Lice in horses

Lice are skin parasites that live on animals. Horses can get lice too. Once one horse gets lice, they can infect a whole herd. How can you recognise and treat? 




Lice can be seen with the naked eye, but they’re often not noticed as long as numbers are low. They hide in the horse's mane and haircoat and bite to feed off of the horse's skin (some uncommon species of lice suck blood). Lice lay eggs in the horse's hair, which are also visible with the naked eye. It takes three weeks for an egg to become an adult via different stages of their lifecycle. The official term for an infection with lice is ‘pediculosis’.

There are many different kinds of lice. The most common lice in horses is Werneckiella equi. It has a yellow-brownish colour. Lice are host specific, so they can only survive on very specific animal species. The lice that live on horses were only built to survive on horses and therefore can’t survive for long on other animals or humans. They can for a little while though, so they can be transferred from one horse to another via humans or other animals. They can also survive in the environment for a little while, so they can spread via materials, clothes, rugs, brushes, hay, straw, horse boxes, etc. Infection occurs most often in wintertime and early spring, when the horse has a long haircoat and there’s more humidity. Horses that have low immunity are more often affected, which may explain why lice infections happen more frequently in young, malnourished or stressed horses. Infection often starts in these horses, after which it can spread to other, healthier horses that would otherwise most likely not have been affected. Horses that have lice should therefore always be seperated from other horses, and the environment and all materials (such as brushes and such) thoroughly cleaned to prevent the infection from spreading.   



Lice itch, which may cause the horse to lick or bite themselves or scratch or rub themselves using objects. When numbers are low this behaviour may not be as noticeable, but with more severe infections horses can even wound themselves by incessive scratching or biting. Often horse owners notice something’s wrong once the horse develops bald patches or wounds. Very severe infections can be very debilitating, cause weight loss and even fever.  



Your vet can diagnose lice for you by doing a clinical exam. There are some other things that can cause itchyness or bald patches, that should also be considered. If lice are visibly present, a diagnosis can be made directly. 



Lice can be treated with topical (on the skin) solutions that are registered for horses. It is very important that these drugs have enough contact-time with the horse, and should therefore not be washed off for at least 3 days. This includes heavy rainfal that can wash out the topical drug. Make sure to apply the drug to the skin, not the haircoat. If you’re unsure about how to aplly the drug, please ask your vet. (Only) if for any reason these topical solutions are not an option, your vet may be able to offer an alternative. Depending on the drug that’s used, a second dose may be needed 3 weeks later, based on the lice’s lifecycle.  

The horse's tack, rug and halter should be cleaned regularly until the infection has passed. The living area should be assessed to see if needs to be cleaned. All things that have come into contact with the horse should be washed. If the horse grazes with any other horses, they should be checked as well and treated if an infection is suspected. Horses with lice should be kept apart from other horses. People should not attend to non-infected horses after they’ve been in contact with infected horses. If they do want to, they should first get cleaned (including their hair) and change their clothes. It’s best to attend to infected horses last.  


If you think your horse may be itchy, or if you have any questions about this article, please contact us and we’ll be happy to answer any of your questions.  


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