Effect of thiabendazole on the migration of Toxocara canis larvae in the mouse

The effects of thiabendazole on the survival and migration of Toxocara canis larvae in mice were studied. Although thiabendazole had a negligible larvicidal effect, it produced marked inhibition of the migration of the larvae in tissues. Larvae were arrested in the liver after oral inoculation and in the lungs after intravenous inoculation. Observations indicated that the drug may have a reversible, as well as a progressive, time-related metabolic effect on the larvae. Significant inhibition of migration required administration of the drug in medicated feed at a concentration of 0.25% or more. Periodic oral administration of a thiabendazole suspension was ineffective in inhibiting larval migration. It was concluded that the immobilizing effect of the drug on the larvae of T. canis may account for the clinical improvement observed after treatment with thiabendazole in cases of visceral larva migrans, the prevention of prenatal or mammary transmission of infection in dogs, and the suppression of tissue damage by nematode larvae in general.