Genetic structure and parasite compatibility of Bulinus globosus (Gastropoda: Planorbidae) from two areas of different endemicity of Schistosoma haematobium in Zimbabwe.

A comparative study of the genetic structure of 8 populations of B.globosus from 2 areas of different endemicity of Schistosoma haematobium was done. Five populations were from Chiweshe (high endemicity) and three were from Plumtree (low endemicity). Genetic structure, as determined by allozyme genetics, revealed high levels of genetic variability in Chiweshe populations (Ho = 0.12-0.26) and low levels in Plumtree (Ho = 0.06-0.12). Populations from Chiweshe were genetically heterogeneous whereas in Plumtree the populations were uniform. There were significant deviations from Hardy-Weinberg proportions at different loci in Chiweshe populations. The observed excess of homozygotes was probably caused by partial selfing. The compatibility studies showed variation between allopatric and sympatric combinations of snails and parasites, and the Plumtree parasite had a significant influence on the compatibility parameters. This strain had a positive correlation (P < 0.01) of its infection rate with allele frequency of Est-2(100) and a negative correlation (P < 0.05) with allele Idh100.