In schistosomiasis, the host/parasite interaction remains not completely understood. Many questions related to the susceptibility of snails to infection by respective trematode still remain unanswered. The control of schistosomiasis requires a good understanding of the host/parasite association. In this work, the susceptibility/resistance to Schistosoma mansoni
infection within Biomphalaria alexandrina
snails were studied starting one month post infection and continuing thereafter weekly up to 10 weeks after miracidia exposure. Genetic variations between susceptible and resistant strains to Schistosoma infection within B. alexandrina
snails using random amplified polymorphic DNA analysis technique were also carried out. The results showed that 39.8% of the examined field snails were resistant, while 60.2% of these snails showed high infection rates. In the resistant genotype snails, OPA-02 primer produced a major low molecular weight marker 430 bp. Among the two snail strains there were interpopulational variations, while the individual specimens from the same snail strain, either susceptible or resistant, record semi-identical genetic bands. Also, the resistant character was ascendant in contrast to a decline in the susceptibility of snails from one generation to the next.