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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #362164

Research Project: Detection and Control of Foodborne Parasites for Food Safety

Location: Animal Parasitic Diseases Laboratory

Title: Cystoisospora belli infections in humans - the past 100 years

item Dubey, Jitender
item ALMERIA, S - Food And Drug Administration(FDA)

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2019
Publication Date: 8/9/2019
Citation: Dubey, J.P., Almeria, S. 2019. Cystoisospora belli infections in humans - the past 100 years. Parasitology. 146(12):1490-1527.

Interpretive Summary: Toxoplasma, Neospora, Sarcocystis, and Cystoisopora are related coccidian parasites that cause severe illness in livestock and companion animals. Oocyst is the environmentally resistant stage passed in feces of the definitive hosts. While Toxoplasma and Neospora have wide host range, Cystoisospora are more host specific. Cystoisospora belli is a pathogenic coccidian of humans. Its life cycle is not fully known. Many cases of C. belli infections in gallbladder of humans have been misdiagnosed as C. belli. In the present paper, the authors provide a comprehensive review of C. belli including its epidemiology and diagnosis. This will provide a useful tool for pathologists and others interested in infectious diseases, and parasitologists in general.

Technical Abstract: Cystoisospora (Isospora) belli is a coccidian parasite of humans, with a direct fecal-oral transmission cycle. It is globally distributed, but infections have been found mainly in tropical and subtropical areas of the world. After the discovery of human immunodeficiency virus (HIV) in 1980’s, many cases of C. belli infections were reported in patients with HIV, and in immunocompetent patients that were given immunosuppressive therapy for organ transplants or those treated for tumors worldwide. The prevalence of C. belli infection is significantly higher in HIV infected patients compared to HIV negative patients in different geographical areas; immunocompromised people can experience more severe disease with extreme diarrhea, anorexia, and weight loss. Unsporulated or partially sporulated oocysts of C. belli are excreted in feces. When sporulated oocysts in contaminated water or food are ingested, asexual and sexual stages of C. belli are confined to the epithelium of intestines, bile ducts and gallbladder. Monozoic tissue cysts (thought to be encysted sporozoites) are present in extra-intestinal organs (lamina propria of small and large intestine, lymph nodes, spleen, and liver) of immunosuppressed humans but a paratenic/transport host has not been demonstrated. Cystoisospora belli infections can be persistent, lasting for months, and relapses are common; the mechanism of relapse is unknown. Recently, the endogenous stages of C. belli were re-examined and attention was drawn to some cases of misidentification of non-protozoal structures in the gallbladder of patients as C. belli. Trimethoprim sulfamethoxazole (TMP/SMX or cotrimoxazole) is the drug most commonly used for treating cystoisosporiasis, but some people are allergic to sulfonamidesides and relapses with clinical disease are frequent in immunosuppressed patients. Here, we review all aspects of the biology of C. belli, including morphology, endogenous stages, prevalence, epidemiology, symptoms, diagnosis and control.