The host-parasite relationship in both the intermediate snail host and the definitive vertebrate host is complex and many questions remain to be answered regarding host-parasite interactions. Susceptibility and resistance of Biomphalaria snails to Schistosoma mansoni miracidia occur in different degrees using Random Amplified polymorphic DNA (RAPD). This work was carried out to determine what genes or gene products are specifically responsible for susceptibility and/or resistance of the intermediate host to infection. Biomphalaria pfeifferi infection by S. mansoni was monitored weekly up to ten weeks after exposure to miracidia. High molecular weight DNA was extracted from suspected and non- suspected snails within the same species of B. pfeifferi. RAPD was undertaken to distinguish between the susceptible and non- susceptible snails. OPA11 primer was used to amplify the extracted DNA by the polymerase chain reaction (PCR) followed by gel electrophoresis. The results showed polymorphisms with OPA11 primer. Polymorphic bands observed only in the suspected strain. OPA-11, amplification of DNA identified a range between 300-600 bp strain-specific fragments in the suspected snails. The genetic diversity of B. pfeifferi snails were demonstrated by different alleles in suspected and non-suspected snails. The understanding of the genetic polymorphisms associated to resistance may contribute to the future identification of genomic sequences related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni and to the development of new strategies for the control of schistosomiasis.

Keywords: Schistosomiasis, Biomphalaria pfeifferi, susceptibility, RAPD.