Effect of praziquantel and albendazole on ultrastructure of protoscolex of Echinococcus granulosus

When protoscoleces of Echinococcus granulosus, maintained in 20% calf serum-RPMI 1640 were exposed to praziquantel 1 microgram/ml for 1-48 h, severe damages to the ultrastructure of protoscoleces were observed. The main lesions of the tegument included indistinct of the matrix, vacuolization and peeling, while vacuolization of perinuclear cytoplasma in tegumental cells, focus lysis in muscle bundles, and destruction in collection ducts and flame cells were also seen. The results suggest that the damages to the tegument, collection ducts and flame cells may interfere with the nutrition and defence functions of protoscoleces, and destroy the osmoregulatory system, which may be the major causes of death in protoscoleces during treatment with praziquantel. When protoscoleces were exposed to albendazole 20 micrograms/ml for 24-72 h, no apparent damage to the tegument was detected, except that some network-like structures appeared in the cytoplasma of tegument and parenchyma cells.