Page 77 - Medical Parasitology_ A Textbook ( PDFDrive )

70 7 Coccidia

3. Granular form measures 10–60 μm in diameter and is seen in old cultures.
4. Cystic form is generally smaller in size and has a thick multilayered cyst wall.

Life Cycle
Thick-walled cysts are passed out in the stool of infected human. Humans acquire
infection via ingestion of contaminated water and food. In the intestine of human,
the cyst ruptures and trophozoite undergoes asexual reproduction and the parasite
may exist in vacuolar form or amoeboid form. The amoeboid form develops into the
thick-walled cyst and is excreted in the faeces of the host.
The parasite completes its life cycle in a single host.

Pathogenesis and Clinical Features
Recent studies have shown the parasite to be associated with diarrhoea. Other clini-
cal manifestations include abdominal pain, abdominal distension, nausea and vom-
iting. Pathogenicity has been shown to be subtype related. Many carriers are
asymptomatic.

Diagnosis
1. Microscopic examination
Demonstration of the organism in stool smear.
2. Culture
In vitro culture in Jones medium.
3. Molecular diagnosis
PCR on stool samples.

Treatment
If diarrhoea is present, metronidazole (250–750 mg orally 3 times/day for 10 days)
can be given. Treatment should be considered when no other infectious agent can be
identified.

Prevention and Control
1. Proper faecal disposal
2. Personal hygiene
3. Boiling of drinking water
4. Filtration of drinking water
5. Wash fruits and vegetables with clean water before eating
6. Health education