Lyme Disease in Horses

Last Updated on February 19, 2022 by Allison Price

Lyme disease in horses is on the rise. Here are the facts.

Stiffness in the right hock of your horse was the first problem. Although the hock is now more flexible, he still seems to be in front. He’s not his usual, perky self. He mopes about in his paddock and pins his ears.

Low energy, lameness on and off, crankiness, or lameness could all be signs of overwork. Lyme disease can cause all of these problems and may become a problem for horses in some parts of the United States. Long-term complications of Lyme disease include long-term damage to your horse’s eyes, joints, nervous system, and vision.

Lyme, a bacterial disease that is spread through tick bites, can be a problem for humans, dogs, and other animals. The number of cases and concerns about Lyme disease is increasing as the spread of tick-borne diseases continues to expand. Are you concerned about your horse’s health? How can you tell if your horse has Lyme disease? And what should you do? How can you protect him? This article will help to understand the threat.

 Lyme Disease in Horses

Who is at Risk?

Lyme disease is named after Lyme, Connecticut where it was first discovered in the 1970s. According to the US Centers for Disease Control (which tracks human cases), it’s the most prevalent vector-borne disease in America. Although the disease is now widespread in all 50 states, CDC data shows that it is most prevalent in the northeastern and mid-Atlantic states. There are also pockets of cases in the Pacific and southern regions.

Thomas J. says that although no one has collected national statistics about Lyme disease in horses but cases do tend to be in the same areas like human cases. Divers, DVM, Cornell University School of Veterinary Medicine. These are the places where disease-carrying blacklegged, mostly deer and Western blacklegged, ticks are most common. Borrelia burgdorferi (Bb), a spiral-shaped bacteria that causes Lyme disease, may be present in up to half of the blacklegged tick populations.

Three life stages are available to ticks: nymph, larva and adult. They need blood meals before they can molt into their next stage.

They carry the bacteria to their next hosts, whether they are a horse, a dog, a horse or any other mammal or bird. As adults, they are more likely to feed on horses. Adults in cold-winter areas usually appear in the early fall and spend the winter dormant in leaf litter and brush before coming out in the spring. This makes fall and early spring prime times for infection. Lyme disease can be transmitted to horses by infected ticks.

According to CDC statistics, there has been an increase in the number of reported cases. Human case numbers are rising sharply in some areas, such as Maryland, Virginia, and northern New England. Maine was one example. In 2009, there were 970 cases in the state, compared to just 0 in 1988. Don Hoenig (VMD), Maine’s state veterinarian, said that Lyme disease is now being reported in new areas due to the increased geographic distribution of vectors, deer ticks. He says, “We now have ticks in areas where there were none six to seven years ago.” The spread of the disease is likely to be due to several factors:

  • Wildlife populations: The ticks can be carried by deer and other wildlife hosts (including migratory birds) and moved to new areas.
  • Changes in landscapes: Many areas of abandoned farmland are being converted to forest. The ticks prefer forest habitat over fields. They are often found in brush at the forest edge, forest edge and suburban yards. These habitats mimic their natural habitat.
  • Warmer climate: Ticks can spread disease to more people in warmer winters because they are active at all temperatures above 40 F.

Lyme disease has been reported to be on the rise as more people become aware of it. Dr. Hoenig states, “We’re trying to find it more.” Lyme is so common in Maine now, he says, that it’s not on the state department’s list for reportable diseases.

Blacklegged ticks can be a problem if your horse lives in an area where they are common. He may not become ill even though he has been bitten. Although a tick may carry the bacteria, it must stay attached to the host for at least 24 hours before transmitting the infection. Even if a horse has been infected, it is possible for him to not show any symptoms. Dr. Divers. The disease-carrying ticks can be found in many areas. Nearly half of all adult horses in the Northeast are infected. He says that although clinical disease (a disease that causes recognizable symptoms) is not common in horses, we don’t have any data.

Is it Lyme?

Lyme disease is best prevented early diagnosis, but it’s not always easy to do. After receiving many phone calls regarding Lyme disease over the years, Dr. Cornell colleagues and divers decided to study the disease. To test the effects of blood and tissue on ponies, they experimented with infecting them. They also evaluated possible treatments and a vaccine.

Dr. Divers. The ticks that bit your horse may not be visible to you. They usually disappear after being fed. The signs of disease can often not be seen for up to six weeks after the bite. These are three of the most common.

  • Stiffness in large joints (e.g., the elbow, knee, elbow, hip, hock, or stifle) It is common to experience sporadic lameness, which affects multiple locations or shifts between limbs. Dr. Divers says polysynovitis is the cause of these clinical signs. It’s inflammation in the membranes surrounding the joints. Divers agrees.
  • Generalized tenderness or sensitivity to sensory stimuli. Your horse may flinch when you curry him or seem to react too strongly to other sensory stimuli. Hyperesthesia is caused by inflammation of the skin and nerves.
  • Behavior changes include a reluctance to work, irritable or depressed attitude.

Other signs include low energy, low-grade fever and joint swelling. Early signs may disappear and not return. Persistent Lyme disease can cause weight loss, stiffness and swelling of the joints, neurological problems, and inflammation of your eyes. The immune response that horses mount against the infection may be partly responsible for some of the damage.

Horse owners who are concerned about the spread of the disease often think Lyme when they see signs of trouble. Dr. Dr. Divers states that it is important to rule out any other causes, such as injuries or overwork. Your veterinarian will conduct a thorough examination and review your horse’s past. The next step in confirming that your horse is infected by Bb bacteria is blood testing.

The most commonly used tests are those that look for antibodies made by the horse’s immune system to the bacteria. These antibodies don’t immediately form in horses, so false negatives are possible if tests have been run as soon as possible after infection.

Snap 3Dx is an instant screening test. It detects antibodies quickly and gives an immediate result without the need for a laboratory.

An ELISA (enzyme linked immunosorbent assay in laboratory) is a method to measure the quantity of antibodies. Infection is indicated by high levels (200-300 units or more). However, antibodies can continue to circulate in the blood long after bacteria have died. A low or high level could indicate that your horse has been exposed to Bb in the past.

The Western blot detects antibodies against certain proteins of the Bb bacteria. It is more sensitive than an ELISA which can’t distinguish between antibodies to Bb bacteria and other organisms. This test is often ordered by veterinarians to confirm a positive ELISA.

Lyme disease diagnosis can be difficult. While blood tests may help to diagnose the condition, they often don’t provide a clear answer. If your vet believes your horse has Lyme disease, he may recommend treatment.


Lyme disease can be treated quickly if it is diagnosed early. Most cases can be treated with antibiotics. Dr. Divers. There are many. However, IV treatment can often mean that horses must be treated at a clinic. This can prove costly. Many veterinarians recommend oral doxycycline to horses who aren’t responding or relapse. To ease the discomfort, your vet might recommend an anti-inflammatory like flunixin meglumine or phenylbutazone.

Although most horses experience improvement within a few days of receiving antibiotics, that does not mean that the bacteria is gone. The treatment usually lasts for 30 days. It is more likely to linger if it is not treated. The bacteria can cause tissue damage in the joints and other areas.


Lyme disease is not an approved vaccine for horses. The Cornell research showed that a vaccine was able to prevent infection in experimental ponies who were not previously exposed. The approval process for a new vaccine can be costly and time-consuming. At the moment, there is no plan to make an approved equine vaccine. Dr. Divers says that approval for an equine vaccine is unlikely due to the limited geographical distribution of the disease, and questions regarding its clinical importance. Divers states.

The best thing for your horse right now is to limit his contact with ticks carrying the Bb bacteria. Lyme disease can be a problem if you live in an area where Lyme disease is common.

  • Permethrins are a good fly repellent. These insecticides can be used to repel ticks and flies. Use repellents only in autumn and spring when ticks are most active, even though they may not pose a problem.
  • Give your horse a thorough daily grooming. Pay special attention to his base, tail, ears, throatlatch, and belly. The blacklegged ticks can be difficult to spot, so it is important to groom your horse regularly. Use tweezers if you spot a tick. Grab it at its mouthparts and pull up gently.
  • Make your horse’s turnout space hostile to ticks. Tick habitats include tall grass, brush, and overhanging branches. The little pests can climb to the tips and latch onto horses as they pass. You’ll be able to reduce the number of ticks by cutting the brush, trimming the branches and mow the grass.

More Trouble with the Ticks

Blacklegged ticks, which can spread Lyme disease to horses, may also transmit another bacterial infection to them: Equine granulocytic and ehrlichiosis. These are the classic signs

  • Fever, usually high (103-104 F) in the first day to three days
  • Depression and lethargy
  • Appetite loss
  • Reluctance to Move
  • Edema is swelling or stocking up in the lower legs.

This disease is caused by a bacteria called Anaplasma Phocytophila (formerly Ehrlichia Equi). This disease is seasonal and most dangerous when ticks are active. Many cases of the disease have been reported in California where Western blacklegged ticks carry it. However, it can also be found in the northeastern, mid Atlantic, and north-central US states, where deer ticks are common.

The bacteria attacks white blood cells, called granulocytes. The signs usually begin a week to two weeks after the tick has been fed on the horse. They are more severe in older horses. Sometimes, the horse may develop a yellowish tint in his eyes or small red spots (petechial haemorrhages), in the mucous membranes. Sometimes, neurological complications can occur. A blood test can confirm the infection. The PCR (polymerase-chain reaction) test can detect segments of the bacteria’s genome. Other tests look for antibodies that are produced to combat the infection.

Anaplasmosis can be treated with the same antibiotics that were used to treat Lyme disease, IV tetracycline or oral doxycycline. This is without any need for extended treatment. Horses usually recover quickly after treatment and have a natural immunity that can protect them against this disease for up two years.

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!