Lice

Description of Injurious Stages and Damage

Each kind of farm animal may have one or more different species of lice feeding upon it, and each species of louse usually can feed on only one kind of farm animal. The different lice vary in size and colour, but all are small in size from 1 to 6 millimetres long, wingless and flattened. Some (the sucking lice) feed on the blood of animals. Others (the biting lice) feed on dead skin, dried blood and serum on the skin. The presence of either kind of lice may result in irritation and itching, so that animals scratch and rub against stanchions, fence posts or other objects, often causing sores. If animals are badly infested with lice they may become unthrifty, often resulting in loss of weight, and a decrease in milk production by dairy cattle.

Summary of Life History

Lice are usually more abundant on farm animals in the winter. They may be found in colonies in certain preferred areas of the animal's body, and when large numbers are present most of the body may be covered. Biting lice may live for a week off the host, as compared with 2 or 3 days at most for sucking lice. They move from animal to animal by contact or by crawling across walls and bedding. Eggs are glued to the hairs of the body, and usually hatch in less than 2 weeks. The young nymphs hatching from the eggs are similar in appearance to the adults, but smaller. A life cycle may be completed in about one month, and there are several generations per year. Populations peak in the winter.

Control Recommendations

Proper animal nutrition and disease management will reduce the impact of louse infestations. Louse control treatments include:

Beef and non-lactating dairy cattle - carbaryl (0.5% spray, 5% ready-to-use dust), fenthion (1% pour-on), cyfluthrin (1% pour-on), eprinomectin (pour-on), ivermectin (1% ready-to-use injectable, pour-on, or bolus), doramectin (injectable, pour-on), abamectin (injectable), moxidectin (injectable), malathion (0.5% spray, 2% backrubber solution, 4% ready-to-use dust), permethrin (0.0125% spray, 1% or 5% pour-on), rotenone dust.

Note: Non-lactating dairy cattle must not be treated with injectable or pour-on abamectin, doramectin, ivermectin or moxidectin products within 2 months, or ivermectin bolus within 184 days, of calving.

Lactating dairy cattle - carbaryl, rotenone (see above); cyfluthrin (1% pour-on), eprinomectin (pour-on), permethrin (1% or 5% pour-on); 2% malathion backrubber solution.

Swine - carbaryl (0.05% spray, 5% dust), fenthion (3% ready-to-use pour-on), ivermectin (1% injectable), malathion (0.5% spray, 4% dust), rotenone dust.