How to Diagnose Lice on a Horse
Two species of lice feed on horses. Haematopinus asini, or H. asini, are a sucking type of lice often found at the base of longer hair such as the mane, tail, forelock and just above the hooves. Damalinia equi (D. equi) are a biting type of lice and feed in the areas of finer hair near the flanks, the base of the tail and the sides of the neck. Both exist worldwide and are more commonly seen in winter and spring. Diagnosis of lice in horses involves recognizing the symptoms, identifying the lice in the hair or on the skin and, if in doubt, contacting a veterinarian to confirm the diagnosis.
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Instructions
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Consider the health of the horse. If the horse is stressed, unhealthy or has a weak immune system he is more likely to develop a severe infestation of lice. Horses kept in large numbers are also more prone to parasitism, even healthy horses.
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Look for the common symptoms of lice infestation. The most common symptoms occur from the horse's general appearance. The coat will look dull, unkempt and lack luster. Hair may be absent on the neck or shoulders and the skin may be raw. Matting of the hair may be present in the mane, tail or body. Behavioral symptoms include itching or biting of the skin. The horse may be seen rubbing against fencing, walls or other structures.
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Identify more extreme symptoms of lice infestation. Look for decreased muscle tone. If fatigue and weakness are present, test for anemia. This will require a blood sample.
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Identify the lice. Lice are 2-4 mm long and have a flattened, wingless body. Biting lice, D. equi, will be on skin scales or loose skin. They tend to move around more than the sucking lice, H. asini, and have a wide head. They are light brown and have a slightly yellow abdomen. Sucking lice are more stationary and range in color from gray to light brown. The head of H. asini is noticeably narrow compared to the abdomen.
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Check for the presence of eggs or lice. Using adequate light, part the hair and inspect the skin and surrounding hair. Check the face, ears, neck, back, under the lower jaw and adjoining part of the neck, base of the tail and the tail bone. The eggs will be attached to the hair close to the surface of the skin. The eggs are slightly oval-shaped and pale. If there are mats, loosen them and check for eggs or adult lice.
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Call a veterinarian if you suspect a horse has lice but are unable to diagnose them.
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Tips & Warnings
Routinely check your horses for lice in winter and spring when they are most prevalent.
While a veterinarian may not be required to diagnose lice in horses, their knowledge and experience are essential for the treatment of the parasites.
