Comparison of the Infectivity and Pathogenicity of six species of African Schistosomes and their Hybrids 1. Mice and Hamsters

In a previous hybridisation study it was found that six African schistosome species could be distinguished by their egg morphology and snail infectivity, and that their hybrids were also distinct. The present paper describes complementary studies on the behaviour of the same parasites in rodents. Statistically significant differences were found between the behaviour of each pair of sibling species with regard to some of the following characters: percentage of worm recovery; rate of egg production; percentage distribution of eggs in the liver, small and large intestines. This is further evidence that these forms are distinct species. There were also significant differences between the hybrids and their “parental” species, and between the behaviour of the parasites in mice and hamsters. The distinct behaviour of the hybrids raises the possibility of genetically modifying these parasites in order to attenuate their pathogenicity with a view to using hybrids as heterologous immunising agents.