Cystoisosporiasis

Cystoisosporiasis, formerly known as isosporiasis, is an intestinal infection caused by the protozoan parasite Cystoisospora belli.

Infection occurs through ingestion of food or water contaminated with sporulated oocysts. Sporozoites released in the small intestine invade epithelial cells, causing inflammation and malabsorption. The incubation period ranges from several days to over 2 weeks.

The prevalence of cystoisosporiasis in patients with HIV is estimated at 2.5% globally.

Risk factors include immunocompromising conditions, such as HIV/acquired immunodeficiency, and residence in or travel to regions with higher endemicity, such as sub-Saharan Africa.

The disease typically presents with watery, non-bloody diarrhea diarrhea, abdominal pain, anorexia, nausea, vomiting, low-grade fever, and weight loss. In immunocompromised patients, the infection can become chronic and severe, causing severe dehydration, electrolyte abnormalities, such as hypokalemia, and malabsorption. Acalculous cholecystitis and reactive arthritis have also been reported.

In immunocompromised patients, the disease may become chronic and recurrent, often requiring long-term suppressive therapy. Dissemination can involve lymph nodes, liver, and spleen.