In vitro effect of praziquantel and albendazole combination therapy on thelarval stage of Echinococcus granulosus

Protoscolices of Echinococcus granulosus were incubated in vitro with prazi quantel (PZ), albendazole (ABZ), or a combination of both (PZ + ABZ). PZ an d ABZ displayed slower protoscolicidal activity when applied separately tha n when used in combination. Despite the low PZ + ABZ concentrations used, p rotoscolex viability dropped rapidly (within 15 days). At this time, cysts did not develop following their inoculation into mice. The ultrastructural changes induced in the protoscolices by PZ + ABZ were (a) the loss of sucke r concavity, (b) tegumental contraction of the soma region, (c) the formati on of digitiform tegumental extensions, (d) destruction of the tegument, an d (e) the degeneration of parenchyma cells as reflected by the presence of numerous lamellar bodies. The PZ + ABZ treatment was effective only against small cysts, which had collapsed at 10 days postinoculation (p.i.). This t reatment caused the following alterations: (a) loss of cyst turgidity at 6 days p.i.; (b) separation of the laminated and germinal layers; (c) loss of microtriches; (d) the appearance of numerous lipid droplets in the inner r egion of the germinal layer; (e) vacuolation of the cyton cytoplasm; and (f ) the formation of abundant autophagosomes, which finally led to loss of th e integrity of the germinal layer.