Abstract
Cryptosporidium andersoni and Cryptosporidium muris infections have been found in the mice and/or cattle. The oocysts of C. andersoni and C. muris have been sporadically detected in human feces, but the infectious capacity and features have been unknown, because of the scarcity of reports involving human infections. To assess the infectivity and the clinical and pathological features of C. andersoni and C. muris in primates, an experimental infectious study was conducted using cynomolgus monkeys. The monkeys were orally inoculated with oocysts of two different C. andersoni Kawatabi types and C. muris RN-66 under normal and immunosuppressive conditions. The feces of the monkeys were monitored for about 40 days after the administration of oocysts using the flotation method, but no shedding oocysts were observed under either both normal or immunosuppressive conditions. Gross and histopathological examinations were performed on the immunosuppressive monkeys, but these revealed no evidence of Cryptosporidium infections, even though the monkeys were subjected to immunosuppressive conditions. It is hypothesized that C. andersoni and C. muris pose little danger of infection in primates even under immunosuppressive conditions.