Lyme Disease in the Equine

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Lyme disease (LD) was first recognized in 1975. It is now the most commonly reported tick-borne illness in the US and Europe, and is also found in Asia. The Centers for Disease Control and Prevention (CDC) showed more than 35,000 reported human cases by 2008. The actual numbers are likely much higher, as many cases go unreported. Most cases are concentrated in about 15 states, mostly on the east coast from Virginia north. However, it can be found almost everywhere, so consider Lyme part of any rule-out list.

Lyme spirochetes – clever opportunists

The Lyme spirochete (Borrelia burgdorferi) is a very mobile, corkscrew-shaped bacteria. In nature, the cycle of life involves Ixodes ricinus ticks on the east coast, with other species used by the bacteria in other parts of the US and the world. Contrary to popular belief, deer are far from the only host for infected ticks, as each tick species prefers different hosts.

Many small mammals are also part of the host cycle, from the white-footed mouse (the main species in the northeast) to the chipmunk, hedgehog and rat, along with humans and dogs. Nymph stage ticks are the source of most infections, although the adult tick is a little larger and easier to see.

Spirochetes possess separate plasmids (DNA strands) and have an inner and an outer protein coat, which is unusual in the bacterial world. The outside coat that contacts the host organism can adapt to whichever species the spirochete has infected.

There are many different outer surface protein coats, called OSPs, and different portions of them are up-regulated while the tick is eating its blood meal, even before the spirochete enters the body. A compound called decorin essentially hides the outer layer of the spirochete from the host immune system so that it can enter the body undetected. The spirochetes can then change themselves in a variety of ways so the immune system does not have one single thing to respond to. The spirochete cells also communicate among themselves and exchange information to evade antibiotics, an event that also occurs with other resistant bacteria.

While in the body, the spirochetes continue to alter their structure from moment to moment. This probably contributes to the variety of symptoms as well as the resistance to treatment.

Spirochetes seem to prefer certain types of cell, particularly collagen. This means that the joints, the aqueous humor of the eye, meninges of the brain, skin collagen and heart tissue (less so in the equine for an unknown reason) are all more susceptible to damage. Spirochetes actually travel faster in collagen then they do in the bloodstream. In Chinese medicine (TCVM), the Liver governs the collagen, sinews, tendons and ligaments, so one of the most important factors in Chinese treatment will be to support the Liver.

Infection with Lyme causes an imbalance in the Th1 and Th2 immune complexes. In the case of a healthy immune response, the T helper cells (Th1) produce type I cytokines such as interleukin-2, tumor necrosis factor-beta and interferon gamma, which have a side effect of infl ammation. Th2 lymphocytes produce the cytokines interleukin (IL) 4, 5, 6, 10 and 13, which essentially help cool down the infl ammation from the Th1 response. If these responses are out of balance, the spirochete can win the battle.

The spirochetes are clever opportunists, and respond to an assault from an antibiotic or the immune system by:

• changing their protective surfaces

• entering a cell

• forming a protective coating inside the cell

• creating completely different forms:

o cysts that can go dormant, then re-activate when conditions are conducive to their reproduction o blebs, which are partial pieces of material that are shed, perhaps to confuse the immune system o Spheroblastic L-forms o Antibiotic treatments especially seem to change the spirochetes into abnormal motile forms, which can be a cyst or a spheroblastic L-form.

Lyme disease appears to actually suppress the body’s natural killer cells (NK), the cytotoxic lymphocytes critical to the innate immune system. Clinically, many horses in the later stages of Lyme disease mount a poor immune response, seen in low white cell counts on a traditional CBC. It is my personal thinking that this is one reason behind the common incidence of low to equivocal Lyme titers.

The longer Lyme spirochetes are in the body prior to treatment, the more adjusted they become to the specific immune situation in that host. For example, spirochetes may stay in the synovial lining of a joint, then evade the immune system or antibiotic by entering the synovial cells. Once the antibiotics are out of the system or the immune system is weakened, the spirochetes re-enter the joint.

Diagnosis is challenging

A combination of thorough medical history (most important) along with a complete physical exam and blood work are required. In many cases, horses have been worked up for subtle lameness and have not responded well to traditional treatments such as joint injections and various anti-inflammatories. Diagnostic imaging may be inconclusive, or may point to joint inflammation yet treatment of that inflammation yields poor results.

Laboratory diagnosis: This can be very difficult, even in humans where testing is significantly more sophisticated. This is partly due to the cleverness and changeability of the spirochete, and partly because the tests are not good enough yet. The test from Cornell University gives the best range of values, yet some horses still test negative, while showing typical Lyme symptoms and responding well to treatment.

Holistic diagnosis: Since Lyme disease has many manifestations, there is no single clear-cut pattern as seen from a holistic perspective. From a homeopathic approach, one needs to take a complete history and prescribe a constitutional remedy based on the animal’s presentation.

From a Chinese perspective, the Liver is the organ most affected, directly and indirectly, by the spirochete. Many horses will exhibit signs of Liver dysfunction, though there is seldom one pattern for all horses. Wind invasion is common and many symptoms are related to that, with shifting signs. There may be Liver Qi Stagnation, Liver Heat rising, Liver Yin deficiency, Liver Blood deficiency and so on. These may be combined with other patterns, often made more complex by long-term drug use.

The real key is to approach each case as an individual, from your perspective and experience, and treat what is in front of you. It may change from month to month as well as from year to year.

No approved vaccines for horses

There are no Lyme vaccines approved for use in the horse. Canine vaccines are being used, but it is my experience that this is very detrimental to the equine immune system, with many horses relapsing post-vaccination. This was the experience with a human Lyme vaccine that was removed from the market about three years after it was approved. Most horses do not seem able to handle any vaccines well once they have Lyme disease.

Since we generally do not want to vaccinate in the face of an infection, there may never be a good time to give a Lyme vaccine. Lyme disease is difficult to detect and may be asymptomatic or go unrecognized for a long time, so many horses have been vaccinated while already harboring the disease. Most people desiring to vaccinate are living in endemic areas; consequently, the horses are likely to be infected. I do not recommend the Lyme vaccine for horses.

Best treatment approach is integrative

The best approach to treating Lyme is truly integrative. Most good human practitioners use antibiotics along with many immune supplements. The real key to treating Lyme is to help the immune system become as strong as possible – not just during the immediate treatment but over the long term. Due to Lyme’s ability to “recur”, the immune system must be ready to go to work at a moment’s notice.

Part of the difficulty in treating Lyme disease is that the bug selectively adapts to the individual’s body, so what works well in one horse may or may not work as well in another. This becomes a real challenge with merely conventional treatment. However, TCVM and homeopathy always treat each individual differently, so they can be very useful in dealing with this adaptogenic disease.

1. Antibiotics In the acute stages, and usually upon initial diagnosis, we generally begin with oral doxycycline. Intravenous tetracycline does have research that proves it works better, but clinically, many horses seem to respond just as well to doxycycline.

The management issues that arise with long-term intravenous therapy can be difficult in many situations. If the situation allows, it can be beneficial to start directly with intravenous treatment. Other antibiotics such as minocycline are being used, with some horses responding better to one or the other.

2. Complementary therapies Probiotics are an absolute necessity. Antibiotics may very well kill off some of the probiotics along with normal gut flora, but that is why I continue probiotics for several to many months after any antibiotic therapy is finished.

Immune system support is key. Many compounds that positively affect the immune system are very expensive, so consideration needs to be given to the client’s financial concerns. Generally, Chinese herbs and homeopathics, prescribed constitutionally for the individual, are the most curative in this author’s experience, and the most economical. Many nutritional compounds are more supportive in nature, but can nevertheless be critical to overall success.

Fortunately, a few useful compounds are relatively inexpensive:

• Vitamin C

• Noni (Morinda citrifolia) contains many antibacterial, antifungal and anti-inflammatory compounds. Studies have shown it is particularly effective for many forms of arthritis, and is also a very good immune regulator. In the fruit leather or powdered form, it is relatively inexpensive; in the juice form it can be quite costly and contains a significant amount of sugar.

• Omega-3 fatty acids are anti-inflammatory as well as supportive to the immune system. They can be obtained through feeding whole flaxseed (inexpensive), or naturally stabilized ground flax, hemp or Chia seeds (a very stable source of Omega 3s).

• Medicinal mushrooms have excellent research showing their positive effects on the immune system with their polysaccharides, glycoproteins, and anti-inflammatory compounds. There is also evidence they are beneficial in various arthritic conditions.

• Glutathione is a powerful antioxidant present in every cell. It is particularly important in the liver and has some direct anti-inflammatory effects on arthritis. For many horses, this may be one of the key ingredients in treating Lyme disease. Intravenous glutathione is available and can be given two to three times a week.


The treatment of Lyme disease is complex and requires a willingness to keep re-evaluating the patient’s progress. Most horses can be returned to full performance, even with chronic Lyme disease, but many will require ongoing maintenance. Using individualized medical treatments such as homeopathy and TCVM is key to maximum recovery.

Dr. Joyce Harman graduated in 1984 from Virginia Maryland Regional College of Veterinary Medicine. She is certified in veterinary acupuncture and chiropractic and has completed advanced training in homeopathy and herbal medicine. Her practice in Virginia uses holistic medicine to treat horses. Her publications include The Horse’s Pain-Free Back and Saddle-Fit Book – the most complete source of information about English saddles.