Description

Ordinarily two kinds of lice affect horses. The sucking louse, Haemtaopinus asini, feeds directly off the horse's blood. If not treated, sucking lice can cause anemia, weight loss, a rough, patchy coat, and slow the growth of young horses.

The chewing louse, Bovicola equi, feeds on skin scales. The areas of the horse most commonly affected by both kinds of lice are the head, face, ears, neck, back, and around the base of the tail. As a horse rubs, bites, and scratches at affected sites, loss of hair and development of scabs and sores on the skin become apparent.

Adult lice are pale-colored insects and can be seen by parting the hair in the affected area. The eggs are called 'nits' and look like white grains of sand attached to the hair shafts. Once a horse becomes affected with lice, treatment of the horse plus all tack and equipment is necessary to kill all lice and keep the horse from being affected again later.

Symptoms

• Rubbing, biting, scratching at coat in affected areas
• Loss of patches of hair
• Sores and scabs
• Visible lice under the mane, forelock, tail, and fetlocks
• Weight loss and failure to thrive

Causes

Horses usually pick up lice from other horses, from infected equipment or tack, by rubbing on trees or rails where another horse has left hair containing lice or eggs, and sometimes from infected poultry. Long winter coats and lack of grooming make ideal breeding conditions for lice.

Prevention

Since infestation is usually from horse to horse, making sure that any infestations are treated promptly and thoroughly will usually prevent further problems with lice. Treatment must include all tack and equipment, especially brushes and blankets. .

Treatment

Three kinds of treatments are often used, although the only approved products for the treatment of horses with lice are powders such as Sevin.

Use of systemic treatments and pour-on products are usually done under the guidance of a veterinarian because dosage and type of product must be controlled to prevent skin reactions or other problems with the horse's health.

Powders are used to dust the entire animal, making sure that the dust reaches the skin. Wetable powders are mixed with water and sprayed on or sponged on, making sure the skin is thoroughly soaked for complete coverage.

Permethrins can be used as pour-on insecticides to control lice. The solution should be applied along the back and down the face. Two treatments, 14 days apart, are recommended for optimum control.

In addition to treating the horse, all equipment, especially blankets and brushes, should be cleansed thoroughly with the same insecticide. Cleansing should be repeated in two weeks. Boiling the equipment will also kill lice, nymphs, and eggs.

Since lice cannot survive for long once they are off the horse's body, paddocks and stalls should be left vacant, if possible, for at least 14 days to starve active lice on trees, rails, or other equipment.

Choice of treatment will depend on the time of year and the number of horses being treated. A veterinarian should be consulted to determine the best treatment options available.