Lice

Veterinary advice should be sought before applying any treatment or vaccine.

Lice

Pediculosis

Lice infestation is rather common in horses, especially in sick, old or otherwise debilitated animals. These animals will often have a longer hair coat and patchy areas of hair loss with scaly skin. They will also demonstrate varying degrees of itchiness, ranging from non-existent to severe. Horses will most often be affected on the neck, shoulders, mane, tail, or, less often, the legs.
There are two species of lice which affect horses--the biting (Datmalinia equi, mallophaga), and the sucking (Hematopinus asini, anoplura) louse. It is useful to identify the species of lice prior to treatment, because the treatment is different between the two species of lice. Hematopinus asini lice are a bit bigger than Datmalinia equi, and are easier to see on the horse. There are usually higher numbers present on the horse, concentrating in the mane, base of tail, fetlocks, and upper and inner thighs. Horses with longer hair coats were tend to harbor higher numbers of lice. Clipping the horse's coat after the lice have already infested may help reduce the number of lice, but isn't an effective method of treatment to rid the horse of them completely.

In order to confirm whether the horse has lice, a visual check of the hair coat can be done. It is best to perform the examination after the horse has been exercised, as when the horse sweats the lice will climb out towards the tip of the hairs. Tools needed include mineral oil, a magnifying glass, ear forceps, and a flea-comb. Applying a small amount of mineral oil on the flea-comb, then combing through the hair coat, will cause the lice to stick to the flea-comb.

Transmission
Lice are easily spread by close contact with other horses, or from sharing brushes or tack.

Symptoms

Mane and tail rubbing
Flank biting
Patches of hair loss
Tiny wingless insects visible in hair coat
Poor quality hair coat
Weight loss

Diagnosis

  • History
  • Clinical signs
  • Physical exam

Treatment

TherapiesDetails
IvermectinAdministered at a dosage of 200 ug/kg PO, twice at a 14-day interval.
Datmalinia equiCan be controlled using most commonly available anti-parasitic treatments
PermethrinSpray full body for 4-6 weeks
Topical synthetic pyrethroidsCypermethrin or permethrin

Prevention

  • Prevent spread between horses by disinfecting all grooming equipment, tack, blankets, and anything else that may have come into contact with an infected horse's skin.
  • Regularly groom horses

Scientific Research

General Overviews

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Age Range

Most common in sick, older horses.

Risk Factors

  • Unsanitary living conditions
  • Lack of or insufficient grooming
  • Large number of horses kept together
  • Horses with long winter coats

Seasonality

WinterSpringSummerAutumn