Page 65 - Medical Parasitology_ A Textbook ( PDFDrive )

58 7 Coccidia

Prevention and Control

1. Individuals at risk, particularly pregnant women, children and immunocompro-
mised persons should avoid contact with cat and its faeces
2. Proper cooking of meat
3. Proper washing of hands, washing of vegetables and fruits before eating
4. Screening for T. gondii antibody on all blood donors
5. Pet cats should be fed with canned or cooked food
6. Cats’ faeces should be discarded daily
Currently, there is no effective vaccine available for humans.

Cystoisospora belli (Formerly Known as Isospora belli)

Distribution

It is more common in tropical and subtropical countries. Cystoisospora belli is a
coccidian parasite which causes diarrhoea in humans.

Habitat

In human, the parasites reside in the epithelial cells of the small intestine.

Morphology

Oocysts of C. belli are elongated , ovoid and measure 25 μm × 15 μm. Each oocyst
is surrounded by a thin smooth cyst wall (Fig. 7.3). Immature oocyst seen in the
faeces of patients contains 2 sporoblasts. On maturation, the sporoblasts become
sporocysts. Each sporocyst contains 4 sporozoites. The sporulated oocyst is the
infective stage of the parasite.

Life Cycle (Fig. 7.4)

(1) Unsporulated oocysts are passed out in faeces of infected person. (2) Humans
acquire infection by ingesting the mature oocysts containing sporozoites via con-
taminated food or water. (3) The mature oocyst ruptures in the intestine releasing
8 sporozoites which invade the intestinal epithelial cells. (4) In the epithelium,
the sporozoites transform into trophozoites, which multiply asexually (schizog-
ony) to produce merozoites. The merozoites invade adjacent epithelial cells to
repeat the asexual cycle. (5) Some of the trophozoites undergo sexual cycle