Is It Lyme Disease?

A veterinarian shares the latest research findings regarding Lyme disease in horses and her practical experience as a veterinary internal medicine specialist in the heart of Lyme country.
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Is It Lyme Disease?
Groom your horse frequently to find and remove ticks before they have a chance to transmit disease. | Photo: iStock

A refresher on this difficult-to-diagnose tick-borne disease

A horse that’s underperforming, lethargic, and repeatedly yet subtly lame—it’s one of the most frustrating scenarios for an owner. At some point in your riding career, you’ve likely encountered a horse with lameness that was either nonspecific or undiagnosed. Maybe you noticed it in one limb one day and another the next.

If this sounds familiar and you live in a Lyme-endemic region (see the map on the next page), someone has likely mentioned the possibility that your horse has Lyme disease. Our knowledge of equine Lyme disease, otherwise known as Borrelia burgdorferi infection, is burgeoning and nascent. Currently, there are more ­questions than answers in the scientific literature. So how do you and your veterinarian determine if your horse is affected? Read on to find out, based on the latest research findings and consensus statements, as well as my practical experience as a veterinary internal medicine specialist in the heart of Lyme country.

What Is It?

Lyme disease is a tick-borne infectious disease caused by the bacterium B. burgdorferi. In humans infection can lead to a wide range of clinical signs, including rashes; arthritis; skin, neurologic, and cardiac issues; and possibly prolonged fatigue. In dogs Lyme disease can also cause kidney issues. The disease is not as well-characterized in horses, however, due to the limited equine studies that exist, but researchers believe its signs include neurologic issues, uveitis (eye inflammation), cutaneous pseudolymphoma (a nodular skin disease around the tick bite), muscle atrophy (wasting), behavioral changes, hyperesthesia (excessive sensitivity to stimuli), and heart rhythm abnormalities, among others

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Written by:

Jean-Yin Tan, DVM, Dipl. ACVIM-LAIM, is an equine internal medicine specialist and faculty member at the University of Calgary Faculty of Veterinary Medicine. She trained previously in New Jersey, Minnesota, and California and subsequently spent six years in private practice, including owning an equine specialty practice in New York State. Her interests include equine infectious disease and respiratory disease.

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