PRELIMINARY-OBSERVATIONS ON DISTRIBUTION, DEFINITIVE HOSTS AND POSSIBLE RELATION WITH OTHER SCHISTOSOMES, OF SCHISTOSOMA-MARGREBOWIEI, LE ROUX, 1933 AND SCHISTOSOMA-LEIPERI, LE ROUX, 1955

In attempting to define the south western limits of the distribution of S. margrebowiei and S. leiperi and investigating their apparent limited distribution in relation to their snail hosts it was found that there was little overlap in the distribution of S. margrebowiei and S. leiperi and that of the human parasites S. haematobium and S. mansoni, and no overlap with S. mattheei within the area surveyed. The presence of either or both lechwe schistosomes apparently prevented the development of the human parasites and prevented the development of S. mattheei in certain areas inhabited or surrounded by certain Kobus spp. The restricted distribution of S. margrebowiei and S. leiperi apparently was due to the restricted distribution of their main definitive hosts Kobus leche and K. vardoni; the poor host susceptibility of cat and possibly Syncerus caffer; and the likelihood of most other common game being unable to maintain the parasites indefinitely outside the confines of lechwe and puku distribution in southern Africa.