Preliminary observations on the 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 Schistosoma 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. It is suggested that the presence of either or both lechwe schistosomes prevented the development of the human parasites and in addition, 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 was thought to be 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.