Chapter-8-Protozoafgagagagagaggagaagagagag

parasitiology

1. Protozoan Parasites
Week 8
Prepared by:
Kier Lambert B. Demain, M.Sc., L.Agr., LPT.

2. Protozoan Parasites
•Protozoan parasites are
single-celled eukaryotic
organisms that can
cause significant
diseases in humans and
animals.
•They are responsible for
a variety of infections,
often transmitted
through vectors,
contaminated food, or
water

3. Classification and Morphology of
Protozoan Parasites
Protozoa are classified based on their locomotion and structure.

4. Sarcodina (Amoebas)
•Morphology: Characterized by
the presence of pseudopodia
(temporary extensions of the
cell membrane) for movement
and feeding.
•Example: Entamoeba histolytica
(causes amoebiasis).

5. Mastigophora
(Flagellates)
•Morphology: Possess
one or more whip-like
flagella for
movement.
•Examples:
•Giardia lamblia
(causes giardiasis).
•Trypanosoma brucei
(causes African
sleeping sickness).

6. Ciliophora
(Ciliates)
•Morphology: Have
numerous short hair-
like structures called
cilia that help in
locomotion and
feeding.
•Example:
Balantidium coli
(causes
balantidiasis, a rare
intestinal infection).

7. Apicomplexa (Sporozoans)
•Morphology: Non-motile
protozoa with a complex life
cycle, often involving both
asexual and sexual reproduction.
Have an apical complex used for
host cell invasion.
•Examples:
•Plasmodium species (causes
malaria).
•Toxoplasma gondii (causes
toxoplasmosis).

8. Life Cycles and
Pathogenesis of Common
Protozoan Infections

9. Malaria
•Causative Agent: Plasmodiumspecies (e.g., P. falciparum, P. vivax).
•Life Cycle:
oHuman Stage(Intermediate Host):
▪Sporozoites are injected into the bloodstream by an infected Anopheles
mosquito.
▪The sporozoites travel to the liver, where they mature into merozoites.
▪Merozoitesenter red blood cells (RBCs), multiply, and cause RBC rupture.
oMosquito Stage(Definitive Host):
▪When a mosquito bites an infected human, it ingests gametocytes, which
develop into sporozoites in the mosquito’s gut and salivary glands.

10. Pathogenesis
oDestruction of RBCs
leads to anemia and
splenomegaly.
oCyclical fever and chills
(paroxysms) due to
synchronized rupture of
RBCs.
oSevere complications
like cerebral malaria and
multi-organ failure
(especially with P.
falciparum).

11. Amoebiasis
•Causative Agent: Entamoeba histolytica.
•Life Cycle:
oIngestionof cysts from contaminated food or water.
oCysts transform into trophozoites in the intestines, where they invade
the intestinal wall and form ulcers.
oSome trophozoites encyst and are passed out in feces, completing the
cycle.

12. Pathogenesis
•Ulceration and tissue
damage in the intestines
cause abdominal pain,
diarrhea, and dysentery
(bloody stools).
•Invasive forms can lead
to extraintestinal
abscesses, particularly
liver abscesses.

13. Giardiasis
•Causative Agent: Giardia lamblia.
•Life Cycle:
oIngestionof cysts from contaminated water or food.
oIn the small intestine, the cysts release trophozoites, which
attach to the intestinal wall and cause malabsorption.
oCysts are passed in feces, allowing further transmission.

14. Pathogenesis
•Leads to
malabsorption,
diarrhea, and
abdominal cramps.
•Often presents as a
chronic or
intermittent
gastrointestinal
disorder.

15. Laboratory Diagnosis and
Treatment of Protozoan
Infections

16. Laboratory Diagnosis
•Microscopy:
oExamination of stool samples for cysts or trophozoites (e.g., for amoebiasis
and giardiasis).
oBlood smears (thin and thick) for detecting Plasmodiumparasites in malaria.
•Serology and PCR:
oSerological tests for antibodies (e.g., for toxoplasmosis).
oPCR can detect specific DNA sequences of protozoan pathogens for precise
diagnosis.
•Antigen Detection:
oRapid diagnostic tests (RDTs) are used to detect Plasmodiumantigens in
malaria.

17. Treatment

18. Malaria
oChloroquine: For P. vivax
and P. ovaleinfections.
oArtemisinin-based
combination therapies
(ACTs): Effective for P.
falciparumand resistant
strains.
oPrimaquine: Targets liver
stages to prevent relapses
(for P. vivaxand P. ovale).
Artemisia annua

19. Amoebiasis
oMetronidazole: Effective against Entamoeba histolytica.
oDiloxanide furoate: Used for asymptomatic carriers to eliminate
cysts.

20. Giardiasis
•Metronidazoleor Tinidazole: First-line treatments for Giardia
lambliainfections.

21. Other Protozoan
Infections
oTrypanosomiasis: Treated with
specific antitrypanosomal
drugs (e.g., Suramin,
Melarsoprolfor African sleeping
sickness).
oToxoplasmosis: Treated with a
combination of pyrimethamine
and sulfadiazine, especially in
immunocompromised patients.

22. Prevention and Control
•Hygiene: Handwashing, boiling water, and proper sanitation to prevent
protozoan infections like amoebiasis and giardiasis.
•Vector Control: Mosquito control (e.g., insecticide-treated nets, indoor
spraying) is crucial for preventing malaria.
•Vaccination: Malaria vaccines (such as RTS,S) are being implemented in
endemic regions.
•Prophylaxis: Antimalarial drugs for travelers to endemic areas.