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Care Guide

About Care Guides[x] These care guides are written to help your clients understand common conditions, tests, and procedures, as well as to provide basic information about pet care. They are based on the most up-to-date, documented information, recommendations, and guidelines available in the United States at the time of writing. Pharmaceutical product licensing, availability, and usage recommendations are based on US product information. Use the Download Handout button to generate a PDF for printing or e-mailing to your clients.

Lice and Your Horse

    • Lice are a common ectoparasite of horses.
    • Lice cause variable degrees of itching, followed by skin wounds and hair loss due to self-trauma.
    • Sucking lice can cause anemia (a decreased number of red blood cells) in severely infested horses.
    • Horse lice don’t infest humans, but they can easily spread among other horses.
    • Your veterinarian can recommend safe and effective products to help protect your horse from lice. 

    What Are Lice?

    Lice are small, wingless, parasitic insects. They can infest a variety of hosts, including cats, birds, horses, dogs, and people. However, lice are host specific, which means that the species of lice that infest humans, for example, don’t infest other types of hosts. Therefore, humans can’t be infested with lice from animals, including horses.

    Two species of lice can infest horses. Damalinia (Werneckiella or Bovicola) equi is a biting louse that grasps onto a host’s hair and eats skin debris and secretions. Haematopinus asini is a blood-sucking louse that similarly attaches to the host’s hair and uses its mouthparts to pierce the skin and drink blood.

    The entire louse life cycle occurs on the host. Adults attach to the host and feed. Reproduction occurs, and female lice lay eggs (called nits) that remain attached to the host’s hairs until hatching occurs. A few developmental stages later, adult lice emerge to continue the cycle. The entire life cycle takes about 3 to 5 weeks to complete, depending on the species of louse.

    Why Are Lice a Problem for Horses?

    The clinical signs associated with lice can vary in severity and may be limited to skin problems. The clinical signs include the following:

    • Scratching, rubbing, and biting
    • Stress due to restlessness and irritation
    • Hair loss
    • Skin wounds and raw areas (from self-trauma)
    • A rough coat and an unthrifty appearance

    If a horse is heavily infested with blood-sucking lice, the parasites can drink enough blood to cause anemia (a significant decrease in the number of red blood cells). Horses can also become very stressed and annoyed by lice, leading to weight loss and contributing to an unthrifty appearance.

    How Do Horses Get Lice?

    Horses most commonly get lice from being in contact with other horses that are infested. Horses in a crowded environment can very easily spread the parasites to each other. Lice can also be transmitted by fomites—objects such as combs, brushes, or blankets that, if shared, can help spread lice from horse to horse. Lice can also live for a few hours on stalls or fences, so if a horse has been rubbing against such an area, another horse can become infested. However, lice can only live in the environment for a very short time, so transmission generally occurs from direct contact between horses.

    Horses that are transported may be exposed to infested horses or areas. Sick, old, or debilitated horses are also more likely to become infested. 

    Lice infestations in horses are more common in the winter and spring, when horses spend more time in close quarters. Also, longer hair during the cold weather gives lice an excellent place to hide, allowing them to go undetected.

    How Are Lice Detected and Treated?

    Veterinarians generally diagnose lice infestation based on clinical signs such as finding evidence of lice on the horse. Lice can be identified by looking closely at the skin and hair with a magnifying glass. Sucking lice prefer the mane, tail, and fetlocks, whereas biting lice are found predominantly on the back. However, with severe infestations, lice can be anywhere on the body. Your veterinarian may also be able to identify nits clinging to the hairs of an infested horse.

    Fortunately, many products can safely and effectively treat lice infestation. Options include sprays, shampoos, dips, and wipes, so ask your veterinarian about the best choice for your horse. It is important to only use products that have been approved for use in horses and to use all products as directed to help avoid skin irritation and other adverse effects.

    An infested horse’s living area should be thoroughly cleaned, and any blankets, brushes, combs, or other fomites should be washed.

    Severely infested horses that are anemic or otherwise debilitated may need hospitalization for initial care. For most horses, however, this is not required.   

    How Can I Protect My Horse From Lice?

    Regular use of products that control lice can help protect your horse if exposure occurs. Using these products before or during travel may be recommended. Ideally, any new horses entering a barn should be examined by a veterinarian to be sure lice or other parasites are not being introduced. A precautionary quarantine period may be advised.

    If one horse in the barn is being treated for lice, your veterinarian may recommend treating other horses in the area at the same time because lice are easily transmitted from horse to horse.     

    If possible, horses that are being treated for lice should be separated from other horses until the problem has been resolved. In most cases, treatment is repeated a few weeks later to eradicate all stages of the parasite. Depending on which product is used, your veterinarian can advise you about the treatment schedule and when it is safe to expose your treated horse to other horses.  

    Fortunately, lice are host specific, so children, handlers, and others who care for horses are not at risk for infestation. However, anyone caring for or handling an infested horse should take precautions to avoid transmitting lice to other horses.