Cryptosporidiosis and isosporiasis in patients with AIDS.

Cryptosporidium and Isospora belli are coccidian protozoan parasites that were long recognized as pathogens of animals. They were brought to the attention of the medical community by the advent of AIDS. These parasites are associated with persistent, devastating enteritis in patients with AIDS and self-limited diarrheal illness in the immunocompetent host. Cryptosporidiosis appears to be more common than isosporiasis in both patients with AIDS and those who are not immunosuppressed. Clinically, cryptosporidiosis is indistinguishable from isosporiasis. Watery, noninflammatory diarrhea, abdominal cramping pain, and weight loss are the characteristic symptoms. Diagnosis is made by identification of the acid-fast organisms in stained fecal specimens. There is no known effective therapy for cryptosporidiosis, whereas patients with isosporiasis respond promptly to treatment with trimethoprim-sulfamethoxazole. Patients with AIDS and isosporiasis have a high frequency of recurrent infection and therefore should be maintained on suppressive therapy. Much more needs to be learned about these two fascinating and unique parasites to be able to intervene successfully in the management of infected patients with AIDS.