A laboratory-based approach to biological control of snails

Development of Schistosoma mansoni in the intermediate host Biomphalaria glabrata is influenced by a number of parasite and snail genes. Understanding the genetics involved in this complex host/parasite relationship may lead to an often discussed approach of introducing resistant B. glabrata into the field as a means of biological control for the parasite. For the snail, juvenile susceptibility to the parasite is controlled by at least four genes, whereas one gene seems to be responsable for adult nonsusceptibility. Obtaining DNA from F2 progeny snails from crosses between parasite-resistant and susceptible snails, we have searched for molecular markers that show linkage to either the resistant or susceptible phenotype. Both restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) approaches have used. To date, using a variety of snail and heterologous species probes, no RFLP marker has been found that segregates with either the resistant or susceptible phenotype in F2 progeny snails. More promising results however have been found with the RAPD approach, where a 1.3 kb marker appears in nearly all resistant progeny, and a 1.1 kb marker appears in all susceptible progeny.

Genetic factors in the susceptibility of biomphalaria glabrata for different strains of schistosoma mansoni

Biomphalaria glabrata selected for genetic differences in susceptibility to infection with a Puerto Rican strain of schistosoma mansoni were exposed to a miracidia of a strain of S. mansoni from St. Lucia. The St. Lucian strain was less effective than the Puerto Rican. Results suggested that in snails susceptibility to the St. Lucian strain were determined by a single gene, with insusceptibility dominant (AU)