Caused by ticks, Lyme disease can have serious consequences for your horse. Protect him by arming yourself with the latest information.
Lyme disease (LD) has been on our radar for 40 to 50 years. It is now the most commonly reported tick-borne illness in the US and Europe, and is also found in Asia, Australia and Canada. Since LD can be found in so many locations, it should be part of a rule-out list for horses when a diagnosis is not clear.
The Lyme spirochete (Borrelia burgdorferi) is a very mobile, corkscrew-shaped bacterium. Its life cycle involves the deer tick or black-legged tick on the east coast, with other tick species involved in other places. Contrary to popular belief, deer are far from the only hosts for infected ticks, since different species prefer different hosts. Many small mammals are part of the host cycle, from white-footed mice (mainly in the northeast) to chipmunks, hedgehogs, squirrels and rats, along with humans and dogs. Fleas, spiders, mosquitoes and mites are also possibly part of the tick life cycle, though available research has not defined their exact role.
Tiny nymph stage ticks are the source of most infections. The adult tick, which is a little larger and easier to see, may be less important but potentially infective.
The difficulty with this organism is that it is incredibly smart (it talks to other spirochetes) and very adaptable. It can change shape and evade the immune system, and go dormant while waiting for an opportunity to reactivate. Its outer surface protein coats (Osp) change as the tick attaches and begins to suck the host’s blood. This and many other adaptations allow it to become resistant to antibiotics, herbs and the host’s immune system.
Symptoms and diagnosis
The characteristic bull’s-eye skin lesion is not seen in horses, most likely because of the hair coat. One of the most common signs is lameness or arthritis that is difficult to identify and may change locations. Other symptoms are anterior uveitis, neurologic signs, low grade fever, sensitivity to touch, lameness, weight loss, tremors, neck pain, lethargy and laminitis. Importantly, there is usually some degree of behavior change.
About 10% to 15% of the horses in my practice area become dangerously spooky when infected with Lyme. The exact reason is unknown but it may be due to one of the different strains. Sometimes Lyme appears along with or before/after cases of equine protozoal myelitis (EPM), particularly in older horses. Sometimes Lyme presents with neurological symptoms that look like EPM, but test positive for Lyme.
Diagnosis of LD can be very difficult, partly due to the cleverness and changeability of the spirochete, and partly because tests are not good enough yet. The main test, performed by Cornell University, is called the Lyme Disease Multiplex Test. It measures different stages of the disease but does not correlate perfectly with clinical signs. The test can be negative, yet a horse can still respond to treatment and behave as if he has LD.
There are no LD vaccines approved for horses, so canine vaccines are used. Vaccination can be stressful to the immune system and has led to relapses. A recent study showed that current canine vaccines produced only short-term responses in horses. It is important to note that many, but not all, of these horses have negative responses to other vaccines, such as rabies, West Nile Virus and others, once they have had LD.
Preventing Lyme disease
Prevention is difficult if you live in an LD-endemic area. Topical anti-parasitics are toxic to animals and the environment (if they are washed off by rain and get into waterways). In some cases, it is easier to support the horse’s immune system to deal with the drugs than it is to treat chronic LD. In other cases, it is beneficial to use a more natural approach. For example, Guinea hens are effective at removing ticks from the environment, though they are noisy and may not fit into the farm environment. Keeping grass mowed in the pasture is also helpful.
Topical essential oils and various insect-repellent sprays can be helpful, but need to be applied frequently. Japanese knotweed root appears to be helpful in endemic areas, but does not guarantee protection. Feeding garlic or apple cider vinegar can be useful.
A new topical spray called Ticks-Off® prevents ticks from adhering to the hair and is an exciting addition to LD prevention protocols. It’s non-toxic and therefore safe to add to a prevention program.
There is no magic bullet in treating LD. The best approach is multi-systemic, using a combination of conventional, complementary and alternative medicine. Successful treatment includes support for the immune system, not just during the immediate treatment period but over the long term. Due to the spirochete’s ability to “recur”, the immune system must be prepared to respond at a moment’s notice.
Antibiotics are useful, especially in freshly diagnosed horses. However, repeated courses, or use spanning two to three months or more, usually produce resistance and are detrimental. It is better to change to herbs and keep the spirochete guessing. Antibiotics suppress the immune system in the gut, so the rest of the plan needs to support it.
• The microbiome is the DNA of the microbes living in the gut. Probiotics are an absolute necessity and should continue being given for many months after antibiotic therapy is finished. The purpose of long-term probiotics is to restore the health of the microbiome.
• Vitamin C is well known for its action in the immune system and collagen. (4g to 6g twice a day).
• Noni (Morinda citrifolia) is an herb that supports the immune system and has excellent anti-inflammatory properties. In fruit leather form, it is relatively inexpensive and concentrated; the juice form can be quite expensive, more dilute and contains significant sugar.
• Omega-3 fatty acids are anti-inflammatory and supportive to the immune system. They can be obtained by feeding whole flaxseed, naturally stabilized ground flax, hemp seeds or chia seeds (a very stable Omega-3 source). Flax or hemp oils can be used but must be refrigerated during warm or hot weather. Three to six ounces twice a day is the usual dose for seeds; less volume is needed with oils. Blue-green algae also contains significant Omega-3 fatty acids.
• Medicinal mushrooms are backed by excellent research showing positive effects on the immune system, and are beneficial for various arthritic conditions. They are safe and can be used over the long term in a tincture or powder.
• Joint supplements are important for any horse with signs of joint-related discomfort. They include glucosamine-based supplements, hyaluronic acid, glycosaminoglycans and green-lipped mussel, as well as Western and Chinese herbal preparations.
Hemp, cannabis and CBD
The use of hemp with cannabinoids (CBD) for equine LD is new, but early clinical use is showing excellent results. In humans, CBDs are being used successfully for LD. The effects of cannabinoids on the immune system, arthritis, pain relief and inflammation are among the reasons they are useful for LD.
CBD is usually available as an oil extract. This is an expensive way to give it to horses, since the dose that seems to have the best clinical effect is about 25mg twice a day. Poor quality CBD is a common problem, and products with low concentration likely have less effect. Hemp will grow anywhere, and extracts toxins from the soil, so it’s important to use organic, traceable products. Recently, a hemp leaf extract has been used.
Cannabis with a THC component is not legal in most states, so has not been researched for use in horses. It would likely have an overly sedating effect in horses, making them unsafe to ride.
• Homeopathics should be prescribed constitutionally, based on presenting signs. Several medicines fit many LD symptoms quite well. Ledum palustre is a major homeopathic for LD; its symptoms include effects from toxic puncture wounds as well as insect bites. A tick bite is both. Rhododendron and Kalmia latifolia are worth considering. Based on the constitution, other medicines have helped individual cases including, but not limited to, Sulphur, Arsenicum album and Rhus toxicodendron.
• Western herbal protocols have also been used successfully. In general, herbal formulas should not be used on a continuous basis using the same herbs, since the spirochete is capable of developing a tolerance to them. Formulas should be rotated every month.
• Acupuncture is excellent for pain control, immune stimulation and tonifying Qi or energy. There is no one-point prescription since each horse is an individual.
• Chinese herbal medicines are effective in both the early and late stages of LD, depending on the pattern presented. Current thinking again suggests changing formulas on a regular basis. Herbs should be prescribed by trained Chinese herbalists, since herb choice and type are based on a correct Chinese diagnosis.
Other treatment suggestions
Additional compounds can be helpful depending on the signs the horse is showing. Magnesium is frequently deficient in human LD patients, and it is easy to supplement horses with magnesium citrate (1g to 3g per day). Topical preparations of magnesium are beneficial if oral supplements cause any intestinal upset; however, the actual dose absorbed is difficult to calculate.
Herbs to support general gut health can be beneficial, especially after prolonged courses of antibiotics. Marshmallow leaf and meadowsweet are examples. Turmeric root shows excellent anti-inflammatory effects for joints and supportive properties for the liver. Garlic may be beneficial; it may also help keep some ticks away and is a good tonic herb. Coenzyme Q-10 is a fat-soluble antioxidant that may help as well. Resveratrol is another antioxidant that can be used in LD cases.
Exercise at the level the horse is comfortable with is an important part of recovery. It’s good for the immune system and helpful for the horse mentally. There is no benefit in pushing the horse beyond what is comfortable, so if he is having a bad day, a short walk will suffice.
Stress relief is an important factor in recovery. It’s beneficial to maintain horses on adaptogenic, stress-relieving herbs such as Siberian ginseng root (Eleutherococcus senticosus), once they have recovered and gone back to competition. It’s also important to note the amount of rest the horse gets at the barn. It has been shown that horses actually get very little rest and sleep at many busy barns. This adds to the horse’s stress, which suppresses the immune system.
Treating LD is complex and requires a willingness to keep re-evaluating the horse’s progress and make changes based on current symptoms. To prevent relapses and maintain optimal health, stress needs to be managed, the immune system needs support, and the way your horse feels needs to be considered. Tick and insect control is always challenging, but needs to be an important part of managing LD. Most horses can return to full performance even with chronic LD, but many will require ongoing maintenance.