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

Protoscolices of Echinococcus granulosus were incubated in vitro with praziquantel (PZ), albendazole (ABZ), or a combination of both (PZ + ABZ). PZ and ABZ displayed slower protoscolicidal activity when applied separately than when used in combination. Despite the low PZ + ABZ concentrations used, protoscolex 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 sucker concavity, (b tegumental contraction of the soma region, (c) the formation of digitiform tegumental extensions, (d) destruction of the tegument, and (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 treatment 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 region of the germinal layer, (e) vacuolation of the cyton cytoplasm; and (f) the formation of abundant autophagosomes, which finally led to loss of the integrity of the germinal layer.