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Lyme Disease in Horses – Symptoms, Diagnosis, and a New Lyme Disease Test

lyme disease in horses

Photo courtesy of E. Goldsmith at equineink.com.

Horses do not appear to be as susceptible to Lyme disease as humans and dogs are, but cases of Lyme disease in horses have been reported by veterinarians across the US. Equine Lyme disease leads to symptoms similar to those suffered by humans and dogs, including lameness, arthritis, fever, oedema, and encephalitis (neurological Lyme disease).

Lameness often comes and goes, shifts from one leg to another, and appears uninfluenced by the horses’ activity levels. Horses may show a rapid decline in performance, such as when racing or showjumping. Laminitis is another feature of Lyme disease in horses, along with anterior uveitis, an inflammatory eye condition sometimes referred to as moonblindness.

Symptoms of Lyme disease in horses can be quite variable however, making the illness difficult to spot, particularly where it is unexpected. Horses with Lyme disease may experience problems with multiple organ systems leading to both acute problems and possible permanent damage and chronic health issues, especially where the infection remains untreated. Lyme disease complications in horses can include liver damage and hepatitis, or severe neurological injury from encephalitis, resulting in ataxia, and/or behavioural changes.

Diagnosing Lyme Disease in Horses

There is a striking variance in the symptoms suffered by individual horses infected with Lyme disease, with some able to tolerate infection without showing signs of illness, and others becoming severely ill. Poor recognition of the infection in horses means that there is little available research material to guide veterinarians. Diagnosis of Lyme disease in horses is further complicated by problems detecting the spirochaetal bacteria, Borrelia burgdorferi, responsible for Lyme disease in samples taken from horses.

Veterinarians will usually apply a process of elimination when investigating symptoms common to Lyme disease and other illnesses in horses. Blood tests, such as ELISA and Western blot, are carried out to check for antibodies to Lyme disease bacteria, although the accuracy of these Lyme disease tests has been questioned, especially in cases of early Lyme disease where insufficient antibodies have built up to trigger detection.

Even if antibodies are detected in a horse this still does not mean that clinical signs are due to Lyme disease. Vaccinated horses, as well as those exposed to Lyme disease bacteria but not suffering from it, will show some level of antibodies to the spirochaetes. In Lyme-endemic areas there may be as many as 75% of horses who will test positive for antibodies to Borrelia burgdorferi, but the majority of these horses show no signs of illness. Where a veterinarian can find no other cause of the symptoms they will usually administer antibiotics to treat a suspected infection with Lyme disease in a horse. Further blood tests help determine the success of treatment at eradicating the infection.

Lyme Disease Vaccination for Horses

lyme disease in horses symptoms

Lyme disease symptoms in horses may include lameness and arthritis

Vaccination of horses against Lyme disease is not currently standard procedure, nor is there an available vaccine approved by the USDA for use in horses. Some horse-owners use the Lyme disease vaccines for dogs, despite a paucity of evidence showing this to be safe or helpful. Indeed, there are some reports of horses becoming clinically ill after vaccination with a Lyme disease vaccine for dogs. The use of such vaccines also makes diagnosis more difficult, due to confusion over the presence of antibodies to Borrelia, should an owner or veterinarian suspect that a horse has been infected with Lyme disease. Most veterinarians recommend the use of insecticides to protect horses and minimize tick-exposure.

In delaying diagnosis of Lyme disease in horses whilst test results are returned the primary window for treating the infection may be missed. Early symptoms are also often put down to exhaustion from work, arthritis, or muscle strain from over-activity. Horses out to pasture have lower detection rates for early infection compared to those in active duty. However, active horses, such as show-jumpers, dressage, or race horses, are more likely to experience misdiagnosis rather than late diagnosis.

Treating Lyme Disease in Horses

Lyme disease treatment for horses is similar to treatments for Lyme disease in humans or dogs, namely antibiotics such as tetracycline or doxycycline (intravenously and orally, respectively). One study of Lyme disease using ponies deliberately infected with Borrelia bacteria showed that tetracycline treatment appeared most effective in eradicating infection. A four-week course of tetracycline, doxycycline, or Ceftiofur resulted in a drop in antibodies in all groups but then a subsequent rise in antibody levels after three months in 75% of the ponies treated with doxycycline and 50% of the Ceftiofur group. Where the antibodies did not begin to rise again after treatment there was no sign of infection with Lyme disease upon autopsies of the ponies.

Tetracycline appears then to be the best option for treating Lyme disease in horses but, unfortunately, the drug is highly damaging to tissues if it leaves the bloodstream. Oral doxycycline is easier to give, therefore, but a course longer than four weeks may be needed. In some cases, particularly where diagnosis is delayed, persistent symptoms of Lyme disease may arise. Even where the infection appears to have been cleared there may still be signs of Lyme disease in horses. Reports of such occurrences lend weight to the argument against Chronic Lyme disease symptoms simply being an ‘imaginary’ syndrome dreamt up by sufferers and disregarded by many. Autoimmune dysfunction may be at the root of some of these symptoms, perhaps connected to the ability of Borrelia bacteria to evade the immune system in some capacity. Such symptoms can also be the result of recurrent infection, permanent damage to tissues induced by the infection, or even persistent infection which is poorly detected by diagnostic tests such as ELISA and Western blot.

New Lyme Disease Test for Horses

A study published in July 2011 looked at antibody profiling for Borrelia in horses with a focus on those living in the New England and Mid-Atlantic regions of the US. Infection with Borrelia burgdorferi is common in such horse populations and the researchers used these animals to assess the efficacy of Luciferase Immunoprecipitation Systems (LIPS) for detecting antibody responses to three antigens used in diagnosing equine Lyme disease. LIPS testing verified that 75% of the horses were seropositive against the synthetic antigen used (VOVO), which was checked against an immunofluorescence assay (IFA) showing 51% to be infected. Just 15% showed seronegativity on both tests however, which strongly suggests that infection is endemic in horses in these regions.

In this study the use of more specific antigens led to higher sensitivity when testing horses for Lyme disease making it possible that commercially available tests for Lyme disease in horses might soon be available. Considering the difficulties in diagnosing and treating the infection and symptoms, as well as the expense of veterinary care for horses, more accurate testing of Lyme disease in horses, such as the new LIPS testing is likely to be warmly welcomed by horse-owners across the US.


Burbelo PD, Bren KE, Ching KH, Coleman A, Yang X, Kariu T, Iadarola MJ, Pal U., Antibody profiling Borrelia burgdorferi infection in horses. Clin Vaccine Immunol. 2011 Jul 20.

{ 27 comments… add one }
  • Denise Brinker November 6, 2011, 7:24 pm

    I have a four yr. old mare with recurring laminitis. No cause is known. I suspect Lyme since we live in Central (Charlottesville) Virginia and my horses are Icelandic (run very warm so attract ticks).

    So far the vet has her on Bute and Banimine for 14 days and she still has digital pulse.

    Should I ask for the LIPS test?

  • sharon November 9, 2011, 10:07 pm

    can you get lymes disease by inhaling infected horses feces?

    • lmatthews November 9, 2011, 10:12 pm

      Hi Sharon,

      this is extremely unlikely as the bacteria are carried by ticks and air not airborne. It is possible however that exposure to a horse infected with Lyme disease means that a person is more likely to have come into contact with infected ticks transferred from the horse or simply from the same environment in which the horse was bitten by an infected tick.

      If both yourself and your horse have symptoms of Lyme disease it is important for both of you to get checked out by a doctor so as to start antibiotic treatment quickly. Exposure to just the horse faeces may not lead to infection but could indicate other avenues for exposure to infection.

      Wishing you and your horse good health!

  • Deryn Singleton February 28, 2012, 1:41 pm

    I brought my horses to the US from Britain where Lymes is rarely seen in horses so they have no resistance to the disease – in fact I had never seen a tick on a horse before. About a year later she became progressively more lame in what appeared to be her stifle and was treated with Naproxin, the lamesness would come and go, her hind fetlocks then became swollen and there seemed to be some suspensory problem in the one, she also developed a ‘hunched up’ stance , lost a lot of weight and was dull and depressed. A Lymes test showed higher than normal levels so she was put on antibiotics for a month and her improvement was pretty amazing She is now taking Previcox as a pain relief, her weight is improving, she looks bright in herself and though still stiff she gallops in at night with her friend. I wonder if the fetlock damage will ever return to normal or if she should have a longer course of antibiotics. I feel certain that Lymes is the cause of her problems.

  • Ashleen March 2, 2012, 4:16 am

    I think my young thoroughbred has Lyme disease but the test that our vet is suggesting is a bit weighty on funds. How much would this type of test cost?

  • Anne-Sophie April 24, 2012, 5:14 pm


    I’ve done a lot of research online about Lyme.
    My horse (who came from France with me nearly 2 years ago) started to act differently last fall.
    Totally not like his normal self, spooky with quite violent reactions.
    I thought it was the winter here (in Maryland) or the impressive number of wild animals that we don’t have in France.
    but recently his changes were so visible, so cranky , and he was really trying to tell me something when having a bad day and not feeling like being ridden (while he always was such a happy willing horse).

    I decided to have him tested. It came back positive with very high numbers. the vet called it chronic.

    Although the vet doesn’t see usual symptoms (he sees nothing) but i see my horses’ face with muscles contacted as if he had a head ache, he has some difficulties chewing treats.

    The vet is OK to start antibiotics 6 weeks of doxycycline. I asked to wait a little in order for me to start some probiotics and complement to boost the immune system before we start the antibiotics.

    We drowned blood yesterday to check the liver, kidneys white cells … I’m worried to start antibiotics on a weakened immune system.

    What would your opinion be.


    • Jen September 14, 2013, 2:08 pm

      Have your Vet look into Australian Stringhalt if he has problems chewing and is spooky.It’s caused by eating Toxic plants..I only know because two of mine just got it from eating Catears weed(false Dandilion).It affects them Neurologically.Does he stomp his back legs and move weird?It can also paralize their Larynx, so they”roar” and have trouble eating.IF that is what’s wrong..you have to take him off the Pasture and let the Toxins get out of his system.It’s not a common thing for them to get and is usually misdiagnosed.I did my research online to prevent a gazillion dollars on Bloodtests/xrays etc..Maybe look into it!And if it IS Lymes, then only Antibiotics will help.Good Luck!

  • colleen May 2, 2012, 12:23 am

    I have a three year old trotter who seems to go lame in a new area at a drop of a pin. He seems to dog track heavy to the left ,this has been the only consistant thing he has done. We have rubbed and injected ,taken pictures, blocked to see where he was lame ,blistered, chiropractic measures … the list go’s on and on. Everytime we adjust or treat he will get better for a day and then be absolutly lame the next. We thought EPM, and now are leaning towards lyme. Lyme is not as common in our area {NY} but there has been a growing amount of cases in all species. Does this sound like lyme to you? We have covered every joint , muscle and vertibrea , this is our last hope for a diagnosis. I love the big guy but I am so frustrated trying to get him sound and I would like to figure this out . If this does sound plausable please let me know. Please. Thank you for any help you may offer. Colleen.

  • Denise June 7, 2012, 10:59 pm

    I have personally suffered from Lyme and have also had to treat several of my horses. I routinely have the vet send blood for testing each spring when I do shots. Cornell charged $36 for the test, well worth the money! If you suspect Lyme, I believe it’s best to have blood drawn but go ahead and start treatment immediately, worse case, your horse will have gotten a few weeks of Doxy for no reason, best case, you save yourself years of chronic problems with your horses. Lyme is very painful and causes all sorts of symptoms, mine included horrible migraines, strange rashes, aches that would hit like stabbing pain then 10 minutes later be gone, extreme fatigue, etc. and everyone that gets it pretty much has different symptoms.

  • Adrian July 28, 2012, 12:25 pm

    I have an 11 year old warmblood I use for dressage. He had his hocks injected 4 months ago and is already acting like he needs them done again. I’m considering testing for lyme disease as I have pulled a tremendous amount of ticks off him and my other horses this year. Some of the ticks have left a lump where they were attached on him and my other horses. In the last 6 months my gelding will occassionally “slip” behind – like his stifle got stuck momentarily. I’ve backed him up a hill and backed him around a small circle, none of which were a problem.

    How likely is Lyme Disease in Mississippi?

    • Rene Clayton July 31, 2012, 2:31 am


      Lymes can occur anywhere, even though it is more prevelant up north. We just found out that our warmblood has Lymes (Cornell University test, $36) , and he came from PA. After 18 months of tests and mylegram, bone scan, every test you can get, we finally found out he has Lymes. Just started treatment and it appears to be helping. His is older and chronic so we do not know what the long term affects will be. The lymes mimic’d some neuro issues, stifle issues, hip issues, respitory, and skin issues. My vet states that the IV treatment works best but it can be fatal. We did 4 days of IV antibiotics and now are doing a 30 day pill treatment (50 , twice a day). Please contact me if you have any questions on how it is going.


      • Dory February 18, 2013, 7:53 am

        Hi Rene,

        Can you give me an update on your boy? I have a mare here who I had since she was 4 yrs old (second year owing her at 6 yrs). At the time she was showing weak hind end issues (dragging feet and misstepping) but she was from a rescue situation and was over 140 lbs under weight. She did improve some once in condition but still has weak hind end issues. I had her tested for EPM (never was tested) and she came up with a low titer. I am in the process of getting a myelogram done because she is a 2-3 (depending on her day) from her lameness exam. One vet thinks it’s wobblers, another vet who seen her before I got her thinks it’s locking stifles and the current vet is not sure what it is but thinks it might be wobblers or EDM. Yet I question that because she never really got worse but a little better through ground strength and balance training. But I was suggested from another blogger that it could be Lyme when in fact I do live only 15 miles from Lyme, CT with some reports of 92% rate. I didn’t know horses could get it like this. So I was wondering how things are going for your horse. Mine is currently 6 years old going on 7 and I am having problems trying to get her up to Tufts for the myelogram test because of all the bad weather we been having the last 3 months. I am wondering if I could have the vets come out again to test her for Lyme but here’s the big question (not that it would change my decision in keeper her) if she has Lyme all this time would the neurological problems be permanent?

  • Bob September 13, 2012, 12:28 am

    My six year old quarter horse became stiff in his shoulders and short-strided this past spring. Also, he was drinking and urinating alot more than usual. We took him to our vet who instantly suspected Lyme. His temp was 105 and he was so lame in the front. She drew blood to send out but started him on doxy immediately. The results came back 3 days later. We were told a titer of 150-160 was positive for Lyme; his was 2580. She told us that at this point, he will probably have chronic Lyme. After two days on doxy, he already felt better, showing no lameness at all. After six weeks of doxy (40 pills per day), another blood test was done, showing significant improvement. We thought we were out of the woods, but within a month, the symptoms came back, even worse. We sent blood out today, and are quite anxious to get the results. I don’t know what is in store for him. If anyone has been through this long-term, please e-mail me. I don’t know what to expect for my horse’s future.

    • Lisa May 10, 2013, 5:02 am

      I have a 17 yr old Paint mare I raised as an Orphan. She has in the last 5-6 yrs has gotten more and more arthritic . Having Major problems walking after stalled overnight and such. She is a big mare , never foundered , BUT I have had Lyme since 1994 and where we used to live was heavy populated with deer. Pulled ALOT of ticks off of her. I am really thinking she has Lyme too. I have had several surgeries and issues with arthritis and I am only 49. She has not been heavily used. These last 5 yrs not really at all. How do I get a vet to test her and how much dothe meds cost? I have been on meds myself for over 6 yrs . I also have Babesia another tick illness. Just would like to be able to get her comfortable , hate to see her like this .

  • Jaime November 8, 2012, 2:17 am

    hello ,
    I have a five year old STB gelding who came up very lame on his front left and swollen back left up to the hock ..had the vet out and she said he might have an abscess starting and that the swelling in the back might be just from a scratch . the next morning after giving some bute he seemed much better in spirit and legs looked better also …when i went over in the evening the only leg that was not swollen was the one that was thought to have an abscess , the lameness in the front has all but gone away also … his manure was very watery too ….could this be lyme ? He has been kept in since he came up lame yesterday morning .
    thank you

  • Pam December 8, 2012, 12:15 pm

    Hello! Glad to have found this forum. A week ago I noticed my little paint gelding looking listless, kind of sleepy and yawning a lot. I didn’t think much of it, until I noticed he wasn’t finishing his grain( unlike him!!) I took his temp, a little high. Vet came out Tue s, but I was at work…..said no fever, feet weren’t hot, no symptoms but he did pull blood. Next day he is SO lame on hindsight. No weight on the heel…looks like he has 3 legs:( no temp. Called the vet , and asked to send Lyme disease test. My other horse, a big th,is also having a weird muscle thing going omnibus right shoulder….so much that I can’t ride him. His range of motion is really limited and he is kind of more pissy …. we are up in central MA. I pull SO many ticks esp off of my paint. I really think that the paint has Lyme but I have to wait another week for results. I am going to see if I can start the foxy now…I will check back!

  • sandi February 18, 2013, 3:58 pm

    I bought my horse 7 years ago, when he was 8 yrs old. He did not pass a flex test and I told the previous owner I needed to return him. She did not want him back and so returned my money asking me to keep the horse! Well I liked him alot and my vet said with the relatively light riding I do (trail) we should be able to keep him sound. He was also surprised such a young, lightly ridden horse had such bad joints! Well for awhile he did ok. Had his joints injected and that kept him going. Then we moved….everything fell apart. His personality changed, he had chronic eye issues, he did not feel sound and he became very spooky. He was over the top reactive to noise. The thing was he had been on a large grass pasture and was moved to a dirt lot. We thought that was what was causing his eye problems. He was miserable in every sense of the word. We moved again, to another grass pastured barn and I had a new vet. She tested him for EPM. He had a positive level and so he was treated. For a year I had a really great horse and then it all fell apart again. He was retested for EPM and it was negative. Things just went from bad to worse. He became increasingly more lame and his back got so sore he could not be ridden. Of course that was the last straw. Had been injected and had ex-rays and ultrasounds, nerve blocks, you name it and NO diagnosis! I finally had no choice but to retire him. My friend who had a lyme horse pushed me to have him tested. Bam! there it was, chronic lyme disease. Reading the symptoms I am shocked. He really had them even excessive drinking. He had the treatment 4 mo. ago and we will be retesting in 2 mo. Not riding him but he seems happier and appears sound. Why oh why can’t vets preform this simple test early on? I am not even sure he really had EPM but the drug is an anti inflamitory and may have just helped the lyme problem for awhile. I believe my horse has has lyme all along, which means he has been suffering for many years.

  • Cillin March 10, 2013, 6:08 pm

    I was just wondering whether my horse could of had lymes disease, he died 4 days ago and the vet knows it was liver failure but we don’t know why his liver failed and I was just thinking that maybe lymes disease could of caused his liver to fail we are now waiting on results of analyse of his liver. The night before he died he came in from a field that is right near a large area of forestry which I know contains deer, in fact all our fields are right beside this forestry, another reason lymes disease came to mind is because a neighbour of mine had lymes disease a while back. I was reading that lymes disease in severe cases can cause liver problems which leads to brain swelling and my vet told me that brain swelling can lead to death. We know for sure that it was liver failure because my vet has seen his liver and he had the exact signs of brain swelling as he was standing in the corner and pressing his head against the wall and seemed to be be in severe pain, he also was excessively drinking and was finding hard to eat and didnt eat his evening feed and then stopped eating altogether. It was very sad and i am just trying to find a reason why this happened

  • Christine July 24, 2013, 2:41 pm

    I’m curious if Lymes Disease can cause Hives in horses.

  • Renee August 23, 2013, 3:50 pm

    Has anyone encountered any issues with behavioral changes with Lyme disease? I have read some of the posts that mentioned some changes in behavior but I am specifically looking to find out if people have had issues with a normally gentle horse now showing crankiness and biting when being saddled.

    • Dutchess September 10, 2013, 2:31 am

      My farrier was the one who first noticed the subtle changes in my mare as she suddenly refused to come out of her stall and just was not her happy self He suggested Lyme and within two days of the doxy. powder treatment in feed she was back to her old self. I did two rounds of treatment now I am noticing so e symptoms and wondering if she is having residual issues or has it again

  • kim September 24, 2013, 4:40 am

    my 13 yr old perfect broke womderful trail horse has all of a sudden stared being very hateful when saddled, swishes her tail constantly throws her head, she looks like she cringes when go to put the saddle on her she twitches, grits her teeth.. this is all just startd in the past 3-4 wks . she still had a good appetite but this is bothering me really bad.. she went from riding perfect calm and slow to prancing swishing tail non stop just awful.. could this be symptoms of lyme disease.

    • Janet May 29, 2014, 6:02 pm

      So, if the last time I pulled a deer tick off my horse was October and it is now June and he doesn’t show any of these symptoms…….does that mean he doesn’t have Lyme disease? I thought the symptoms could be delayed for quite a long time, months even years???

      • lmatthews May 29, 2014, 6:40 pm

        Hi Janet,

        Just like in humans and dogs, yes, horses may have few (if any) early visible signs of Lyme disease and then develop symptoms months later. If there was no sign of a rash around the tick bite after removing it, or a rash elsewhere, and if they haven’t shown any symptoms (lameness, change in behaviour, loss of appetite, fever, irritability) it’s likely they’re in the clear.

        You could always get them tested just to be sure but as false negatives are possible and antibiotic treatments can have undesirable side effects (including increasing antibiotic resistance) your vet will probably tell you to let your horse be unless there’s reason to suspect infection.

  • joann December 13, 2013, 6:31 pm

    hi my 13 year old registerd quarter horse just got tested for line its positive hes being treated with doxy and bute since the 4th no change vet came back today 13 th more blood work wait for test to come back were testing for cushins to any advice thanks this is getting costley

  • Kelley Decker July 14, 2014, 12:49 pm

    I was looking for articles or literature that describes the effect on the fetus in the event the mare contracts Lyme Disease. Is there a safe treatment for both? I would appreciate your comments.

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