Lyme Disease in Horses: Symptoms, Treatment and Prevention

Last Updated on February 22, 2022 by Allison Price

Lyme disease in horses can be a confusing and mysterious equine illness, but it is easily treatable.

Showing , Timed Events , Trail Riding , Ranching

These symptoms can appear vague or mysterious. Lyme disease in horses can cause a variety of symptoms, including a lump the size of a thumbnail, general lethargy, and sore joints.

Lyme disease can be a problem for horses and humans if you live in an area with ticks. Although it can be treated, prevention is the best way to avoid it.

How do horses get Lyme Disease?

Lyme disease is named after the Connecticut town in which it was first recognized as a rare syndrome, Lyme, Connecticut-in 1975.

Borrelia burgdorferi is the cause of the disease. Infected ticks can transmit it to horses. Although there are many types of ticks capable of transmitting the bacterium to horses, the most prevalent is the deer tick (Ixodes capularis).

Researchers believe that the infected tick must be bitten by the horse to transmit the bacteria. Horses don’t transmit the disease to other horses.

The bacteria must be transmitted via ticks. This makes the disease more common in tick-friendly environments such as woodsy areas.

SallyAnne DeNotta was a long-time practitioner in the Northeast United States, where Lyme disease is well-known. She now works as a clinical assistant professor of large animal internal medicine at the University of Florida.

Dr. DeNotta states that Lyme disease can be found in horses and humans, but not in dogs or people. You can be exposed to Lyme disease, and you can get antibodies or even immunity. However, there are no negative effects.

The veterinarian estimates that about 30% of tick populations in endemic areas are infected by the bacteria. However, Lyme’s impact on these populations is much lower than this estimate.

Dr. DeNotta says, “If there was a 100 percent correlation between Lyme disease and infection with Borrelia, then all horses in the Northwest would have Lyme Disease.” “But it’s not. It is much, much lower. It is not known why horses get sick. However, we know that many horses have been exposed to borrelia and are immune.

Horses can show signs of antibodies in their blood but they are often healthy and symptom-free.

Dr. DeNotta states, “That’s an important concept because the only way to test for Lyme disease is to measure these antibody levels.” It can be confusing for people to see that a horse has antibodies. However, the veterinarian might say that they don’t believe that horse may have Lyme disease. The presence of antibodies in the blood does not necessarily mean that the horse has been exposed. Borrelia is very common in endemic areas. To diagnose Lyme disease in horses, they must have the following: compatible clinical signs, borrelia antibodies, and other symptoms.

Lyme Disease in Horses

Lyme Disease and Horses

Lyme disease diagnosis can be difficult.

Dr. DeNotta states that Lyme disease symptoms in horses can be vague and nonspecific. This makes it a difficult disease. There’s a lot to be confused about and a lot more controversy.

These signs can indicate a variety of other diseases.

These are Clinical signs that have been documented

  • Tick bite site swelling
  • Swollen joints
  • Uveitis (eye inflammation).

Other signs that are not yet documented but could be:

  • Stiffness
  • Lameness
  • Lethargy
  • Behavior changes generally


Neuroborreliosis is a rare, but serious, form of Lyme. This is where the bacteria infects the horse’s central nervous systems, causing severe problems including neurological issues.

  • Neurologic signs
  • Fever
  • Muscle wasting
  • Sensitivity to skin
  • Difficulty in eating.

This can lead to death.

Lyme Disease in Horses

Diagnostics are the first step in diagnosing Lyme disease.

Dr. DeNotta states, “When we find signs that indicate Lyme disease in a horse, we need to rule out any other possible causes.”

A veterinarian usually begins with a thorough physical exam, bloodwork, and diagnostic workup.

Dr. DeNotta states that it’s what we refer to as a diagnosis or exclusion. “The reason is that most of the times, it’s something (other than Lyme disease).

First, the veterinarian must rule out any possible causes of the abnormality that the horse’s owner reports.

Another problem is that bacteria can’t be detected in high levels in easily sampled fluids like blood. This would make it difficult to perform a direct test. The antibody levels are also checked in blood work.

If all of these reasons are not compatible and the horse still has antibodies, the veterinarian might recommend Lyme disease treatment.

Lyme Disease Can Be Cured in Horses?

The most common forms of Lyme disease, which are non-neurologic, can be treated with antibiotics like intravenous oxytetracycline and oral doxycycline.

The treatment usually lasts between four and eight weeks. It is possible for horses to still have antibodies in their blood after treatment. These levels are indicative of the body’s reaction to infection and not necessarily the immune response to treatment.

A single treatment should usually be successful and the horse shouldn’t be expected to relapse. Although it is possible for horses to become symptomatic in the long-term, this is uncommon and the veterinarian would not expect that the horse will experience long-term side effects.

Dr. DeNotta explains that there are two more serious dangers. If the horses are still experiencing problems after treatment, this could indicate that there is something else.

“Just to muddy the water a little more, tetracycline antibiotics are really good anti-inflammatories,” she says.

If the horse has a lameness problem that is not being detected, it might seem to be improving while taking the medication. The pain will then get worse once the medication is stopped.

Dr. DeNotta states that one cycle of antibiotics should be sufficient. “If the horse is able to tolerate the antibiotic but then becomes worse when it is removed, I wonder if the horse has pain that was caused by the anti-inflammatory property and not the bacteria infection.”

Lyme Disease Prevention in Horses

Lyme disease cannot be prevented, so offense is the best defense.

This involves making the horse’s environment as hostile to ticks as possible. This means mowing the pastures, removing debris and any other areas where ticks feel at ease.

“We call it ‘tick-scaping,'” Dr. DeNotta says. If you have pastures in an area where ticks can be found, remove the low-lying brush and woodsy areas. This will reduce tick exposure for your horse.

Sprays that repel ticks such as picaridin, DEET or permethrin can be helpful in deterring them. However, the best defense is to groom the horse. It takes 24 hours for bacteria to spread from a tick to a horse. If you can get rid of a tick in 24 hours, your horse will be healthier. You should schedule a time each day to thoroughly groom your horse, including his ears and tailhead.

Dr. DeNotta explains how to find the tick: “You’ll feel quite a big bump.” You can become quite proficient at grooming your horse by doing it every day.

Horse owners have good news: Lyme disease, which is the most common type of Lyme disease, is easily treatable. Researchers are still trying to find out more, but prevention is a good way to protect your horse.

Dr. DeNotta said, “You can see how much of a headache this disease is.” It’s a difficult disease. It can be frustrating for both owners and veterinarians as well as researchers. We are trying to solve it, and there are many good people doing research. Although we know more than ever before, there are still many questions to be answered.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!