Due to the small size of lice, most infestations go unnoticed until they have started causing damage to the horse's coat, or when nits (the eggs) are so numerous they are obvious in the horse's hair. Once an infestation is large enough to be noticable, it has likely already spread to any horses who have been in contact with infested horses, their tack, or their blankets.
There are two types of lice that can be found on horses. The first feeds by biting the horse's flesh, the Damalinia equi. The second species, Haematopinus asini, sucks the horse's blood. Both types cause severe itching, and can lead to unsightly issues with the horse's coat.
Treatments for lice may include:
- roaching and body clipping
- externally applied powder designed to kill lice (applied weekly or bi-weekly)
- insecticidal medication (administered at the recommendation of your vet)
Generally, there should not be any long-term effects once an infestation is resolved.