Fall Cattle Louse Treatments

By Dave Boxler

 

As livestock producers start planning for fall weaning, pregnancy observation, and vaccinations they often will apply an endectocide treatment for internal and external parasites such as cattle lice. While this practice is efficacious for most internal parasites and horn flies, it does not always completely control a cattle louse problem. Cattle lice are a cold weather insect, thriving during wintery conditions. During summer months cattle lice undergo a process called estivation (a period of dormancy) when their reproduction is reduced significantly. If fall temperatures (September, October, and mid-November) are above 78° F, cattle skin temperature will exceed 100° F and suppress louse development. Thus, if endectocide treatments are applied too early during a warm extended fall, such as we saw in 2016, lice will be developing slowly and can largely escape the endectocide treatment. Later when cold weather does set in, lice outbreaks can occur if the endectocide has broken down. Livestock producers who utilize a fall treatment strategy should monitor their cattle for signs of lice especially during the months of December, January, and February.

 

In Nebraska we can encounter four different cattle lice species. The biting or chewing louse (little red) Bovicola (Damalinia) bovis, is reddish brown in color with dark bands running transversally across the body (Figure 1 http://go.unl.edu/mmvu). 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, can be found on the sides and sometimes over the whole animal. 

 

The other three species are sucking lice, which feed on blood, and can cause irritation, anemia, impact weight gain, and even death in extreme cases. 

 

The short-nose cattle louse, Haematopinus eurysternus, is the largest louse (Figure 2 http://go.unl.edu/d4za) at 3-5 mm 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 long-nose cattle louse, Linognathus vituli, is about 2.5 mm in length, bluish in color (Figure 3 http://go.unl.edu/rue3) 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. 

 

The little blue cattle louse, Solenopotes capillatus (Figure 4 http://go.unl.edu/7wcu) is about 1-2 mm in length, bluish in color, and smallest of the sucking lice species. It often can be found in dense patches on the dewlap, muzzle, around eyes, and neck. Heavy populations can greatly impact cattle weight gains.

 

Nebraska cattle are usually infested with more than one species of louse and calves, yearlings and older poor conditioned cattle usually have the heaviest lice infestations. Heavy louse populations can lower milk production, stunt growth, cause hair loss, an unthrifty appearance and anemia.