PROTOZA

Entamoeba histolytica

Overview:

● Intestinal amoeba causing tissue

invasion

● Infective stage: cyst

● Transmitted via fecal–oral route

Life cycle:

Cyst (ingested) → excystation in small

intestine → trophozoites colonize large

intestine → invade mucosa →

encystation → cyst in stool

Disease:

● Amoebiasis

Signs/Symptoms:

● Bloody diarrhea (dysentery)

● Abdominal cramps

● Liver abscess (severe)

Prevention:

● Safe drinking water

● Hand hygiene

● Sanitation

Balantidium coli

● Only ciliated protozoan infecting

humans

● Reservoir: pigs

Life cycle:

Cyst ingestion → excystation in colon →

trophozoite multiplies → encystation →

cyst passed in feces

Disease:

● Balantidiasis

Signs/Symptoms:

● Severe diarrhea (sometimes

bloody)

● Ulceration of colon

Prevention:

● Proper sanitation

● Avoid contaminated water (pig

exposure)

Giardia lamblia

Overview:

● Flagellated protozoan

● Causes malabsorption in small

intestine

Life cycle:

Cyst ingestion → excystation in

duodenum → trophozoites attach to

intestinal wall → encystation → cyst

excreted

Disease:

● Giardiasis

Signs/Symptoms:

● Greasy, foul-smelling diarrhea

● Bloating, flatulence

● Weight loss

Prevention:

● Boiled/filtered water

● Hygiene

Trichomonas vaginalis

Overview:

● Only protozoan STI listed

● NO cyst stage

Life cycle:

Trophozoite transmitted during sexual

intercourse → multiplies in urogenital

tract

Disease:

● Trichomoniasis

Signs/Symptoms:

● Frothy yellow-green discharge

● Itching, burning urination

Prevention:

● Condom use

● Treat both partners

Acanthamoeba

Overview:

● Free-living amoeba in water/soil

● Opportunistic infection

Life cycle:

Cyst/trophozoite enters via eye/skin →

infects cornea or CNS → forms cysts in

tissues

Disease:

● Keratitis

● Granulomatous amoebic

encephalitis

Symptoms:

● Eye pain, blurred vision

● Brain inflammation (rare)

Prevention:

● Contact lens hygiene

● Avoid contaminated water

Naegleria fowleri

Overview:

● Thermophilic “brain-eating

amoeba”

● Lives in warm freshwater

Life cycle:

Trophozoite enters nose → migrates via

olfactory nerve → brain invasion → rapid

tissue destruction

Disease:

● Primary amoebic

meningoencephalitis (PAM)

Symptoms:

● Severe headache, fever

● Vomiting, stiff neck

● Rapid death in severe cases

Prevention:

● Avoid water entering nose

● Clean water for nasal irrigation

Leishmania spp.

Overview:

● Intracellular parasite

(macrophages)

● Vector: sandfly

● Two forms: promastigote (vector),

amastigote (human)

Life cycle:

Sandfly injects promastigote → enters

macrophages → becomes amastigote →

multiplies → sandfly ingests parasite

Disease:

● Visceral (donovani)

● Cutaneous (tropica)

● Mucocutaneous (braziliensis)

Symptoms:

● Fever, enlarged spleen (visceral)

● Skin ulcers (cutaneous)

● Tissue destruction (mucosal)

Prevention:

● Vector control

● Protective clothing

Trypanosoma cruzi

Overview:

● Causes Chagas disease

● Vector: kissing bug

Life cycle:

Bug feces enters bite → trypomastigote

in blood → invades heart/muscle →

amastigote multiplication

Disease:

● Chagas disease

Symptoms:

● Heart enlargement

● Digestive dysfunction

Prevention:

● Housing improvement

● Vector control

Trypanosoma brucei

(gambiense/rhodesiense)

Overview:

● Causes African sleeping sickness

● Vector: tsetse fly

Life cycle:

Fly bite → bloodstream trypomastigote

→ lymph → CNS invasion

Disease:

● Sleeping sickness

Symptoms:

● Fever, lymph node swelling

● Sleep disturbances → coma

Prevention:

● Tsetse fly control

Plasmodium spp.

Overview:

● RBC parasite

● Vector: Anopheles mosquito

● Stages: sporozoite → liver →

merozoite → RBC

Life cycle:

Mosquito injects sporozoites → liver

stage → merozoites released → infect

RBC → rupture cycles → gametocytes

picked up by mosquito

Disease:

● Malaria

Symptoms:

● Cyclical fever, chills, sweating

● Anemia

● Severe cerebral malaria

(falciparum)

Prevention:

● Mosquito nets

● Antimalarial drugs