Occurrence of clinical signs by infection with Baylisascaris potosis, the roundworm of kinkajous (Potos flavus), in mice, rats, and rabbit were studied, and the migration behavior of larvae in mice were compared with that of Baylisascaris transfuga, the roundworm of bears (Ursus spp.). Three groups of 8 mice, 3 groups of 6 rats, and 3 groups of 2 rabbits were inoculated with either 10, 100, or 1,000 B. potosis eggs. The other 8 mice were inoculated with 1,000 B. transfuga eggs. Animals were monitored for the occurrence of clinical signs until 60 days postinoculation (DPI). The carcass, viscera, brain, and eyes of each of 6 mice inoculated with 1,000 eggs of B. potosis or B. transfuga at 60 DPI were removed individually, and the number of larvae was counted. One mouse inoculated with 100 B. potosis eggs showed rolling at 27 DPI, and 1 larva was found in the medulla oblongata of this mouse. No clinical signs were observed in the other mice or in the rats and rabbits. A mean of 387.2 larvae was recovered from mice inoculated with 1,000 B. potosis eggs, and a mean of 422.0 larvae from mice inoculated with 1,000 B. transfuga eggs. The highest number of larvae was recovered from the carcasses for both B. potosis and B. transfuga. In the viscera, higher numbers of B. transfuga larvae (mean 131.8) were seen than B. potosis larvae (mean 33.1). In the brain, only 1 larva was detected in 1/6 mice inoculated with 1,000 B. potosis eggs, whereas a mean of 21 larvae was detected in mice inoculated with 1,000 B. transfuga eggs. A few larvae (range 0–1) were detected in the eyes of both mice inoculated with B. potosis or B. transfuga eggs. The result indicated that B. potosis larvae do not show a higher tendency to migrate into the brain of mice than B. transfuga larvae. However, 1 mouse inoculated with 100 eggs had 1 larva in the central nervous system and showed a serious neurological sign. This result may underline a potential risk of B. potosis to cause neural larva migrans in humans.

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