Studies are being performed on three parasitic parasites: schistosomes, Giardia, and Cryptosporidium. Nine more isolates of Giardia have been axenized and their DNA, surface antigens, and biologic behavior are being studied. Although still incomplete, these studies, thus far, confirm the large heterogeneity noted among the previously studied 15 isolates. Monoclonal antibodies to a 170,000 Kd major surface antigen of WB and WB-like isolates were produced. These monoclonal antibodies are specific for the WB-type of isolate and are cytotoxic to these organisms. In order to study biological importance and differences between isolates, a model infection of Giardia in jirds was established. Isolates differ in ability to invoke self cure, immunity and protection to challenge with heterologous isolates. An ELISA assay to measure antibody to Crytosporidium antibodies to oocysts was developed. IgG and/or IgM antibody responses in non-AIDS patients were practically always detected. IgG antibodies were found commonly in AIDS patients. In additon, IgG antibodies to Cryptosporidium were detected frequently in patients with other parasitic diseases suggesting that infection is common. A study evaluating the use of ultrasonography in the diagnosis of Symmers' fibrosis in on-going in Khartoum, Sudan.