Not all ticks carry the Lyme-causing bacterium Borrelia burgdorferi and an estimated 90-95% of infected horses don’t actually get sick. But when horses do develop clinical illness, Lyme disease is usually a mysterious and frustrating beast. It presents with a wide range of vague symptoms that mimic many other conditions.
“It’s a hard disease to diagnose, very, very difficult,” said Dr. Carla Francheville, owner of Sunny Coast Veterinary, a practice based in Nova Scotia and Florida.
As the bacterium travels through the bloodstream, it can cause localized inflammation affecting various tissues in the body such as joints, tendons, ligaments, muscles, organs and the brain. Symptoms may appear immediately, within weeks, or even years down the road. Often, they’re extremely subtle, said Dr. Francheville. “You might have a horse that’s just lame in the right front and that’s it. Or the horse has a travelling-limb lameness where its one leg one time, another leg a different time.” General stiffness, weight loss, a low-grade fever, increased sensitivity to touch, grumpiness or lethargy are also signs.
When left to run amok, Lyme disease can lead to serious long-term complications including damage to the joints, skin, eyes and nervous system, which said Dr. Francheville, “are really hard to treat and get rid of.”
Early treatment of Lyme disease is key. And therein lies the conundrum. With such non-specific symptoms, often by the time a definitive diagnosis is made – if ever – Borrelia burgdorferi is well established in the horse’s body.
Transmission: Blacklegged Tick & Climate Change
The female blacklegged (or deer) tick transmits the disease. In eastern North America the offending species is Ixodes scapularis and on the west coast, Ixodes pacificus. The tick has a two-year life-cycle and goes through four stages: egg, larva, nymph and adult. After hatching, the tick needs a blood meal from a host to mature to the next stage.
A tick can’t fly or jump; instead it sits atop long grass or vegetation waiting to climb onto its next host, be it mammal, bird, reptile or amphibian. And there’s more ticks than ever lurking in Canadian pastures and farm environments hoping your horse (or your dog or you) will accommodate their need for blood.
That’s because climate change is expanding the blacklegged tick’s geographical range. In the early 1990s, blacklegged tick populations were detected only in specific areas of southern Ontario. Today the species is in every province and territory and is currently considered endemic in Manitoba, Ontario, Quebec, Nova Scotia, New Brunswick and British Columbia.
According to the Public Health Agency of Canada, the number of reported Lyme disease cases in humans has risen steadily from 144 cases in 2009 (when it became a federally notifiable disease) to 2,025 in 2017. Increased identification and reporting of Lyme disease by health care professionals accounts for a portion of that upswing, yet it remains an under-diagnosed condition, so the actual number of people affected may well be much higher.
Research shows that in areas where humans are getting Lyme disease, so too are the horses.
When Nova Scotia native Dr. Francheville started her practice in Florida 15 years ago, she saw four or five cases of Lyme disease a year. She estimates that number has at least tripled. And, as global temperatures continue to rise, ticks will move further northward, meaning an ever-increasing risk of exposure.
Diagnosis: A Process of Elimination
Diagnosis of Lyme disease is based on a number of factors, blood tests being one. However, results aren’t necessarily definitive and may only indicate the horse was previously exposed to Borrelia burgdorferi and the body has produced antibodies (blood proteins that battle infection) against the bacterium. Laboratory tests include the ELISA (enzyme-linked immunosorbent assay) and the Western blot, while the SNAP 4Dx, offers quick on-farm screening.
A newer, more specific test, the Lyme multiplex assay, by Cornell University’s College of Veterinary Medicine, can detect and measure separate antibodies at different stages of infection through blood or cerebrospinal fluid. This allows vets to detect Lyme disease earlier than other tests; determine whether a positive result is from vaccination, acute or chronic infections; and measure the level of antibodies, which can also aid in evaluating effectiveness of treatments.
Veterinarians rely on a process of elimination, first ruling out other possible causes for the horse’s symptoms, which can be varied and many. Considering the clinical signs, they then look at the horse’s history and exposure risk. (i.e. does it live or has it travelled in an endemic area?)
Dr. Francheville and her associates use a blend of both Eastern and conventional Western medicine to diagnose and treat all their patients. To start or end nearly every physical exam, they use what’s called a diagnostic acupuncture point scan. Based on the theory that energy is constantly flowing through 12 channels in the horse, “there are certain acupuncture points that when you scan them and the horse is reactive on those points, it means different things,” she explained. To perform the scan, Dr. Francheville runs a 22-gauge needle’s hub on the skin “very much like the strokes you use with the dandy brush.”
In a horse with Lyme, the scan will invariably find body soreness everywhere, she said adding, “and they’re usually ulcery.” When she gets to a particular acupuncture point on the hind end and the horse reacts, she automatically tests for Lyme disease. “The horse does this weird thing where they almost collapse when you scan that point and it’s pretty shocking to most clients. They’ll buckle their stifle and catch themselves or they’ll fire out and kick, so you have to be careful. Or they’ll do this thing where their whole back end will go off to the side and they’ll almost lose their balance away from you.”
Treatment: Sooner is Better
Promptness is the name of the game when it comes to treating this tricky ailment. “If you catch it early and you’re diligent when you treat [Lyme disease], you should have much greater success sooner,” said Dr. Francheville.
Treatment usually consists of an antibiotic regimen and supportive care. Dr. Francheville uses the antibiotic doxycycline, Chinese herbs, an immune system booster and acupuncture to reduce inflammation, help the body fight the disease and generally make the horse feel better. “I try to convince people to let me do the first acupuncture treatment immediately. Often the horse has a pretty dramatic improvement in their clinical signs, sometimes in hours, sometimes it’s a couple of days, but invariably the client says the horse changes, their eyes change, the way they move changes. You can tell when your horse is feeling better.”
Dr. Francheville will also do allo-injections, which involves taking the horse’s own blood and reinjecting it into several acupuncture points. “A lot of time, Lyme disease flies under the immune system’s radar. It just hangs out and the immune system forgets about it or doesn’t recognize it. So, when you pull the blood and inject it back into the horse, the immune system says, ‘Oh my gosh! There’s something here to fight. I’d better do something about it.’ It’s kind of the same principle as vaccinating.”
She continues with acupuncture, gradually decreasing the periods between treatments until they’re at every 12 weeks for maintenance. “Once a horse has Lyme disease it’s very rare for them to ever get rid of it. I’m not going to say in every case, but in most cases, the horse will have it for life. Then it’s a matter of getting them to what I call remission – get them to a point where they’re not critically affected and keeping them there.”
No equine-specific vaccine is available. A canine vaccine has been used extensively by U.S. vets, especially in high-risk locations. Anecdotal evidence suggests it is effective and safe for use in horses, but research out of Cornell suggests antibody responses are low and short-lasting.
Limiting your horse’s exposure to ticks is the best way to prevent Lyme. Ticks are most active from April to September, but can also remain active in mild winters with little snow cover. Ideally, although difficult for most horse owners, avoid wooded areas, tall grass, leaf piles and shrubs. On your property, mow regularly, keep brush from fence lines, clear garden debris, tend to overgrown areas and manage rodent populations.
Applying insect repellents that specifically address ticks can help, especially applied in areas where they tend to climb on such as the legs, belly, head, neck and tail. But effectiveness wears off quickly, so regular application is necessary. Continue using even after fly season, because, as previously mentioned, ticks can remain active into cooler weather.
Studies show it takes 16-24 hours after a tick has attached to a host for it to transmit the Lyme bacteria. Therefore, immediate removal reduces the chance of disease.
“The best thing I can recommend to horse owners is be really diligent about grooming,” said Dr. Francheville. “Look and run your hands through your horse’s coat – don’t just do it with brushes. Get your fingers in there, not just legs, but body, mane. It’s kind of a daunting task, but you’d be surprised at how many times you’ll find a tick if it’s there.”
A study led by Dr. Luis Arroyo at the Ontario Veterinary College and published in 2019 set out to determine the prevalence of Lyme Disease and Anaplasmosis in the Ontario horse population. To read the full report, click here.