GENETIC-STRUCTURE AND PARASITE COMPATIBILITY OF BULINUS-GLOBOSUS (GASTROPODA, PLANORBIDAE) FROM 2 AREAS OF DIFFERENT ENDEMICITY OF SCHISTOSOMA-HAEMATOBIUM IN ZIMBABWE

A comparative study of the genetic structure of 8 populations of B. gl obosus from 2 areas of different endemicity of Schistosoma haematobium was done. Five populations were from Chiweshe (high endemicity) and t hree were from Plumtree (low endemicity). Genetic structure, as determ ined by allozyme genetics, revealed high levels of genetic variability in Chiweshe populations (H-o = 0.12-0.26) and low levels in Plumtree (H-o = 0.06-0.12). Populations from Chiweshe were genetically heteroge neous whereas in Plumtree the populations were uniform. There were sig nificant deviations from Hardy-Weinberg proportions at different loci in Chiweshe populations. The observed excess of homozygotes was probab ly caused by partial selfing. The compatibility studies showed variati on between allopatric and sympatric combinations of snails and parasit es, and the Plumtree parasite had a significant influence on the compa tibility parameters, This strain had a positive correlation (P<0.01) o f its infection rate with allele frequency of Est-2(100) and a negativ e correlation(P<0.05) with allele Idh(100).