RESUMEN
We report here the ultrastructural changes in the third advanced larval stage (AL3) of Gnathostoma binucleatum Almeyda-Artigas, 1991, induced by in vitro treatment with albendazole and the metabolite albendazole sulfoxide. During the whole period of the experiment, the controls remained active and vital throughout the 108-h exposure period. The primary site of action of both drugs appears to be the mitochondria and myofibrils of the polymyarian musculature. Degenerative changes in the secretory portion of the esophagus and somatic musculature were clearly observed. These degenerative changes, leading to complete muscular and glandular necrosis, were interpreted as the consequence of drug-induced blockade of metabolic energy production. Cuticular disruption had also been observed in the experimental groups. We observed a dramatic reduction in the number of mitochondria and muscle fibers, as well as the formation of large autophagic vesicles as result of an irreversible degenerative phenomenon. The passive cutaneous elimination of larvae in human infections is probably a consequence of parasite immobility, due to the effects of this antihelminthic drug.