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Lice Control In Animals Housed Over Winter

Lice Control In Animals Housed Over Winter

November 2010

Every winter, Pediculosis (Lice infestation) presents a serious challenge to the cattle farmers of Ireland. Lice are a particular menace because they spread rapidly within the shed and cause severe irritation to the infested cattle. The resulting irritation can cause scratching which in-turn causes hair loss, bleeding skin and in very severe cases, thickening of the skin at the worst affected areas. Where animals are carrying a particularly heavy infestation of lice, there is invariably a loss of condition due to the incessant need to scratch, to the detriment of the animals feed intake. As a result, lice infested cattle not only look unsightly but fail to maximise their feed intake and their growth rate and as a result, cost the herdowner money.

Lice are wingless, flattened insects and can be as large as 4 mm in length and are spread from one animal to another by direct contact or touch. Their spread during the winter in houses is particularly helped by a longer winter coat and stock lying in close contact for prolonged periods. Lice are categorised into two main groups; Biting Lice and Sucking Lice. As their name implies, biting lice cause discomfort by biting into the skin of the affected animal. Sucking lice bite into the skin of the animal, pierce the tiny blood vessels of the skin and suck the affected animal's blood along with whatever fluid that oozes from the wounds they inflict. As a result, sucking lice can cause all of the problems described above and also deplete the bovine's blood supply leaving an anaemic animal.


Above: This is an image of a biting louse as found on cattle.


Female lice lay one or two eggs every three days. These lice eggs 'nits' are found stuck to the hairs of the animal and from a distance, large numbers of them resemble dandruff. After nine to ten days, the eggs hatch and a nymph (an immature stage that physically resembles the adult, merely much smaller in size) emerges. Three weeks later, after moulting (shedding the hard outer shell) three times, a young adult emerges and in a matter of days, this adult is capable of laying more eggs. The entire life cycle takes three to four weeks in total depending on the exact species of lice involved.


Lice control can vary slightly depending on whether the species you are dealing with are biting lice or sucking lice, as biting lice present a far greater challenge. It is prudent to treat for the presence of biting lice as they are quite common.

Sucking lice are very susceptible to ivermectins such as Bimectin Pour On. This preparation kills the nymph stages and adults of both biting lice and sucking lice. However, the eggs that are attached to the animal's hair are much harder to kill. As a result, a second treatment, applied 2-3 weeks later when the eggs have hatched, of Bimectin Pour On is required to completely eradicate lice for the season. Ectospec works similarly and also requires a second treatment to completely eradicate lice. However, products such as Abinex Forte pour on kill all stages of the life cycle of lice and therefore a once off treatment is all that is required to control lice for the winter.

Product Used

Treat at Housing

Treat 2-3 weeks after housing

Bimectin Pour On






Abinex Forte



For further information on any of the Bimeda product range or if you have any questions relating to animal health and well being, please contact; William FitzGerald, Commercial Veterinarian, MVB MVM, Cert CSM, Mobile: +353 (0) 86 043388, This email address is being protected from spambots. You need JavaScript enabled to view it. or visit; www.bimeda.com