Cattle Lice

C. L. SMITH AND IRWIN H. ROBERTS.

FOUR species of bloodsucking lice and one species of biting lice are pests of cattle in the United States.

The damage lice do to cattle varies in proportion to the degree of infestation. Infestations of lice on cattle generally appear in the fall and increase, slowly at first and later more rapidly, in winter and spring. Louse populations gradually decline as the weather becomes warmer, but seldom do they disappear from a herd until an effective insecticide is applied.

Lousy cattle rub and scratch themselves and lose patches of hair by the rubbing. The loss of hair generally is linked with the presence of the biting, or red, louse.

Animals heavily infested with the bloodsucking species, especially the short-nosed louse, Haematopinus eurysternus, often look as if they had been rubbed with used crankcase oil.

The bloodsucking lice that attack cattle are Linognathus vituli, Solenopotes capillatus, Haematopinus eurysternus, and Haematopinus quadripertusus. The biting louse is Bovicola bovis.

The bloodsucking louse H. quadripertusus, commonly called the tail louse, was discovered in Florida a few years ago. By 1956 it was found only in the Southern States in areas along the coast. All the other species of lice occur in all parts of the United States.

Infested animals usually are in poor physical condition. Calves, yearlings, and old, undernourished cattle suffer most. Large numbers of lice may retard the growth rate of calves, prevent proper weight gains in cattle on feed, and reduce milk production of dairy cattle. Deaths due to lice are rare, but old cattle of low vitality, particularly skinny range cows that are exposed to bad weather, may die from the effects of lice. Extensive infestations of the short-nosed louse can cause pronounced anemia, even in well-fed adults.

CATTLE LICE do not live long off the host. They are seldom seen except on animals. The habits and life history of the various species of cattle lice are similar. The adult females glue the eggs to the hairs of the host. The hatching time of the eggs varies with the species, their place on the animal, and temperature to which they are exposed. The nymphs of lice differ from the adults mostly in size and color.

G. H. Lamson, Jr., observed at Connecticut Agricultural Experiment Station, that the eggs of B. bovis hatched in about 7 days and that the nymphs reached sexual maturity in 15 to 18 days. The hatching time for the eggs of Linognathus vituli, a bloodsucking louse, was 8 to 14 days, and its nymphs matured in 11 to 18 days. Normally the eggs of H. eurysternus hatch in 12 to 18 days, and the nymphs reach maturity in 13 to 23 days. In Texas some of the eggs hatched in 33 days.

BECAUSE CATTLE LICE live nearly all of their lives on the host, they are more easily controlled than some other insect pests are. The residual insecticides used in summer against hornflies may reduce the louse potential so much that a heavy buildup in winter is impossible. Thorough. treatment of animals when the last treatment is applied for horn-flies in the fall delays the development of lice in the herd and often makes unnecessary a later treatment for lice.

Some older insecticides, such as rotenone, nicotine, pyrethrins, sodium fluoride, the arsenical dips, and coal-tar creosote preparations, have been used for controlling lice on cattle and for certain other pests. They have some disadvantages: They are effective for the initial kill of lice, but they have little residual value and two or more treatments usually are needed to control lice. Nicotine, sodium fluoride, coal tar, and the arsenicals are highly poisonous and have to be applied to cattle with utmost care.

We now have better materials--the chlorinated hydrocarbons, commonly called residual insecticides, such as DDT, toxaphene, chlordane, methoxychlor, and BHC. They have replaced most of the older insecticides for lice on cattle. The problem thus has become one of thorough treatment of each animal rather than a problem of choosing one of only a few not entirely satisfactory insecticides.

Nearly all the chlorinated hydrocarbon insecticides that are satisfactory against lice are commercially available as wettable powders and emulsion concentrates. Among them are: DDT, methoxychlor, chlordane, toxaphene, TDE, and BHC. A few of the insecticides also can be bought as dusts. Some are available in oil to be used in rubbing or the self-treatment devices.

The wettable powders and emulsion concentrates usually are prepared to be used as dips or sprays. Regardless of the formulation selected, the insecticide should be used according to recommendations issued by State agricultural experiment stations and the Department of Agriculture and at no greater concentration than is recommended for satisfactory control. There is little difference in the insecticidal performance of the wettable powders and emulsion concentrates.

The insecticides may be applied in the form of dips, sprays, dusts, and oil solutions. The method of application depends on what equipment is available and the location and number of animals to be treated. The amount of spray, dip, or dust required to treat an animal varies with the equipment, the breed of cattle, and the density and length of the animal's hair. The amount of spray required to wet an animal thoroughly may be as little as 2 quarts in the Southeast or as much as 2 to 6 gallons in the Southwest and Northern States. The important point is that the animal must be wetted thoroughly.

Dipping vats used to be considered the surest and best way to control lice on cattle, especially those in large herds. Improved power sprayers have come into use. They are of many types and makes. All are similar in operation. They differ mainly in capacity and output of spray.

The spray should be premixed in the spray tank before it is applied.

That can be done by running the sprayer as the insecticide is added to the water. Afterwards the spray stream should be directed back into the tank for a few minutes to insure a thoroughly mixed spray. The agitators with which the power sprayers are equipped will keep the spray well mixed as it is used. A pressure of 100 to 200 pounds to the square inch usually is adequate for spraying cattle with short hair. Pressures up to 350 pounds may be needed if the hair is dense and long. The animal's crotch, dewlap, forelegs, tail, and ears should be sprayed especially well. The spray stream should not be aimed directly into the ears, because damage to the inner ear may result at these pressures.

If there are only a few animals, hand-operated equipment can be used. A knapsack or cylindrical garden-type sprayer is satisfactory, although with them it may be harder to wet the animal thoroughly. Because some hand sprayers are not equipped with agitators, they have to be turned over or shaken every few minutes to insure a well-mixed spray.

Dusting may be preferable in winter in the colder climates because wetting the animals may endanger their health. Dusting is more laborious than dipping or spraying. Only gentle cattle can be dusted satisfactorily, because the dust must be sifted through the dense hair by rubbing the animal's back with the fingers. Because of the difficulty in obtaining good penetration and coverage,dusts are less effective than sprays or dips. Usually about 6 ounces of a 5- to 10-percent dust are requited to treat an adult animal.

The application of insecticides with backrubbers or self-treatment devices has been recommended in many States. Robert A. Hoffman, of the Entomology Research Branch laboratory, Corvallis, Oreg., found that B. bovis and L. vituli could be controlled with DDT, chlordane, methoxychlor, and toxaphene by self-treatment devices. To be successful, they must be used consistently.

The backrubbers should be accessible to the cattle near watering places and places where the cattle rest. They may be placed in lanes where the cattle would be forced to use them. Unless the cattle are able to rub themselves thoroughly, however, satisfactory control might not be had. The backrubbers seem to be better adapted for use in small pastures or feed lots where there are few trees and other natural objects on which cattle can rub.

Generally the insecticides are used at 5-percent concentration in the back-rubbers. The technical material may be dissolved in fuel oil or kerosene to the desired concentration. Used crankcase oil is not recommended for use in these devices. Homemade back-rubbers are as efficient as manufactured ones and are less expensive.

ON DAIRY CATTLE, methoxychlor, lindane, rotenone, and pyrethrum have been recommended for use against lice. They are usually applied as sprays. Methoxychlor should be applied at 0.5-percent concentration in sprays, 5.0-percent concentration in self-treatment devices, and 5.0- to 10.0-percent in dust. Lindane should be applied at a concentration of 0.03 to 0.06 percent in sprays and 1.0 percent in dust.

A concentration of 0.006 percent of rotenone in sprays (1 pound derris or cube containing 5.0 percent rotenone to 100 gallons water) and 1.0 percent in dust is recommended. Sprays containing pyrethrum should contain 0.025 percent active ingredient.

One can buy pyrethrum concentrates that contain a synergist, which tends to increase the effectiveness of the pyrethrum. Piperonyl butoxide, sulfoxide, and n-propyl isomer are commonly used synergists. The ratio of synergist to pyrethrins should be about 10 to 1 in formulations for lice.

A second application of lindane, rotenone, or pyrethrum 14 to 18 days after the first may be necessary.

ON BEEF CATTLE, methoxychlor, lindane, rotenone, and pyrethrum at the concentrations used on dairy cattle will control lice. The following insecticides will also control lice on beef cattle:

DDT at 0.5 percent in sprays and dips; 5.0-percent in oil applied in a self-treatment device; and 5.0 to 10.0 percent in dust;

TDE at the same concentrations and in the same manner as DDT;

Toxaphene at 0.5-percent concentration in sprays and dips and 5.0 percent in oil in backrubbers;

Chlordane at 0.5-percent concentrations as a spray and 5.0 percent in oil for a self-treatment device.

BHC, the technical chemical from which lindane is made the gamma isomer in the spray should be the same as for lindane (0.03 to 0.06 percent of lindane).

To control the tail louse, it may be necessary to spray beef cattle with a 1.0- to 1.5-percent concentration of DDT or the same concentration of methoxychlor as recommended on dairy cattle. A limited number of tests in Texas indicated that the tail louse can be controlled with the same concentrations of DDT, methoxychlor, BHC, toxaphene, and chlordane as recommended for the general control of lice.

C. L. SMITH became assistant station leader in the Department's laboratory in Kerrville, Tex., in 1951.

IRWIN H. ROBERTS, a parasitologist and veterinarian in the Department of Agriculture, has been concerned with investigations of parasitic diseases of livestock since 1940.