Schistosoma leiperi Le Roux, 1955 from a Bushbuck in Uganda

Abstract

Schistosoma leiperi was first described by Le Roux (1955, Trans. R. Soc. trop. Med. Hyg. 49: 293-294), who noted that the adult worms, recovered from 21 species of herbivore, were rather small, but the eggs were large, resembling those of S. spindale, measuring 240 ,m x 45 ,m to 300 ,um x 60 ium. The type host of S. leiperi, as noted by Le Roux is the African antelope, the sitatunga (Tragelaphus spekei selousi) and the type locality is Mazubuka, Northern Rhodesia (=Zambia). It became later apparent that earlier reports of S. spindale in Africa probably referred to S. leiperi. In a checklist of definitive hosts exhibiting evidence of the genus Schistosoma acquired naturally in Africa, Pitchford (1977, J. Helminth. 51: 229-252) listed those of S. leiperi as follows: cattle in Zambia, East Caprivi and Tanzania; horse and sheep in Zambia; goat in Tanzania; African buffalo (Syncerus caffer) in Zambia and several species of antelopes in Zambia, Botswana and East Caprivi. It should be noted that the reports from Tanzania are from the southern region, close to Zambia. Pitchford (1976, J. Helminth. 50: 111-123) believed that cattle and the African buffalo are poor hosts for S. leiperi; that sheep and goats have hard, dry pellets and are not water-loving animals (presumably compared with species of the genus Kobus and Tragelaphus spekei), and thus may not be suitable hosts in nature, and that antelopes seem to be the best and the natural hosts. He earlier (1974, Rhod. Vet. J. 4: 57-61), reported eggs of S. leiperi in the feces of antelopes in the Chobe National Park, Botswana, namely the puku (Kobus vardoni), lechwe (K. leche), waterbuck (K. ellipsiprymnus) and reedbuck (Redunca arundinum). One pseudo-infection was reported in man in northern Zambia (Buckley, 1946, J. Helminth. 21: 111-174). The present paper reports on S. leiperi adult worms recovered from the liver of a bushbuck (Tragelaphus scriptus) in Uganda. The adult male worm measures 7.5 mm, and the female 9.5 mm. The in utero eggs measure 257.5 ,m x 45.5 ,m to 272.5 Am x 58.8 ,m. The worms and the eggs conform in morphology with that of specimens of S. leiperi from the mesenteric venules of a lechwe in Mazubuka, Zambia, the type locality of this schistosome species, given to the senior author by the late Dr. P. L. Le Roux of the London School of Hygiene and Tropical Medicine. The present report extends the geographical distribution of S. leiperi further north in Africa than previously known, and refutes Pitchford's (1976, J. Helminth. 50: 111-123) view of the restricted distribution of this southern African schistosome species. He stated that this species is limited to the region from Chobe game reserve in Botswana, through eastern Caprivi to Zambia, and also including the extreme western comer of Zimbabwe through to northern Zambia and southern Tanzania. We disagree with his statements in the conclusions and abstract that the restricted distribution of S. leiperi is due to the restricted distribution of the main definitive hosts, the lechwe (Kobus leche) and puku (K. vardoni); the poor host susceptibility of cattle and possibly Syncerus caffer, and the likelihood of most other game being unable to maintain the parasite indefinitely outside the confines of lechwe and puku distribution in southern Africa. He showed by maps the geographical distribution of some common game, other species of the genus Kobus, for example K. ellipsiprymnus and K. defassa, and this distribution extends further north, east and west than Zambia and the rest of the area of S. leiperi. As to the snail intermediate hosts, Le Roux (1955, Trans. R. Soc. trop. Med. Hyg. 49: 293294) reported that mice were exposed to cercariae from several naturally infected Bulinus africanus and adult S. leiperi were subsequently recovered. Moreover, Southgate et al. (1981, Z. Parasitkde 66: 63-81) found that snails of the Bulinus africanus group (B. africanus, B. globosus, B. hightoni and B. nasutus) were among those susceptible to isolates of S. leiperi from both Botswana and Zambia. The exposed snails included those from within, and those from outside the known area of distribution of S. leiperi. Among the susceptible snails from outside the