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Cryptosporidium (part 1 of 2) Page 3 of 13 �. 6-IZ immunocompetent individuais with an incubation period of 2 to 10 days. Some of the associated symptoms include anorexia, weight loss, dehydration, abdominal cramping, and vomiting (i.e., headache, aching muscles, fever). On average, the symptoms last for 12 days with rare instances lasting as long as 4 weeks. In patients with depressed immunity due to disease (i.e., HIV infection, chemotherapy, etc.) or congenitally depressed immunity (e.g., hypogammaglobuinemia), similar symptoms are observed. The duration, however, can be much longer and some individuals never clear Cryptosporidium from their systems. In cases where suppression of the immune system cannot be reversed (e.g., by stopping immune suppressant therapy) these symptoms may persist untii death. P�evalence Methods for determining the prevalence of infection with Cryptosporidium have been undergoing rapid change. Interpretation of the results is not without controversy. Nevertheless, human cryptosporidiosis has been identified on all six continents.3,5,14,55 Among people with gastrointestinal complaints, the prevalence of Cryptosporidium oocysts in patient's stools range from 1 to 4 percent in developed countries and up to 16 percent in developing countries. Specific North American surveys indicated similar levels. For example, in British Columbia, Canada, the prevalence was 0.6 percent, in Massachusetts it was 2.8 percent, and in South Carolina 4.3 percent. In England, Cryptosporidium is the fourth most common cause of diarrhea.53 In the immunocompromised population, particularly those infected with HIV, the prevalence is higher. Estimates of the percent of HIV-infected patients with cryptosporidiosis range from 1 to 2 percent up to 10 percent. Of AIDS patients with diarrhea, Cryptosporidium has been identified as an agent in 10 to 15 percent of the cases.6,55 Immunity Exposure to Cryptosporidium does not necessarily lead to clinical disease. There is some indication that prior exposure results in protective immunity from cryptosporidiosis, though the duration of this immunity is unknown. Serological testing has found Cryptosporidium-associated antibodies in 25 to 35 percent of people tested in North America, indicative of a moderate level of Cryptosporidium exposure. With the more widespread use of cocktail therapy, the health of AIDS patients has been improving. It is unclear what impact this will have on their susceptibility to cryptosporidiosis. Treatment Over 90 antimicrobial agents have been used against Cryptosporidium in animals and man, but no specific effective treatment for cryptosporidiosis has yet been found. While this is not of great importance among immunocompetent individuals (except for days of work lost) where the infection is self-limiting, it is vital for immunosuppressed patients. Several clinical trials are currently evaluating some promising agents including letrazuril, azithromycin, paramomycin, and a hyperimmune bovine colostral immunoglobulin. The last mentioned agent shows great promise; it is being evaluated at San Francisco General Hospital.ai http://sfwater.org/printContent.cfin/C ID/446/ 10/19/2004