SUSCEPTIBILITY OF SCHISTOSOMA JAPONICUM OF DIFFERENT DEVELOPMENTAL STAGES TO PRAZIQUANTEL

The susceptibility of Schistosoma japonicum of different developmental stages to praziquantel has been studied by several methods. The results showed that praziquantel was more effective against 3-h old schistosomule (d 0) and 28-day old to 42-day old adult worms (d 28 to d 42), but had no effect on 3-day old to 21-day old schistosomules (d 3 to d 21). Since praziquantel could be excreted and secreted from the skin of mouse after administration, the drug exhibited a prophylactic effect when it was given to the host before infection. The susceptibility of 12-h old to 48-h old schistosomules to praziquantel was much lower than that of 3-h old schistosomule. This difference may be ascribed to varied immuno-reaction on the worm surface within 2 days after infection. Besides, d-21 worms lodging in rabbits with higher specific antibody level could be killed by praziquantel.