The purpose of this study is to develop a field-applicable assay for the detection of the liver fluke, Schistosoma mansoni. Rhesus monkeys experimentally infected with S. mansoni are the source of infection-related sera. This material will be used to identify schistosome-specific antigens. Once identified, these antigens will be used to develop specific diagnostic tests. In the previous 2 years 5 rhesus monkeys were infected with 300 S. mansoni cercariae. Blood and stool samples were collected bimonthly from the infected animals. At week 60 the animals were treated with Droncit and samples continued to be collected following treatment. Ultimately the animals were necropsied. The presence or absence of adult schistosomes was determined and quantified, if present. Some animals remained parasitemic although treated with a curative dose of Droncit. Immunological analysis of these serum samples for antibodies to S. mansoni showed that some animals were successfully trea ted. Studies during the past year focused on determining if antibody status reflects successful treatment. Preliminary evidence showed that antibody levels correlated to successful treatment in some monkeys. Related studies in humans have also been continuing. Human studies have focused on determining the risk of S. mansoni infection in persons traveling to Malawi and Ethiopia. Efforts are being made to differentiate treatment success or failure by monitoring changes in specific antibody responses to S. mansoni after treatment. Immunological analysis of these samples are currently in progress.