Equine Lyme Disease Doesn’t (Officially) Exist In Australia – Here’s How it Affected One NSW Horse

Lyme-headerAccording to various authorities, Australia has no Lyme disease, human or equine. Despite this, many Australians are testing positive – and that’s happening with horses, as well.

 

The following guest post by Cherry Kawamoto charts a journey about the difficulties of identifying and testing for Lyme disease. It relates to her 3yo mare, an unstarted performance horse that I have worked with several times. It first appeared as an article in Equine News, an equine magazine published in Northern New South Wales.

Lyme disease is tick-borne, and a bite from an infected tick transfers the bacteria to humans and animals, including horses. For horses, the varied signs may include stiffness, swollen joints, shifting lameness, muscle tenderness, behavioral changes and certain neurological effects. The sheer range makes it hard to diagnose, yet if caught early, the prognosis for full recovery is good, following administration of antibiotics.

That uneasy feeling that something wasn’t quite right

A single horse in a herd can suffer Lyme disease

A single horse in a herd can suffer Lyme disease

My mare was always the odd one out in a small herd of youngsters. Dull coat, an incidence of unexplained hind leg tremor, uveitis-like syndrome blamed at the time on an old corneal scar, general gait stiffness and on and off right hind lameness accompanied by swelling of the hock joint and below.

Then there were the little things, such as positions that would worry her when being trimmed, and unexplained twitchiness about some joints when being body worked. But she showed no aggression, choosing instead to walk away or use her weight to make her point. We shrugged this off as something that she would overcome, given time and training.

At first, I insisted on vet visits for each significant incident. Each visit ended with practical recommendations to treat the symptoms and monitor. With most cases, she improved and seemingly recovered. There was no need to dig deeper.

But as the number of such incidences – both recurring and new – grew, I knew that it was well beyond the law of probability: how could one horse be singled out for so many issues? Something was definitely wrong.

In the meantime, this normally laid back and gentle mare was becoming irritable and a little intimidating. She bit an unsuspecting bystander on the chin (my unlucky husband) and even launched an attack on the household dog.

She became increasingly sensitive to being groomed on her near side and she twitched when she felt our hand touch the sides of her face. The rugs started to consistently slip to the left as she shaped her body to attain a position of comfort under their weight.

But there were days or weeks at a time when she seemed better. On those days, I gently worked her from the ground, mostly at a walk. Even then, I found her somewhat reluctant, and the performance variable. On some days, her hind end engaged effortlessly, and on others, she just resisted all efforts towards a square halt. So after a while, I took the hint and left her in the paddock to take an indefinite holiday.

What next? A worsening of the signs, that’s what

The following Spring, the fresh winds brought her to new heights of sensitivity. She remained on high alert and shied at seemingly nothing. Even the dangling belly straps on her rug became threatening enough for her to consider bolting off.

Then suddenly, she had another inflammatory attack, this time on her left hind. It was a significant departure from the usual pattern: for the past 2 years, the problem had always been her right hind, fueling suspicions that it was some sort of a paddock trauma with periodic setbacks.

But this time it was her left hind. I analyzed the situation. She was not in work, so it could not be work-induced. She was not nursing any stiffness, so it could not be a compensatory problem.

I looked to the paddock for clues. Although generally the type that likes to remain ‘parked’, she hypes herself up during herd gallops and launches her massive frame into the air like a 747 – a reminder of her lineage of Grand Prix showjumpers. But the ground itself gave no indication of any such activity. I wondered if it might even be an unfortunate kick from a paddock mate.

My fears disappeared in a few days, when the inflammation subsided.

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A growing suspicion: could it be Equine Lyme disease?

The black-legged tick carries Lyme in the US, but isn't found in Australia

The black-legged tick carries Lyme in the US, but isn’t found in Australia

Then one morning, as on so many mornings before, I found myself scrutinizing the mare from a distance and contemplating the situation. As I stood there, the drifting information in my mind seemed to crystallize and I suddenly knew what to do. I found myself calling our horse vet to ask whether we can conduct a blood test – one that would specifically include Lyme Disease.

In all honesty, I wasn’t sure if my request would go down well. Has there ever been a documented case of equine Lyme in Australia? I was well aware of its controversial nature for human cases.

On the other hand, I was quite comfortable that the clinical symptoms of equine Lyme could explain all of my mare’s unfathomable health history.

My vet patiently heard me out, and agreed to test for Lyme. He also suggested a general blood test, as well as tests to cover other viral and bacterial diseases that might cause one or more of the mare’s symptoms. I thought it was an excellent suggestion.

The test results offer hope – of a kind

Several weeks later, we had the full results. Blood biochemistry and hematology was normal. She was negative for leptospirosis, which might have otherwise explained her uveitis. There were many other viruses she tested negative for.

Equine Lyme mare

All looks normal, but the test for Equine Lyme is positive

But, she came back positive for earlier exposure to Ross River Virus (not currently active) and Lyme. It’s quite common for horses in endemic regions to have full immunity and therefore test positively for Ross River Virus (RRV), without it ever having been detected in the past.

Yet for those horses that succumb to significant clinical symptoms upon infection, it may take many months, even years, for them to build up full immunity. Until such time, symptoms associated with RRV may recur, especially in times of stress.

It was difficult to think about the implications of a RRV diagnosis in my mare’s case: it could explain some of the symptoms, such as recurring stiffness and swollen joints. On the other hand, she may already have attained full immunity. Yet as there’s no medication to eradicate the virus, there wasn’t much we could do in any case.

Lyme, however, is treatable. This gave us the possibility of confirming or disproving the diagnosis by observing my mare’s response to treatment.

 

Ticks usually carry Equine Lyme

Australia has no shortage of tick species – here are just three

But what about the Equine Lyme disease test?

The Lyme blood tests are notoriously unreliable indicators, producing false positives and – more often – false negatives. The fact that the bacteria can remain undetected by the horse’s immune system means there are fewer antibodies and therefore a greater chance of a false negative result.

There’s also an issue in that there’s no central body controlling the standard of the tests. This means that the ‘gold standard’ approach is to undertake at least 2 blood tests based on different methodologies.

We sent off a request to the US for more testing, with a 6-week wait for results.

There are now suggestions from reputable sources (ie, producing peer-reviewed published research) that different strains of bacterium may be present in Australia, and that these may be vectored by the biting March fly rather than ticks. Here is a starting point for more reading.)

 

Could the March fly carry Lyme disease?

Could the March fly carry Lyme disease?

To act or not with a partial Lyme Disease diagnosis

With a second test underway, my vet and I decided to place faith in the results so far, and started my mare on an initial 6-week treatment for Lyme. This consisted of a course of three different antibiotics.

The early signs were encouraging. For each new course of antibiotics, she presented with inflammation in different parts of her legs, and patchy sweating on different parts of her body. This is consistent with the Jarisch-Herxheimer reaction, which is well-documented in human Lyme cases. It’s the body’s response to endotoxins released by a mass of dying bacteria.

We continue to monitor her closely. She is becoming more social and less flighty under windy conditions. She is no longer so sensitive around her head.

Is it Lyme? Possibly. Will she be cured? I hope so.

Our journey continues.

 

The intention of this article is not to pinpoint Lyme as the culprit of all vague and unexplained ‘unwellness’ and ‘misbehavior’ in horses. It is written in the hope that the information will provide horse owners with other avenues for investigation where the more familiar possibilities have been exhausted. Most importantly, it will hopefully encourage all horse owners to diligently keep a record of their horse’s health and psychological well being, as it was just such an approach that has helped us.

 © All text copyright of the author, at www.thehorsesback.com. No reproduction of partial or entire text without permission. Sharing the link back to this page is fine. Please contact jane@thehorsesback.com for more information. Thank you!

About the author: Cherry Kawamoto (BSc) recently moved back to Australia from Singapore to set up MF Equestrian, a boutique training facility in Nana Glen, NSW. This caters for young horses and riders. For more information, please contact Cherry on mfequestrian88@gmail.com

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