Lice (Pediculosis) in Horses
Key takeaways
Lice are tiny insects that live on the skin and hair of horses, causing damage and itchiness.
- There are two types of lice affecting horses: sucking lice, which feed on blood, and chewing lice, which feed on skin
- The main clinical signs are irritated skin, scratching, rubbing, and biting the affected areas, rough or matted appearance of the hair coat, and in some cases, weight loss
- A diagnosis is usually reached on observation alone, by identifying the presence of lice with a penlight and magnifying glass
- Treatment consists of thorough application of insecticidal products such as shampoo, spray, powder, or dust
- Potentially contaminated objects must also be washed and treated with insecticides
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A closer look: Lice (Pediculosis) in Horses
A louse typically spends its entire life cycle on the horse. Females deposit eggs (nits) near the base of the horse’s hair shafts. Nits hatch after 5 to 20 days and the larvae (nymphs) start feeding on the host immediately. Sucking lice feed on blood, while chewing lice feed on skin. Nymphs reach the adult stage after 2 to 4 weeks.
Lice live on the host throughout the whole year but the population tends to be highest in the winter months.
Risk factors
Lice infestation (pediculosis) is uncommon in horses. It is not a life-threatening condition, but does require prompt veterinary treatment to prevent spread to other horses. Horses that are immunosuppressed or sick are more likely to develop pediculosis.
In more severe infestations, skin scarring and hair loss can occur.
Severe sucking lice infestations can also lead to significant blood loss.
Possible causes
Pediculosis is caused by Haematopinus asini, the horse bloodsucking louse, and Damalinia equi, the horse biting louse. Lice are easily spread through direct contact with infected horses, but also through contaminated objects such as blankets, saddles, or brushes.
Main symptoms
Testing and diagnosis
Usually, a diagnosis can be reached based on observation alone. Lice can be seen on horses’ hair and skin through the use of magnifying glasses and penlights during a physical examination.
Steps to Recovery
Treatment consists of thoroughly washing the horse with shampoos containing insecticides. Other methods include the use of dusts or powders containing approved insecticides.
Treatment should be repeated regularly for at least two weeks to eliminate all nits that may have survived the first treatment application. Oral deworming medications may be helpful in treating sucking lice infections.
Contaminated objects such as brushes, saddles, blankets, etc., also require treatment with insecticides to avoid reinfection and spreading to other horses.
The duration of treatment varies depending on the treatment of choice and the severity of the infestation.
It usually takes from 2 to 5 weeks of regular application of insecticidal products to completely rid a horse of lice. The prognosis with appropriate treatment is excellent.
Prevention
Lice spread very easily from direct contact and fomites (contaminated objects). Infested horses must be kept separate from the rest of the herd, and any potentially contaminated objects must be washed and cleaned thoroughly.
Early detection is fundamental in preventing an extensive infestation. Regular grooming allows for early identification of lice.
Is Lice (Pediculosis) in Horses common?
Lice are uncommon in horses.
Typical Treatment
- Thorough washing with specific shampoos containing insecticides
- Application of insecticidal powder or dust directly on affected areas
