Biological control of the snail hosts of schistosomiasis in areas of low transmission: the example of the Caribbean area

The biological control of schistosomiasis has already proven its efficiency in several habitats in the Caribbean area. Two main types of biological co ntrol agents, either trematode parasites or competitor snails have been stu died and tested against the snail hosts of schistosomiasis in this region. The first one, Ribeiroia guadeloupensis, a trematode sterilizing Biomphalar ia glabrata was successfully tested in a Guadeloupean pond housing a natura l population of B. glabrata. The second agent involves several species of c ompetitor snails belonging to the Ampullariidae (Pomacea glauca, Marisa cor nuarietis) and Thiaridae (Tarebia granifera, Melanoides tuberculata) famili es. Ampullarid snails were tested with success in several West Indian islan ds such as Guadeloupe. Thiarid snails have also proven their efficiency but also their limits in several types of habitats in Guadeloupe, Martinique, St. Lucia and Venezuela. Competitor snails have also proven to be useful in preventing the recolonization by the snail hosts after molluscicide treatm ents. The case of the rivers of the littoral central part of Venezuela is p articularly relevant to this issue. The island of Martinique also constitut es a good example of the importance of competitor snails in a post-transmis sion phase of schistosomiasis control. This island is a well-developed coun try where schistosomiasis transmission was interrupted in the 1970s. Howeve r, the reactivation of some transmission sites was observed in the 1980s. T he introduction of M. tuberculata into these sites resulted in the interrup tion of transmission and the near total disappearance of the snail hosts. P resently, the thiarid snails have colonized the whole Martinican hydrograph ic system and maintain dense populations preventing an eventual recolonizat ion by the planorbid snails and thus are maintaining a sustainable control. (C) 2000 Elsevier Science B.V. All rights reserved.