Hybridization between different strains of Schistosoma intercalatum Fisher, 1934 from Cameroun and Zaïre.

The offspring from hybridization experiments between Schistosoma intercalatum, Cameroun (intermediate host Bulinus forskalii) and S. intercalatum, Zaïre (intermediate host B. globosus) was investigated. Reciprocal crosses between the two forms were performed. F1- and F2-miracidia developed in both parental intermediate hosts. The minimum prepatent period was 24 days at 26 degrees C, an average of the prepatent periods for the two parental strains. The total cercariae production per 100 exposed snails decreased sharply from 121 000 for the parental strain from Cameroun in B. forskalii to 21 000 and 5000 from the F1- and F2-generations, respectively. The figures for S. intercalatum, Zaïre in B. globosus were 270 000, 134 000 and 3000, respectively. F1- and F2-generations were from the cross between males from Cameroun and females from Zaïre. The viablility of the four cross-breeding experiments carried out (two with each combinations of the parental strains) were low. It was only possible to obtain F2-cercariae. No miracidia were hatched from eggs produced by the F2-gerneation.