RESULTS OF EXPOSING MICE TO SCHISTOSOMIAS IS BY IMMERSION IN NATURAL WATER* BY

PESIGAN et al. (1958) reported immers ing mice in natural waters in the Phi l ippines, "as a check upon the direct cercarial (Schistosoma j ponicum) counts " which were done on the same waters. The results conf i rmed " the direct count in a h ighly satisfying manner, " and " the per iodic i ty of cercarial densit ies in the f ield " was " thus establ ished f rom tWO independent sources." One of the object ions to cercarial counts on Transvaal waters is that there are always two (S. haematobium and S. mattheei), and in many areas three species (the two former plus S. mansoni) of mammal ian schistosomes present which, because the cercariae cannot be dif ferentiated satisfactori ly would make the results somewhat meaningless. I t was decided, therefore, to immerse mice in an i rr igat ion canal, as part of an invest igat ion to deter-mine the role of wi ld rodents in the epidemio logy of bilharziasis. More informat ion than was or iginal ly p lanned for was obviously for thcoming and the mice immers ions were con-t inued for 2 years and have recent ly been extended to cover as many water types as possible, with the object of conf i rming the present findings. MATERIALS AND METHO