A comparison of the susceptibility to niridazole of Schistosoma mansoni and S. intercalatum in mice

Abstract

Further investigation on the susceptibility of different species of schistosomes to niridazole has been carried out in mice. S. intercalatum was found to be much less susceptible than S. mansoni. This is the first record of experimental chemotherapy of S. intercalatum but is consistent with the clinical observations of Brumpt et al. (1968) . S. intercalatum was markedly more resistant than S. mattheei was in the previous study and thus susceptibility to niridazole can differ markedly between different sibling species of schistosomes as it does between different geographical strains of S. mansoni ( Taylor and Nelson, 1971 ). A shift of drug-affected parasites from the portal system to the lungs was found to occur both with S. mansoni and S. intercalatum but was more pronounced with S. mansoni, especially in infections of longer duration and it was commoner in treated than in untreated mice. The higher propensity of S. mansoni to show a “lung shift”, attributed to the higher fecundity of S. mansoni compared to S. intercalatum with consequent higher levels of liver damage, was not responsible for the higher worm kill in the S. mansoni infections, since this disparity in worm kill was maintained in infections treated at a relatively early stage, when few “lung shifts” occurred.