IDENTIFICATION OF SCHISTOSOME-INFECTED SNAILS BY DETECTING SCHISTOSOMAL ANTIGENS AND DNA-SEQUENCES

Cercarial shedding tests do not provide species identification of the schistosomes concerned and cannot detect prepatent schistosomal infect ions. We have demonstrated that both immunodetection by ELISA of schis tosomal antigens in snail hemolymph, and dot hybridization of snail ex tracts by a DNA probe representing highly repeated sequences, proved s uitable for detecting infected snails during prepatency as well -as pa tency. A group-specific monoclonal antibody was found to be suitable f or detecting Schistosoma mansoni infection in Biomphalaria sp., but no t for positive identification of S. haematobium in Bulinus sp. Compara tive evaluation of the diagnostic qualities, and technical aspects and cost of these tests, point to the superiority of the immunodetection approach for large scale detection of snails prepatently infected with S. mansoni. This approach is potentially useful for providing extende d information on schistosome-snail epidemiology that may facilitate ra pid evaluation of the danger of post-control reinfection, and help mak e decisions on the time and place of supplementary control measures. I n this context the potential usefulness of the immunodetection or DNA probing approach for facilitating catalytic model representation of sc histosome-snail epidemiology warrants further evaluation. Specific ide ntification of S. haematobium in Bulinus by either of these approaches may be possible depending on the development of suitable antibodies o r DNA probes.