CLINICAL PARASITOLOGY (LECTURE)

- Other Modes of Transmission:

o Imported malaria – acquired by visitors
Plasmodium spp. and Babesia spp. or residents of country with endemic
- Under the Phylum Apicomplexa disease.
- The protozoan parasite characterized by the o Transfusion malaria – associated with
production of the spore-like oocyst containing blood transfusion from infected donors.
merozoite
the sporozoites is known as the Sporozoa. induced
o Mainline malaria – sharing of needles
- They live intracellularly (inside the cell) and syringes among drug users.
- At some stage in their life cycle, they possess a o Congenital malaria – natural form of
structure called apical complex (important for merozoites induced malaria where the
attachment and penetration in the host cells) parasite is transmitted transplacentally
from the mother to the fetus.
Plasmodium spp. ▪ Rare but possible
• Plasmodium falciparum - Vector Biology: Anopheles flavirostris
responsible for 95% of all
• Plasmodium vivax human malaria cases - Aquatic Habitat: slow flowing streams; shaded
• Plasmodium malariae streams
• Plasmodium ovale - Adult biting: Night biting (indoor and outdoor)
• Plasmodium knowlesi - Adult resting: inside walls

Babesia spp. LIFE CYCLE OF MALARIA PARASITE

• Babesia microti
• Babesia divergens
• Babesia bovis

- Malaria from Italian word "mal'aria" which

means "bad air"
- The name Malaria was given in the 18th Century
in Italy.
- Believed to be caused by emanation from the
marshy soil.
- Considered to be the most important parasitic
disease affecting man (Belizario, 2015)
- Leading parasitic disease that causes mortality
worldwide Sporogony
- Identified by WHO as one of the major infectious
disease threats along with HIV, AIDS, and
tuberculosis
- Peak transmission of Malaria: beginning and end
of rainy season.
- Mostly, the children and pregnant women are
affected with malaria.
o Children: chronic malaria may lead to
anemia, impaired physical, and mental
growth and development.
o Pregnant women: anemia is the leading
contributor of maternal morbidity and
mortality.
- Vector: female Anopheles mosquito (Anopheles - The sexual phase takes place in the female
minimus var. flavirostris) Anopheles mosquito, making it the definitive
- Other spp. under Anopheles family: host of the parasite
o Anopheles litoralis - It is the sexual cycle in the mosquito which leads
o Anopheles maculates to the formation of sporozoites
o Anopheles mangyamus - Union between the microgamete and
- Final Host: female Anopheles mosquito macrogamete (sex cells of Plasmodium spp.
(invertebrate and definitive host) developed in the RBC of humans).
- Intermediate Host: Man (vertebrate and o Resulting product: formation of
intermediate host) sporozoites
- Infective stages: o Zygote > ookinete > oocyst > sporozoites
o Sporozoites (man) - Gametes:
o Gametocytes (mosquito) o Male sex cell: microgamete
- Source of Exposure to infection: Vector borne o Female sex cell: macrogamete
(Arthropod borne)
 CLINICAL PARASITOLOGY (LECTURE)

- The maturation and fertilization takes place in - Schizogony in liver is an essential step before the
mosquito giving rise to a large number of parasite can invade the erythrocyte it is called as
sporozoites (sporos = seed) Pre-erythrocytic Schizogony.
- Hence, this phase of sexual multiplication is - Resulting product: merozoites (whether
called as sporogony erythrocytic or exoerythrocytic)
- Also called as invertebrate, extrinsic, and - Target: Sporozoite infect liver parenchymal cells
exogenous phase (because it occurs outside the (since the detoxifying organ is the liver, the
human body) sporozoites infect it)
- Exflagellating male gametocytes: the nuclear o Sporozoite enters the liver cell and will
material and cytoplasm of the male gametocytes develop as Schizont
divides to produce 8 microgametes with long, o The hepatocyte is distended by the
actively motile, whip-like filaments. enlarging schizont and the liver cell
- The female gametocyte does not divide but nucleus is pushed to the periphery.
undergoes a process of maturation to become o Rupture liver cells releases merozoites,
the female gamete or macrogamete. It is which will go to the erythrocytic cycle
fertilized by one of the microgametes to produce o These normally rupture in 6-15 days and
the zygote. release thousands of merozoites into
- Ookinete: the zygote, which is initially a the blood stream.
motionless, round body, gradually elongates - In the latent stage of Plasmodium vivax and
becomes a vermicular motile (traveling Plasmodium ovale two kinds of sporozoites are
vermicule) form with an apical complex seen.
anteriorly. o Some multiply inside the hepatic cell to
- Oocyst: rounded into a sphere with an elastic form schizonts while others persist and
membrane within which numerous sporozoites remain dormant/resting stage
are formed. ▪ Hypnozoites (hypnos: sleep):
- Sporozoites: when the oocysts ruptures, the resting forms in Plasmodium
sporozoites enter into the hemocele or body vivax and Plasmodium ovale
cavity, from where some find their way to the o Some are activated to become schizonts
mosquito's salivary glands. and release merozoites, which will infect
- The mosquito is now infective and when it feeds RBC producing clinical relapse.
on humans, the sporozoites are injected into skin ▪ Clinical relapse is associated
capillaries to initiate human infection. with Plasmodium vivax and
Plasmodium ovale.
Schizogony (Pre-erythrocytic Cycle)
Schizogony (Erythrocytic Cycle)

- The merozoites will invade the RBCs while some

merozoites of Plasmodium vivax and
Plasmodium ovale reinvades the liver cells
forming the hypnozoites.
- Inside the RBCs they will develop to become
young trophozoites (ring forms)
- Mature trophozoites > Schizonts > Ruptured
- Asexual phase schizonts > merozoites
- In this stage, the malaria parasite multiplies by - Some proceed to the development of
division or splitting process – Schizogony gametocyte
o Schizo (split) gony (generation) - Trophozoites can develop into schizonts or
- Occurs in humans (vertebrate, intrinsic, and gametocyte
endogenous phase) making humans as the - The merozoites released by pre-erythrocytic
intermediate host. schizonts invade the red blood cell:
- In humans, Schizogony occurs in two locations: o The receptor for merozoites is
o RBC (erythrocytic schizogony) glycophorin, which is a major
o Liver: (exoerythrocytic schizogony or glycoprotein on the red cells.
pre-erythrocytic schizogony)
 CLINICAL PARASITOLOGY (LECTURE)

o Merozoites are pear-shaped bodies,

about 1.5 um in length, possessing an
apical complex (rhoptery). They attach
to the erythrocytes by their apex.
o Ring forms or young trophozoites: the
merozoite loses its internal organelles
and appears as a rounded body having a
vacuole in the center with the cytoplasm
pushed to the periphery and the nucleus
at one pole.
o Malaria pigment or haemozoin
pigment: parasite feeds on the
hemoglobin of the erythrocyte but it
does not metabolize hemoglobin
completely and therefore, leaves behind
a hematinglobin pigment as residue

GAMETOGONY
- Development of gametocytes generally takes
place within the internal organs and only the
mature forms appear in circulation.
- The appearance of malaria pigments varies in - The mature gametocytes are round in shape,
different species as follows: except in P. falciparum, in which they are
o P vivax: numerous fine golden-brown crescent-shaped.
dust-like particle - In all species, the female gametocyte is larger
o P. falciparum: few 1-3 solid blocks of (macrogametocyte) than the male gametocyte
black pigment (microgametocyte).
o P. malariae: numerous coarse dark - The gametocytes do not cause any clinical illness
brown particles in the host, but are essential for transmission of
o P ovale: numerous blackish brown the infection.
particles. - Gametocyte – Infective stage to mosquito
- Amoeboid form or late trophozoite form: as the - A gametocyte concentration of 12 or more per
ring form develops, it enlarges in size becoming cumm of blood in the human host is necessary
irregular in shape and shows amoeboid motility. for mosquitoes to become infected.
- When the amoeboid form reaches a certain
stage of development, its nucleus starts dividing
by mitosis followed by a division of cytoplasm to
become mature schizonts or meronts.
- The merozoites invade fresh erythrocytes within
which they go through the same process of
development.
- The rupture of the mature schizont releases
large quantities of pyrogens. This is responsible
for the febrile paroxysms (on and off fever)
characterizing malaria.
 CLINICAL PARASITOLOGY (LECTURE)

COMPONENTS OF THE MALARIA LIFE CYCLE Benign Malaria

- The typical picture of malaria consists of periodic
bouts of fever with rigor, followed by anemia
and splenomegaly.
- Severe headache, nausea, and vomiting are
common.

Classical Malaria Paroxysms

➢ Cold stage
o sudden coldness and apprehension
- If a mosquito bites a gametocytemic person, the o mild shivering turns to teeth chattering
mosquito will acquire the micro and and shaking of the whole body
macrogametes o may last for 15 to 60 minutes
- It will undergo the sporogonic cycle, which will ➢ Hot stage/ flush phase
produce the sporozoites o best stage to collect blood sample
- When the mosquito has sporozoites, it is now in o High temperature (40-41°C), headache,
the infective period palpitations, epigastric discomfort,
- If a mosquito bites an uninfected person, thirst, nausea and vomiting. May lead to
sporozoites can now be transmitted (pre-patent convulsion
and incubation period starts) o patient is confused and delirious
o Pre-patent period: interval from the o may last for 2 to 6 hours
sporozoite injection to the detection of ➢ Sweating stage (Defervescence or Diaphoresis)
the parasite in the blood o profuse sweating, temperature lowers
▪ At the end of the pre-patent and symptoms diminishes
period, parasites are now visible o may last for 2 to 4 hours
(ring forms and gametocytes in
the peripheral blood) Malignant Tertian Malaria
o Incubation period: Time between the
- The most serious and fatal type of malaria is
sporozoites injection and the
malignant tertian malaria caused by P.
appearance of the clinical symptoms
falciparum.
▪ At the end of the incubation
- Pernicious malaria: Has been applied to a
period, signs and symptoms can
complex of life-threatening complications that
now be observed (such as
sometimes supervene in acute falciparum
paroxysms)
malaria.
- The pre-patent and incubation period depends
- Cerebral Malaria: Is the most common cause of
on the parasite strain, dose of sporozoites
death in malignant malaria, capillary plugging of
inoculated, immune status of the host, and the
cerebral microvasculature, which results in
host malaria chemoprophylaxis therapy
anoxia, ischemia, and hemorrhage in brain.
o Late stage schizonts of P. falciparum
Interval
secretes protein on the surface of RBC to
Species Prepatent period Incubation period
form knob-like deformities. This knob
P. falciparum 11-14 days 8-15 days
P. vivax 11-15 days 12-20 days produces specific adhesive proteins,
P. malariae 3-4 weeks 18-40 days which promote aggregation of infected
P. ovale 14-26 days 11-16 days RBC to other non-infected RBC and
capillary endothelial cells.
Periodicity/Febrile Cycle - Blackwater fever (Malarial hemoglobinuria): is
Interval Age of infected sometimes seen in falciparum malaria. Clinical
Species Febrile cycle
(hours) erythrocytes manifestation includes bilious vomiting and
* Malignant RBC of all prostration, with passage of dark red or blackish
P. falciparum 36-48
tertian stages
urine (black water). There is a massive
P. vivax Benign tertian 48 Young RBC
P. malariae Quartan 72 Aging RBC
intravascular hemolysis caused by anti-
P. ovale Ovale tertian 48 Young RBC erythrocyte antibodies, leading to massive
- The interval between the attacks is determined absorption of hemoglobin by the renal tubules
by the length of erythrocytic cycle. (hemoglobinuric nephrosis).
- Tertian: paroxysm occurs in alternate days or
every second day.
- Quartan: paroxysm occurs on day 1 and day 4 or
every third day.
- Aestivoautumnal malaria – associated to P.
falciparum (it occurs commonly in late summer
and autumn)

- Algid Malaria: Peripheral circulatory failure,

CLINICAL FEATURE
rapid thready pulse with low blood pressure, and
- No absolute clinical feature of malaria except for cold clammy skin. There may be severe
regular paroxysms (sudden attack or violent abdominal pain, vomiting, diarrhea, and
expression of fever with asymptomatic intervals) profound shock.
 CLINICAL PARASITOLOGY (LECTURE)

- Septicemic malaria: High continuous fever with PATHOLOGICAL PROCESS OF THE RBC
dissemination of the parasite to various organs,
• Poikilocytosis – variation in shape of the RBCs
leading to multiorgan failure. Death occurs in
• Anisocytosis – variation in size of the RBCs
80% of the cases.
• Altered RBC membrane transport
• RBC stiffness and cytoplasmic viscosity
Merozoite-induced Malaria
- Injection of merozoites can lead to direct
MORPHOLOGY
infection of red cells and erythrocytic schizogony
with clinical illness. Such merozoite-induced
malaria may occur in transfusion malaria,
congenital malaria, renal transplantation, and
mainline malaria.

Tropical Splenomegaly Syndrome

- Also known as hyper-reactive malarial
splenomegaly (HMS) is a chronic benign
condition seen in some adults in endemic areas,
mainly tropical Africa, New Guinea, and Vietnam.
- Abnormal immunological response to malaria
causing splenomegaly, high titers of circulating
anti-malaria antibodies, and absence of malaria
parasites in peripheral blood smears,
hypergammaglobulinemia (lgM), presence of
rheumatoid factor without arthritis, and
cryoglobulinemia reduced C3
- The immune system is very active even though
malarial parasites are not detectable in the
circulation

RECRUDESCENCE AND RELAPSE

Recrudescence
- New malarial attacks that appear after a period
of latency usually within 8 weeks after the
primary attack and resulting from persistence of
the erythrocytic cycle of the parasites.
- Renewed outbreak of the disease. The disease is
reduced to the point that it is undetectable but
still persist in the body and will reoccur after
some days or weeks.
- May persist inside the body but they are not
active to cause signs and symptoms.
- Reduced/light infectivity – undetectable in blood
smear.
- Stopping of the treatment early.
IMMUNITY
Relapse ➢ Duffy negative RBCs: It has been found that
- Common to P. vivax and P. ovale infections, as persons, who lack the Duffy blood group (Fya
result from the reactivation of hypnozoite forms and Fyb alleles) antigen, are refractory to
of the parasite in the liver infection by P. vivax. These genetically
- Suffering deterioration after a period of determined blood group antigen appears to be
improvement. the specific receptor for P. vivax
- Pre-mature stage of organism resides in the body ➢ Nature of hemoglobin:
that are in dormant stage and will cause disease o Since malaria infects RBC, any
after recovering completely from the previous alterations to the hemoglobin, which is
occurrence of the disease. essential to RBC function, generally
Recrudescence Relapse protects the RBC from the invasion of
Seen in P. falciparum and P. Plasmodium parasites or replication
Seen in P. vivax and P. ovale
malariae within the RBC.
Due to persistence of the Due to reactivation of o Problem with hemoglobin – it will not
parasite at a subclinical level in hypnozoites present in liver
sustain the life cycle of malaria
circulation cells
Occurs within a few weeks or Occurs usually 24 weeks to 5 (resistance to the disease).
months of a previous attack years after the primary attack o Hemoglobin E provides natural
Can be prevented by adequate
Can be prevented by giving
protection against P. vivax. P. falciparum
drug therapy or use of newer does not multiply properly in sickled red
primaquine to eradicate
antimalarial drugs in case of
hypnozoites cells containing HbS. Sickle cell anemia
drug resistance
trait is very common in Africa, where
 CLINICAL PARASITOLOGY (LECTURE)

falciparum malaria is hyperendemic and ➢ Serologic Tests (IHA, FAT, ELISA)

offers a survival advantage. HbF present ➢ Molecular Methods through PCR (low cases and
in neonates protects them against all mixed infection
Plasmodium species.
➢ G6PD deficiency:
o Innate immunity to malaria has also
been related to G6PD deficiency found in
Mediterranean coast, Africa, Middle
East, and India
➢ HLA-B53:
o HLA-B53 is associated with protection
from malaria. There is some evidence TREATMENT
that severe malnutrition and iron - Anti-malaria drugs are used with various
deficiency may confer some protection objectives like clinical cure, prevention of
against malaria relapse, prevention of transmission, and
prophylaxis.
DIAGNOSIS
➢ Microscopy Protective
o Gold Standard Used before the infection occurs or become evident
o "Thick and Thin Blood Smear" ➢ Chemoprophylaxis: Objective is to prevent
o stained with Giemsa or Wright's stain infections in non-immune person visiting
o perform multiple sets of blood films endemic areas (Mefloquine and Doxycycline)
(blood collected every 6 to 12 hours for
up to 48 hours) Curative
o Manner of Reporting: Action on established infection
▪ Qualitative ➢ Therapeutic: Objective is to eradicate the
+ 1-10 parasite/100 thick field erythrocytic cycle and clinical cure
++ 11-100 parasite/100 thick field
+++ 1-10 parasite/thick field
➢ Radical cure: Objective is to eradicate the
++++ more than 10/thick field exoerythrocytic cycle in liver to prevent relapse
▪ Quantitative o Artemether-Lumefantrine (CoartemTM)
– first line drug for confirmed P.
𝑛𝑜. 𝑜𝑓 𝑝𝑎𝑟𝑎𝑠𝑖𝑡𝑒𝑠
𝑴𝒂𝒍𝒂𝒓𝒊𝒂 𝒑𝒂𝒓𝒂𝒔𝒊𝒕𝒆/𝒖𝑳 = 𝑥 8,000 falciparum cases. Not recommended in
𝑊𝐵𝐶
pregnancy, lactation, and infants.
o Quinine (plus Tetracycline or
Doxycycline) – second line drug for
confirmed P. falciparum cases which AL
fail or not available.
o Quinine IV drip – drug of choice for
severe P. falciparum malaria.

Preventive
➢ Quantitative Buffy Coat (QBC) ➢ Gametocidal: Objective is to destroy
o uses a special capillary tube with gametocytes to prevent mosquito transmission
acridine orange and thereby reducing human reservoir.
o (+) bright green and yellow under o In addition to AL and Q+T,D, Primaquine
fluorescent microscope is given on the 4th day as single dose to
prevent transmission

PREVENTION
• Use of mosquito repellant
• Use of insecticide treated nets (lTN)
➢ Rapid Diagnostic Test (RDT) • Take prophylactic medication
o Use test kits if (-) with microscopy and • Wearing of light-colored clothing which cover
you are suspecting a malaria most of the body
o detects Plasmodium-specific antigens in
finger prick sample CONTROL
▪ Histidine-rich protein Il (HRP Il) • Environmental cleanliness (stream cleaning to
– water soluble CHON produced speed up water flow and exposing to sunlight)
by trophozoites and young • Indoor residual spraying
gametocytes (e.g., Paracheck Pf • Zooprophylaxis – use of carabao to deviate
test, ParaHlT f test) mosquitoes
▪ Plasmodium LDH – produced by • Use of biologic control methods
both sexual and asexual stages. o Bacillus thuringiensis – larvicidal
Can distinguish between P. o Larviparous fishes (e.g., Oreochromis
falciparum and non-P. niloticus)
falciparum (DiaMed OptiMAL IT)
 CLINICAL PARASITOLOGY (LECTURE)

- Humans are dead end host

- When humans are bitten by ticks, trophozoites
- A primate malarial parasite common in
will develop to become merozoite
Southeast Asia
- Merozoites can also become trophozoites
- Causes malaria in long tailed macaques (Macaca
- It can be transmitted from human to human via
fascicularis)
blood transfusion
- May also infect humans
- Mouse play an important role in the life cycle of
- The appearance of P. knowlesi is similar to that
the parasites since gametes may develop inside
of P. malariae
their body
- PCR assay and molecular characterization are
the most reliable methods for detecting and
diagnosing P. knowlesi infection PATHOLOGY
o However, P. vivax appears to interfere - Associated with excessive pro-inflammatory
PCR testing (cross-reactivity) cytokines such as the tumor necrosis factor
(TNF)
- Most cases are subclinical and may occur as self-
limiting
- Includes Babesia microti (rodent strain), Babesia - Headache, high-grade fever, chills, vomiting,
divergens (cattle strain), and Babesia bovis myalgia, DIC, hypotension, respiratory distress,
(cattle strain) and renal insufficiency.
- First described to cause "Texas cattle fever or
red water fever”
DIAGNOSIS
- Blood parasites that cause malaria-like infections
- "Babesiosis" – pathology due to Babesia spp. - Microscopy of the Giemsa-stained peripheral
o Also known as nantucket fever blood smear
- Parasites divide through binary fission or o Merozoites in Maltese cross
budding arrangement
- Cycle in the tick is still uncertain o Ring form → most frequent
- Vector: Ticks (Ixodes scapularis) intraerthrocytic form found
o Hard ticks - PCR (gold standard)
o Scapularis – capable of carrying Borrelia - Immunofluorescent assays (IFA)
burgdorferi (CA of Lyme disease) - Immunochromatographic test (ICT)
- Definitive host: Ixodid ticks
- Intermediate host: Man or other mammals
- Infective form: Sporozoites
- Mode of Transmission: bite of the nymphal stage
of Ixodid ticks
- Other modes of transmission:
o Blood transfusion
o Organ transplantation
o Transplacental route
- Diagnostic stage: "Maltese cross" arrangement
of the merozoites and ring-form trophozoite

TREATMENT
➢ Clindamycin – Drug of choice
➢ Drug combination: Clindamycin and Quinine or
Life Cycle of Babesia spp. Azithromycin and Atovaquone
➢ Chloroquine – former drug of choice (it only
improves the symptoms but not the degree of
the parasitemia)

Note:
In the Philippines: human babesiosis is not yet reported
however, it could be present in dogs (Babesia canis).

PREVENTION AND CONTROL

• avoidance of places where ticks are usually
found
• wearing of light-colored pants tucked into one's
socks
• tick check (especially for children)
- Undergoes 3 stages: • Rodent population should be controlled –
o Merogony in the RBCs rodents are the major carriers and reservoir of
o Gamogony in the gut and epithelium the parasite.
o Sporogony