Ticks are blood-sucking parasites that attach themselves to animals and people. As they feed, ticks can transmit a number of diseases. Skin wounds caused by ticks can lead to secondary bacterial infections and screwworm infestations. Severe tick infestations can lead to anemia and death. The international movement of horses infected with the tick-transmitted blood parasites Theileria, Babesia, Anaplasma, and Cowdria species is widely restricted.

Each species of tick has a favored feeding site on a host, although in dense infestations, ticks may attach themselves wherever they can find a feeding location. Some ticks feed chiefly on the head, neck, shoulders, and pubic area. In other species, the favored sites may be ears, near the anus and under the tail, or in nasal passages.

Direct contact with ticks frequently results in tick infestation. Animals that spend time outdoors, especially in wild areas, are more often affected. Thus, among horses, animals roaming in the wild or being ridden in wilderness areas are mostly likely to be infested, although any horse spending time outside can acquire ticks.

Spinous ear tick (Otobius megnini)

There is one tick that can hide unusually well. This is the Otobius megnini, also called the spinous ear tick. These ticks prefer to attach themselves in the ears of their hosts and are often overlooked by horse owners and other animal care givers. These ticks are found in dry areas of the western US and in Mexico and western Canada. Horses can suffer severe irritation from ear canal infestations. The infestations may cause paralysis. Secondary infections by larval screwworms are also reported.

The definitive sign of tick infestation is the presence of a tick on the animal. Ticks that have been on an animal only a short time (an hour to a few days) appear flat. Ticks that have been on an animal for several hours or days appear much more rounded due to the blood they have consumed. Diagnosis is by appearance of tick bite marks on the animal and the presence of the offending pest.

Treatment and Control

Ticks should be removed as soon as possible to minimize disease and damage. To remove a tick correctly, use tweezers to carefully grasp the tick close to the skin and pull gently. Never try to remove a tick with your bare hands, as some tickborne diseases can be immediately transmitted through breaks in your skin or contact with mucous membranes. The use of hot matches to remove ticks should also be avoided. Infested horses should also be treated with insecticides that kill attached larvae, nymphs, and adults. Contact your veterinarian for a prescription or a recommendation for the best tick control product for your horse. Be sure to tell the veterinarian what other animals you have because this may make a difference in the veterinarian's recommendation. Monitor the site(s) from which you have removed ticks. If a tick bite site turns red or swells, a call to the veterinarian is warranted.

If a horse is severely infested with ticks, it is recommended that you immediately contact your veterinarian regarding tick removal. Heavy infestations will not only severely damage the skin, but the chances of anemia and other complications are high.

Keeping animals away from tick-prone areas is the most effective step you can take to control exposure. Most ticks live in particular microhabitats, such as tall grass or the borders between pastures and woodlands. Destruction of these microhabitats reduces the number of ticks. Removing tall grass and weeds from your property and keeping pastures mowed can help protect your horse. Insecticide treatment of vegetation can slightly reduce the risk of ticks. However, it is not recommended for wide use because of environmental pollution and the cost of treating large areas.

Last full review/revision July 2011 by Karen A. Moriello, DVM, DACVD; Carol S. Foil, DVM, MS, DACVD; John E. Lloyd, BS, PhD; Bertrand J. Losson, DVM, PhD, DEVPC; Wayne Rosenkrantz, DVM, DACVD; Patricia A. Talcott, MS, DVM, PhD, DABVT; Alice Villalobos, DVM, DPNAP; Patricia D. White, DVM, MS, DACVD; Thomas R. Klei, PhD; David Stiller, MS, PhD; Stephen D. White, DVM, DACVD