Lyme Disease in Horses

Published Jan. 22, 2025
Horse grazing in tall grass

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In This Article

Summary

You’ve probably heard about the dangers of Lyme disease in dogs, but what about Lyme disease in horses? Just like our canine companions, it’s important to understand the signs, treatment, and preventative options for Lyme disease in our equine friends.

Key Takeaways

  • Lyme disease in horses is transmitted through tick bites.
  • Horses exhibiting symptoms of Lyme disease should be examined by a veterinarian.
  • Treatment for Lyme disease in horses includes antibiotic medication.
  • There are no FDA-approved Lyme disease vaccines for horses, despite the vaccine availability for dogs.

What Is Lyme Disease in Horses?

Lyme disease is caused by the bacteria Borrelia burgdorferi, which is transmitted through tick bites.

Lyme disease is not as common in horses as it is in dogs, but horses living in the Northeast, Pacific Coast, and Midwest where a specific species of deer tick is common may be at a higher risk of contracting this disease.

Lyme disease typically causes a gradual onset of vague symptoms; however, if your horse suddenly becomes very stiff or hypersensitive, displays behavioral changes, or has any other rapidly developing symptoms, it’s safest to have them examined by your veterinarian.

Severe Lyme disease in horses can lead to death, so early intervention is key.

Symptoms of Lyme Disease in Horses

The most common symptoms of Lyme disease in horses include:

  • Uveitis, which typically develops very quickly if caused by a Lyme infection. Some horses may lose complete vision in less than a month.

  • Neuroborreliosis, which is caused by the bacteria entering the horse’s nervous system. This may cause symptoms such as ataxia (wobbliness), respiratory distress due to paralysis of the larynx, and cranial nerve deficits (depression, head tilt, irregular eye movements, circling).

  • Bursitis, or inflammation of bursas, which are fluid-filled sacs located near a horse’s joints.

  • Cutaneous pseudolymphoma, which are superficial bumps at the tick bite site.

Other potential symptoms of Lyme disease may include:

  • Behavioral changes

  • Stiffness

  • Hypersensitive skin

  • Muscle atrophy (wasting)

  • Weight loss

  • Lethargy

  • Lameness

  • Joint swelling and pain

Causes of Lyme Disease in Horses

A horse may develop Lyme disease after being bitten by an Ixodes tick (also known as the deer tick or black-legged tick) infected with B. Burgdorferi. A tick will pick up this bacterium by first feeding on mice or other small mammals that carry it.

It is believed that ticks typically need to be attached to a horse for at least 18 hours to begin transmitting this bacterial disease. This timeframe allows the bacterial organisms to modify themselves enough to enter the horse’s body and survive in the new environment.

Lyme disease cannot be transmitted from horse to horse, and at the time of this publication there have been no documented cases of a foal acquiring the disease from their mother. Horses are therefore considered “incidental or dead-end” hosts for Lyme disease, just like humans.

It may take anywhere from three weeks to several months for a horse to develop signs of Lyme disease. Many horses do not develop any obvious symptoms.

How Veterinarians Diagnose Lyme Disease in Horses

Diagnosing Lyme disease can be somewhat difficult while the horse is alive, since most horses that are exposed to B. burgdorferi do not develop clinical symptoms. However, if your horse experiences any concerning clinical signs including visible tick bites or live ticks, always contact your veterinarian to examine your horse.

After their initial exam is performed, veterinarians will typically take blood work to check for antibody production targeted toward the B. Burgdorferi bacteria. These tests may come back positive even from simple exposure, so this test is not recommended unless a horse is showing clinical signs consistent with Lyme disease and other conditions have been ruled out.

Severe Lyme disease in horses can lead to death, so early intervention is key.

If a horse tests positive for antibody production against Lyme disease antigens, other tests may be performed, including cytology and histopathology. These tests examine affected tissues to evaluate for characteristic signs and cells of inflammation consistent with Lyme disease.

A tentative diagnosis of Lyme disease can only be made if clinical signs are present, tests are positive, and all other potential causes of a horse’s symptoms are ruled out.

Samples or culture swabs taken from the horse’s brain or central nervous system can confirm diagnosis if a horse dies or is euthanized due to severe disease progression.

Treatment of Lyme Disease in Horses

If a horse is diagnosed with Lyme disease, the typical approach for treatment is antibiotics. While there is no “gold-standard” therapeutic approach for Lyme disease in horses at this time, the most commonly used antibiotics for Lyme disease include:

These medications are typically given to horses for two to six weeks but can be prescribed for treatment up to a few months.

If your horse is experiencing painful symptoms, NSAIDs like phenylbutazone or flunixin meglumine may also be administered for a time.

Additional therapies including acupuncture, herbal therapy, and chiropractic have also been used with reasonable success for a horse’s discomfort if they have Lyme disease.

Recovery and Management of Lyme Disease in Horses

Even after a horse has completed a course of antibiotics and their symptoms have improved, retesting for the disease is not typically recommended since antibody numbers may remain high, yielding positive results for months or even years after exposure or disease.

Treatment of Lyme diseases in horses is considered successful if symptoms improve and the horse returns to their normal state.

The prognosis for mild Lyme disease in horses is typically good with rapid diagnosis and treatment.

On the other hand, horses that develop neuroborreliosis typically have a guarded to poor prognosis due to the severity of disease this brings and worsening of clinical signs even with treatment.

If a horse has prolonged joint inflammation or pain due to Lyme disease, recovery may take up to a few months or longer, and these horses may later develop arthritis.

Your veterinarian may recommend NSAIDs such as firocoxib, joint supportive therapy, or supplements during or after treatment of Lyme disease, or later in life if arthritis develops.

Prevention of Lyme Disease in Horses

A horse owner can help to prevent Lyme disease in horses by helping them avoid or repel ticks and through controlling their environment as much as possible.

There are a variety of commercially available tick-repelling sprays and topical preventions that can help keep ticks off your horse. These are not 100% effective however, so it’s vital that you remain vigilant for ticks.

Check your horse for ticks daily and remove any that may be present, especially if you live in a prevalent area. This can be an easy touch and scan during feeding or grooming time.

It's also important to help keep the environment as unappealing to ticks as possible. This may involve keeping pastures mowed, removing wood piles or leafy debris, and keeping stalls and paddocks well-lit, since ticks prefer shady, moist environments and plant cover.

Unfortunately, there are currently no FDA-approved vaccines for Lyme disease in horses. However, the canine Lyme vaccine has been shown to give partial and short-lasting protection.

Lyme Disease in Horses FAQs

What happens if my horse tested positive for Lyme disease?

If your horse is not displaying any symptoms suggestive of Lyme disease, this may indicate your horse had previously been exposed to a tick carrying B. burgdorferi. In regions where the deer tick is common, around 50% of horses may test “positive” for exposure but never develop true Lyme disease symptoms.

Is Lyme disease in horses contagious?

No. Lyme disease cannot be transmitted from horse to horse, so it is not contagious.

How long does it take to cure Lyme disease in horses?

Lyme disease is typically treated for two to six weeks, and most of the minor symptoms will resolve in this time frame. A horse may be considered cured of Lyme disease when they are no longer displaying any clinical signs.

Can you ride a horse with Lyme disease?

If your horse is experiencing any wobbliness, difficulty breathing, hypersensitivity, lethargy, muscle loss, behavioral changes, or vision issues, they are likely not safe to ride. Always discuss your horse’s rideability with your veterinarian.

References

AAEP Infectious Disease Guidelines. Borrelia burgdorferi infection and Lyme disease. 2020.

Divers T, Cornell University College of Veterinary Medicine. Lyme disease in horses. 2023.

Straubinger R. Merck Veterinary Manual. Lyme Disease (Lyme Borreliosis) in Horses. 2019.

Elsevier. Robinson’s Current Therapy in Equine Medicine, 7th edition. 2015.

References


Courtnee Morton, DVM, CVA, CVC

WRITTEN BY

Courtnee Morton, DVM, CVA, CVC

Veterinarian

Dr. Courtnee Morton is a 2017 Ross University School of Veterinary Medicine graduate. Since graduation, she completed an equine internship...


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