Bulinus tropicus from Central Kenya acting as a host forSchistosoma bovis

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Abstract
One hundred and twelve snails were collected from two habitats on the Mau Escarpment, Kenya and were provisionally identified asBulinus tropicus from the characteristics of their shell and soft parts, chromosome number (n=18), electrophoresis of egg protein on cellulose acetate strip and isoelectric focusing of AcP, GPI, HBDH, MDH and PGM digestive gland enzymes. Of the 55 specimens examined alive in London, 10 were infected with amphistome and schistosome larvae, 9 with amphistome larvae and the remainder were uninfected. The GPI and MDH separations of known infected smail showed two distinct areas of activity: host and parasite. Individual hamsters were exposed to schistosome cercariae emanating from each snail with a double infection (apart from one which died prematurely) and examination of the resulting adult worms showed that all were monomorphic for AcP with a band of enzyme activity at pH 6.45, characteristic ofSchistosoma bovis. Examination of eggs found in two infections proved to beS. bovis in shape and size. Exposure of laboratory-bred snails ofB. tropicus from the Mau Escarpment and other populations ofB. tropicus proved negative. Thus, it is suggested that the presence of the amphistome infection may have a suppressive effect on the immune system of the snail, thereby allowingS. bovis to develop.