Effect of dose and route of application on the action of decamethrin against cattle grubs.

The efficacy of pour-on or orally administered decamethrin against bovine hypodermosis was investigated on naturally infested yearlings. Treatment at dose rates of 1, 2 or 10 mg per kg body weight were ineffective, but the highest dose had a long-term lethal effect on warbles. The severe side effects which followed the high dose suggest that this drug is unsatisfactory for systemic grub control. Investigations on the dynamics of circulating anti-Hypoderma antibodies in the post-treatment period showed that there is some sub-lethal activity of decamethrin on the larval physiology even at the lowest doses.