Specific cross-protection between Schistosoma bovis and S. haematobium induced by highly irradiated infections in mice.

Significant levels of resistance against Schistosoma haematobium challenge were developed by mice exposed to highly irradiated (20 krad) cercariae of the homologous species (46-53%) or of the closely related species, S. bovis (34-56%) but not of S. mansoni (-6-28%). This ability to cross-protect reflects the phylogenetic relationships between these species; S. mansoni and S. bovis, as well as S. mansoni and S. haematobium, failed to cross-protect. The cross-protection demonstrated between S. bovis and S. haematobium in mice was non-reciprocal.