The first step in treating lice on horses is to administer a wormer paste or shot. Once this is done a topical treatment can be applied to kill the lice, but this treatment should be repeated again in about two weeks' time. It is important to take steps to ensure that the lice do not transfer to other horses, and to prevent the horse from being infested again.
A healthy horse will rarely get lice, but infestation is more likely when intestinal parasites are present. Administering a wormer paste is recommended, but your vet may have to prescribe a shot if the infestation is severe. Experts recommend ivermectin products for this purpose, but your vet could prescribe a suitable alternative.
Treating the lice infestation itself should be the next step, and there are various products available for this purpose. Some treatments take the form of a spray, while others come in powder form. It is suggested that the sprays be used during the summer months, as the spray will make the horse's skin wet. During winter months, it is best to use a powder based treatment, and this can also be used on horses that will not tolerate being sprayed.
Repeat the treatment again in two weeks to ensure that the eggs that have been left behind, along with any surviving lice, are killed. This will help prevent the infestation from recurring. Additional measures, including a thorough cleaning of the stall and any equipment the horse has been in contact with, should also be taken. A mixture of water and bleach can be used to do this, but insecticides are considered to be more effective.
Lice on horses can spread from one horse to another, so it is recommended that you treat all horses that have been in contact or in close quarters. Horses will often rub up against objects or each other in order to relieve the irritation, and this can help transfer the lice. Horse lice cannot be transferred to humans or vice versa.
There are ways to prevent lice on horses, and keeping the horse in top condition is chief among these. Grooming equipment should never be shared, as this is creates an easy way for the lice to spread. Regular cleaning of the stall is also recommended. Horses in colder climates tend to suffer lice infestations more easily because their long winter coats create the ideal environment for the lice.
To check for lice on horses, scrape underneath a horse's chin and catch the debris on a piece of paper. If a lice infestation is present there will be bits of skin, dried blood and lice on the paper.