Variations in innate resistance to experimental Toxocara canis infection in two strains of mice

Strain-, sex- and age-based resistance of mice to Toxocara canis infection was demonstrated. Infection doses of similar numbers resulted in significantly (P less than 0.05) greater worm establishment in CD1 mice than in NIH mice, as well as a greater heterogeneity of responses between individuals. Male mice had significantly (P less than 0.05) fewer larvae in the brain and more larvae in the liver than female mice, when mice of greater than or equal to 3 months old were used. Appreciably more larvae were retained in the liver of male CD1 mice than in NIH mice. Orchidectomized mice had higher levels of brain infestation and a lower larval recovery from the liver compared with intact male mice. Infections in young mice of both strains showed more diversity in establishment and migration pattern between individuals than in older mice. Despite these differences in distribution of larvae and in the numbers recovered from experimental infections, the acute and chronic clinical signs observed in the two strains were very similar.