The migration of larval Toxocara canis in mice. II. Post-intestinal migration in primary infections.

Following oral infection of NIH mice with Toxocara canis embryonated eggs the L2 pass the visceral phase of migration during te first week of infection. Larvae reach the liver and lungs and peak in number in these organs 2 and 3 days after infection, respectively. Larvae are then dispersed throughout the body and enter the myotropic--neurotropic phase by the 7th day of infection. Larvae injected directly into the brain are capable of migrating into the viscera and musculature. Considerable pathology occurs due to larval migrations, especially through the liver and lungs, and both acute and chronic disease are recorded. Studies of infections extending over a year show that the number of recoverable larvae declines gradually with periods of stable populations. On Days 3, 4 and 5 after infection, larvae were demonstrable in the faeces of infected mice. Prenatal infection was observed in a third of the offspring of mice infected the same day as conception.