Scanning electron microscopic observation of protoscolices of Echinococcus granulosus damaged by praziquantel and albendazole

When protoscolices of Echinococcus granulosus maintained in 20% calf serum-RPMI 1640 were exposed to praziquantel at 0.05-1 ug/ml for l-48 h, their appearance was transformed from an invaginated to an evaginated form, followed by fusion and dropping of microtriches from the tegument of the rostellum and suckers. Loss of the rostellar hooks, deformation of the suckers and formation of numerous vesicles in the tegument were also observed. The tegumental damage to the posterior part of the body consisted of swelling, fusing and wrinkling of the tegumental ridges. Praziquantel-induced tegumental damage to the invaginated protoscolices was less than that for the evaginated protoscolices. When the protoscolices were exposed to albendazole at 20 ug/ml for 24-72 h, only the evaginated protoscolices were strongly contracted and showed severe damage to the tegument.