Wyatt managed a community pasture southeast of Regina. Being an excellent horseman, one of the gratuities his job offered was starting young horses for clients, the opportunity to instill cow-sense into green horses while conditioning them, readying them for competition and ranch life.
Wyatt’s call conveyed panic. He had found a promising and expensive filly down and unable to rise with no history of being ill. “Saw her yesterday and everything seemed fine,” he lamented. “There are no signs of struggle or other injury. Please come right away if you can. She’s a good one.”
The bay filly lay quietly on a small rise in the pasture. She appeared to be a picture of health but was totally unresponsive. Basic health parameters such as temperature, heart rate and breathing seemed normal. Neurological signs other than a depressed response to pain stimuli seemed within normal ranges. I initially drew a blank until I lifted a hind leg and looked in the inguinal area. In an area covering the size of a pie plate were at least 50 ticks in various stages of engorgement. They appeared to be Dermacentor variabilis.
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In North America, D. andersoni (the Rocky Mountain wood tick) and D. variabilis (the American dog tick) are common tick species. Sheep, cattle, dogs and people can be infested.
Ticks are becoming an increasingly significant parasite of horses across North America. In many areas where they have not occurred before, they are now commonplace. Some blame it on global warming while others believe the increase in deer and other wildlife populations, that also suffer from tick infestation, has resulted in ticks becoming more prevalent. Regardless of the reason, ticks are a major problem.
Ticks cause local skin and tissue irritation, which often results in the horse constantly rubbing on trees or fences resulting in hair loss, hair coat damage, and anemia due to blood loss. Ticks transmit several serious diseases including equine piroplasmosis, Lyme disease, equine granulocytic anaplasmosis (ehrlichiosis) and tick paralysis. Ticks are not host-specific so the same ticks that feed on horses can also feed on dogs and humans.
Ticks are blind and find hosts by detecting ammonia emitted when horses breathe and sweat. Heat, moisture and vibrations attract ticks. Ticks wait on the tips of grasses and shrubs with their first pair of legs outstretched. When horses brush by, the tick quickly climbs aboard. Some ticks attach immediately while others move around the horse’s body, looking for areas where the skin is thinner, the reason ticks are most often found on a horse’s chest, underbelly, mane, tail, or inner flank. Attachment is often followed by a local skin reaction that appears as a small, firm nodule. Once filled with blood, ticks drop off to moult and progress to the next stage of their life cycle or in the case of adult females, lay eggs.
Check horses for ticks thoroughly after a ride and at least daily if on pasture. It is easier to feel ticks than see them. Scratch with your fingertips in areas where ticks like to attach (underbelly, inguinal region, mane, tail head, chest). Small bumps may indicate immature ticks, which can be hard to see.
Forget most anecdotes about tick removal. Old-fashioned remedies usually cause more damage than benefit (e.g. baby oil, Vaseline, heat). Use small tweezers placed just above the head and pull away from the skin until the head comes free. Drop detached ticks in a small jar of rubbing alcohol to kill them. Tick-specific topical acaricides applied directly on the horse can be effective. Environmental controls such as brush and grazing management are a big help. Your veterinarian can assist with choices.
Wyatt and I started to remove engorged ticks. The filly started to respond before we finished removing ticks and by the next day appeared nearly normal.
I only saw one other case of tick paralysis while in practice. It involved an old collie with long hair and several hundred engorged ticks — an unbelievable sight; the stuff nightmares are made of. The dog responded after a bath in a solution of Malathion, available for animal use at the time.
