Efficacy of fenbendazole against migrating Ascaris suum larvae in pigs.

Twenty-four weanling crossbred pigs were inoculated with 10,000 embryonated Ascaris suum eggs. The infection was aborted in 1 group (n = 8 pigs) with fenbendazole (3 mg/kg of body weight) given on postinfection days 2, 3, and 4 and in a 2nd group (n = 8 pigs) given fenbendazole at the same rate on postinfection days 6, 7, and 8; a 3rd group (n = 8 pigs) was not treated with fenbendazole. All pigs were necropsied at 24 days after they were inoculated. Fenbendazole was 99% effective against A suum larvae in the 2 treated groups. Early treated pigs had significantly higher daily weight gains (P less than 0.05) and were 22% more efficient in feed conversion than were nontreated pigs. Lung weights increased linearly with length of exposure to migrating A suum larvae (P less than 0.10). Liver weights were greater in treated pigs than in non-treated pigs (P less than 0.01). A negative correlation existed between number of liver lesions and liver weights of all pigs (P less than 0.05).