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Shaken up - The Horse Owner's Resource

Shaken up

False leads, shifting signs and unexpected test results complicate the search for answers about a gelding’s mysterious and persistent headshaking.
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Early one spring, several years ago, I got “that call” from the barn that so many horse owners dread: Something was wrong with my beloved horse, a handsome Thoroughbred named Whisper.

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Whisper was 9 years old then, and I’d had him for nearly four years. At first, I had taken him in only to foster him for CANTER, the national nonprofit organization that helps find new homes for retiring racehorses. But I quickly fell in love with his friendly, laid-back, puppy-like personality. I ended up adopting him even though I knew he’d be able to handle only light work due to a fetlock injury and the arthritis that was likely to develop as a result. Still, I was able to do some dressage and trail riding with him.

At the time I’d received that call, the pain in Whisper’s fetlock had been acting up, and he’d been in his stall off and on for a few weeks, with limited turnout. The situation was difficult, but it was about to get much more complicated.

Whisper had begun shaking his head, flipping it up and down almost frantically. It was so persistent that he wasn’t even stopping to eat. At first the staff thought he might have developed the repetitive movement because he was bored in his stall, so they moved him to a small paddock, but he continued to shake and flip his head.

When I arrived at the barn, he was standing in the corner of the field, tossing his head up and down rhythmically, while occasionally flipping his nose in the air as if he was being bitten or shocked.

He looked confused, agitated and miserable.

After a close examination, my vet- erinarian said he thought Whisper’s head flipping was probably due to ear mites, and he prescribed a medication to put in the gelding’s ears twice a day for a week. But the headshaking did not stop. What’s more, Whisper developed a swelling under his jaw.

After a new examination, my veterinarian decided Whisper’s issue might stem from some type of infection, unrelated to his ears. Although he had been immunized against strangles, and he had no fever or nasal discharge, the lump under his jaw was suspicious. The veterinarian prescribed an antibiotic and anti-inflammatory medication for the pain and told me my horse should be feeling better in a few days.

To my great relief, Whisper did improve. He began eating again, the lump diminished and he appeared to be more relaxed. Still, I dove into a search for any information I could find on headshaking.

But the more I read, the more confused I seemed to get. This syndrome, in which a horse will constantly flip his nose and jerk his head, can have many causes and potential treatments. Triggers for the behavior can include exposure to bright sunlight, exercise, loud sounds, smells or allergies. In some horses, the behavior is limited to the spring and summer, while in others it can occur year-round. Often, headshaking can result from a malfunction of the trigeminal nerve, a sensory nerve in the face, that causes a constant itching, burning, tingling sensation in the muzzle. Sometimes, the cause of a horse’s problem remains a mystery.

Treatment options seemed equally varied, depending on the triggers. Some horses stop headshaking while wearing specialized nets that hang over the nose; others respond to being kept out of bright sunlight. The dietary supplements melatonin and magnesium can help some horses, while others respond to drug treatments to ease neuropathic0 pain. Sometimes, even when a horse responds to a treatment, the headshaking might still recur. And then there are the horses who never respond to any form of therapy.

It seemed like there were no solid answers, and it might take a long period of trial-and-error to get at the root of Whisper’s problem---if we found it at all. My search grew even more urgent when, after improving for several days, Whisper once again began frantically shaking his head.

I called my veterinarian again, who suggested an endoscopy to look for abnormalities within Whisper’s sinus cavities. He referred me to another veterinarian in a different practice who could do the procedure at the farm. This veterinarian arrived that same day, but to my surprise, he said he didn’t think the endoscopy was necessary and suggested that acupuncture and chiropractic work might help.

Whisper was already stressed. Rather than putting him through a procedure that would require sedating him and inserting a tube with a camera up his nose, I decided to try this other route first. The veterinarian did the acupuncture and chiropractic work and, within 24 hours, Whisper had stopped shaking his head.

I was thrilled. The pain in his fetlock eased, and we returned to our old routines. But four months later, the headshaking started again.

This time the shaking was more intermittent but violent. It was as if bugs were flying up his nose or landing on his face, causing a sudden and hugely dramatic startle response. Whisper was flipping his head so forcefully that I began to worry that his poll would fly back hard and fast enough to hit me while I was riding. I dramatically cut back on my time in the saddle, and on the ground I stayed away from his head.

Another opinion

I decided to work through some of the management changes that can help with headshaking. It was late summer, so I started with the assumption that it might indeed be the bugs that were bothering him. I increased my diligence with fly masks and fly spray. The headshaking didn’t stop entirely, but it did improve enough that I was able to convince myself that Whisper was just sensitive to bugs and heat.

When winter came and the headshaking persisted, I had to admit that it wasn’t heat or bugs. Whisper---my friendly puppy dog of a horse---was miserable and irritable. He was very sensitive to touch and couldn’t even tolerate a gentle grooming without kicking at me. He also seemed stiff under saddle and appeared to be getting very arthritic.

We muddled through the winter, with some good days and some bad. But I wasn’t prepared to accept this as the new normal for my horse. By spring, I’d read everything I could find on headshaking and spoken with every horseperson I knew. I didn’t find any answers, but I was still determined to help my horse.

Finally, in late May I called in yet another new veterinarian, Shanna Baker, DVM, from 3H Veterinary Services in New Hill, North Carolina. I’d never worked with anyone from this practice before, but she came highly recommended. After giving Whisper a full physical examination, Baker raised the possibility of allergies, which wasn’t a new thought. But then she also suggested a theory that I hadn’t yet encountered: Lyme disease.

A tick-borne bacterial illness that is fairly rare outside of New England and the upper Midwest, Lyme disease is low on the list of things horse owners or veterinarians in North Carolina worry about.

Nevertheless, Baker pointed out, Whisper did show two classic signs of infection: general irritability as well as joint pain that tends to come and go. Headshaking isn’t a commonly cited sign of Lyme disease, but Baker explained that she had seen the two occur together, so she suggested testing.

Baker drew blood to test Whisper for antibodies to Borrelia burgdorferi, the bacterium that causes Lyme disease. We wouldn’t get the results for a few days, but to get a head start on a potential infection, she started Whisper on a course of doxycycline, one of the antibiotics considered to be most effective against Lyme.

When the blood results came in, it looked like we were back to square one. Whisper’s titer, a measure of antibodies to B. burgdorferi in his blood, was low enough to be considered negative. Even if he had been exposed to the bacterium at some point, there was no evidence that it was causing active disease---even in endemic areas, where as many as 50 percent of horses may encounter the bacteria, only about 10 percent of those exposed ever develop any signs of illness. Baker advised me to continue with the doxycycline, however, to combat any other organism that might be lurking while we tried to gather more clues.

I was beginning to think we might never figure this out.

Double-check

Two weeks later, a second veterinarian from 3H, Tracy Tinsley, DVM, was scheduled to make a farm call to see another horse. I asked if she could take a look at Whisper while she was here. When she came, she gave Whisper the standard physical workup I’d seen so many times now. As she worked, I told her my long tale of frustration and disappointment with the headshaking. I was eager to hear her take on it, hoping for a new avenue to pursue. I was surprised when she said she still thought it might be Lyme disease.

Tinsley explained that while her experience with Lyme was very limited---she had trained and practiced in areas where the disease is not common--- recently she had been speaking with colleagues from the Northeast, and one had mentioned that he had seen a few cases of headshaking associated with Lyme. In people, Tinsley continued, the infection has been shown to cross over into the central nervous system, causing headaches and neuropathic pain---sharp, stinging sensations such as those that might cause a horse to flip his head as if he were being bothered by bugs. She had shared this information with Baker after she’d heard it, which led to the initial testing.

When I said that Whisper had just had a negative result on the blood tests, Tinsley explained that part of the difficulty in diagnosing Lyme is interpreting the titers. Results from an individual test can be deceptively low, especially if the horse has a chronic infection or hasn’t yet mounted a large-scale immune response. She suggested we start him on a second round of doxycycline and test him again, just to be sure.

This time, the results were strongly positive for Lyme. I found this confusing. If Whisper had Lyme disease, why wasn’t the first round of doxycycline already controlling it? Tinsley said that perhaps the bacteria were “hiding” in the nervous system, or maybe Whisper hadn’t been treated long enough. She encouraged me to be patient and continue the medication. After all we’d been through in the past year, this was the closest we’d been to an answer, so I was willing to wait it out.

Over the next few days, Whisper’s headshaking, stiffness and irritability began to improve. Within two weeks, his signs were gone. I had my happy puppy-dog horse back. A month later, I was able to start riding him again.

Today, two years later, Whisper is retired due to his fetlock injury. But his headshaking has never returned.

We still have lingering, unanswerable questions about what Whisper went through that year: Were the headshaking and Lyme disease really connected? Why did it take so long for the antibiotics to work? Is the problem gone for good? Tinsley has warned me that signs of Lyme disease can return years later. So I’ll always have a lingering worry that I’ll get another call from the barn one day. But if that day ever comes I’ll take solace in the fact that persistence paid off once, and I’ll resolve to not give up until my horse is better again.

This article first appeared in EQUUS issue #447, December 2014. 

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