Distribution and habitats of Gyraulus costulatus, potential snail intermediate host of intestinal flukes of the family Echinostomatidae in South Africa

Abstract

This paper focuses on the geographical distribution and habitats of Gyraulus costulatus as reflected by the 736 localities currently on record in the database of the National Freshwater Snail Collection (NFSC) of South Africa. Although a wide variety of water body types was reported for this species, the largest number of samples were yielded by rivers, streams and dams which were described as perennial with predominantly fresh and clear water. A mainly stony substrate and the presence of aquatic vegetation were recorded for the majority of localities at the time of survey. An integrated decision tree constructed from the data indicated that altitude, temperature and water bodies were the most important of the factors investigated that determined the documented geographical distribution of this species in South Africa. This was supported by the effect size values calculated separately for each factor. Since the early eighties of the previous century, surveys to monitor and update the geographical distribution of freshwater snails and snail-borne parasitic diseases have been relegated to a low priority issue and this is a matter of concern. It is recommended that the exact role of G. costulatus in the epidemiology of economically important helminth parasites in South Africa should be investigated.