ABSTRACT
Laboratory bred hamsters, weight 125-185 g each, were examined in this study and classified into three groups. In the first group, 15 hamsters were exposed simultaneously to 100 cercariae of S. Mansoni and 100 cercariae of S. haematobium. Experimentally infected hamsters and their controls were scarified at 7 and 10 weeks postinfection. In the second group, 20 hamsters were exposed each to 100 cercariae of S. mansoni for 7 weeks then superinfected with 100 cercariae of S. haematobium and scarified 25 days later. Their controls were 20 hamsters exposed to 100 cercariae of S. mansoni. In the third group, 20 hamsters exposed each to 100 cercariae of S. Haematobium for 10 weeks, then superinfected each with 100 cercariae of S. Mansoni and scarified 21 days post challenge infection. Their controls infected with 100 cercariae of S. Haematobium. In mixed infection with Schistosoma mansoni and S. haematobium in hamsters, either simultaneously or after the full maturation of an initial infection with either schistosome species, a high level of acquired resistance was observed. The degree of immunity was magnified by the significant reduction in the number of eggs per gram tissue and hatchability of mature eggs. Some disturbance was also observed in the oogram pattern