Cattle lice thrive through winter; have treatment plan read

US - We usually think of the winter as our escape from pesky insects, however, cattle lice thrive during the cold weather and increase their populations on cattle. Now is the time of the year to evaluate cattle for lice and plan a treatment if necessary.
calendar icon 16 February 2007
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Lice have been accused of being the most underestimated livestock insect in terms of economic loss; USDA estimates that U.S. producers lose $125 million a year to cattle lice. Cattle that are infected with lice are generally in poor condition with rough, patchy hair coats. Lice or their eggs can be visually detected, especially those severely infected. Heavy lice populations cause lowered milk production, decreased flesh growth, unthriftiness and anemia which can also affect reproduction and the immune system. Research at the University of Nebraska has shown that moderate to heavy lice infestation can depress weight gain by 0.12 pounds per day in the feedlot. Understanding the treatment and prevention of lice would be beneficial in any cattle operation.

There are five species of lice that live on cattle. The shortnosed cattle louse are the most common in adult animals and often cause the most loss. This type is frequently found in and on the ears, along the dewlap and brisket, and on the tailhead. Shortnosed lice are the largest of the five species found in the U.S., measuring about 1/8 of an inch and their eggs are whitish.

Longnosed cattle louse tend to infest younger calves. They can be found anywhere on the animal, usually few in number on adult cattle. Longnosed louse are smaller and more slender than shortnosed and they have a pointed head. The eggs from longnosed louse are bluish-black in color.

The Little Blue cattle louse tends to stay on the head of cattle - near the eyes, cheeks and muzzles. This species is the smallest of the cattle lice and are more common in the southwest and Gulf of Mexico portion of the country.

Cattle Tail lice look similar to the shortnosed lice and prefer the long-haired portions of cattle like the tail. These lice are more abundant in late summer to early fall and are not usually seen in the winter. They, like the Little Blue louse, are most common in the southern parts of the U.S.

These four species of louse feed on the blood of cattle.

The fifth species, Cattle Biting louse, feed on the skin cells of cattle. These lice cause severe itching and are common in small numbers on many cattle. Severe infestations can occur in winter when cattle are in close quarters. This species can be a large problem for dairy herds. Cattle Biting lice look different than the others because of its very rounded head. They are about 1/16 of an inch long and are brown with pale cream-colored abdomens.

Lice have life cycles that last about a month and they must remain on the host animal to survive. They will die within days if they do not have a feed supply, especially if exposed to sunlight or extreme cold.

They start as eggs that have been deposited on hair, especially the tailhead and tail area. Immature lice grow and feed on the cattle until they reach the adult stage and lay eggs, starting the cycle over again.

Eggs hatch anywhere from 6 to 11 days after being laid, therefore it is necessary to repeat treatment at least twice to stop an infestation.

There are several treatment options, however, all are poor at killing lice in the egg stage. Many pour-ons and sprays are effective at killing lice. Injectables are effective at killing lice that feed on blood, but Cattle Biting lice do not consume enough blood for the injectable to be effective. Your herd veterinarian can help you choose the most effective product for your situation.

Lice are spread in animal to animal contact, so close housing conditions increase the infestation. Feeding and breeding usually increase animal to animal contact, as does cold weather. When bringing new animals into the herd, they should be visually inspected for lice and treated while they are quarantined for a month because of the life cycle.

In some herds, 1 to 2 percent of animals may be “carriers.” These animals are usually the older bulls or cows in poorer condition that always seem to carry high loads of lice. It is thought the lack of grooming, either due to the large size and thick hair coats of bulls or the inability of old cows, is the culprit. Many “carrier” cows have calves that are “carriers” so culling these cows may be the best option.

Preventing a louse infestation will prevent the economic loss that lice can bring. If rough, thin hair-coats are present the problem is already too big. Incorporating a louse prevention plan into your regular herd health calendar will have economic returns and will keep your cattle itch-free.

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