Toxocara canis infection in the paratenic host: a study on the chemosusceptibility of the somatic larvae in mice.

ABSTRACT

A research on formulation and dosage strategies of anthelmintics have been conducted in mice experimentally infected with eggs of Toxocara canis. Multidose treatments commenced at days 2, 14, 81, 87 and 123 postinfection. Results indicated no detectable difference in the chemosusceptibility of the migrating early infection larvae and the resting hypobiotic chronic infection larvae. Application of medicated dry food (pellets) may be a simple way of improving efficacy of treatment compared to oral drenching. The larvicidal potential of fenbendazole (FBZ), albendazole (ABZ), flubendazole (FUBZ), oxibendazole (OBZ) and ivermectin was assessed. Reductions of 84.2 to 99.7 or 88.8 to 100% of group mean larval counts were recorded after 20-30-day courses of feeding pellets containing FBZ at 6 g kg-1 or ABZ at 1.6 g kg-1 food, respectively. Efficacies of 57.8 to 88.2 or 81.1 to 32.0% were achieved by 20-day courses of feeding pellets medicated with FUBZ and OBZ at 1.6 g kg-1 or 6.0 g kg-1 food, respectively. Ivermectin at various dosing regimens showed only moderate larvicidal potential. Efficacy rates were not closely correlated with the amount of drug taken by the animals. The blood-brain barrier is permeable for the anthelmintics tested, and the brain of mice does not provide a site promoting survival of larvae.