Effect of praziquantel on Schistosoma japonicum cercariae

When Schistosomo joponicum cercariae were exposed to praziquantel in dechlorinated water, the body and tail muscles contracted incoordinately, and the anterior part of the tail was separated from the posterior pole of hind-body region of cercariae. In normal saline or glucose solution (5 %) the tail loss of cercariae caused by praziquantel was remarkably inhibited. No effect of EDTA, 5-hydroxytryptamine, atropine and dipterex on tail loss induced by praziquantel was observed. Methylene blue and NaF tests indicated that the surface of cercariae was damaged with enhancement of permeability of the larva. All these alternations recovered to normal after transferring the above mentioned tail-less cercariae to normal saline or Hanks’ balanced salt solutions. The conclusion was also supported by scanning electron microscopic observation.