Five species of lice parasitize cattle in the U.S. Four of these are blood feeders, and the fifth is a biting or chewing louse. Cattle with hair loss, an unthrifty appearance, and leaving hair on fences and other objects from rubbing may be a sign of lice infestation. However, other factors can mimic lice infestations such as natural shedding, poor nutrition, mite infestations, mineral deficiency, photosensitivity and other diseases. To determine if lice is the problem, secure the suspect animal(s) in a chute and perform a two-handed hair parting on the top line, withers and face. Lice numbers between one to five per square inch represent a low population, six to 10 per square inch represent a moderate population, and more than 10 lice per square inch is considered a heavy population.
The impact of cattle lice can range from reduced weight gain, milk production, blood loss and anemia (sucking species) to animal mortality in severe cases. Factors that can increase lice numbers include colder air temperatures, longer hair coats, drier skin, animal crowding, animals in poor condition and poor nutrition (low protein).
Factors that can reduce lice numbers include a shorter hair coat, increased oil secretion from the skin (sebum), warmer temperatures and increased sunlight. Cattle skin temperatures above 100ºF can negatively impact lice populations.
Cattle lice generally decline in the summer and increase as cooler weather begins, with the exception of cattle tail louse, Haematopinus quadripectusus, which is more active in the spring and summer months in the Gulf Coast states.
This is a close-up photo of chewing louse (little red). Photo provided by Dave Boxler.
Type of lice
The biting or chewing louse (little red) Bovicola (Damalinia) bovis, is reddish brown in color with dark bands running transversally across the body. Typically, the chewing louse feeds on hair, skin, skin exudates and debris near the skin surface. This species is initially found on the shoulder, top line and back, but as populations increase, it can be found on the sides and sometimes over the whole animal. This species of louse does not require a male for eggs to be fertilized.
The four sucking species of cattle lice, which feed on blood, can cause irritation, anemia, impact weight gain and even death in extreme cases. The short-nosed cattle louse, Haematopinus eurysternus, is 3 to 5 millimeters in length and is typically found on older animals but can be found on any age or breed of cattle. This species can usually be found in the neck region, dewlap, back and base of tail. The life cycle from egg to egg-laying adult averages about 28 days, with eggs normally hatching in 13 days.
The long-nosed cattle louse, Linognathus vituli, is about 2.5 millimeters in length, bluish in color and differs from other louse species by its long slender head. This louse can be found on the dewlap, shoulders, sides of neck and rump, but when numbers are high, they can be found over the entire body. Their life cycle from egg to egg-laying adult normally takes 25 days.
The little blue cattle louse, Solenopotes capillatus, is about 1 to 2 millimeters in length, bluish in color and the smallest of the sucking lice species. It often can be found in dense patches on the dewlap, muzzle, around eyes and neck. The life cycle from egg to egg-laying adult normally takes between 21 to 22 days. Heavy populations can greatly impact cattle weight gains.
Pictured from left to right are examples of little blue cattle louse, long-nosed cattle louse and short-nosed cattle louse. Photos by Dave Boxler.
The cattle tail louse, Haematopinus quadripectusus, is the largest louse species found on cattle, averaging 4.5 millimeters in length and very similar in appearance to the short-nosed cattle louse. The eggs are normally deposited on the hairs of the tail switch. After the eggs hatch, the immature lice leave the switch area and move to other parts of the body such as the perineum and vulva. The entire life cycle (egg to egg-laying adult) can be completed in 25 days under ideal conditions. The cattle tail louse may be carried into a herd by the introduction of infested animals. Once an infestation is in a herd, it may be spread by direct contact. The cattle tail louse may be spread from animal or herd to herd by flies (phoresy). Infested cattle may experience reduced weight gain, reduced milk production and anemia.
Studies conducted by the University of Nebraska and others indicate heavy lice populations may reduce weight gains by as much as 0.21 pound per day. These studies also indicate calves fed at a higher nutrition level had lower lice populations and were affected less severely by lice than calves fed a maintenance ration.
Treatment
Cattle louse treatment products fall into several categories: animal sprays, nonsystemic (contact) pour-ons and endectocides (systemic pour-on, absorbed internally and systemic injectable). Some nonsystemic pour-ons require just one application, and some require two applications spaced 14 days apart. Systemic injectables work better on the three species of sucking lice than on the little red chewing louse. A systemic pour-on effectively kills both chewing and sucking lice.
If an endectocide or systemic control product was applied during fall weaning or after heel fly (cattle grub) season, they may be used to control cattle lice later in the season. The application timing of systemic or endectocide products for cattle lice control should observe the “safe cutoff date” for your area. Cattle treated with a systemic or endectocide after the treatment cutoff date could experience a host-parasite reaction from killing developing cattle grubs while they are in the esophagus or spinal canal of the animal. Consult with your state’s extension service or your veterinarian for your area’s specific cutoff date.
Successful louse control depends on application timing. Many livestock producers will administer an endectocide treatment at weaning time, usually late September or October with the intention of controlling internal parasites, cattle grubs and cattle lice. These fall applications may help reduce lice populations but may not remove the infestation. A warm, extended fall may slow down developing lice numbers. Livestock producers who use this management strategy should monitor their cattle for signs of lice, especially during the months of December, January and February. If replacement animals are brought into a herd during the winter months, they should be examined for lice. If present, the animals should be isolated and treated before introduction into the existing herd.
For current control recommendations, please visit the Veterinary Entomology website. When applying any insecticide control product, please read and follow the label instructions.
