Experimentally produced resistance of Schistosoma mansoni to hycanthone.

Genetically transferred resistance to the antischistosomal drug hycanthone has been observed in several strains of Schistosoma mansoni: 1) in the progeny of worms to whose hosts hycanthone had been administered 54 to 70 days after exposure to cercariae (Type I); 2) in the progeny of worms to whose hosts hycanthone had been administered when the worms were still in an immature stage (27 to 29 days after percutaneous cercarial exposure) (Type II); and 3) in the progeny of worms from hosts that had been infected with cercariae of one sex followed by infection with the opposite sex 2 to 58 weeks later (Type III). In types I and II, drug resistance was transferred maternally. Hycanthone-resistant schistosomes were cross-resistant to antischistosomal drugs structurally related to hycanthone, such as oxamniquine and two chloro-indazole analogs of hycanthone, but not to niridazole and to another nitroheterocyclic compound.