Management of lice on cattle over winter

Lice infestation causes great concern for cattle farmers in Ireland. Heavy lice burdens reduce the welfare of animals as the parasite causes intense itching.

Lice infestation also reduces productivity in animals as a reduction in feed intake is often seen. This article covers what you need to know about lice when preparing for the winter housing of cattle.

Lice lifecycle

The adult louse will lay eggs on cattle which will stick to the hair. These eggs will then hatch in to the nymph stage. The size of the lice increases through a series of nymphal moults until the adult stage is reached. All of these stages occur simultaneously on cattle.

When do lice cause a problem?

Lice cannot survive for more than three to five days without cattle to feed from. Generally the worst times for lice are late winter and early spring. When animals are housed over winter lice can easily spread from animal to animal. Over winter, the hair will grow longer allowing them somewhere to hide from the elements.

Over summer numbers tend to stay low as less direct contact occurs between animals and a thin coat exposes lice to high temperatures and direct sunlight which they find disadvantageous.

Clinical signs:

  • Hair loss;
  • Intense itching;
  • Rubbing and licking;
  • Inflamed skin;
  • Anaemia from sucking lice, e.g. pale gums (young animals).

Types of lice

Lice are divided into two groups:

A. Biting lice

Biting lice have robust round heads and feed on skin and hair debris, bacteria and hair. There is generally one species of biting lice found in cattle – Bovicola bovis (also called Damalinia bovis). It is usually found on the head, neck, shoulders, back and rump of cattle.

In extreme infestations, the lice may spread down the sides and even cover the rest of the body. This louse cases extreme itching by cattle and self-trauma may cause wounds which in turn may lead to secondary bacterial infections.

Sucking lice

Sucking lice have piercing mouthparts and feed on the blood and fluid of cattle. There are generally three species of sucking lice found on cattle:

  • B. The long-nosed cattle louse is generally found around the head, neck and dewlap;
  • C. The little blue cattle louse tends to cluster on the face, neck, head, under the jaws and may spread to the shoulders, back and tail when infestation is heavy;
  • D. The short-nosed cattle louse is commonly found on the skin of the poll, at the base of the horns and ears and around the eyes and nostrils and the tail switch.
Lice (all females) of cattle. (A) Cattle biting louse (Bovicola bovis). (B) Long-nosed cattle louse (Linognathus vituli). (C) Little blue cattle louse (Solenopotes capillatus). (D) Short-nosed cattle louse (Haematopinus eurysternus). (Lance A. Durden, in Medical and Veterinary Entomology (Third Edition), 2019)

Diagnosis

When dealing with lice infestation in cattle it’s important to differentiate between biting lice and sucking lice as treatment strategies may vary; however, most topical lice treatments will tackle both.

Diagnosis is done by visual inspection of the cattle. Conducting three or four hair partings in four places on the body is recommended – neck, sides, backline and rump.

Bovicola bovis will look like small brown spots moving around the skin. The sucking lice will look black on the skin of the cattle. The best place to find lice is outside the bald spots in the surrounding hair.

Samples should be obtained – either a coat brushing or a ‘sellotape test’ which can be viewed under the microscope by a veterinarian or at the lab.

Treatment

A range of synthetic pyrethroids in spot-on or pour-on formulations are available (deltamethrin, cypermethrin).These will treat biting lice and sucking lice.

Injectable macrocyclic lactones (ML’s) are also available (ivermectin, eprinomectin, moxidectin, doramectin). Injectable treatments generally treat sucking lice, but will also aid in the control of biting lice. Pour on MLs will treat both sucking and biting lice.

Always read the label to ensure that you are treating the correct parasite, applying the product correctly, know the retreatment time, calibrate the applicator and the withdrawal period.

Many of the different products treat other external and internal parasites as well. When introducing new animals to the herd they should be treated and quarantined.

Product focus

Dectospot

This pour-on deltamethrin product will treat both biting and sucking lice on cattle. The dose rate is 10ml for cattle and it is applied in one spot between the shoulder blades of the animal.

For the Dectospot 250ml and 500ml pack sizes, a graduated chamber attached to the container is used to administer the product. A 10ml applicator is suitable for use with Dectospot 1L and 2.5L pack sizes, and is available free of charge for first-time users.

One application will generally eradicate all lice. Complete clearance of all lice may take four-to-five weeks during which time lice hatch from the eggs and are killed. Dectospot has a convenient zero milk withdrawal and an 18 days’ meat withdrawal period.

Ectospec

Ectospec is a cypermethrin pour-on which has been used by Irish farmers for over two decades to control lice on cattle.

Ectospec offers a convenient 10ml dose rate per treatment which should be applied at an even rate along the backline from the crown of the head to the top of the rump. In cases of heavy challenge, if necessary, a repeat dose may be applied after four weeks.

Ectospec’s convenient zero milk withdrawal and 10-day meat withdrawal make it a popular choice with Ireland’s farmers.

Find a stockist

Both Dectospot and Ectospec are proudly manufactured in Ireland by Bimeda Animal Health Limited. To find your local Dectospot or Ectospec stockist, call Bimeda on Lo Call: 1850 51 52 53.