Intermediate Hosts of Schistosoma: African Biomphalaria and Bulinus

The African snails belonging to the genera Biomphalaria and Bulinus are of medical importance since they serve as intermediate hosts for human or animal schistosomiasis. In the literature authors have assigned these snails to a number of genera, e.g., Planorbis, Planorbula, Afroplanorbis, Australorbis, Segmentina, Physa, Isidora, etc., as well as Biomphalaria and Bulinus. In reference to species, however, the plethora of names given to these snails has reached a superfluous meaningless state as attested by everyone who is familiar with the synonomy. The main cause for the confusion of names has come from the fact that the shells of these freshwater snails are susceptible to alteration when subjected to different environments. They exhibit, therefore, a wide range of variation, both in size and shape. Large numbers of these ecological forms have been described as species, the description being based only on the shape or some other variable character of the shell.