Failure of targeted mass treatment to control schistosomiasis

An attempt was made to control schistosomiasis mansoni with mass treatment of all subjects excreting more than 100 eggs/g of faeces. No other means of control to reduce transmission were used. A very low dosage of hycanthone (0.75 mg/kg) appeared insufficient to achieve a satisfactory reduction of the worm load. A higher dosage (1.5 mg/kg) resulted in a significant reduction of the egg output. However, reappearance of eggs, probably indicating reinfection, was very rapid. One year after treatment the egg counts were at about two-thirds of the original level again.