There are two types of lice that can affect horses and both are highly contagious among herds. Biting lice feed on flakes of skin and hair particles while suckling lice actually penetrate the skin and live off your horse's blood which can lead to anemia. Horses located in the northern part of the US or other cold climates are more prone to have lice. During the winter months, horses will often migrate to each other for warmth, spreading the lice from one horse to another and the lice can flourish in a horse's winter coat.
The most obvious sign that a horse is infected with lice is itching. A horse will scratch on anything available including stalls and posts. The entire body can house the lice but areas that seem to be most affected include the base of the tail, the neck, jaw area, shoulders, and flanks. When itching becomes excessive, a horse may even bite or chew if they can reach the area. The itching can become so severe that the horse becomes intolerable and bad-tempered toward other animals or even their handler.
When a horse begins to exhibit signs of itchy skin, your first step is to rule out ringworm. Many times ringworm will not cause excessive itching but it can lead to hair loss. Once you have ruled out ringworm, you can easily detect the lice by scraping an area under the jaw and let the falling debris fall onto a piece of white paper. Not only will you notice the dried blood or dirt spots but you will also see the lice. Lice can range in color from a cream color to light brown and they are very tiny. You may need a magnifying glass to clearly see the oblong-shaped parasites.
When lice have been diagnosed, you will have several options for treating the lice. There are approved louse powders and insecticide sprays available for use on horses. Dust powders are recommended during the winter months to prevent the horse from becoming wet from sprays. Dips can be purchased for use in the spring or summer months which should be applied using rubber gloves. Use these chemicals according to the manufacturer's directions or as instructed by your veterinarian. The treatment will need to be repeated in approximately two weeks to kill any lice that have hatched. When using these treatments, be careful to not get the product in your horse's nostrils, eyes, mouth or any feeding and watering containers.
All grooming supplies and tack should be treated with an insecticide or thoroughly washed in a mixture of water and bleach (insecticides are recommended over bleach). Stalls will need to be carefully sanitized and any hair removed from the horse during grooming sessions should be burned. Be cautious when attending functions where other horses are present. Never share grooming tools among horses and avoid borrowing horse trailers or loaning your trailer to others if possible. All horses that have been within the vicinity of an affected horse should be treated. And lastly, owners should always seek veterinarian care for their horse if they are unsure about the diagnosis or treatment of lice on their animal.