Two types of lice -- chewing and sucking -- affect equines. All lice are species specific, so you don't have to worry about catching lice from your horse. Infested equines easily spread these parasites to other horses, though, either from direct contact or by the use of shared grooming materials or living spaces. Well cared-for horses living in low stress conditions aren't likely to suffer from a lice infestation, although it's possible. Horses most vulnerable to lice are those with compromised immune systems or in high-stress situations, such as animals going through auctions. If you suspect your horse has lice, call your veterinarian.
Lice Infestation Symptoms
Lice are generally too small to see with the naked eye, but you might see their whitish eggs -- or nits -- on the hair shafts of dark horses. Biting lice are easier to spot than sucking lice, since the former are more active and you might see the movement. Lice usually congregate on the tail base, mane, head and neck, but can appear anywhere. Sucking lice often latch on to the lower legs. A lousy horse may rub the affected areas or bite at places he can reach with his teeth. Frequent rolling could indicate he's trying to relieve itching on his back or neck. He may lose hair in those areas, or develop lesions. If sucking lice are the culprit, their gorging can result in infections and even anemia if there's sufficient blood loss. Hair in severely afflicted horses might mat.
Getting Rid of Lice
Your vet might recommend the natural approach of clipping your horse's coat, even in winter. That's actually the time lice are most prevalent, since long hair offers lice more protection. You can keep your horse warm with a blanket once clipped, but short hair discourages lice infestation, and especially reproduction.
Various types of insecticides are used for lice eradication, in powder or spray form. It's not a one-time treatment. Horses must receive a minimum of two treatments, as the insecticide doesn't get rid of the nits, which hatch in about two weeks. You must also disinfect all brushes and any tack used on your horse. If possible, disinfect any stall or trailer used by a lousy horse, and keep it empty for a few weeks to kill off any stragglers.
Regular deworming with an ivermectin-based product lessens the odds of your horse becoming contaminated with lice but doesn't completely eliminate them. You're unlikely to have an issue with sucking lice, who feast on blood, but chewing lice consume dander.