Bulinus guernei (Mollusca: Gastropoda) of West Africa: taxonomic status and role as host for schistosomes

The basommatophoran freshwater snail Bulinus guernei (Dautzenberg, 1890; type-locality in Sénégal, West Africa) has been treated as a full species, subspecies of B. truncatus (Audouin) or synonym of the latter. Improved knowledge of B. guernei is desirable as this snail has been implicated as a host in Senegambia for Schistosoma haematobium , the blood parasite causing human urinary schistosomiasis (bilharzia). Snail samples from 18 localities were studied: from The Gambia (3), Sénégal (9), Mali (1), Mauritania (1) and, to represent B. truncatus , Morocco (2) and Egypt (2), Characters investigated were morphological (shell, radula and certain soft parts), biochemical (egg proteins and enzymes from body tissue extracts) and cytological (chromosome number). Multivariate analyses (principal components analysis and canonical variate analysis) were performed on data from the shell and radula. Comparison with the holotype shell of B. guernei confirmed that this taxon is represented by recently collected specimens from Senegambia. Variation in the total material examined did not appear to warrant making any taxonomic subdivision, and thus the taxa guernei and truncatus appear to be conspecific. Further sampling is desirable, particularly to determine the possible value of variation in the enzyme HBDH in defining infraspecific units. Experimental infection showed some individual B. guernei to be a compatible host for 5. haematobium (isolate from Sudan; transmitted locally by B. truncatus ). Snails identified as B. guernei apparently have little importance in the transmission of S. haematobium in the Sénégal river basin at present, but such snails could constitute a health hazard if a compatible form of the parasite were to be introduced into this region of Africa.