Variation in the larval recovery of Toxocara canis from the murine brain: implications for behavioural studies

The migratory pathway of Toxocara canis larvae was determined by infecting mice with a low, medium or high dose of embryonated T. canis eggs and determining numbers of larvae present in the brain, liver, lungs, kidneys and muscle on days 5, 14 and 26 post infection. Variation was seen in the numbers of larvae recorded in the organs of mice which had received the same number of eggs and were at the same stage of infection. This variation was particularly marked in the brain indicating that, for the purposes of behavioural studies, the actual numbers of larvae found in the brain rather than the number assumed from the dose would have to be taken into account when analysing the behaviour of infected mice.