I have a 15 year old quarter horse mare who has gotten markedly more aggressive the past several months. In addition to getting snappy with her teeth, she is very unwilling to be touched, groomed, patted, etc. I can still halter her and lead her but anything more than that results in ear-pinning and teeth snapping. This is not something that was present when I acquired her almost two years ago. My farrier suggested having her tested for Lyme Disease, which I will be doing next week—but wondered if anyone has experience with this and can share thoughts and/or advice. She has also started to snap at her pasture-mate who has always been the Alpha mare till now.
Ulcers and Lyme would be my first thoughts. Lyme will be easier to test for, so I agree with doing that first. If that comes back “not a chance”, then I’d start treating for ulcers and see what happens.
If the Lyme titer comes back anything other than “not a chance”, I’d consider treating anyway. as I’m not convinced that a given horse NEEDS a “yep, there it is” titer to have issues.
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I’ve tested for lyme disease even though titers showed he was positive i didn’t treat. Not showing any symptoms vet said don’t treat. Only treat is they are showing signs of the illness. I’m doing same for ulcers not showing symptoms i don’t treat. But your horse sounds like he’s got something going on so i’d be inclined to treat then.
A good friend of mine owns a QH mare who became quite stallion-like. Her vet noticed the behavior when working on another horse (the behavior had been going on for a few months) and thought it was hormonal, and ultrasound on her uterine horns uncovered a large tumor on one. She had it removed at the local vet hospital. Might be something to check out? The ultrasound didn’t cost much.
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Would be curious to know if other COTH members have experienced Lymes causing a horse to be aggressive? When we’ve dealt with Lymes, our most common symptoms are lethargy, joint soreness and a general disinterest in one’s surroundings.
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Lyme will definitely cause this. EPM will too. Other types of pain will too.
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Succeed has a simple inexpensive accurate ulcer test. Sounds like ulcers to me.
Aggressiveness isn’t a symptom of lyme disease. My one horse that had lyme disease was never aggressive. Body sore, lethargic, shifting lameness grumpy when being groomed. Your mare might be having repo issues time to get her checked. I’d have a full repo exam done before testing for lyme disease.
I would try Ulcer meds first. See the Nexium thread for a cheap trial to see if it helps. Pull blood and see if that shows anything. I’ve never had a Lyme horse or EPM horse get overly aggressive. Grumpy and not feeling well but not aggressive, like come after you attack mode. The one horse we had get insanely aggressive had a brain tumors, his blood work came back off the charts weird. He got dangerous fast and was PTS about a 2 weeks after diagnosis.
I’m dealing with something similar going on with my mare, though she doesn’t have ulcers or Lyme. Lyme can definitely cause sensitivity to touch and grumpiness, but so can repro issues, epsm, ulcers, even Cushings. I’d check Lyme first and then repro issues, as that can cause aggression to other horses. Good luck, mystery ailments are so stressful 
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Lyme disease manifests in so many ways. I had a young mare who absolutely became aggressive due to Lyme disease. So while I don’t think it’s among the “typical” consequences, it is possible. Mine went back to her sweet self after about ten days of treatment and never looked back.
I guess my motto with Lyme is “never say never!”
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Reported
It’s not all that accurate an ulcer test. All it does is show blood where it shouldn’t be, but does not tell you the cause, which are several. It’s useful as part of a diagnostic, just not standalone. Not all ulcers result in blood, not all blood comes from ulcers.
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It absolutely can be. Some horses who hurt become aggressive. It’s not that Lyme itself causes aggressiveness, it’s a matter of how the horse feels. Any number of issues that make a horse hurt or feel oddly can cause one to be aggressive.
My one horse that had lyme disease was never aggressive.
Your N=1 does not dictate what 1000s of other horses experience
Body sore, lethargic, shifting lameness grumpy when being groomed
Your mare might be having repo issues time to get her checked. I’d have a full repo exam done before testing for lyme disease.
What does “full repro exam” mean to you? It means palpations and ultrasounds and more, which is a LOT more expensive and invasive than pulling blood to check Lyme titers. Why not go for something that’s easier to rule out first, before hitting the more expensive possibilities?
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Vet I use has treated many, many horses more then 1000’S. None of which were aggressive.
1 vet treating many more than 1000s of horses with Lyme? Not sure I quite believe that.
http://www.equinews.com/article/lyme-disease-horses-just-basics
What signs does an infected horse show? Horses with Lyme disease can show joint and muscle stiffness, lameness, fever, poor performance, lethargy, weight loss, eye inflammation, laminitis, hypersensitivity to touch, and behavioral changes including nervous or aggressive actions.
My gelding was having neurological symptoms the first time he was diagnosed with Lyme Disease. He was spooking, tripping, slow, physioligically depressed, aggressive to other horses.
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As someone who’s had more experience with Lyme disease in my (late) horse than I could ever have wished (although the n still equals 1), I’d second what JB said.
Lyme disease can definitely cause all kinds of behavioral changes in a horse. It may not be that Lyme disease directly causes aggressive behaviors, but it makes the horse hurt and some horses when they hurt become hyper-reactive and can react aggressively to things, people or other horses that they previously would not have been previously bothered by.
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Another Lyme horse here ,agreeing with other posters: My puppy-dog draft -cross and was very sensitive on his right flank to brushing, water, etc. He would reach back with teeth bared if groomed or sprayed there which was a huge clue that he was sick and one of the symptoms that led us quickly to test for Lyme. This symptom, which I would call agressive for him, went away completely once treated.
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I, too, have a boarder in my barn who tested very high positive for Lyme. (Titer over 1:40,000). She presented as being aggressive with behavior changes and very sensitive to touch. It took almost two years for her titer to return to a suitable level (about 1:8,000). She was treated once with IV oxytet and doxycycline and again with doxycycline, then treated for ulcers. She is still the boss mare, but not nearly as aggressive as she was. She is still touchy as well, but at least she’s not going to fly over her stall door if you touch her side now. I am very careful with her if anything changes at all, as she tends to behaviorally “relapse” if she’s stressed at all.
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I rescued a horse that started out doing great, and as time went on, he started acting badly, but never semed lame or sore. Turns out he had Chronic Lyme disease and it DID affect his behavior. he became too much for me to feel safe and we were able to rehome him. ( owner knew everything, i did not lie to her.) Lyme is still a mystery and it can manefest in many ways.
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