infectious diseases
Cystoisosporiasis
Introduction
Cystoisosporiasis is infection with the protozoanCystoisospora belli(previously known asIsospora belli). Symptoms include watery diarrhea with gastrointestinal and systemic symptoms. Diagnosis is by detection of characteristic oocysts in stool or intestinal biopsy specimens. Treatment is usually withtrimethoprim/sulfamethoxazole. (See also Overview of Intestinal Protozoan and Microsporidia Infections .) Cystoisosporiasis is caused by obligate intracellular coccidian protozoa that infect intestinal epithelial cells. Transmission is by the fecal-oral route via food or water contaminated with feces from an infected person. Cystoisosporiasis occurs worldwide and is most common in tropical and subtropical climates. Residents and travelers to endemic areas are at risk. is similar to that of Cryptosporidiosis , except that oocysts passed in stool are not sporulated. Thus, when freshly passed in stools, the oocysts are not infective, and direct fecal-oral transmission cannot occur. The oocysts require days to weeks in the environment to sporulate and, therefore, direct person-to-person transmission is unlikely. The sporulated oocysts are ingested in contaminated food or water and excyst in the gastrointestinal tract, releasing sporozoites. The sporozoites invade the epithelial cells of the small intestine, replicate, and mature into oocysts, which are shed in stool. 