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Cryptosporidium is a parasite of the human gastrointestinal tract and has a worldwide distribution. We developed a sensitive and reproducible enzyme immunoassay for detection of serum IgG or IgM to Cryptosporidium. For IgG, 13 of 15 patients with cryptosporidiosis and 26 of 26 patients with cryptosporidiosis and AIDS were positive, whereas 57 of 60 presumably uninfected individuals were negative. All three IgG-positive presumably uninfected individuals had been potentially exposed. Sensitivity and specificity of this assay was 95%. Patients without AIDS showed an early rise and fall of IgM and later elevation of IgG; some patients with AIDS produced IgM, and all produced IgG. Sera from 9 (20.9%) of 44 Ecuadorian children with diarrhea were positive for both IgM and IgG antibodies; 106 sera from persons with other parasitic illnesses showed a normal distribution for IgG antibody. These ELISA data show that patients without and with AIDS have serum antibody response to Cryptosporidium and suggest that exposure to or infection with Cryptosporidium is common.

Cryptosporidiosis, a zoonosis caused by Cryptosporidium species, is a newly recognized coccidial protozoan infection causing severe protracted watery diarrhea in humans. In August 1981, the first case of cryptosporidiosis in a homosexual man with acquired immune deficiency syndrome (AIDS) was reported; diagnosis was determined by intestinal biopsy. It is necessary to adopt a simple laboratory diagnostic procedure to screen large numbers of suspected cases. A three-step stool examination was developed to demonstrate Cryptosporidium oocysts and the diagnostic and infective stages of the infection in 10 homosexual men with AIDS. This is a less invasive, less costly, and more sensitive test than intestinal biopsy and has been designed to prevent confusion caused by yeast cells that are frequently present in stool, leading to a false diagnosis. The examination consists of preliminary differential determination by iodine wet mount, definitive identification by modified Kinyoun acid-fast staining, and a more effective method of concentrating oocysts, by Sheather's sugar cover-slip flotation method.

Note from Dr. Merle A. Sande ? Diarrhea is one of the most common and most exasperating conditions complicating human immunodeficiency virus (HIV) infection. Two relatively newly recognized protozoa, Cryptosporidium sp. and Isospora belli, have emerged as common pathogens in HIV-infected patients; to date, Cryptosporidia! infections have been especially resistant to treatment. Drs. Rosemary Soave and Warren D. Johnson have both made significant contributions to our understanding of infections caused by these pathogens. In this AIDS Commentary they approach the diseases from the clinician's perspective by describing clinical presentations, differential diagnoses, diagnostic tests, and what, if anything, can be done to treat them.