If lice are going to be a problem, winter is the time when they will show up. In Ohio, cattle can become infested with both biting and sucking lice. Both types of lice can build up to very high numbers on cattle during the winter months. In most herds, 1-2% of the animals may be carriers, most often bulls and/or older animals. During the summer months the thin hair coat of the animal permits self-grooming, sunshine, and rain to keep lice populations at low levels. However as hair coats thicken in the late fall into winter period, it becomes easier for the lice to survive and thrive. Winter stress and inadequate nutrition are contributing factors to a lice problem on cattle. Lice are spread between animals by direct contact and lice problems are typically more severe when cattle are in a confinement situation.
The lifecycle of the louse is egg, nymph and adult. Depending upon the species and the environmental conditions, a complete life cycle from egg to egg can occur in 21 to 30 days. Once cattle are infested, all 3 life stages will be found on the same animal. Signs that cattle may be suffering from a lice include frequent rubbing and scratching against fences, trees, feed bunks or other objects. In more severe cases, cattle may have patches of bare skin. Cattle can be checked for the presence of lice by parting the hair coat at several strategic locations such as the neck, withers, brisket, mid-back and tail head and looking for eggs, nymphs or adult lice.
Common control options for lice include insecticide sprays, pour-ons, spot-ons, injections and dusts. Insecticides generally are not effective on the egg stage, so if there is a lice infestation a second insecticide treatment about 3 weeks after the first treatment should be made to kill newly hatched lice before they mature. There is one consideration that needs to be kept in mind when treating for lice and that is cattle grubs. Check the labels of insecticides. Some systemic insecticides are also labeled as grubicides and will warn of possible harmful host/parasite reactions which can cause paralysis of the animal when used after the safe cut-off date.
In Ohio, the cut-off date to use an insecticide that kills grubs in cattle is November 1. Grubicides should not be used from November 1 through December. After January 1, grub larvae have migrated from the spinal canal, or esophagus, and usually encyst in the back region. At this point, cattle can be treated with a grubicide that will also control lice with a very minimal risk of a host/parasite reaction. If lice need to be treated during the November and December time period, make sure that a non-systemic, non-grubicide type of insecticide is used. Some of the pyrethroid insecticides that contain cyfluthrin, lambdacyhalothrin or permethrin may be labeled for lice control at any time through the autumn and winter periods. Always read and follow label directions.
Source: Rory Lewandowski, Extension Educator, Athens County and Buckeye Hills EERA