Early treatment of schistosomal infection with praziquantel in mice.

The first single dose of praziquantel (Pra) was given ig to mice on the day of infection with Schistosoma japonicum cercariae, or 7 d, 14 d, and 21 d after infection. Afterwards, the same dose of Pra was given once at 1-3 wk intervals for 2-3 times. The prophylactic effect was estimated by the reduction of average number of total and female worms, the number of mice without female worm, and the gross change of the liver. When mice were treated with Pra 300-500 mg.kg-1 initially on d 21 after infection and repeated once every 1-2 wk for 2-3 times, almost all the female worms lodged in the host were killed, showing that either the host was protected from the infection of schistosomes or a great decrease in the intensity of the infection resulted.