RELATIONSHIP BETWEEN THE PATHOGENICITY OF SCHISTOSOMA-MANSONI IN MICEAND THE SUSCEPTIBILITY OF THE VECTOR MOLLUSK .3. MORTALITY BODY-WEIGHT AND VISCERA WEIGHTS

The relationship between the development of hepatomegaly, splenomegaly , body weight and mortality rate and the degree of susceptibility of B iomphalaria glabrata and B. tenagophila at which infective cercariae d eveloped was studied. The study utilized Swiss mice, SPF, as definitiv e hosts and populations of snails genetically selected for character s usceptibility as intermediate hosts. Low body weight and smaller visce ra were observed in infected mice with cercariae originating from snai ls that showed a high degree of susceptibility. The higher susceptibil ity of molluscs infected with S. mansoni corresponded to a lower survi val of the infected mice. These results lead to the conclusion that th e higher degree of adaptation of the parasite to its intermediate host s, evidenced by the high indexes of susceptibility, leads to different behaviour on the part of this parasite in ifs definitive host.