Lyme Disease in Horses
In the last few years there has been increasing awareness about the presence of Lyme disease in Southern Manitoba. Lyme disease is caused by a bacteria (Borrelia Burgdorferi) and can infect multiple species including dogs, cats, horses, humans, and is carried in wildlife such as deer and mice. This is a vector disease which means the bacteria is spread by another species, in this case ticks. The deer tick is the most common carrier of the disease and as its range increases so does the prevalence of the disease. We have been answering an increasing number of questions with regards to Lyme disease in the equine population and address the most common ones below:
1. Is my horse at risk? In a word, YES. The population of ticks that carry this disease is present in Manitoba. We frequently see this disease in dogs and have found it in horses as well. The map below is from fall 2015 showing prevalence of ticks carrying the bacteria.
2. Can you test for it? Yes. There is a simple and affordable stall side blood test that looks for antibodies to the disease, and an excellent screening test, called the 4DX test. This test was designed for dogs but will also show positive results for lyme disease in horses as well. The most specific test is known as a multiplex test that provides a quantitative measure (gives a number) that requires a blood sample sent away to a lab. Depending on the results of the stall side test we may choose to send this sample away.
3. Is it treatable? YES. Because this disease is a bacteria it can be treated by antibiotics, specifically Doxycycline, which we get as a powder that can be added to the feed. Antibiotic therapy must be at least 4 weeks in duration to eliminate the bacteria. It can also be treated with shorter courses of intravenous oxytetracycline followed by oral oxytetracycline.
4. Can I vaccinate for it? Yes and No. This is a difficult question because currently there is no vaccine available for horses that is labelled to prevent the disease. There is a vaccine available for dogs that has been suggested to be effective in horses but it is still being tested and proven. This vaccine has been used extensively in the U.S with promising results for both safety and reasonable effectiveness. It is currently being given with a one month booster and at 6 month intervals. Using this vaccine is off-label which means that it is not designed specifically to work in horses, and any adverse reactions will not be covered by the vaccine company. The choice to vaccinate or not will be based on risk factors such as location, travel, housing, and how you use your horse.
5. How do I prevent ticks? You can aid prevention through management of the horse and environment. Listed below are a few tips for deterrence.
a. Apply fly repellants that contain permethrins such as Ultra Shield and Wipe. These are insecticides that are effective for both flies and ticks. Pay particular attention to coat the base of the mane and tail. Continue to use these products into the fall even when the fly population has subsided.
b. Daily grooming. Ticks take 24 hours of attachment before they transmit the disease, and although they are small and difficult to find early removal is key. Again, focus is usually on the areas around the head, mane, and tail.
c. Keep out of long grasses where the ticks usually convalesce (they love moist temperate environments), short pasture or a dry-lot will have a much lower population of ticks.
6. If my horse in infected what will I see? Signs of Lyme disease are nonspecific in horses and include any of the following - chronic weight loss, low-grade fever, sporadic or shifting leg lameness, muscle tenderness, cloudy or watery eyes, and arthritis. Some horses also develop poor performance, high sensitivity to being touched, behavioral changes, or neurologic signs. There is also a population of horses that will appear normal but still have a positive test. There is concern regarding chronic infections in these animals.
7. How soon will they show signs? Ticks must be attached for 16-24 hours to transmit the disease and once it is in the system clinical signs usually follow in 2-5 months. Testing will often not show up positive immediately after infection but in the weeks following. In some cases the issues that develop, like arthritis, can become irreversible and cause long term pain or discomfort and in the worst case scenario organ failure and death.
Lyme disease is still a relatively new disease in the horse world and as such there are questions regarding the right way to diagnose and treat the disease. As Lyme becomes a concern in Manitoba an increase in testing is leading to more successful treatments and for many conditions that appear unrelated Lyme disease becoming a more likely diagnosis.
This year we are offering a fall promotion on exams, testing, treatments, and vaccination for Lyme disease. To see the details of the promotion click here. Our goal is to raise awareness of Lyme disease as an emerging problem in the province, test animals that are at risk, and develop vaccination or prevention protocols that work for you and your horse.