High infectivity of Toxocara cati larvae from muscles of experimentally infected rats

The organ distribution of Toxocara cati larvae in albino rats Rattus norvegicus (n = 6/group) experimentally inoculated with 1000 embryonated eggs was examined 1, 2, 3, 7, 30, 90, and 180 days post inoculation (dpi), and the infectivity of recovered larvae was evaluated by bioassay in mice. The intestines, liver, lungs, muscles (carcass) and other organs (heart, brain, spleen, kidneys and genital organs) were digested for larval recovery. Larvae were recovered from all rats, with the mean number of recovered larvae ranging from 13.3 at 1 dpi to 135.6 at 90 dpi. Most of the larvae recovered were detected in the intestines (56.3%) and liver (43.8%) at 1 dpi; liver (21.6%) and lungs (69.6%) at 2 dpi; muscles (45.9%) and lungs (36.9%) at 3 dpi. Subsequently, most of larvae were recovered from muscles at 7 dpi (92.5%), 30 dpi (97.8%), 90 dpi (99.4%) and 180 dpi (99.1%). In the mouse bioassay, 43.8% of 90-day-old larvae and 43.0% of 180-day-old larvae recovered from rats established in mice. The present study demonstrated that T. cati larvae persist predominantly in rat muscles and nearly half of them retain infective for at least half a year. The results indicate that R. norvegicus may be a suitable paratenic host of T. cati under natural conditions.