Hybrids between Schistosoma haematobium and S. mattheei and their identification by isoelectric focusing of enzymes.

Some biological features of F1 hybrids between South African strains of Schistosoma haematobium and S. mattheei are described and compared with those of both parental species. The distinctive patterns of the G6PD and PGM isoenzymes, resolved by isoelectric focusing, of both species and of the hybrid are defined and the results of enzyme analyses of parasites isolated from human infections in the Transvaal are reported. These show that hybridization does occur naturally in man and that the shape of the eggs produced is not necessarily a guide to the genetic constitution of the enclosed larvae. The experimentally produced F1 hybrids exhibit heterosis in their increased infectivity to both snails and hamsters, in their more rapid growth and earlier maturation and in the increased daily egg production per female worm when compared with both of the parental species. The possible practical implications of this are discussed.