Influence of parasite strain on chemotherapy of murine infections with Schistosoma mansoni.

The effectiveness of chemotherapy in human schistosomiasis varies from one area to another, and limited data from experimentally infected animals suggest inherent differences in the susceptibility of certain parasites to drugs. In the present study, groups of mice infected with each of several geographic strains of Schistosoma mansoni were treated with one of four selected drugs and parasiticidal effects were compared.Responses to treatment were generally similar among strains except in two trials involving a Puerto Rican strain that was unusually sensitive to hycanthone and relatively resistant to stibophen.Selective killing of male worms occurred consistently with lucanthone and hycanthone treatment. The use of portal perfusion rather than dissection to recover surviving worms appears to have been instrumental in allowing the relatively resistant female worms to be found, namely in the liver.The results of this study indicate that strain differences in susceptibility to drugs do occur in S. mansoni, and apparent refractoriness or unusual sensitivity encountered in the field should be evaluated in the laboratory.