Scanning electron microscope observation on tegumental alteration of Schistosoma japonicum induced by levo- and dextro-praziquantel.

When mice infected with Schistosoma japonicum for 35 d were treated ig with levo-praziquantel (L-Pra) 150 mg.kg-1 or dextro-praziquantel (D-Pra) 150-600 mg.kg-1, the alterations of the worm tegument were examined by scanning electron microscopy within 1-24 h after administration. The results showed that L-Pra induced apparent and extensive damage on the worm surface including severe swelling, fusion, erosion and peeling of tegument accompanied by attachment of the host leukocytes. The discoid-like sensory structures usually showed swelling, deformation and collapse. With D-Pra 150 mg.kg-1, only slight damage of tegument was seen. When the dose was increased to 600 mg.kg-1, the damage of worm tegument was similar to that induced by L-Pra 150 mg.kg-1 but the intensity of the damage was slighter as compared to that induced by L-Pra. The results suggested that the actions of the 2 optical enantiomers of praziquantel were different in quantity but not in quality.