Interactions betweenSchistosoma intercalatum(Zaire strain) andS. mansoni

Abstract

AbstractSchistosoma mansoniandS. intercalatum, two schistosomes from different evolutionary lineages, are parasitic in humans and therefore able to co-infect the same host where they occur sympatrically in Africa. Previous studies of mating interactions between these species in mice, using the Lower Guinea strain ofS. intercalatum, have demonstrated the competitive dominance ofS. mansonioverS. intercalatumin terms of pairing ability, which is potentially an important mechanism restricting the distribution ofS. intercalatumin Africa. The study presented here examines the mating interactions in mice betweenS. mansoniand the Zaire (Democratic Republic of Congo) strain ofS. intercalatum, which differs from the Lower Guinea strain in many biological characteristics. Analysis of the data showed a preponderance of intraspecific pairs over interspecific, demonstrating a specific mate preference system for both species. Mating competition between these species and the ability of males of both species to effect a change of mate by pulling paired females away from their partners was indicated. Comparisons are made between the competitive mating abilities of both strains ofS. intercalatumrelative to those ofS. mansoni, with the data suggesting thatS. mansoniis competitively dominant toS. intercalatum(Zaire) in sequential infections but to a lesser extent than forS. intercalatum(Lower Guinea). Additional factors which may contribute to the confinement ofS. intercalatum(Zaire) to the Democratic Republic of Congo are discussed.