| invasion of the nile valley in egypt by a hybrid of biomphalaria glabrata and biomphalaria alexandrina, snail vectors of schistosoma mansoni. | two years (1996-1997) of systematic survey showed that a hybrid of biomphalaria glabrata and biomphalaria alexandrina has invaded the irrigation and drainage systems in the nile delta and the valley nor the of el-menya. however, the infestation of water courses by and the population density of this snail were variable in various localities. the infestation rate ranged between 7.1% in el-fayoum governorate and 52.6% in el-dakahliya governorate and the snail density from 2 snails/site to 69.7 snai ... | 1998 | 9707685 |