Horse Lice

What Is Horse Lice?

In horses, lice infestation, also called pediculosis, is common. Lice are small, flightless insects with flat segmented bodies. They can vary in color from yellow to brown or gray. Typically they like to live in the feathers or hair of animals and people. Generally, lice spread easily and will move from host to host by direct contact. Horses, in particular, have plenty of hair over a large surface area for these pests to invade, making horse lice infestation an issue that many horse owners may encounter.

Types of Horse Lice

Two types of lice typically infest horses.

Biting or Chewing Lice: These lice prefer to lay eggs on the finer hair on the horse’s body, typically on the sides of the neck, flank, and base of the tail.

Blood-Sucking Lice: These lice are typically found at the roots of the forelock and mane, around the base of the tail, and on the hair (coronet) above the hoof.

Symptoms of Horse Lice

Common signs you may see if your horse has lice include:

• Biting, rubbing, or scratching infested areas of the body

• Restlessness or irritation

• Hair loss

• Skin loss

• Matted hair

• Wounds that may become infected

• A rough coat with a shabby, unkempt appearance

Lice can typically be seen on a horse by parting the hair. Chewing lice, in particular, are often active and can be seen moving through the hair.

Causes of Horse Lice

Lice can easily pass from horse to horse, which can make them easy targets.

Female lice attach their eggs to the hair of their host near the skin. Eggs, also called nits, are pale, translucent, and oval in appearance. Once the eggs hatch, the lice will go through three life stages before reaching adulthood:

1. Egg: Pale translucent oval eggs are laid in the horse’s hair near the skin by adult female lice.

2. Nymph: Small pale larvae that are smaller than adult lice but similar in appearance.

3. Adult: Adult lice live on the horse for about a month.

It takes about 3–4 weeks (depending on the species) for most lice to mature from egg to adult.

While a healthy, mature horse may have some natural immunity against lice (as they do with internal parasites), some factors can increase their risk for becoming infected. These include:

• High stocking density (horse-to-environment ratio)

• Sharing equipment such as brushes and blankets among horses

• Poor nutrition

• Sickness or compromised immune system

• Underlying health conditions, such as Cushing’s disease

• Gestational (pregnancy) status, as pregnant mares have a reduced immune response

• Longer hair, such as a winter coat or feathers

• Seasonal (infestations are more commonly seen in winter and early spring)

How Veterinarians Diagnose Horse Lice

Veterinarians are typically able to diagnose horse lice based on visual observation of lice on the horse.

Lice can be identified typically based on the location they are found. Biting or chewing lice typically lay eggs on the finer hairs of the horse’s body found on the neck, flank, and base of tail. Bloodsucking lice are found at the roots of the forelock and mane, as well as around the base of the tail and hair above the hoof.

Treatment of Horse Lice

If you have a horse who has been diagnosed with lice, it’s important to understand why they may have been at risk. Make sure there are no underlying health concerns, such as too many horses crowded together, or poor nutrition. These conditions that may put your horse at risk.

The good news is that lice are typically easy to treat. There are many treatments for lice available, so working with your veterinarian to develop the best plan for your horse is key. It’s important to note that normal bathing processes will not dislodge lice eggs, so special treatment is needed.

A common treatment option used to rid horses of lice is pyrethrin, such as Pyranha® or pyrethroid, which may be in a spray or wipe-on formula.

If your horse has a long coat, you may also need to clip their hair.

If the horse has a skin infection or wounds, your primary vet may also recommend further treatment with a topical antimicrobial ointment such as SSD Cream®.

It’s important to keep in mind that repeated treatments are often necessary to control and remove a horse lice infestation.

Recovery and Management of Horse Lice

Make sure to follow your primary veterinarian’s instructions for the length of treatment and any husbandry changes to prevent spread and future infestations.

In cases of severe infestation, horses can develop conditions such as severe infections or anemia. These issues will also need to be addressed with your veterinarian.

With proper treatment, horse lice infestations generally have a good prognosis. This will depend on the infestation and health status of the horse. It could take weeks to months to fully recover.

Prevention of Horse Lice

Horse lice can be prevented by providing good husbandry practices and normal medical care, including:

• Annual veterinary exams

• Annual vaccines

• Fecal testing and parasite management plan

• Brushing and consistent cleaning of a horse’s coat

• Cleaning all equipment periodically

• If sharing equipment, cleaning more regularly to prevent potential spread

• Providing balanced nutrition for a horse’s lifestyle and age

• Maintaining a good horse stocking ratio

If there are any concerns with a horse’s coat condition, body condition score, or overall performance, make sure to address this quickly with your vet.