Cystoisospora belli infection (cystoisosporiasis)
Cystoisospora belli (formerly known as Isospora belli) infection causes a self-limiting gastroenteritis in patients who are immunocompetent – antimicrobial therapy is not usually indicated. Infection can cause chronic diarrhoea in people with advanced HIV infection, and rarely in other patients with significant immune compromise (eg solid organ or bone marrow transplant recipients, haematological malignancy, tumour necrosis factor [TNF] inhibitor recipients, human T-lymphotropic virus type 1 infection).
For treatment of children with diarrhoea caused by C. belli, seek expert advice.
The mainstay of therapy for diarrhoea caused by C. belli is rehydration.
To treat diarrhoea caused by C. belli in adults who are immunocompetent with symptoms not improving after 2 weeks, use:
trimethoprim+sulfamethoxazole 160+800 mg orally, 12-hourly for 7 days. For dosage adjustment in adults with kidney impairment, see trimethoprim+sulfamethoxazole dosage adjustment. trimethoprim + sulfamethoxazole trimethoprim+sulfamethoxazole trimethoprim+sulfamethoxazole
To treat diarrhoea caused by C. belli in adults with immune compromise, useLa Hoz, 2019:
trimethoprim+sulfamethoxazole 160+800 mg orally or intravenously, 12-hourly for 10 days1. For dosage adjustment in adults with kidney impairment, see trimethoprim+sulfamethoxazole dosage adjustment. trimethoprim + sulfamethoxazole trimethoprim+sulfamethoxazole trimethoprim+sulfamethoxazole
Trimethoprim+sulfamethoxazole is the drug of choice to treat infectious diarrhoea caused by C. belli. For patients who report trimethoprim+sulfamethoxazole hypersensitivity, verify their allergy. In some patients it may be appropriate to directly delabel their allergy by taking an extensive allergy history (see Trimethoprim+sulfamethoxazole hypersensitivity in adults); in these patients trimethoprim+sulfamethoxazole should be used.
For patients with a verified allergy to trimethoprim+sulfamethoxazole, seek expert advice from an infectious diseases physician or clinical microbiologist. For patients who have had a nonsevere (immediate or delayed) or a severe immediate hypersensitivity reaction, desensitisation may be considered with expert advice. There are limited data to support the use of ciprofloxacin or nitazoxanide.
Maintenance therapy (secondary prophylaxis) in patients with immune compromise may be required; seek expert advice.
For patients with a new diagnosis of HIV, see Cystoisospora (Isospora) belli gastroenteritis in adults with HIV infection for information on starting antiretroviral therapy.