The efficacy of levamisole and ivermectin against a morantel-resistant strain of Trichostrongylus colubriformis.
A controlled slaughter trial was undertaken to evaluate the efficacy of ivermectin (0.2 mg/kg) and levamisole (8 mg/kg) against a morantel-resistant field strain of Trichostrongylus colubriformis in sheep. Mean worm count reductions of greater than 99% were recorded with both anthelmintics. The apparent contradiction between the high efficacy of levamisole and the common belief that resistance to levamisole and morantel is co-inherited, is discussed.
McKenna
P B
PB
Palmerston North Animal Health Laboratory.