equine lyme disease

In recent years there has been a dramatic increase in cases of Lyme disease in horses in Eastern Ontario. Lyme disease is caused by a bacterium called Borelia burgdorferi, which is transmitted through the bite of an infected tick. In our area the carrier tick is Ixodes scapularis, commonly called the Blacklegged or Deer tick. Ticks are seen throughout Eastern Ontario, and Leeds and Grenville counties are now considered to be areas endemic for Lyme disease. As a result, many horses living in these areas will test positive for exposure to the Lyme disease organism, although most will not appear ill.

Lyme disease has often been nicknamed “the great imitator”, as many of its symptoms can mimic those of other disease. Fever, along with lameness, may be the most important clues for horses with Lyme disease, as these two symptoms aren’t seen together in other conditions. Other symptoms that have been connected to the disease are muscle tenderness, behavioural changes, laminitis, and uveitis (moon blindness). There have also been cases of encephalitis (brain inflammation) in horses with Lyme disease infection. However, they do not seem to suffer from the potential heart, kidney and/or liver disease that can be seen in people with Lyme disease.

Exposure to the Lyme agent can be confirmed by a quick and simple blood test performed right in our hospital. Testing should be done eight weeks after a tick is found attached to your horse. In areas where ticks are frequently seen, this screening test should be done once a year.

Lyme disease is treatable with a course of antibiotics that must be administered twice daily for at least one month. The cost of this treatment is between $400 - $500 for the average horse. Unfortunately, having Lyme disease does not convey any immunity to your horse. Even if treatment has been successful, he/she can be re-infected at a later date. Continued monitoring for the relapse of Lyme symptoms is necessary for the remainder of the horse’s life.

The good news is that studies have revealed that Lyme disease can be prevented in horses by vaccinating them with the canine Recombitek Lyme vaccine. These studies indicate that the vaccine is highly effective in preventing Lyme disease when given to horses that have not already been exposed to Borelia burgdorferi. The initial vaccine must be followed by a booster one month later and then given every six months to provide protection.

Ticks must be attached to your horse for at least 12-24 hours before Lyme disease can be transmitted. Thoroughly examining your horse EVERY DAY and removing any ticks is the best way to prevent Lyme disease. Do not apply anything to the tick as this can cause it to regurgitate and increase the likelihood of disease transmission.

Keeping pastures mowed and clearing brush and wood piles are also essential elements of tick prevention. Topical insect repellent sprays and products that contain permethrin may help repel ticks when applied to the head, neck, legs, belly and under the tail.  This must be done on a regular basis in order to be effective. Repeat applications of these products depend on the degree to which your horse sweats, gets wet or is bathed. At RSLVS, we recommend applying a topical product to your horse called ADVANTIX as a monthly preventative. For a 1000 lbs. horse, the cost would be about $40 per month. Although this seems like a lot, it is less expensive than treatment of Lyme disease and may prevent your horse from getting sick.

(RSLVS 2017)