RELATIONSHIP BETWEEN THE PATHOGENICITY OF SCHISTOSOMA-MANSONI IN MICEAND THE SUSCEPTIBILITY OF THE VECTOR MOLLUSK .2. NUMBER OF EGGS IN THE FECES AND NUMBER AND SIZE OF GRANULOMAS IN THE VISCERAS

The influence of the susceptibility of the vector snails of S. mansoni on the development of die pathogenicity of die worm to the host was s tudied. Off-spring of snails Biomphalaria glabrata and Biomphalaria te nagophila were used, selected with regard to the susceptibility to S. mansoni of the strains BH and SJ trait, respectively. Parenteral, F1, F2, F3 and F4 generation cercariae were used for the infection of Swis s mice, which were killed eight weeks after infection. The number of e ggs in the feces and the number of granulomas in the liver, spleen and intestines were counted. The size of the granulomatous reactions was evaluated. The results led to the conclusion that greater susceptibili ty of B. tenagophila was associated with a larger egg production in th e feces and a higher density of granulomas in the liver. There is a cl ear inverse relationship between the area of hepatic, spleenic and int estinal granulomas and the rate of infection of the snails which serve d as intermediate hosts for the S. mansoni.