Susceptibility to chemotherapeutic agents of strains of Schistosoma mansoni isolated from treated and untreated patients.

Seven strains of Schistosoma mansoni were isolated from the feces of patients. Three of the patients had been unsuccessfully treated with hycanthone or oxamniquine; the remaining four had not been given any specific treatment. Mice infected with these strains were treated 45 days later with niridazole (50 or 100 mg/kg body weight per day for 5 days, per os), hycanthone (single dose of 80 or 160 mg/kg, intramuscularly), or oxamniquine (single dose of 50 or 100 mg/kg, per os). Significant differences in the strains' responses to the schistosomicidal agents used were observed. Oogram changes in mice treated with the same drug ranged from 10--100%, and percentages of dead worms from 0--45. Such differences seemed to be dependent on the strain's specific characters rather than t their having been exposed to schistosomicidal drugs.