SUITABILITY OF TROPICAL FISH FOODS FOR LABORATORY CULTURE OF FOUR SPECIES OF FRESHWATER SNAILS ACTING AS INTERMEDIATE HOSTS FOR ECONOMICALLY IMPORTANT HELMINTH PARASITES IN SOUTH AFRICA

SUMMARY

Four different kinds of tropical fish food from Tetra Werke, West Germany, as well as a mixture of two of these, were evaluated as possible nutrients for the laboratory culture and maintenance of four freshwater snail species of economic importance in South Africa. These included the intermediate hosts of both the local human schistosome species, i.e. Biomphalaria pfeifferi (Krauss) (intestinal bilharzia) and Bulinus africanus (Krauss) (urinary bilharzia). The other two species, Bulinus tropicus (Krauss) and Lymnaea natalensis Krauss are both of veterinary importance acting as inter mediate hosts of the trematode parasites causing paramphistomiasis and fascioliasis respectively. Age-specific life-tables were compiled for five cohorts of each snail species, each fed on one of the five nutrients and the values of the relevant population parameters compared to each other. The results showed that Tetra Min Baby Food ‘E’ for egg-layers was superior to all the other nutrients tested in respect of juvenile and adult survival, onset of egg production and fecundity. It can therefore be highly recommended for the laboratory breeding and maintenance of all the fresh water snail species included in this investigation.