🔬
The proglottids disintegrate and release the egg packets.

Larvae of the typical flea intermediate host ingests egg

packets. Oncospheres hatch and develop into
cysticercoids.
4 Flea larvae mature into adult fleas, which continue to
harbor infective cysticercoids.

cysticercoids. ☣️
5 Definitive host is infected by ingesting fleas containing

➔ Incidental human transmission via ingestion of infected

fleas.
6 Scolex
7 Cats and dogs can harbor fleas infectious to humans.
Some of the egg capsules may remain in the fur of the host
or in the host’s resting place. Here, larval fleas ingest the ova
as they feed on epidermal debris.

Dipylidium caninum (Egg)

➔ 25-40 μm size
➔ present in groups of 15 (egg packets containing
8-15/5-30 embryonated eggs)
➔ Eggs are spherical, thin shelled with a hexacanth Dipylidium caninum gravid segment.
embryo
 Dipylidiasis
➔ Infection is rarely heavy and symptoms are minimal.
➔ Slight intestinal discomfort, epigastric pain, diarrhea,
anal pruritus, and allergic reactions have been reported.
➔ While most patients are asymptomatic, moderate
eosinophilia has been reported.

Laboratory Diagnosis
➔ Diagnosis is established upon recovery of the
characteristic gravid proglottids passed out singly or in
chain.
➔ Gravid proglottids may crawl out of the anus, and may
be passed out involuntarily
➔ Proglottids should be pressed or flattened between two
glass slides for examination.
➔ Stool examination for the presence of the egg capsules
is not recommended, since the gravid proglottids do not
disintegrate in the intestines but in the environment.
➔ Egg capsules are rarely recovered from the stool.
➔ The diagnosis is made by detection of proglortids or
eggs in stool (Paniker)

Treatment
Praziquantel ➔ 5 to 10 mg/kg given as a single dose.
LIFE CYCLE (CDC)
Belizario: The life cycle has a dual pathway:
Prevention and Control
● direct development - host ingests eggs, which
➔ Periodic deworming of pet cats and dogs is hatch in the duodenum
recommended. ● indirect development - via the accidental
➔ Insecticide dusting of dogs and cats are effective against ingestion of infected arthropod intermediate hosts
fleas. like the rice and flour beetles (Tenebrio sp.) and
➔ The potential danger of playing with pets must be sometimes through fomites, water, or food
included in the health education of children. contaminated with the larvae.
1 Eggs of H. nana are immediately infective when passed

🔬☣️
Hymenolepsis nana with the stool; cannot survive more than 10 days in the
external environment.
Common name Dwarf tapeworm 2 When eggs are ingested by an arthropod intermediate
Intermediate ➔ Direct: do not require intermediate host (various species of beetles and fleas may serve as
host host intermediate hosts), they develop into cysticercoids.
➔ Indirect: Beetles, fleas, moths 3 Cysticercoids can infect humans or rodents upon
Definitive host
Diagnostic stage
Infective stage
Man
Embryonated eggs
➔ Direct: Embryonated eggs
☣️
ingestion and develop to adults in the small intestine.

**morphologically identical variant, H. nana var.

➔ Indirect: cysticercoid larva fraterna, infects rodents and uses arthropods as
Habitat Small intestine intermediate hosts
Mode of ➔ Direct: Ingestion of food and water 4 When embryonated eggs are ingested (in
transmission contaminated with eggs contaminated food or water or from hands

More info galing

➔ Indirect: Accidental ingestion of
intermediate host containing larva
➔ a cyclophyllidean tapeworm 5
in the eggs are released. ☣️
contaminated with feces), the oncospheres contained

The oncospheres (hexacanth larvae) penetrate the

kay Belizario ➔ smallest tapeworm infecting intestinal villus and develop into cysticercoid larvae.
humans 6 Upon rupture of the villus, the cysticercoids return to
➔ the only human tapeworm which the intestinal lumen, evaginate their scoleces and attach
can complete its entire life cycle in to the intestinal mucosa.
a single host, meaning it does not
7 Develop to adults; reside in the ileal portion of the small
require an obligatory intermediate
intestine producing gravid proglottids.
host.
8 Eggs are passed in stool when released from proglottids
through its genital atrium or when proglottids
disintegrate in the small intestine.
9 ALTERNATE
autoinfection ☣️MODE OF INFECTION: internal

- eggs release their hexacanth embryo, which penetrates

the villus continuing the infective cycle without passage
 through the external environment. (aka autoinfection in a more or less straight pattern across the segment).
within the small bowel) Genital pore opens laterally on the same side.
- also, autoinfection via fecal-oral route ➔ When segments become gravid, the testes and the
ovary disappear while the uterus hollows out and
**life span of adult is 4 to 6 weeks, but internal becomes filled with eggs.
autoinfection allows the infection to persist for years ➔ Uterus has lobulated wall and there are only three
testicular follicles
Egg (H. nana) ➔ It resides in the small intestine (upper two thirds of the
➔ Egg is round to slightly oval, 30 to 47 μm size ileum).
➔ colorless or clay-colored
➔ It has two membranes (outer egg shell and an inner
embryophore) and an oncosphere with six hooklets.
Space between the two membranes is filled with yolk
granules
➔ Polar filaments: Both the poles of embryophore are
thickened from which four to eight polar filaments
emerge
➔ The oncosphere has a thin outer membrane and a thick
inner membrane with conspicuous bipolar thickenings,
from each of which arise four to eight hair-like polar
filaments embedded in the inner membrane.
➔ Immediately infectious when passed in stool and cannot
survive more than 10 days in the external environment

Hymenolepsiasis
➔ H. nana infection is usually asymptomatic (light worm
burden).
➔ Clinical manifestations include headache, dizziness,
anorexia, pruritus of nose and anus, diarrhea, vomiting,
abdominal pain, pallor, and weight loss.
➔ When infection is intense and the worm burden
exceeds 1000 - 2000 worms, patients develop
symptoms like anorexia, abdominal pain, headache,
dizziness and diarrhea.
➔ Low grade eosinophilia of 5% or more
➔ Children with heavy infections may present with loose
stools or even diarrhea containing mucus
➔ Persistent, diffuse abdominal pain seems to be the
most common symptom
➔ Heavy infection may be attributed to autoinfection,
may lead to complications in immunocompromised
patients. May result in enteritis due to necrosis and
desquamation of the intestinal epithelial cells.

Adult (H. nana) Laboratory diagnosis (H. nana)

➔ The adult form is small, 1 to 4 cm in length and consists ➔ Stool examination
of head, neck and strobila. ◆ Recovery of eggs containing polar filaments
◆ Head/scolex: It is globular with four suckers and a (fresh specimens or specimens preserved in
rostellum bearing single row of 20 - 30 Y shaped formalin based fixatives)
hooklets ◆ Direct wet or concentration wet mount is
◆ Neck: It is long and gives rise to proglottids recommended: eggs collapse in permanent
◆ Strobila: Consists of 175 - 220 proglottids. All stained smears
segments are wider than long. Proglottids are ◆ In light infections, concentration of the stool
craspedote (overlapping) wherein the anterior specimens on alternate days is useful.
proglottids are short and the posterior ones are ◆ Generally, proglottids are not recovered
broader than long. Rarely seen in stool. because they undergo degeneration prior to
➔ Mature proglottids contain both male and female passage with stools.
reproductive organs (three ovoid testes and one ovary
 Treatment (H. nana)
Praziquantel ➔ 25 mg/kg once (single dose)
➔ is the treatment of choice, since it
acts against both the adult worms
and the cysticercoid larvae in the
intestinal villi.
➔ causes vacuolization and disruption
of the tegument in the neck region.
➔ The drug dosage for hymenolepiasis
is higher than that for taeniasis
because of the relatively resistant
cysticercoids in the intestinal tissue.
Niclosamide ➔ may be used as an alternative
Nitazoxanide (500 mg orally for 3 days) may be used as
alternative drug

Prevention and Control (H. nana)

➔ Good personal hygiene and improved sanitation can
eradicate the disease. Epidemics
➔ have been controlled by mass chemotherapy
➔ coupled with improved hygiene.
➔ Infected cases should be thoroughly treated.
➔ Rodent control must be observed.
➔ Food must be properly stored and protected from
possible infestation with grain beetles.
Medical Parasitology Lec
CESTODES

cysticercoid larvae persist through the arthropod’s

Hymenolepis diminuta morphogenesis to adulthood.

3 H. diminuta infection is acquired by the

Common name rat tapeworm mammalian host after ingestion of an
intermediate host carrying the cysticercoid larvae.
Intermediate Arthropod (rat flea, flour beetle, Humans can be accidentally infected through the
host flour moths, cockroach)
ingestion of insects in precooked cereals, or other
food items, and directly from the environment
Definitive host Rat, mice
(e.g., oral exploration of the environment by
Accidental host Man children).

Diagnostic Embryonated eggs 4 After ingestion, the tissue of the infected

stage arthropod is digested releasing the cysticercoid
larvae in the stomach and small intestine. Eversion
Infective stage Cysticercoid larva of the scoleces occurs shortly after the
cysticercoid larvae are released. Using the four
Mode of ingestion of contaminated food
suckers on the scolex, the parasite attaches to the
transmission with
small intestine wall.
infected arthropod
5 Maturation of the parasites occurs within 20 days
and the adult worms can reach an average of 30
cm in length. Eggs are released in the small
intestine from gravid proglottis that disintegrate
after breaking off from the adult worms. The eggs
are expelled to the environment in the
mammalian host’s feces.

Egg (H. diminuta)

• H. diminuta eggs are circular, about 60 to 80

μm in diameter and are bile-stained.
• The oncosphere is enclosed in an inner
membrane, which has bipolar thickenings
but lacks the bipolar filaments.
LIFE CYCLE (CDC) • The oncosphere is enclosed in an inner
membrane, which has bipolar thickenings
1 Eggs of Hymenolepis diminuta are passed out in but lacks the bipolar filaments.
the feces of the infected definitive host (rodents,
man). The mature eggs are ingested by an
intermediate host (various arthropod adults or
larvae) and oncospheres are released from the
eggs and penetrate the intestinal wall of the host
which develop into cysticercoid larvae.

2 Species from the genus Tribolium are common

intermediate hosts for H. diminuta. The
Medical Parasitology Lec
CESTODES

Hymenolepsiasis

• Clinical manifestations are minimal and non-

Adult (H. diminuta)
specific.
• Most infections have been reported in
• The adult tapeworm is larger than H. nana
children younger than 3 years: however,
and about 60 cm in length.
infected adults have also been reported.
• Scolex: 4 suckers having a rudimentary
• Symptoms that have been reported include
unarmed rostellum.
diarrhea, anorexia, nausea, headache, and
• Mature proglottids are broader than they are
dizziness: they are the most likely to be seen
long
in infected children with heavy infection.
• The proglottids are larger and may reach 0.75
mm in length and 3.5 mm in width.
• Proglottids are craspedote (overlapping)
• The genital pores are unilateral. Laboratory diagnosis (H. diminuta)
• Each gravid proglottid contains a sac-like
• Diagnosis is based on the identification of
uterus filled with eggs.
eggs from the stool. H. diminuta eggs are
distinguished from H. nana eggs by their
more circular shape, larger size, and lack of
bipolar filaments.
• At times, the whole worm is expelled and the
morphology of the scolex may be used as an
aid in diagnosis.

Treatment similar with H. nana

Praziquantel ➔ 25 mg/kg once (single dose)

➔ is the treatment of choice,
since it acts against both the
adult worms and the
cysticercoid larvae in the
intestinal villi.
➔ causes vacuolization and
disruption of the tegument in
the neck region.
➔ The drug dosage for
hymenolepiasis is higher than
that for taeniasis because of
Medical Parasitology Lec
CESTODES

the relatively resistant

cysticercoids in the intestinal
tissue.
Niclosamide ➔ may be used as an alternative

Nitazoxanide (500 mg orally for 3 days) may be

used as alternative drug

Prevention and Control (H. diminuta)

Prevention and control measures include rodent

control, elimination of the insect intermediate hosts,
protection of food, especially the precooked cereals
from such insects, sanitary disposal of human waste,
and treatment of human cases. LIFE CYCLE (CDC)

1 The adult Echinococcus granulosus (sensu lato)

Echinococcus granulosus
(2—7 mm long) resides in the small intestine of
the definitive host. Gravid proglottids release eggs
Common name Hydatid worm
that are passed in the feces and are immediately
Intermediate usually ungulates, including sheep infectious.
host and goats, cattle, moose, swine,
horses 2 After ingestion by a suitable intermediate host,
Definitive host wild and domestic canids (coyote, eggs hatch in the small intestine and release six-
red fox, etc.) hooked oncospheres that penetrate the intestinal
wall and migrate through the circulatory system
Accidental host Man into various organs, especially the liver and lungs.

Diagnostic Hydatid cyst 3 In these organs, the oncosphere develops into a

stage thick-walled hydatid cyst that enlarges gradually,
producing protoscolices and daughter cysts that
Infective stage To Final Host: Hydatid Cyst
fill the cyst interior.
To Intermediate Host:
Embryonated eggs 4 The definitive host becomes infected by ingesting
Habitat Small intestine (final host) the cyst-containing organs of the infected
Egg (Intermediate host)
intermediate host. After ingestion, the
Mode of ingestion of egg (will develop into
protoscolices evaginate, attach to the intestinal
transmission hydatid cyst in man)
mucosa , and develop into adult stages in 32 to
80 days.

Humans are aberrant intermediate hosts and

become infected by ingesting eggs. Oncospheres
are released in the intestine, and hydatid cysts
develop in a variety of organs. If cysts rupture, the
liberated protoscolices may create secondary
cysts in other sites within the body (secondary
echinococcosis).
Medical Parasitology Lec
CESTODES

Egg (E. granulosus) Hydatid Cyst

• E. granulosus eggs are morphologically • Measures 1-7 cm in diameter: a unilocular

similar to Taenia eggs, consists of an cyst: cyst contents are held within a single
oncosphere with six hooklets surrounded by limiting cyst wall • Very slow-growing in
an embryophore humans
• Oncosphere contains a hexacanth embryo • Has an outer, laminated hyaline later (cyst
wall) and an inner, nucleated germinal layer
• Brood capsules: form from the germinal layer
and contains protoscolices
• Daughter cysts: miniaturization of the entire
hydatid cyst (has both the protective cyst wall
and the germinal layer)
• Hydatid sand: components fond in the fluid
of older E. granulosus cysts that typically
include daughter cysts, free scolices,
hooklets, and miscellaneous nondescript
material (resemble grains of sand)
• In other cases, hydatids may become sterile
because of secondary bacterial infection or
they may die and become calcified

Adult (E. granulosus)

• 3–6 mm long, consists of head, neck and

strobila
• Head/scolex: It is pyriform shaped (300 μm
diameter), bears four suckers and a rostellum
armed with two rows of hooklets (30-36)
• Neck: Short and thick
• Strobila: Made up of only three proglottids/
segments: one immature, one mature and
one gravid segment.
• The gravid segment is widest and longest

Cystic disease/Hydatid disease

• Echinococcus granulosus infections often

remain asymptomatic for years before the
cysts grow large enough to cause symptoms
in the affected organs. The rate at which
symptoms appear typically depends on the
location of the cyst.
• Hepatic and pulmonary signs/symptoms are
the most common clinical manifestations, as
these are the most common sites for cysts to
develop In addition to the liver and lungs,
other organs (spleen, kidneys, heart, bone,
and central nervous system, including the
brain and eyes) can also be involved, with
resulting symptoms. Rupture of the cysts can
Medical Parasitology Lec
CESTODES

produce a host reaction manifesting as fever, a diagnosis of cystic echinococcosis. Imaging

urticaria, eosinophilia, and potentially techniques, such as CT scans,
anaphylactic shock; rupture of the cyst may ultrasonography, and MRIs, are used to
also lead to cyst dissemination. detect cysts. After a cyst has been detected,
Liver cysts serologic tests may be used to confirm the
• Most common and most important site of diagnosis.
involvement (70% cases) • Alveolar echinococcosis is typically found in
• May cause early symptoms if the location in older people. Imaging techniques such as CT
the liver is sucj that their expansion produces scans are used to visually confirm the
pressure on a major bile duct or blood vessel parasitic vesicles and cyst-like structures and
or if intrabillary rupture occurs serologic tests can confirm the parasitic
• Symptoms can include pain, hepatomegaly, infection
cholestasis, biliary cirrhosis, portal
hypertension, ascites
• If a cyst becomes infected with bacteria, it Treatment (E. granulosus)
resembles an abscess
• Cyst rupture can also lead to cholangitis and Surgical
cholestasis removal
Lung cysts
Exploratory • Puncture – percutaneous
• Lungs are involved in 20-30% of the cases, cyst procedure puncture of the cyst
cysts in the lungs are usually asymptomatic (P-A-I-R • Aspiration – 10-15ml of
until they become large enough to cause method) cyst fluid
chronic cough, shortness of breath or chest • Injection –
pain protoscollicidal solution
• Cyst rupture can lead to expectoration of is injected (95% ethanol
hydatid fluid or membranes, followed by the or hypertonic saline)
development of infection and lung abscess • Reaspiration – fluid is
• If the rupture occurs into the lung, it may reaspirated after 5 mins
cause pneumothorax and empyema, allergic (15-20 if hypertonic
reactions and even anaphylactic shock saline is used
• Sputum may contain frothy blood, mucus, Chemotherapy albendazole, (or albendazole +
hydatid fluid, and bits of membrane praziquantel) mebendazole

Laboratory diagnosis (E. granulosus)

Prevention and Control (E. granulosus)
• Hydatid fluid microscopy (direct mount or
staining with acid fast stain)—detects brood • Administering praziquantel to infected dogs
capsules and protoscolices • To improve personal hygiene to reduce
• Histological examination (H & E)— contamination of food and water with dog’s
demonstrates cyst wall and attached brood feces
capsules • Vaccinating the sheep
• Antibody detection—IHA, LAT, IFA, ELISA, • Limitation of stray dogs population.
• Western blot
• Antigen detection—ELISA, CIEP, LAT
• Imaging methods—X-ray, USG
(demonstrates Water lily sign), CT scan, MRI
• Molecular method—PCR, PCR-RFLP
• Skin test (Casoni test)
• The presence of a cyst-like mass in a person
with a history of exposure to sheepdogs in an
area where E. granulosus is endemic suggests
Medical Parasitology Lec
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Taenia saginata survive for years. The adult tapeworms attach to

the small intestine by their scolex and reside in the
Common name Beef tapeworm small intestine. Length of adult worms is usually 5
m or less for T. saginata (however it may reach up
Intermediate cattle to 25 m) and 2 to 7 m for T. solium.
host
4 The adults produce proglottids which mature,
Definitive host Man become gravid, detach from the tapeworm, and
migrate to the anus or are passed in the stool
Diagnostic Eggs or gravid proglottids
(approximately 6 per day).
stage
T. saginata adults usually have 1,000 to 2,000
Infective stage Cysticercus bovis
proglottids, while T. solium adults have an
Habitat Small intestine average of 1,000 proglottids. The eggs contained
in the gravid proglottids are released after the
Mode of ingestion of undercooked beef proglottids are passed with the feces. T.
transmission saginata may produce up to 100,000 and T.
solium may produce 50,000 eggs per proglottid
respectively.

Egg (T. saginata)

• Taenia spp. ova are spherical or subspherical

in shape, measuring 30 to 45 µm in diameter
• The original thin outer membrane
surrounding the egg is rarely retained after
passage from the proglottid.
• The ova are brownish in color, with a thick
striated shell (embryophore)
• Contains a hexacanth (six-hooked) embryo
(oncosphere)
• May be unembryonated or embryonated:
indistinguishable from T. solium; Acid-fast
LIFE CYCLE (CDC)

1 Eggs or gravid proglottids are passed with feces;

the eggs can survive for days to months in the
environment. Cattle (T. saginata) and pigs (T.
solium) become infected by ingesting vegetation
contaminated with eggs or gravid proglottids.

2 In the animal’s intestine, the oncospheres hatch,

invade the intestinal wall, and migrate to the
striated muscles, where they develop into
cysticerci. A cysticercus can survive for several
years in the animal. Humans become infected by
ingesting raw or undercooked infected meat

3 In the human intestine, the cysticercus develops

over 2 months into an adult tapeworm, which can
Medical Parasitology Lec
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T. saginata (Cysticercus bovis) Adult (T. saginata)

• 25 m but often measures half this length ;

may contain 1000-2000 segments
• Head Large and quadrangular
• Scolex: cuboidal with 4 acetabula; No
rostellum, No hooklets
• Four suckers present which may be
pigmented
• Longer neck compared with T. solium
• Mature proglottids, broader than long
• Gravid proglottids, narrower and longer
• Uterine lateral branches:15-20 (ave:
18)/dichotomous or tree-like in appearance

Taeniasis bovis

• produces only mild abdominal symptoms

• The most striking feature consists of the
passage (active and passive) of proglottids.
• Occasionally, appendicitis or cholangitis,
pruritis ani can result from migrating
proglottids.
• Rarely, entangled proglottids may result in
intestinal obstruction
Medical Parasitology Lec
CESTODES

Laboratory Diagnosis

• Stool examination / perianal swab /

concentration techniques
• Recovery and examination of gravid
proglottids in which the main uterine lateral
branches are counted Double slide
compression technique – use of India ink dye
through genital pore
• Scolex is recovered after therapy (may require
purge)

Treatment

• Praziquantel is given at a dose of 5 to 10

mg/kg as a single dose for both adults and
children.
• It is not necessary to recover the scolex unless
species-specific diagnosis is needed. Criteria
for the cure include the following: (a) recovery
of the scolex, or (b) a negative stool
examination 3 months after treatment.

Taenia solium

Common name Pork tapeworm

Intermediate Pig or man

Egg (T. saginata)
host
• They measure 30 to 45 µm and have a thick
Definitive host Man
brown striated embryophore surrounding a
Diagnostic Eggs or gravid proglottids hexacanth (six-hooked) embryo
stage (oncosphere).
• The eggs of T. solium are indistinguishable
Infective stage • Cysticercus cellulosae from that of T. saginata. May be
(intestinal taeniasis) unembryonated or embryonated; Acid-Fast
• Embryonated eggs
(cysticercosis)
Habitat Small intestine

Mode of • Ingestion of
transmission undercooked pork
(intestinal taeniasis)
• Ingestion of
embryonated eggs
(cysticercosis)
Medical Parasitology Lec
CESTODES

Taeniasis

• Adult Worm – usually causes no problems

other than slight irritation at the site of
attachment or vague abdominal symptoms
(hunger pains, indigestion, diarrhea, and/or
constipation).
• There may be a low-grade eosinophilia,
usually under 15%, and increased levels of
immunoglobulin E (IgE) in serum.
Cysticercosis
located in striated muscle and in the brain, but the
Adult (T. solium)
subcutaneous tissues, eye, heart, lung, and peritoneum
• It is shorter than T. saginata and has less may be involved
number of proglottids, <1000 (Garcia) Subcutaneous cysticercosis
• The adults measure 2 to 7m (Garcia) or 1.5- It is frequently asymptomatic but may manifest as
8m (Bailey) in length and may have 8,000 to palpable nodules
10,000 (Belizario) proglottids. Muscular cysticercosis
• The scolex of T. solium has four acetabula, but Manifest as muscular pain, weakness, or pseudo
it is smaller (1 mm) and more spherical that hypertrophy
that of the beef tapeworm
• Scolex: quadrate, 1 mm in diameter; has
rounded rostellum and containing a double
row of 25 to 30 small hooks hooklets (armed);
4 large suckers
• The neck region: short and about half the
width of the Scolex
• Immature proglottids: wider than long
• Mature proglottids: square
• Gravid proglottids: longer than wide
• Uterine lateral branches: 7-13/7-15 lateral Ocular cysticercosis
branches; dendritic/finger-like appearance • Can involve eyelids, conjunctiva and sclera.
Common symptoms like proptosis, diplopia,
loss of vision and slow growing nodule with
focal inflammation.
• In the eyes, cysticerci are often retinal or
subretinal in location. They may float freely in
the vitreous or aqueous humors. Vision is
usually affected due to chorioretinitis and
vasculitis. Detachment of the retina has also
been reported. The patient may complain of
intraorbital pain, photopsia, and blurring or
loss of vision
Medical Parasitology Lec
CESTODES

• Hydrocephalus (most common

extraparenchymal feature)
- Increased intracranial pressure and
Neurocysticercosis (NCC) hypertension presented as headache,
vomiting and vertigo
• Most common parasitic disease of the CNS, - Chronic meningitis
most common cause of adult epilepsy - Focal neurological deficits
throughout the world - Psychological disorders and dementia
- Parenchymal: Involves brain parenchyma • The death of the larva leads to inflammation
- Focal neurologic deficits are usually of the affected region. Calcification is the end
encountered in parenchymal NCC. result of the cellular reaction.
• Extraparenchymal sites are meninges, • Autoinfection is possible (external and
ventricles and spinal cord internal)
- subarachnoid or meningitic,
intraventricular, and spinal
- They would depend on the location of Laboratory diagnosis (T. solium)
the cysts. Focal or generalized seizures
are observed when cysts are located in • Taeniasis (same with t saginata)
the cortex.. In this form, - Specific diagnosis of taeniasis rests on
- there is a proliferation of cysts in the identifying the characteristic proglottids,
base of the brain. This form has a poor or scolex
prognosis. In the intraventricular form, • Coproantigen detection; ELISA even in the
cysts are usually present in the third or absence of eggs
fourth ventricle and often lead to • Cysticercosis
obstructive hydrocephalus. The spinal - Radiodiagnosis— CT scan and MRI
form is rare - Antibody detection in serum or CSF—
• The subarachnoid form may lead to an - ELISA, Western blot (EITB)
aggressive form of NCC called racemose - Antigen detection in serum or CSF- ELISA
cysticercosis - Lymphocyte transformation test
- Proliferating form, composed of several - Histopathology of muscles, eyes,
bladders that are connected and are subcutaneous tissues, or brain biopsies
often found in the brain, particularly the - Del brutto diagnostic criteria
fourth ventricle and subarachnoid space
- Within these bladders, no scolices are
found and growth of a metastatic tumor
- Prognosis for such infections is very poor
(very large cysts and the racemose type
of NCC appear to be more frequent in
HIV positive patients
• Seizure is the most common manifestation
(70% of cases). NCC accounts for 50% cases
of late onset epilepsy
• Convulsions are the most common
manifestations of cerebral cysticercosis.
Visual and motor deficits, headache, and
vomiting may occur. Treatment
• Cerebrospinal fluid (CSF) tap results may
• Adult worms – praziquantel or
show an increased opening pressure,
niclosamide
elevated protein, decreased glucose, and
• cysticercosis – surgical removal;
increased mononuclear cells. Half of the cases
praziquantel or albendazole
may present with CSF eosinophilia without
peripheral blood eosinophilia
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

🡪 Amoeba Amoeba excreted as trophozoites

PROTOZOA cannot mature to cysts

TOPIC OUTLINE
1 Introduction to Protozoa
2 The Cell of Protozoa
3 Developmental Stages of Protozoa
4 Reproduction of Protozoa
5 Major Classification of Protozoa
a. Sarcomastigophora
b. Apicomplexa
c. Microspora
d. Ciliophora Developmental Stages: Cystic Stage
🡪 Resting stage
INTRODUCTION TO PROTOZOA 🡪 Non-motile
→ Kingdom: Protozoa 🡪 Resistant to drying and chemicals (cyst wall)
→ are single-celled eukaryotes 🡪 Frequently found in formed stools
→ found in moist habitat 🡪 May be studied in fresh condition by staining with
→ are heterotrophic D’ Antoni’s Iodine stain, but more
→ free-living and aerobic satisfactory method is to stain permanent
→ feeds on bacteria, particulate nutrients and other preparations with iron hematoxylin
protozoa 🡪 Encystation- process of a trophozoite turning
→ most has defined shapes except amoeba into a cyst
→ at least 30 species parasitizes humans (widely
distributed)

PROTOZOA: CELL
🡪 lack cell walls
🡪 presence of organelles (used for locomotion,
nutrition, respiration, excretion and attachment)

🡪 has one or more nuclei

● Macronucleus- metabolic and
developmental functions
● Micronucleus- reproduction Reproduction of Protozoa
ORGANELLES 🡪 Binary fission
Asexual
Pellicle Osmotic shield 🡪 Budding
Reproduction
Hyaline ectoplasm Locomotion 🡪 Multiple fissin/Schizogony
Peristome/ Mouth Food Ingestion Sexual 🡪 Gametogenesis
Reproduction 🡪 Conjugation
Contractile Vacuoles Excretion
Cyst Wall Protection
Ectoplasm
Cytoplasm
Major Classification of Protozoa
Endoplasm Food vacuoles (nutrition),
🡪 Amoeba, moves by
nuclei, centrosome (cell
pseudopodia
division)
Sarcodina ● Entamoeba histolytica
● Naegleria fowleri
Developmental Stages: Trophozoite Stage ● Acanthamoeba spp.
🡪 Motile 🡪 Moves by flagella
🡪 Active feeding and reproduction Mastigophora
● Giardia lambia
🡪 Prone to drying /Flagellates
● Trichomonas vaginalis
🡪 Found in diarrheal and liquid stools Ciliata 🡪 Cilia for movement
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

● Balantidium coli CILIATES/ 🡪 ciliate protozoa moves through

🡪 No locomotory organs, CILIOPHORA cilia (fine hair like structure attached
Sporozoa sexual/asexual reproduction with their body).
● Plasmodium spp. ● cover their entire body
surface
🡪 some protozoa have special kind
PHYLUM SARCOMASTIGOPHORA of cilia for feeding and attachment.
FLAGELLATES/ 🡪 Mastix: whip or flagellum 🡪 Most are harmless.
MASTIGOPHOR 🡪 Flagellates move by help of flagella 🡪 only Balantidium coli is pathogenic
A ● Flagella: a tail-like structure for humans. causes dysentery.
🡪 The movement is whip-like or
oar-like
🡪 Examples:
● Trypnosoma, Leishmania
(blood pathogen)
● Giardia (intestinal parasite)
● Trichomonas (reproductive
tract pathogen)

SPECIES
🡪 Balantidium coli

SARCODINA 🡪 Sarcos: flesh or body

🡪 major locomotory organelle is
pseudopodia Pseudo means false,
podia means foot)
● common example: Amoeba
🡪 Example:
● Entamoeba spp. parasitic
on humans, causes
intestinal disease
🡪 most species are harmless

SPECIES
🡪 Chilomastix mesnili,
Dientamoeba fragilis, Giardia
lamblia, Trichomonas (homini,
tenax, vaginalis), Leishmania
(braziliensis, dovani, tropica), SPECIES
Trypanosoma brucei complex, 🡪 Acanthamoeba castellani,
Trypanosoma cruzi Endolimax nana, Entamoeba coli,
Entamoeba dispar, Entamoeba
histolytica, Iodamoeba butschlii,
Nagleria fowleri
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

Brachiola vesicularum,
SPOROZOATES/ 🡪 Sporozoates are the only non Microspodium spp.
APICOMPLEXA motile form of protozoa.
NS 🡪 tissue parasites
🡪 Apical complex: organ of SUBPHYLUM SARCODINA
attachment to host cells at some 🡪 Have protoplasmic processes, pseudopodia, for
stage in their life cycle. locomotion
🡪 have well developed sexual and 🡪 Possess in their life cycle the trophozoite stage >
asexual stages precystic stage > cystic stage > metacystic stage
● alternating sexual and 🡪 The most common means whereby amoeba are
asexual generations transferred to humans is through ingestion of the
🡪 entire group is parasitic in nature infective cyst in contaminated food or water
and are harmful 🡪 With cystic stage except for E. gingivalis
🡪 some common examples of 🡪 Inhabit the large intestine except for E. gingivalis
Sporozoites and their infections are: 🡪 Commensals except for E. histolytica
● Plasmodium (causative 🡪 Karyosome (karyosomal chromatin): small,
agent of Malaria, causes central mass of chromatin in the nucleus
100 to 300 million infection 🡪 Peripheral chromatin: chromatin material
world wide surrounding the karyosome
● Toxoplasma gondii (causes 🡪 Chromatid bars/ chromatoidal bodies:
Toxoplasmosis) unorganized chromatin material that transforms into
squared or round ended structures
🡪 Glycogen mass: a cytoplasmic area without a
defined borders that is believed to represent stored
food (young cysts)
🡪 Similar to all intestinal amoeba
🡪 Most common mode of transmission: ingestion of
infective cysts in contaminated food or water
🡪 Trophozoites: susceptible to environment outside
host and are not usually transmitted to humans
🡪 Excystation: morphologic conversion from the cyst
to the trophozoite in the ileocecal area of the intestine
SPECIES 🡪 Encystation: conversion of trophozoites to cysts
🡪 Bebesia spp., Cryptosporidium when environment becomes unacceptable for
hominis, Cyclospora cayetansis, continued trophozoite multiplication
Isospora belli, Plasmodium spp., 🡪 If the organism is genus Entamoeba (true amoeba)
Toxoplasma peripheral chromatin (visible nuclear membrane in
both trophozoite and
MICROSPORA 🡪 contains many minute intracellular cyst) ad chromatoidal bodies in cysts only
protozoan parasites 🡪 If the organism is genus Endolimax or Iodameoba
🡪 frequently cause disease in (other amoeba) neither possesses peripheral
immunodeficient subjects chromatin nor chromatoidal bodies

ENTAMOEBA HISTOLYTICA
🡪 The only pathogenic intestinal amoeba (true
pathogen)

DESCRIPTION
Common 🡪 Intestinal amebiasis, Amebic colitis,
SPECIES Name Amebic dysentery
🡪 Enterocytozoon bineusi,
Encephalitozoon spp., Vittaforma Infective 🡪 Mature quadrinucleate cyst
cornea, Trachipleistosphora Stage
hominis, Pleistophora spp.,
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

Diagnost 🡪 Trophozoites/Cyst
ic Stage
Mode of 🡪 Fecal-oral route
Transmis
sion

MORPHOLOGY
Trophoz 🡪 Measurement: 8 to 65 μm, with an
oite average size of 12 to 25
μm
🡪 Movement: rapid, unidirectional,
progressive movement
with the aid of Pseudopods (Brownian
movement)
🡪 Karyosome/karyosomal chromatin:
small central mass Cyst 🡪 Measurement: 8 to 22 μm, with an
of chromatin in single nucleus average size of 12 to 18 μm
🡪 Peripheral chromatin – fine and 🡪 Has hyaline cyst wall
evenly distributed Young Cyst
🡪 Cytoplasmic inclusion – ingested 🡪 Chromatoid bars
RBC (erythrophagocytosis) (cigar/coffin-shaped) – squared or
🡪 Endoplasm consists of RBCs but no round end structured chromatin
bacteria or cell detritus 🡪 Diffuse glycogen mass – food
🡪 Nucleus not visible when stained, storage
nucleus consists of thin nuclear 🡪 Cytoplasmic inclusion – ingested
membrane with later of uniformly sized RBC
fone chromatin granules distributed Mature Cyst
along inside border of nuclear 🡪 One to four nuclei (quadrinucleated),
membrane (finely granular/ground eccentrically located
glass appearance) 🡪 Peripheral chromatin: fine, uniform
🡪 Fine, centrally located karyosome granules, evenly distributed
🡪 Can occur free in the lumen of the 🡪 Karyosome: small, compact, usually
intestine as a commensal and is known centrally located
as its minuta form 🡪 Glycogen Mass – disappear
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

Symptomatic Intestinal Amebiasis

Patients infected with E. histolytica who exhibit
symptoms often suffer from amebic colitis, defined
as an intestinal infection caused by the presence of
amebas exhibiting symptoms. In some cases,
these patients may transition from amebic colitis
into a condition characterized by blood and mucus
in the stool known as amebic dysentery.
● Dysenteric – presence of blood and
mucus in stools (up to 10 per day)
● Nondysenteric colitis – diarrhea,
abdominal pain, flatulence
Secondary bacterial infections may develop after
the formation of flask-shaped amebic ulcers in the
colon, cecum, appendix, or rectosigmoid area of
the intestine. As noted, stools recovered from
patients suffering from amebic dysentery are
characterized by the presence of blood and/or pus
and mucus.
Entamoeba coli (Trophozoite)
● Measurement: 15 to 50 μm (usual range, Symptomatic Extraintestinal Amebiasis
20 to 25 μm) E. histolytica trophozoites that migrate into the
● Movement: tries to move in several bloodstream are removed by and take up
directions at the same time; sluggish residence in the liver. The formation of an abscess
motion, sends out several pseudopods at in the right lobe of the liver and trophozoite
the same time; pseudopods thrusted out extension through the diaphragm, causing amebic
slowly pneumonitis, may occur.
● Endoplasm contain bacteria, yeasts, and ● symptoms similar to liver infection
cell detritus ● right abdominal pain with fever
● Stained nucleus contains a thicker nuclear ● Weakness, weight loss, sweating,
membrane with layer of variously sized pronounced nausea, and vomiting
chromatin granules unevenly distributed ● migrate to and infect other organs,
along the inside border of nuclear including the lung, pericardium, spleen,
membrane skin, and brain. Venereal amebiasis may
● Large, eccentrically located karyosome also occur
● Ameboma – chronic granulomatous
Entamoeba coli (Cyst) lesion in cecal or rectosigmoid colon
● Measurement: 10 to 35 μm (usual range,
15 to 25 μm) Men become infected with penile amebiasis after
● Splinter-like chromatoidal bars experiencing unprotected sex with a woman who
● Mature Cyst with 8 nuclei has vaginal amebiasis. The disease may also be
● Peripheral chromatin: coarsely granular, transferred during anal intercourse.
may be clumped and unevenly arranged
● Karyosome: large, may or may not be
compact and/or eccentric
● Glycogen Mass – diffuse; may be absent
in mature cysts

PATHOLOGY
Asymptomatic Carrier State
Three factors:
● the parasite is a low-virulence strain
● the inoculation into the host is low
● the patient’s immune system is intact. I
In these cases, amebas may reproduce but the
infected patient shows no clinical symptoms.
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

2. Serologic tests to detect SREHP (serine-rich E.

histolytica protein) and galactose-specific adhesin

Histology – trophozoites within the tissue; periodic

acid-Schiff staining wherein organisms appear
bright pink with a green blue background

Trophozoites, unstained
Suggestive: progressive motility; hyaline
pseudopodia; no ingested bacteria; nuclei not
visible
Diagnostic: ingestion of red blood cells
Trophozoites, stained (Hematoxylin, Trichrome)
Suggestive: clear differentiation of ectoplasm and
endoplasm; no ingested bacteria
Diagnostic: fine, uniform granules of peripheral
chromatin and small central karyosome in nucleus;
ingested red blood cells; average size over 12um

Cysts, unstained
Suggestive: four nuclei; rodlike chromatoidals
Cysts, stained (Hematoxylin, Trichome)
Suggestive: maximum of four nuclei having both
karyosome and peripheral chromatin; diameter
over 10um
Diagnostic: typical nuclear structure; chromatoidal
bars with rounded or squared end; diameter over
10um

TREATMENT
Metronid 🡪 acute amebic colitis
azole
Paromo 🡪 intestinal (luminal) infection, prevent
mycin relapse
Diloxani 🡪 only pass cyst
de
furuote

PREVENTION
● good food handling
● water treatment through boiling or iodine
● avoid using human feces as fertilizers
● hand hygiene
DIAGNOSIS
1. Enzyme-Linked Immunosorbent Assay (greater TISSUE FLAGELLATES
sensitivity)
● RIDASCREEN Entamoeba histolytica – Leishmania spp.
detects IgG antibodies 🡪 an obligate intracellular protozoa that causes
● ProSpecT Entamoeba histolytica Leishmaniasis
microplate assay – detects E. histolytica 🡪 21 out of 30 Leishmania species infect mammals
specific antigens (EHSA) in human fecal 🡪 morphologically indistinguishable
samples 🡪 can be differentiated by isoenzyme analysis,
● E. histolytica II Test – fecal antigen test molecular methods, or monoclonal antibodies
(detects E. histolytica adhesin) that can
differentiate E. histolytica or E. dispar and
E. moshkovskii from the rest of the
Entamoeba spp
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

DESCRIPTION
Infective Promastigote stage
Stage
Diagnost Amastigote stage
ic Stage MORPHOLOGY
Mode of 🡪 bite of female phlebotomine sandflies Amastig 🡪 diagnostic stage
Transmis ote 🡪 ovoid or rounded bodies
sion 🡪 measures 2 to 4 μm in diameter
🡪 small spherical non-flagellated cells
🡪 cells are among the smallest
nucleated cells
🡪 nucleus and kinetoplast surrounded
by small ring of vacuolated cytoplasm
🡪 large nucleus while an axoneme
arises from the kinetoplast and extends
to the anterior tip
🡪 live intracellularly in monocytes,
polymorphonuclear leukocytes, or
endothelial cells
🡪 may also be transmitted congenitally,
through blood transfusion, by
contamination of bite wounds, and by
direct contact with contaminated
specimens.
Vectors Arthropods, particularly sandflies of the
genera Phlebotomus (Old World) and
Lutzomyia (New World)
Reservoi 🡪 Dogs (primary reservoir in urban
rs areas)
🡪 Rodents (can act as reservoirs in
both urban and rural areas)

Promasti 🡪 infective stage

gote 🡪are thin, elongate cells which
measure 2 to 4 μm in diameter
🡪 range in size from 5-14 μm in length
by 1.5-3.5 μm in width
🡪 lance-like in shape
🡪 anterior kinetoplast and an emergent
free flagellum
🡪 the infective promastigotes in the
proboscis of the sandfly are injected
into the host’s skin during feeding
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

EPIDEMIOLOGY
🡪 Leishmania spp. are divided into Old World and
New World leishmaniasis.
2) Cutaneous Leishmaniasis
Old World - most common form of the disease
🡪 the common species involved are L. tropica (Asia - caused by several species of Leishmania,
and Eastern Europe), L. aethiopica (Africa), and L. including L. tropica (dry or urban oriental
major. sore), L. major (moist or rural oriental
sore), and L. mexicana (chiclero ulcer,
New World usually affecting the ears)
🡪 affects Mexico, Central America, and some parts - incubation period ranges from two weeks
of South America, as well as the Amazon rainforest to several months
🡪 usually caused by L. mexicana, L amazonensis, - an erythematous papule or nodule, called
L. guyanensis, L. braziliensis, and L. chagasi. an “oriental button,” is produced at the
inoculation site
PATHOGENESIS & CLINICAL MANIFESTATIONS - causes skin lesions, mainly ulcers, on
Leishmaniasis exposed parts of the body, leaving
🡪 a vector-borne disease which is transmitted by life-long scars and serious disability or
female phlebotomine sand flies of over 90 different stigma
sandfly species
🡪 reside in tropical and subtropical environment
🡪 classified as a neglected tropical disease (NTD)

1) Visceral Leishmaniasis
- also called kala azar
- a disseminated parasitosis primarily
caused by L. donovani complex: L.
donovani, L. chagasi, and L. infantum
- incubation period of 2 to 8 months
- has a greater than 95% mortality ratel if
left untreated
- characterized by irregular bouts of fever,
weakness, weight loss, loss of appetite,
hemorrhage, anemia, enlargement of the
spleen and liver, and abdominal
enlargement associated with
hepatosplenomegaly
- one of the top parasitic diseases with
outbreak and mortality potential

3) Mucocutaneous Leishmaniasis
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

- develops in about 2 to 5% of persons primary isolation of the New World

infected with L. braziliensis, either cutaneous leishmania
concurrently or even several years after ● Schneider’s medium was also found
the resolution of skin lesions helpful
- may also be due to the continuous spread ● Leishmanin skin test (Montenegro skin
of cutaneous leishmaniasis caused by L. test) can be used to identify exposure to
tropica the parasite
- leads to nasal stuffiness, discharge, ● Serological tests
epistaxis, and partial or total destruction of ● Molecular characterization
mucous membranes of the nose, mouth, ● Immunological assays such as ELISA and
and throat rk39 antigen dipstick test
- progression into the pharynx and larynx ● Direct agglutination, urine antigen assays,
may threaten the airway passage, and and newer techniques such as flow
may lead to dysphonia, dysphagia, and cytometry and molecular diagnostic
even aspiration pneumonia modalities (PCR, RFLP analysis) are also
being used.

TREATMENT
● some cutaneous infections require no
treatment
● systemic therapy with pentavalent
antimonials (sodium stibogluconate and
n-methyl-glucamine or meglumine
antimonate)

DIAGNOSIS
● based on the microscopic demonstration
of Leishmania from lesion and tissue
scrapings, aspirates, or biopsy ● Intravenous amphotericin B is the drug of
● amastigotes detected microscopically in choice in areas where resistance is high
biopsy tissues, smears or secretions ● Lipid-based preparations of the drug
● best visualized using Giemsa’s, (AmBisome) are currently being utilized as
hematoxylin-eosin, or Leishman’s stains a highly effective, better tolerated, and
overall cost-effective drug formulation for
cutaneous and visceral leishmaniasis.
● miltefosine and aminosidine
(paromomycin) have shown promise as
treatment options, especially when
combined with immunotherapy

PREVENTION & CONTROL

● Early diagnosis and effective prompt
treatment
● Usage of insect repellents containing
DEET and permethrin, insecticide-treated
● use of nutrient agar-blood mixture clothing, and fine-mesh bed nets
(conventional) ● Vector control
● Novy, Macneal, and Nicolle medium ● Effective disease surveillance
(NNN) was reported for successful ● Control of animal reservoir hosts
 BMD 4202-3 MEDICAL PARASITOLOGY LEC
PROTOZOA
PPT NI MAAM/Clinical Parasitology 2nd Ed./Medical Parasitology in the Phils. 3rd Ed.

● Mobilization and education of the

community
 Protozoa Reference: PPT & Belizario & De Leon

TOPIC OUTLINE (with long free

I. Tissue Flagellates flagellum)
• Trypanosoma spp. → or stumpy non-
• Trypanosoma cruzi dividing infective
• Giardia lamblia (metacyclic) forms
• Trichomonas vaginalis (with no free flagellum
II. Balantidium coli
• Ciliophora – Balantoides coli
III. Apicomplexa
• Plasmodium spp.
• Cryptosporidium spp. Epimastigotes → anterior kinetoplast
• Babesia spp. and short undulating
membrane
TRYPANOSOMA BRUCEI → variable in size
→ African Trypanosomes or “Old World ranging from 10-35 um
Trypanosomes” in length by 1-3 um in
width
→ Morphologically indistinguishable subspecies
• T.b. gambiense – (West African Sleeping
Sickness)
• T.b. rhodiense – (East African Sleeping
Sickness)
• T.b. brucei – infects cattle and other animals
Infective Stage Metacyclic Trypomastigotes LABORATORY DIAGNOSIS
Diagnostic Circulating Trypomastigotes → microscopic examination (wet mount) of chancre
Stage fluid, lymph node aspirates, blood, bone marrow, CSF
Mode of Tsetse fly → Buffy coat concentration method is recommended
Transmission • The parasite is usually to detect parasites when they occur in low numbers
transmitted via the bite of → Giemsa’s stains
the blood sucking tsetse fly → Concentration techniques can be used prior to
(Glossina spp) feeding from microscopic examination
an infected mammalian → Antibody detection tests
host.
→ Card agglutination test for trypanosomiasis (CATT)
detecting circulating antigens in persons infected with
LIFE CYCLE T. brucei complex is available commercially and can be
used in the field setting to screen at-risk populations.

AFRICAN TRYPANOSOMIASIS
→ Two stages:
• Haemolymphatic stage – first stage
o Symptoms: Headache, Malaise,
weakness, fatigue, pruritis and
arthralgia
o Signs after a week: Weight loss,
intermittent fevers and
hepatosplenomegaly
o Lymphadenopathy may also occur
• Meningoencephalitic stage – second stage
o Occurs after 300-500 days (T.b.
gambiense)
Trypomastigotes → with posterior o Occurs after 21-60 days (T.b.
kinetoplast and long rhodiense)
undulating membrane o Determined by observing
→ pleomorphic in size trypomastigoes in CSF
→ 16-42 um in length o Sleep/wake cycle becomes reversed,
by 1-3um in width hence the common name “African
→ occur as elongate sleeping sickness”
slender dividing forms

bpcc | pjlm | ects | jvsv 1

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TRYPANOSOMA CRUZI
Infective Stage Metacyclic Trypomastigotes
Diagnostic Trypomastigotes
Stage
Mode of Triatomine bugs
Transmission

LIFE CYCLE

TREATMENT
→ Pentamidine, melarsoprol, trypusamide
→ Other drugs (suramin, berenil, eflornithine, and
nifurtimox when used in combination with eflornithine)
→ A second-line drug,nitrofurazone, is used in cases of
melarsoprol treatment failure.

PREVENTION AND CONTROL

→ Minimizing contact with tsetse flies
→ Wearing long-sleeved shirts and pants with neutral
colors
→ Inspect vehicles before entering
→ Avoid bushes
→ Use of insect repellants MORPHOLOGY = AMASTIGOTE
→ Several programs developed to eliminate the insect → Amastigotes are oval bodies measuring 2-4 µm
vector have been in place in Africa. The Kwando- in diameter having a nucleus and kinetoplast
Zambesi Regional Tsetse Eradication project started in → Flagellum is absent
Botswana, and in 2000, the Pan African Tsetse and → Morphologically, it resembles the amastigote of
Trypanosomiasis Eradication Campaign (PATTEC) was Leishmania spp., hence, it is frequently called as
established. leishmanial form.
→ Multiplication of the parasite occurs in this stage
EPIDEMIOLOGY → This form is found in muscles, nerve cells and
→ Affects around 300,000 to 500,000 people in 36 reticuloenodothelial systems
countries within sub-Saharan Africa
→ During the turn of the century, between 10,000 and
40,000 annual cases of HAT were being reported.

MORPHOLOGY = TRYPOMASTIGOTE
→ Trypomastigotes are non-multiplying forms
found in the peripheral blood of man and other
mammalian hosts
→ In the blood, they appear either as long, thin
flagellates about (20 mcm long) or short stumpy form
(15 µm long).
→ Posterior end is wedge-shaped.

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→ In stained blood smears, they are shaped-like → polymerase chain reaction (PCR) and ELISA testing
alphabet "C''; "U''; or "S'; having a free flagellum of methods
about one-third the length of the body
→ These forms do not multiply in humans and are
taken up by the insect vectors.

CHAGAS DISEASE: AMERICAN TRYPANOSOMIASIS

MORPHOLOGY = EPIMASTIGOTE
→ spread through contact with the poop
→ Epimasrigote forms are found in the insect vector,
of an infected triatomine bug (or “kissing
the reduviid bug and in culture also
bug”),
→ It has a kinetoplast adjacent to the nucleus
→ occurs immediately after infection,
→ An undulating membrane runs along the anterior
and can last up to a few weeks or months
half of the parasite.
→ Epimastigotes divide by binary fission in hindgut of → Two phases:
the vector
• Acute phase
o found in blood circulation,
usually mild and
asymptomatic
o swelling around inoculation
site and fever
o rarely causes severe
inflammation of heart and
Trypomastigotes → terminal kinetoplast, a
brain muscles
centrally located nucleus, an
undulating membrane, • *”chronic indeterminate” – may
flagellum happen after acute phase
• Chronic phase
→ 12 to 30 µm in length o dilated heart, esophagus, or
colon
→ amastigotes are Clinical → Chagas’ disease may be asymptomatic,
morphologically Symptoms chronic, or acute in nature.
indistinguishable from those → The most common initial symptom is
of Leishmania spp. the development of an erythematous
nodule, known as a chagoma, at the site
of infection produced by the proliferation
of the T. cruzi organisms
→ This lesion may be present anywhere
on the body, but it is most frequently
located on the face.
LABORATORY DIAGNOSIS → Edema as well as a rash around the
→ microscopic examination (same with T.b.) eyes and face may subsequently occur.
→ Patients who contract T. cruzi through
→ Hematoxylin and Eosin stain and Giemsa stains
the ocular mucosa develop a
(Amastigotes)
characteristic conjunctivitis and unilateral
→ Use of immunoserological tests (Antibody)
edema of the eyelids, a condition known
→ A number of serologic tests, including complement
as Romaña's sign
fixation (CF), DAT, and indirect
→ Patients suffering from acute Chagas’
immunofluorescence (IIF)
disease typically experience fever, chills,
→ Molecular characterization
fatigue, myalgia, and malaise.
→ Epimastigotes may rarely be seen in the circulating
→ An attack of acute infection may
blood; however, this form is primarily found only in the
result in one of the following scenarios:
arthropod vector.
(1) recovery;

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(2) transition to the chronic stage of GIARDIA LAMBLIA

disease; or → Giardiasis, Traveler’s diarrhea
(3) death, which usually occurs a few Infective Stage Cyst
weeks after the attack. Diagnostic Trophozoites/ Cyst
Stage
Mode of Fecal-oral route
Transmission
Habitat Upper part of Small
Treatment • Benznidazole and Nifurtimox intestine
(Lampit)
• Allopurinol, and the anti-fungal LIFE CYCLE
agent ketoconazole.
Prevention • improved housing and spraying
and insecticide for eradication of
Control reduviid bug nests
• screening of blood donations for
Chagas
• early detection and treatment of
new cases
• Educational programs designed
to inform people, especially in
endemic areas, of the disease, its
transmission, and possible
reservoir hosts

MORPHOLOGY = TROPHOZOITES
→ Measurement: 8 to 20 μm in length by 5
to 16 μm width
→ Bilateral, symmetrical paired structures (pear
shaped, teardrop)
→ The broad anterior end of the organism tapers off at
the posterior end
→ Movement: erratic and slow oscillation like falling
leaf
→ Flagella – four pairs
→ Two median bodies, two axonemes, sucking disk
→ Nuclei – two ovoid-shaped with large karyosome
centrally located
→ Peripheral chromatin is absent.
→ The trophozoite is supported by an axostyle made
up of two axonemes, defined as the interior portions of
the flagella.
→ Two slightly curved rodlike structures, known as
median bodies, sit on the axonemes posterior to the
nuclei.

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LABORATORY DIAGNOSIS
Specimen → Diarrheal stool

Methods → Stool examination, String test/

Enterostest Wet preparation or
Staining technique or Culture (TYI-
S-33)
Other methods → ELISA, EIA, Direct fluorescence
→ real-time polymerase chain
reaction (RTPCR). This molecular
method is sensitive enough for
MORPHOLOGY = CYST environment monitoring because
→ Measurement: 8 to 17 μm, by 6 to 10 μm studies suggest that a single
→ Ovoid in shape Giardia cyst may be detected using
→ Colorless smooth cell wall molecular methods.
→ Central karyosome What to look for?
→ Immature Cyst I. Trophozoites, → Suggestive: progressive, “falling
- Two nuclei and two median bodies unstained leaf” motility; pear-shaped body
→ Mature Cyst with attenuated posterior end
- Four nuclei and four median bodies II. Trophozoites, → Diagnostic: nuclei in the area of
→ The cytoplasm is often retracted away from the cyst stained a sucking disk; the two median
wall, creating a clearing zone. This phenomenon is - Trichrome* bodies posterior to the sucking
especially possible after being preserved in formalin. - Hematoxylin disk; typical arrangement of
axonemes
III. Cysts, → Suggestive: ovoid body shape,
unstained numerous refractile threads in
cytoplasm
IV. Cysts, stained → Diagnostic: four nuclei; four
- Trichrome median bodies; jumble of
- Hematoxylin axonemes

GIARDIASIS
Pathology and → Asymptomatic Carrier State
Clinical → Symptomatic – Giardiasis
Manifestations (Traveler’s diarrhea)
• Children is more frequently
affected
• Mild foul-smelling diarrhea,
flatulence, anorexia, crampy
abdominal pain, epigastric
pain, steatorrhea, and full-
blown malabsorption

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• Excessive flatus smelling like TRICHOMONAS VAGINALIS

rotten eggs

• Severe Giardiasis - copious

light colored, fatty stool,
hypoproteinemia

Symptoms → The typical incubation period is 10

to 36 days, after which symptomatic
patients suddenly develop watery, Common Name Trichomoniasis, Vaginitis
foul-smelling diarrhea, steatorrhea, Infective Stage Trophozoites
flatulence, and abdominal cramping. Mode of Transmission Sexual intercourse
Habitat Vaginal mucosa/Prostate
Treatment → Metronidazole gland, epithelium of urethra
→ Tinidazole
→ Nitazoxanide LIFE CYCLE
Prevention → Proper water treatment that
includes a combination of chemical
therapy and filtration, guarding water
supplies against contamination by
potential reservoir hosts
→ Good personal hygiene
→ Food hygiene
→ Avoidance of unprotected oral-
anal sex

MORPHOLOGY - TROPHOZOITES

Measurement 8 to 30 um
Shape Ovoid, round or pear shaped
→ Pyriform shape, measuring 7 to 23
um with four free anterior flagella
that appear to arise from a simple
stalk, and a fifth flagellum embedded
in the undulating membrane.

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Movement Rapid jerky nondirectional BALANTIDIUM COLI

Flagella Four to six originated in anterior end; CILIOPHORA
one posteriorly (axostyle) BALANTIOIDES COLI
Short undulating membrane (formerly Balantidium coli)
Nuclei Single, ovoid, nondescript

LABORATORY DIAGNOSIS
Specimen Urine, vaginal discharges, urethral
discharges, and prostatic secretions
Method Saline wet preparations is preferred
Other methods Phase contrast microscopy,
Papanicolaou (Pap) smear,
fluorescent stains, monoclonal
antibody assays, enzyme
immunoassays, and cultures
What to look Trophozoites → A large ciliated protozoan parasite
for? → Only pathogenic protozoan ciliate; causes a
diarrhea-type infection called balantidiasis
PATHOLOGY AND CLINICAL MANIFESTATIONS Distribution → Worldwide; pigs are an
Asymptomatic Most frequently in males animal reservoir, human
Carrier State infections occur more
Symptomatic Persistent Urethritis (Men) frequently in areas where
• Enlarged tender prostate, pigs are raised.
dysuria, nocturia, and → Other potential animal
epididymitis reservoirs include rodents
• Release a thin, white and nonhuman primates
urethral discharge that
contains the T. vaginalis LIFE CYCLE
trophozoites.
Persistent • Foul-smelling, greenish-
Vaginitis yellow liquid vaginal
(Female) / discharge
Trichomoniasis • Burning, itching, and
chafing
• Urethral involvement,
dysuria, and increased
frequency of urination.

TREATMENT
→ Metronidazole (Patient and Partner)
→ Tinidazole 2 g as single dose

PREVENTION
→ Good personal hygiene
→ Avoidance of sharing douche equipment and
communal bathing
→ Avoidance of unprotected sex

EPIDEMIOLOGY
→ 170 to 190 million individuals with trichomoniasis.
→ Prevalence is higher among women of child-bearing
age. MORPHOLOGICAL CHARACTERISTICS
→ In the Philippines, the prevalence of trichomoniasis B. coli trophozoites → Average about 75 um
among commercial sex workers varies with the method in length
of diagnosis used, from 15% in studies using only → Large dumbbell or
microscopic examination of vaginal swabs to 37% in bean-shaped
studies using culture.

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macronucleus, and less vegetable cells (both cells and parasites are larger
visible micronucleus than other intestinal protozoa). The cilia tend to be
→ Has a cytostome, an short and can be missed on microscopic
oral apparatus at the examination. Specimens for proficiency testing.
tapered anterior end, 3 → These organisms do not stain well (too large and
through which it acquires thick) on the permanent stained smear and can be
food, and a cytopyge at confused with fecal debris (including helminth
the rounded posterior eggs), hence the need to make the diagnosis by
end through which it using wet smears (from direct mounts or
excretes waste. concentrate sediment).

CLINICAL DISEASE
→ Balantiosis
→ Asymptomatic in some cases
→ Severe dysentery in some cases
→ Has the potential to invade tissues, on contact with
the mucosa

B. coli cysts → Large size (40 um to TREATMENT

more than 70 um) → Tetracycline is the drug of choice, although it is
→ Presence of cilia on the considered investigational for this infection.
cell surface and → Iodoquinol or metronidazole may be used as
cytostome alternatives.
→ Macronucleus often
visible PREVENTION
→ Increased attention to personal hygiene and
sanitation measures, since the mode of transmission is
ingestion of infective cysts through contaminated food
or water.

EPIDEMIOLOGY
→ Cosmopolitan and is more prevalent in areas with
poor sanitation, close contact with pigs or pig feces,
and in overcrowded institutions
→ Warm and humid climates in tropical and subtropical
LABORATORY DIAGNOSIS (KEY POINTS) countries can also contribute to the survival of cysts.
→There is an estimated 1% worldwide prevalence of
human B. coli infection. Pigs are the major host of
balantidiasis, although primates have been reported to
harbor infection.

1 → Since the organisms are so large, they can

frequently be seen under low power (100),
particularly in a concentration sediment wet mount
2 → If wet mounts are examined using high dry
power (400), the organisms may be confused with

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APICOMPLEXA → The infected female Anopheles mosquito bites and

PLASMODIUM SPP. sucks blood from the human host. In the process,
Malaria salivary fluids containing sporozoites are also injected.
→ These sporozoites, the infective stage of the
parasite, are immediately carried to the liver and enter
the parenchymal cells.
→ The parasites then commence exo-erythrocytic
schizogony, which produces the merozoites in varying
duration and amounts, depending on the species.
→ Within the red blood cell, the merozoite grows as a
ring form developing into a trophozoite.
→ The parasites feed on the hemoglobin resulting in
the production of pigment known as hematin. Soon
after, the erythrocytes rupture and the merozoites are
released into the blood, ready to enter new
erythrocytes.
→ Some merozoites develop into microgametocytes
(male) or macrogametocytes (female) which are picked
up by feeding female mosquitoes for completion of the
life cycle.
→ Morphologically, the early trophozoite form is ring-
shaped with a red chromatin dot and a scant amount of
PLASMODIUM blue cytoplasm, which is spread through the
erythrocyte.
→ The gametocyte stage fills the entire red blood cell
and is characterized by a large chromatin mass and a
blue cytoplasm with pigment. It is round to banana-
shaped.
→ The life cycle of P. knowlesi is microscopically
indistinguishable from P. malariae, and differentiation
is only achieved through polymerase chain reaction
(PCR) assay and molecular characterization.
→ These protozoans are pigment producers and are
ameboid in shape, with some being more ameboid than
the others. Their asexual cycle occurs in humans, the
vertebrate and intermediate host, while the sexual
cycle occurs in the Anopheles mosquito, the
invertebrate and definitive host.

EPIDEMIOLOGY
1 Plasmodium falciparum
2 Plasmodium vivax
3 Plasmodium ovale
4 Plasmodium malariae
5 Plasmodium knowlesi

→ The asexual cycle in humans consists of schizogony,

which leads to the formation of merozoites, and
gametogony, which leads to the formation of
gametocytes.
• The sexual cycle in mosquito involves
sporogony, which leads to the formation of
sporozoites

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MALARIA

→ No clinical signs and symptoms when the malaria

parasites are developing in the liver.
→ In the erythocytic cycle (where signs and symptoms
are): P. knowlesi has the shortest cycle, approximately
24 hours, while for P. falciparum, P. vivax, and P. ovale,
it is approximately 48 hours, and for P. malariae, it is 72
hours.
→ Pre-patent period: sporozoite injection to detection
of parasites in the blood.
→ Incubation period: the time between sporozoite
injection to appearance of clinical symptoms
→ The severity of complications and mortality increase
as the level of parasitemia increases.
→ Recrudescence -renewal of parasitemia or clinical
features arising from persistent undetectable asexual
parasitemia in the absence of exoerythrocytic cycle
• Relapse as a result of reactivation of
hypnozoite in ovale and vivax malaria

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CLINICAL PRESENTATION OF MALARIA LABORATORY DIAGNOSIS

DETERMINANTS OF HUMAN MALARIA

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BABESIA SPP.

TREATMENT
Main uses of anti-malarial drugs → Referred to as piroplasm or piroplasmids
→ Protective (prophylactic) – chloroquine, atovaquone Disease Babesiosis (other names are tick fever,
– proguanil, doxycycline, mefloquine, and tafenoquine splenic, redwater Texas or Nantucket
→ Curative (therapeutic) – Artemisinin-based fever)
combination therapies (ACTs), quinine in combination → 1st documented in cattle in 1888 by Scientists Babes
with tetracycline, doxycycline or clindamycin, 3 Stages in the Life Cycle
artemether-lumefantine • Merogony in the RBC and in the tick vector
→ Preventive – RTS, S malaria vaccine • Stages of gamegony in the gut and epithelium
Sporogony accompanied with multiple fission in various
PREVENTION cells and organs
→ Chemoprophylaxis Infective Sporozoites
→ Vector control stage
→ Personal Protection Measures against Mosquito Diagnostic Trophozoites
bites stage

LIFE CYCLE

→ Undergoes three developmental phases. In the

mammalian host,
• Merogony in the RBC
→ In the tick vector,
• Stages of gamogony in the gut and epithelium
• Sporogony accompanied with multiple fission
in various cells and organs forming
sporokinetes, and the development of
infective sporozoites

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→ A few hours after blood ingestion, the intra- → Babesia spp. are grouped into the small Babesia spp.
erythrocytic merozoites in the gut of engorged thicks (1.0 to 2.5 um), which include B. gibsoni, B. microti, and
undergo morphologic, physiologic/metabolic, and B. rodhaini, and the large Babesia spp (2.5 to 5.0 um)
antigenic changes, and differentiate into gametocytes which include B. bovis, B. caballi, and B. canis
that eventually develop into gametes → Pleomorphic forms in different hosts obscure their
→ Post-fertilization, the zygote begins to infect the gut identification at the species level
epithelial cells where it undergoes multiple fission, and → They do not undergo exoerythrocytic merogony
eventually forms sporokinetes. → Daughter progeny are not housed in
Once the sporokinetes are released, they continue to parasitophorous vacuoles
infect and multiply in various organs, including the → Residual bodies are non-existent in infected RBCs
ovaries of the replete tick, until death ensures.
→ The transovarian route represents one pattern of BABESIOSIS
parasite transmission in the vector, which terminates CLINICAL DISEASE (IN HUMANS)
with the death of the vector. → Age and breed of farm animals AND the health and
immunity of humans
→ Incubation period is 1-4 weeks
→ May be asymptomatic (IgG seropositive) or a mild,
self-limited influenza-like illness
→ May be a serious disease with hemolytic anemia,
renal failure, splenomegaly and hypotension
→ Transfusion-associated babesiosis is an emerging
problem, particularly in transplant patients and among
neonates.

LABORATORY DIAGNOSIS
BIOLOGY OF BABESIA SPP.

→ Heteroxenous parasite requiring mammals as

primary host and ticks (Ixodes) as intermediate hosts

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→ Detectable in blood smears during the acute stage of

infection
→ Definitive diagnosis requires direct microscopic
examination of Giemsa-stained peripheral blood
smears for the presence of Babesia, showing its
established unique morphological features.
→ Several serological tests are generally employed for
the detection of babesiosis.
→ The PCR is highly specific and is generally considered
to the gold standard for Babesia detection.

TREATMENT
→ A drug combination of clindamycin and quinine OR
→ Azithromycin and atovaquone
→ Supportive and asymptomatic management is
important
→ Drug resistant B. microti may emerge
→ Pyrimethamine, artesiminin and pamaquine can
strongly inhibit the life cycle in vitro

PREVENTION
→ The application of bug repellants in clothes like DEET
and acaricides
→ Rodent control
→ Consider including screening procedures for B.
microti for blood and organ donors in high risk areas.

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