Proliferative epithelial lesions of the urinary bladder in cynomolgus monkeys (Macaca fascicularis) infected with Schistosoma intercalatum.

Five cynomolgus monkeys (Macaca fascicularis) were infected with Schistosoma intercalatum, a helminth that is morphologically similar to Schistosoma haematobium. Infections were readily established and remained active until the monkeys were sacrificed 21 to 84 weeks after exposure. Although the schistosomes were located predominantly in mesenteric and hepatic portal venules, schistosome eggs were found in the bladders of 3 monkeys. Nodules of atypical epithelial cells interpreted as superficially infiltrating undifferentiated bladder carcinomas were found in one monkey 23 weeks after infection. These sessile tumors differ strikingly from the well-differentiated, papillary transitional cell tumors previously reported from several species of experimental animals infected with S. haematobium. The tumors are also dissimilar to the squamous cell bladder tumors associated with S. haematobium infection in man but may nonetheless be useful for investigations of schistosomal bladder cancer.