Effects of benzimidazole anthelmintics on the survival and migratory behavior of Toxocara canis larvae in the mouse.

Nine benzimidazole anthelmintics-thiabendazole, mebendazole, fenbendazole, cambendazole, flubendazole, albendazole, parbendazole, oxibendazole, and oxfendazole--were tested for their larvicidal effects and capabilities to inhibit migration of larval Toxocara canis in mice. The drugs were administered in medicated diets containing 0.1% (w/w) of the pure compounds (130 to 160 mg/kg each day), starting 24 hours after oral inoculation with 500 infective eggs. Groups of mice were continued on medicated diets until day 8 after inoculation when half of the mice were killed; the other half were placed on normal diet and killed on day 22 after inoculation. Control groups were killed at the same times and the numbers of larvae recovered in pepsin digests of the liver, lungs, and carcass, as well as in press preparations of brain, were recorded. In mice killed after 8 days of treatment, all of the compounds except thiabendazole produced significant arrest of the migrating larvae in the liver. In mice given the normal diet for 2 weeks after termination of treatment with the different drugs, the percentages of larvae that remained in the liver showed wide variation. Significant larvicidal effects were observed only in mice treated with albendazole, oxfendazole, and cambendazole.