MOLECULAR GENETIC VARIATIONS AMONG ADJACENT POPULATIONS OF FRESHWATER SNAILS THAT ARE TARGET AND NON-TARGET TO SCHISTOSOMA INFECTION

Schistosomiasis is one of the most important public health problems in many developing countries and it is the prime health problem in Egypt. Since the infection of Biomphalaria alexandrina and Biomphalaria glabrata snails by the parasitic trematode Schistosoma mctrisoni depends on the complex interactions by both parasite and snail genes , genetic conttal is one of the successful means for control of schistosomiasis . A number of laboratory derived stocks of B. alexandrina and B. glabrata have been used to sort out this complex genetic relationship . In the present study genetic variations between adjacent snail populations., target ( B. alexandrina and p. glabrata) and non-target ( Lymnaea truncatulaLand Physa acuta ) to Schistosoma infection was investigated using DNA amplification by random amplified polymorphic DNA - polymerase chain reaction ( KAPD-PCR ) at different developmental stages . The amplification products were analyzed on 6 % polyacrylamide gel/and siamed with silver. Eighteen primers were selected, since they have previously *been useful to detect polymorphism among B. alexandrina and / or B. glabrata .The results showed polymorphism with 3 primers; OPA-01, OPA-02 and OPA-18 . Stable reproducible RAPD markers with utilized primers OPA-01, OPA-02 of B. alexandrina and B. glabrata showed highly genetic variation among different snail types and ages . £uife©r»mere- Hybrid snails obtained genetic polymorphism at one strain ( susceptible or resistant ) among different developmental stages by primers OPA-01 , OPA-02 and OPA-18 .u|e results resolved the problem of susceptibility / age association of ttttermediate: snail host. The~^^sen^-&tudy-showed-that-by. ^comparing iargets (both susceptible and resistant strains ) withiiar^target^ecies to Schistosoma infectiojii^mere is a genetic polymorphism^ specific for resistant snails .and contirmed in non-target species obtained by primer OPA-01 /"Since, the resistant character is heritable like susceptibility"; it would be beneficial to select actively resistant snails and mass culture -them to increase the proportion of alleles for insusceptibility as a possible mean for biological control of schistosomiasis in natural population.