Larval Migratory Behavior of Long-term-maintained Toxocara canis Embryonated Eggs in Mice

Larval migratory behavior of Toxocara canis embryonated eggs that had been maintained in 2% formalin for 14 months at 4℃ was evaluated using a larval recovery study in mice at between 1 and 469 days post infection (DPI) . Three infected mice and 2 aged-matched uninfected control mice were sacrificed daily for acid-pepsin digestion of the liver and lungs (hepatopulmonary phase) as well as the musculature and brain (myotropic-neurotropic phase). Larval recovery from the hepatopulmonary phase reached a peak at 5 DPI, not at 2 DPI; thereafter, they began to migrate to the myotropic-neurotropic phase. Statistically, larval recoveries from the hepatopulmonary and myotropic-neurotropic phases respectively showed negative and positive correlations with time (r = - 0.688, P = 0.005; r = 0. 138, P = 0.327). Altogether, although there seemed to be a delay in the migration of 14-month-cultured T. canis larvae to the hepatopulmonary phase, most of them still exhibited the myotropic-neurotropic phase, especially in the brain.