Treatment Options for the Eradication of Intestinal Protozoa

Michael JG Farthing


Nat Clin Pract Gastroenterol Hepatol. 2006;3(8) 

In This Article

Isospora Belli

I. belli is a small-bowel protozoon. Infection with I. belli is relatively uncommon in the developed world, but its role as an opportunistic agent in patients with AIDS has confirmed its importance as a human pathogen. The infectious form of the parasite is the oocyst, which releases invasive sporozoites that enable the parasite to take up an intracellular location in the intestinal epithelial cell. Like cryptosporidiosis, isosporiasis leads to self-limited diarrhea in the immunocompetent patient, and chronic diarrhea in the immunocompromised patient.

Treatment with oral co-trimoxazole (sulfamethoxazole 800 mg and trimethoprim 160 mg) four times daily for 1 week ameliorates the diarrhea, and eliminates the parasite in a proportion of cases.[48] Unfortunately, this is followed by relapse in 50% of patients, usually within 12 weeks. Re-treatment is usually effective, although prophylactic co-trimoxazole might be necessary.[49,50] Pyrimethamine–sulphonamide combinations (such as Fansidar®, Roche, which contains pryimethamine 25 mg and sulfadoxine 500 mg) are also effective.[50] There is little information on the regimen of choice for those patients who are intolerant to sulphonamide. Ciprofloxacin is also effective ( Table 2 ).


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