BSML – 2211| CLINICAL PARASITOLOGY

Unit #5: Protozoans

2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

CLASSIFICAITON

 Kingdom Protista
 Phylum Sarcomastigophora
o Subphyla
 Subphylum Mastigophora
 Flagellate or Hemoglagellates
 Subphylum Sarcodina
 Subphylum Sarcodina

SUBPHYLUM SARCODINA

 Entamoeba
 Endolimax
 Iodamoeba
 Acanthamoeba
 Naegleria

ENTAMOEBA HISTOLYTICA

 Fedor Alexandrewitch L o ̈s c h describes amoebae associated with severe dysentery in a patient in 1873.
 He transferred amoebae to a dog by rectal injection, which became ill and showed ulceration of colon.
 The patient who died from infection showed similar ulcers upon autopsy.

Trophozoites
Habitat reside in the mucosa and submucosa of large intestine in man

Forms
 trophozoite
 precyst
 cyst

Morphology

Trophozoite
 multiple well defined pseudopodia often extended
eruptively
 motile; results from movement from long finger -like
pseudopodial extensions of the ectoplasm into which
endoplasm flows
 appears in diarrheic feces & survives only for a few hours
engulf red blood cells, leukocytes, & tissue
debris found within the food vacuoles

MANYLL REIGNE MAGANA 1

BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

Trophozoites encyst and cysts mature as they travel through the colon. Only mature cysts are
infective.

Pre-Cyst
 smaller in size, oval with blunt pseudopodium
projecting from the periphery
 food vacuoles disappear

Cyst
 round 10-16 µm, 4 nuclei
 150 nm cyst wall with fibrillar structure
 chromidial bodies and bars are semicrystalline
arrays of ribosomes
 spherical, surrounded by thick chitinous wall
 present in the lumen of the colon, and in formed
feces

MANYLL REIGNE MAGANA 2

BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

Life Cycle

Protozoan Parasites of Human

 carried asymptomatically in the digestive tracts of humans
 no animal reservoir exists
 infection occurs by drinking water contaminated with feces containing cysts
types of amebiasis can result from infection:
o luminal amebiasis
o invasive amebic dysentery
o invasive extraintestinal amebiasis
Note: Maintaining clean water is important in prevention.

MANYLL REIGNE MAGANA 3

BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

 major sources for human infection are contamination of drinking water and vegetables
(fertilization with material containing or contaminated with human feces)
 patients without any symptoms might nevertheless shed large amounts of cysts
 if kept cool and most (water or soil) cysts can stay infectious for up to a month
 cysts are fairly resistant to chlorination of drinking water

Amebiasis
 Clinical Features:
o luminal amebiasis: asymptomatic infection
o invasive amebic dysentery: intermittent and mild
- various gastrointestinal upsets, including colitis and diarrhea, dysentery,
appendicitis, toxic megacolon, amebomas
o invasive extraintestinal amebiasis
- liver abscess, peritonitis, pleuropulmonary abscess, cutaneous and genital
amoebic lesions
Colitis
 most common form of disease associated with amoebae
 gradual onset of abdominal pain, watery stools containing mucus and blood
 some patients have only intermittent diarrhea alternating with constipation
 fever is uncommon
 formation of ulcers
Infection  amoebae invade mucosa and erode through lamina propria causing characteristic flask
shaped ulcers contained by muscularis

Amebic Liver Abscess

 most common form of extraintestinal amebiasis
 fast growing abscess filled with debris, amoebae are found only
at borders
 lead symptoms are right upper quadrant pain and fever
acute as well as chronic illness, with gradual or sudden onset

MANYLL REIGNE MAGANA 4

BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

E. histolytica or E. dispar must be differentiated from E. coli, E. hartmanni, E. gingivalis, E. nana and I.
Diagnosis buetschlii (the non-pathogenic amoebas) based on morphologic characteristics of cysts and
trophozoites E. histolytica or E. dispar (a non-pathonetic amoeba) is morpholigaclly identical or E.
histolytica – by isoenzymatic or immunologic analysis (IFA, ELISA, IHA) and through molecular
methods.

Laboratory Diagnosis:
stool examination
 blood examination: moderate leukocytes
 serological tests
 culture: Boeck and Drbohlav’s diphasic medium
 diagnostic aspiration
 liver biopsy
molecular methods

Metronidazole (Flagyl)
 drug of choice for extraintestinal amebiasis

Note: several drugs are also available to treat symptomatic and asymptomatic enteric (luminal
Treatment
infection) (e.g., dichloroacetamides) which have unknown mode of actions

 drug of choice for invasive amoebiasis (and should be combined with a lumen acting drug
as it is not fully effective on luminal stages
 prodrug which is activated by an enzyme involved in the fermentative metabolism of E.
histolytics

Asymptomatic Carrier State

 parasite is a low-virulence strain
 inoculation into the host is low
 patient’s immune system is intact

Note: In these cases, amoebas may reproduce but the infected patient shows no clinical symptoms.

MANYLL REIGNE MAGANA 5

BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

ENTAMOEBA DISPAR

 non-invasive, non-pathogenic specie

Characteristic  cysts of E. histolytica and E. dispar cannot be differentiated microscopically
 morphologic resemblance with E. histolytica but their DNA and ribosomal RNA are different

ENTAMOEBA MOSHKOVSKII

 1st detected in sewage

 morphologically identical with E. histolytica and E. dispar (differs biochemically & genetically)
 other characteristics:
Characteristic
o osmotolerant
o grows at RT 25-30° C
o can survive at 0-41° C

ENTAMOEBA HARTMANNI

 morphologically similar to E. histolytica, but both its trophozoites & cysts are smaller & the
never contain ingested red blood cells
Characteristic
 “small race” E. histolytica
 non-pathogenic amoeba

ENTAMOEBA COLI

Characteristic  lives freely in the lumen of the large intestine of man

non-pathogenic

Difference Between E. histolytica and E. coli:

Characteristic E. histolytica E. coli
Red Blood Cell in Cytoplasm present absent
Chromatin Body cigar shape splinter-like (broomstick)
Type of Pseudopod finger-like blunt
Movement directional (active) sluggish
Nucleus (Cyst) 4 8
Infective Stage cyst cyst
Pathologic yest (flask-shape ulcers) no
Location of Karyosome central peripheral

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BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

ENTAMOEBA GINGIVALIS

 1st parasitic amoeba to be recognized in the soft tartar between the teeth in 1849
 only the trophozoite stage has been found
 commensals in the gingival tissue around the teeth, particularly if there is suppuration
 the only amoeba that ingests white blood cells

Characteristic

ENTAMOEBA POLECKI

 considered as parasite of pigs and

monkeys
 motility of trophozoite is sluggish
 cysts only contain 1 nucleus
 morphologically identical if E.
chattoni in apes and monkeys
Characteristic

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BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

ENDOLIMAX NANA

 cosmopolitan
 non-pathogenic
 small amoeba found in the
lumen of the large intestine
in humans, primates, and
pigs
 exists as trophozoite, pre-
cyst, and cyst
 transmitted from man to
man by ingestion of viable
cysts in polluted water or
food
Characteristic
Trophozoite
 sluggish
 nonprogressive motility
 accompanied by blunt
hyaline pseudopods

Note: The absence of peripheral chromatin is a key feature that aids in the identification of E. nana
trophozoite.

Cyst
 1-4 nuclei
 presence of blot-like karyosome, centrally located
 absence of peripheral chromatin

IODAMOEBA BUETSCHLII

 lives as harmless commensal in the lumen of the large

intestine of man, monkeys, and pigs
 cyst is irregularly pyriform in shape and ovoid
 transmitted from man to man when viable cyst is ingested

Characteristic Cyst
 well-defined glycogen mass with definite borders
(characteristic)
 “basket of flowers” in shape

Note: It is called “Iodamoeba” because it stains well with iodine.

 Lugol’s Iodine
Diagnosis  Formalin-Ether Concentration Technique (FECT)
No treatment necessary because these amebae do not cause disease.

Treatment Prevention and Control:

 proper disposal of human waste
 personal hygiene

FREE-LIVING PATHOGENIC AMOEBA

 facultative parasites of man

 ubiquitous in nature
 commonly found in soil and water where they feen on bacteria
 as opportunists, they may produce serious infection of the central nervous system and the eye

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BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

NAEGLRERIA FOWLERI

Forms
 amoeboid trophozoite
 flagellates
 cyst

Cyst
 uninucleate
 spherical
Morphology  surrounded with a thin cyst wall

Trophozoite
 amoeboid: elongate, broad anteriorly & tapered posteriorly; motile by means of eruptive,
blunt pseudopodia called lobopodia; reproduction is by binary fission of the amoeboid form;
invasive form
 flagellate: cigar or pear-shaped with 2 flagella at the broader end; moves rapidly forward or
spin slowly in circles. Amoeba that can transform into flagellates are known as
amoeboflagellates

Life Cycle

The amoeboid form of N. fowleri is the invasive stage of the parasite.

Man acquires infection by nasal contamination during swimming in freshwater lakes, ponds or
swimming pools containing infective forms.

The amoeboid forms invade the nasal mucosa & travel along the olfactory nerves to brain leading
to a rapidly fatal infection known as primary amoebic meningoencephalitis (PAM).
 microscopic identification of living or stained amoeba in CSF
 tissue samples and nasal discharges
 culture of clinical specimens (the amoeboid trophozoites show a characteristic trailing effect
Diagnosis
when placed on agar plates that have been previously inoculated with gram negative
bacilli)
 PCR assay, monoclonal Ab testing, flow cytometry, DNA hybridization

NAEGLRERIA AUSTRALIENSIS

 a specie that could possibly infect humans in the future

Characteristic
 pathogenic in mice exposed to the parasite by intranasal instillation

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BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

ACANTHEMOEA SP.

Species:
 Acanthamoeba culbertsoni
 Acanthamoeba castellanii
o causes most CNS and eye infections in humans
 Acanthamoeba hatchetti
 Acanthamoeba polyphaga
 Acanthamoeba rhysodes

 exists as active trophozoite and

resistant cyst
 no flagellate form

Trophozoite
 larger than those of Naegleria
 have irregular appearance with
Morphology acanthopodia (spines or thorns)
 tapering spike-like pseudopodia

Cyst
 double-walled
 inner smooth cell wall surrounded by
an outer jagged cell wall

Life Cycle

Man acquires infection by inhalation of aerosol or dust containing trophozoites & cysts.

Trophozoites reach the lower respiratory tract & from there they invade the CNS thru the blood stream.
The infection may also be acquired by direct invasion thru broken skin or ulcerated skin or eye.

It also causes granulomatous amoebic encephalitis (GAE).

 aspiration or nasal inhalation of the organisms.
Route of Entry
 direct invasion of the parasite in the eye (Acanthamoeba keratitis)
 demonstration of trophozoites in CSF or trophozoites & cysts in brain tissue
 corneal scrapings (infections of the eye)
Diagnosis
 culture on non-nutrient agar plates seeded with gram negative bacteria; look for tracks
 indirect immunofluorescent Ab stain (for speciating Acanthamoeba)

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BSML – 2211| CLINICAL PARASITOLOGY
Unit #5: Protozoans
2nd SEMESTER | S.Y 2022 – 2023 BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
LECTURED BY: MARILOU HONCULADA TRANSCRIBED BY: MANYLL REIGNE MAGANA

BALAMUTHIA MANDRILLARIS

Morphology  newly described amoeba

 does not have a flagellate stage

Trophozoite
 irregular or branching in shape
 sluggishly motile
 found in tissue

Cyst
 characterized by having 3 layers in cyst wall
 outer: wrinkled ectocyst
 middle: structureless mesocyst
 inner: endocyst
Infection  chronic CNS infection
Route of Entry  same with Acanthamoeba sp.

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