Page 69 - Medical Parasitology_ A Textbook ( PDFDrive )

62 7 Coccidia

Fig. 7.5 Cryptosporidium
parvum oocysts

Pathogenesis and Clinical Features

Clinical manifestations of cryptosporidiosis depend on the immune status of the
host. Infection in immunocompetent persons may be asymptomatic or cause self-
limiting watery diarrhoea, nausea, abdominal cramping and weight loss. It can also
cause traveller’s diarrhoea, as well as water borne outbreaks. In immunocompro-
mised hosts and AIDS patients, diarrhoea can be profuse, chronic and persistent
causing severe fluid and electrolyte depletion and weight loss. The small intestine
may show villous atrophy, crypt hyperplasia and lymphocyte infiltration. Incubation
period is 2–14 days.

Diagnosis

1. Microscopic examination
Diagnosis is made by the detection of oocysts in faeces. Stool concentration
methods facilitate detection of oocysts. The oocysts are small and difficult to
visualize in unstained wet preparations. Modified acid fast Ziehl Neelsen stain-
ing is the method of choice and oocysts appear as pink spheres. Definitive iden-
tification can be made by indirect immunofluorescence microscopy using specific
antibody.
2. Molecular diagnosis
PCR on stool sample.
3. Antigen detection test
Enzyme immunoassays for detection of Cryptosporidium antigens in stool
samples.
4. Biopsy
Histopathological examination of biopsied small bowel specimen.