University of Missouri Extension

G7011, Reviewed October 1993

Beef Cattle Lice Control

Robert D. Hall
Department of Entomology

Two types of lice may be found on cattle in Missouri

Chewing lice feed on hair, scabs and excretions from the animal's skin and irritate the skin with their sharp claws and mandibles. Chewing lice infestations weaken the animal, interrupt normal feeding activities and make the animal more susceptible to diseases.

The cattle biting louse is the only species of chewing louse occurring on cattle in Missouri. It is yellowish-white with a reddish head. It can be found all over the animal's body and when full grown will be about 1/12 inch long. It is a pest of both young and mature cattle.

Sucking lice feed by piercing the animal's skin with their sharp mouth parts and withdrawing blood. The loss of blood can stunt growth and reduce weight gain. The irritation caused by lice also hinders the animal's feeding activities, which can reduce the growth rate. Sucking lice may be found on the head, neck, withers, around the base of the tail, brisket, and along the inner surfaces of the legs. Continued severe infestations weaken the animal to the point that stress from disease or extreme cold weather may cause death.

Three species of sucking lice can be found on cattle in Missouri. The longnosed cattle louse is generally a pest of young cattle and is about 1/10 inch long. The shortnosed cattle louse is about 1/16 inch long and is more often a pest of older cattle. The little blue louse is about 1/16 inch long. It is generally a pest of older animals and is more common around the animal's head.

Life history

The eggs (nits) are glued to the hair and hatch in one to two weeks. The nymphs that hatch from these eggs become full grown and start to lay eggs in about two weeks.

Both chewing and bloodsucking lice are most abundant during the winter. Infestations usually are small during the summer and early fall, but increase rapidly in the winter and spring. Some animals may be continuously infested with lice throughout the year. You may notice that certain animals are particularly prone to lice infestations. Schedule these "carrier" animals for disposal.


Just because cattle are scratching or rubbing against solid objects during the winter and early spring doesn't mean they are lice-infested. Examine them before applying control measures. Part the animal's hair where lice are most likely to be found and look for lice or for eggs attached to the hair.

Cattle lice may be controlled with insecticides applied by sprayers, backrubbers, dust bags, "pour-on" or injection methods. Insecticide sprays will not affect the eggs; therefore, a second spray in 14 to no more than 18 days will be necessary to kill the nymphs that hatch following the first spray.

Control methods

Sprays (an asterisk preceding any insecticide means that all or some uses of the product have been restricted by the U.S. Environmental Protection Agency. Applicators must be certified before they may purchase restricted products.)


No preslaughter interval is required with dioxathion (Delnav) or permethrin, but do not treat more often than once every two weeks. No pre-slaughter interval is required with coumaphos (Co-Ral) or malathion.

The species of lice present and the area of body infested will determine the amount of coverage needed. For complete body coverage, apply one to two gallons of spray per animal depending upon size of animal and density of haircoat. Use smaller amounts of spray on calves 3 to 6 months old and do not treat calves less than 3 months old.

Use a sprayer that will produce at least 200 pounds of pressure so as to wet the skin, not just the hair. The first spray should be applied around Nov. 1. Make a second application 14 to 18 days after the first application.



No preslaughter interval is required with permethrin.

If a backrubber, as used for horn fly control, is used all year long, the cattle should not become louse-infested enough to need spraying. If necessary, relocate the backrubber where cattle loaf during the winter. Apply 1 to 2 quarts of solution to cable-type backrubber or fill the reservoir of the oiler type to capacity every 10 days to two weeks or as needed.

The initial charging of cable-type backrubbers will require approximately 1 gallon of solution. Do not apply entire amount at one time. Allow backrubber to soak up material by making split applications until the backrubber is soaked. Do not locate backrubbers where drippage or spillage will contaminate water supplies. Do not let cattle use a backrubber that is dripping with the insecticide mixture.

Dust bags

Use tightly woven or multiple-layer burlap bags containing:


No preslaughter interval is required with these self-treatment applications.

Lice should not build up on cattle using dust bags containing one of these insecticides if the bags are located where cattle will use them regularly. Place the bags near salt and mineral blocks, in alleyways, feed lots and loafing sheds. Keep the bags as dry as possible. A simple tin roof is effective and easily constructed.

Pour-on method

Starting at the shoulders, pour the required amount of insecticide along the backline for a distance of 18 to 24 inches.

This product can be used any month of the year because it does not control cattle grub. Read the label carefully because of restrictions on exotic breeds of cattle.

This product can be used any month of the year because it does not control cattle grubs. Use on calves and lactating and non-lactating dairy cattle.


On native Missouri cattle, do not apply famphur (Warbex) or fenthion (Lysoff, Tiguvon) as pour-ons during October, November and December unless applications were made earlier for grub control. Follow label restrictions for use on cattle imported from other states. Do not treat with famphur (Warbex) or fenthion (Lysoff, Tiguvon) within 35 days of slaughter. Do not apply famphur (Warbex) to Brahman bulls.


Do not apply in conjunction with oral drenches of other internal medications, such as phenothiazine, or with natural or synthetic pyrethroids or their synergists, or with other organic phosphates.

Brahman and Brahman-crossbred cattle are sensitive to most organic phosphate insecticides. Read and heed label restrictions when using organic phosphate insecticides on Brahman cattle.

Do not contaminate feed, water, or feed and water utensils. Do not locate backrubbers where excess insecticide or spillage will contaminate water supplies. Observe required time interval between applications of any insecticide and slaughter of treated animal. Read and follow all restrictions and precautions printed on the container label.

Injection method

Use a 16-gauge, 1/2-inch to 3/4-inch needle and veterinary syringe. Inject subcutaneously under the loose skin in front of or behind the shoulder. Use sterile equipment and sanitize the injection site by applying a suitable disinfectant. Use clean, properly disinfected needles to reduce the potential for infection. No special handling or protective clothing are required.

Body weight Ivomec dose
110 to 220 pounds 2 milliliters
220 to 330 pounds 3 milliliters
330 to 440 pounds 4 milliliters
440 to 550 pounds 5 milliliters
550 to 660 pounds 6 milliliters
660 to 770 pounds 7 milliliters
770 to 880 pounds 8 milliliters
880 to 990 pounds 9 milliliters
990 to 1,100 pounds 10 milliliters


Do not use ivermectin within 35 days of slaughter and do not use during October, November and December. Cattle treated with ivermectin in August or September may be re-treated with ivermectin during the winter for internal parasites, mange mites or lice without danger of grub-related reactions.

G7011 Beef Cattle Lice Control | University of Missouri Extension

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