Depending on the region, Ear Ticks (Otobius megnini) can be a significant problem for horses. They tend to be more common in horses at pasture, but can occur in any horse. In most cases, ticks just cause local irritation that cause head shaking, head tilt, and ear cocking. The ear canal may become irritated, and develop secondary bacterial infection.

In some cases, however, ear ticks can cause more serious problems. The presence of ear ticks (and an undetermined toxin) can cause a neuromuscular reaction that can take a variety of forms. The most common of these is muscle trembling with spasm. Signs of abdominal pain (colic) may occur. The third eyelid may intermittently cover the eye. In rare cases, horses are severely uncoordinated and may fall down.

DIAGNOSIS requires an examination of the external ear canal. Ticks are usually visible there. A veterinary examination (using an otoscope) may be required.

TREATMENT - involves physical removal of the ticks using a forceps. Care must be taken not to injure the eardrum or inner ear. In many cases, sedation will be necessary to safely remove the ticks. Application of tick killing topical medications (pyrethrins and other insecticides/acaricides) will also be effective. The choice of chemical should be guided by your vet, as serious The ticks die and the horse can shake them out of the ears. Ivermectin and moxidectin may be helpful.