Inhibition of Egg Production of Schistosoma mansoni in Mice Treated with Nicarbazin

The reproduction of Schistosoma mansoni, in experimentally infected mice, was suppressed by treatment with nicarbazin (complex of 4,4'-dinitrocarbanilide and 2-hydroxy-4,6-dimethylpyrimidine). When fed to mice at 0.2% in the diet, nicarbazin completely suppressed the deposition of schistosome eggs, but did not kill the worms. The worms were not killed even when the drug was fed at 0.3% for 18 weeks, or at 1.0% for 2 weeks (the highest dosage tested). Inhibition of egg production was observed as early as 2 days after the onset of nicarbazin treatment. The inhibitory effect was reversible, and clinical relapse occurred when the drug was withdrawn. No effect was observed when nicarbazin was administered by gavage as a series of 10 doses at 250 mg/kg.