The Horse's Back

Body Talk for Thinking Owners

Recent Posts

Revealed: the Common Equine Arthritis You Won’t Read About in Textbooks

by 144 Comments

elbow-header2

 

Sometimes, a person from outside a profession successfully identifies something that has been unnoticed, overlooked or wrongly assessed for a long, long time. Coming from another direction, they see something that has been hidden in plain sight, simply because nobody looked there before.

Update: this post was written with Sharon’s support in 2013. Finally, in 2022, Dr May-Davis is publishing her findings. This article will be updated with full details once her paper is in print in a peer-reviewed journal.

© All text copyright of the author, Jane Clothier, https://thehorsesback.com. No reproduction of partial or entire text without permission. Sharing the link back to this page is fine. Please contact me for more information. Thank you!

 

One lady who’s working in the field

If you’re looking for a different set of eyes for equine musculoskeletal pathologies, they don’t come much sharper than those of Dr Sharon May-Davis. Few people have the razor sharp eye she has for a hidden pathology or condition in the horse.

Teaching biomechanics, Sept 2013
Sharon, seated, teaching biomechanics, Sept 2013

Sharon is also a biomechanics expert and – significantly – a practical anatomist. She has been conducting private equine autopsies for many years – it’s not for nothing that she’s been labeled The Bone Lady and Equine CSI.

She also uses these 2-3 day dissection workshops to teach equine professionals and horse owners more about how their horses move and the damage their bodies can incur as a result of breeding, illness, injury or work.

Sharon is therefore uniquely placed to provide a source of raw data that is all but unparalleled.

Evidence from the dissection table

Some years ago, Sharon noticed an unusual action in the elbow of horses. She mentioned this to qualified practitioners and was informed that this action was quite normal. Not convinced, she began videoing horses prior to dissection and, within a short period of time, was able to match this action to a change in the elbow.

Humerus, radius and ulna, showing damage to cartilage
Humerus, radius and ulna, showing damage to cartilage

Not to beat around the bush, it’s an unusual form of degeneration in the horse’s elbow joint that involves all three bones. It’s a form of osteoarthritis that strikes the humeroradial joint and the ulna, causing deep and dramatic gouges into the cartilage, and eventually eroding bone.

When the joint is opened up, blood is frequently found in the synovial fluid (haemarthrosis). The fluid also displays decreased viscosity.

This is more than a little bit odd, as arthritis of the elbow is supposed to be rare in the horse.

Yet Sharon has found it to be present in numerous horses that have been euthanized under veterinary supervision for completely unrelated reasons.

Note: that’s not just some horses, but many.

Do you know where the nuchal ligament attaches on the cervical vertebrae? You think so? Evidence from the dissection table might prove you wrong – read more about Sharon’s findings on the nuchal ligament’s lamellar attachments…

This equine arthritis is visible in the living horse

The vital connection from video to dissection has enabled Sharon to indicate the presence of the elbow osteoarthritis in the horses she had been treating as an equine therapist.

It’s easy to spot, being a noticeable jarring in the elbow as the horse moves downhill – a kind of double action. Significantly, it’s what can be termed a gait anomaly, rather than lameness.

Does it sound – and look – familiar? It’s very likely that you’ve seen it in horses before and wondered what it was. The fact is that it’s so common, many people think it’s a normal action. It’s not. It’s a form of equine arthritis.

Sharon tells us she has seen the elbow problem in all types, breeds, sizes and ages of horses. Some affected horses have been elite dressage and eventing competitors. Interestingly, the problem is only presenting in ridden and driven horses.

If never worked, horses appear to remain forever free of this particular joint change.

Why the fuss – isn’t this just regular arthritis?

No. Arthritis of the horse’s elbow is considered to be rare in equine veterinary medicine.

How it should look: healthy radius and ulna (unridden horse)
How it should look: healthy radius and ulna (unridden horse)

The key to why it doesn’t often get diagnosed and is considered rare could be the absence of visible lameness. The arthritis identified by Sharon does not cause a distinctive lameness in the horse, although it does bring on a notable gait change, with the double step in the joint’s motion on the downhill.

Riders of such horses often just feel that their horse is a bit ‘off’, feeling a hesitation in the movement, but without being able to define the point of origin.

There are a couple more reasons why it’s not very visible: first, the action of the elbow is highly integrated with the overall shoulder action, and second, the massive triceps muscle has a further stabilizing effect on the joint.

Radius and ulna of ridden horse, showing cartilage wear and blood in joint
Radius and ulna of ridden horse, showing cartilage wear and blood in joint

And even if the elbow is explored, the relatively tight joint space means that degenerative problems are rarely seen in diagnostic imaging, although inflammation can show up in thermographic images.

When, unusually, a problem has been recognized and vets have attempted a corticosteroid injection of the joint (which happens to be the most difficult joint to access), blood has been found to be present.

A closer look at Sharon’s findings

Sharon May-Davis first presented some of her findings into elbow arthritis at a conference in Australia in February 2013: the Bowker Lectures at the Australian College of Equine Podiatherapy. Presenting alongside Prof Robert Bowker and Dr Bruce Nock amongst others, she discussed the club foot in the horse, and noted how the elbow degeneration she observes on the dissection table is always worse in the forelimb with the more upright hoof.

If the condition is bilaterally present, it unfortunately appears worse on the side with the slightly upright or higher hoof. What’s more, and according to Sharon, this also applies to the limb where an inferior check ligament desmotomy (surgery undertaken with the aim of correcting an upright hoof) has taken place and the ligament has later reconnected.

She has, as already mentioned, since established that it can occur in any ridden or driven horse. Here, she describes the problem in her own words.

“The action looks like a slip and or clunk into the shoulder or a shudder or a sliding / slipping action. It depends upon your perspective. The actual change in the action begins when the foreleg is in the ‘Stance Phase’ during the stride as the limb goes into the posterior phase of the stride. It is more obvious going down a hill.

“So far, 100% of ridden horses exhibit this condition to a varying degree (under dissection). Horses not ridden and with no abnormalities do not exhibit this condition (under dissection). Horses in harness also exhibit this condition.

“What does the joint look like? There appears under dissection to be substantial degradation in the cartilage of the humerus, radius and ulna.

“Most horses appear to handle this condition and continue with a normal life if not pushed to extremes. Although this sounds career-ending, in fact it is not. Once the horse gets through the worst of the wear pattern they re-settle in the joint and continue on with work.

“High level competitors require joint support to help sustain the elbow and other joints that may compensate for the change in action.

“Horses that jump are more inclined to land with straighter forelimbs. Be mindful that jumping and downhill work could possibly make the condition worse.

“Riders often feel instability in the horse’s forelimbs when traveling downhill and some even question the horse’s proprioception.

“Bodyworkers massaging the triceps (particularly the lateral triceps) actually exacerbate the condition as the massage releases the cast-like formation that this muscle provides.”

Here are some more examples of the elbow in action.

More research is needed, but so is support

Humerus and radial bones of ex-racehorse, showing arthritic wear
Humerus and radial bones showing arthritic wear

Despite finding and documenting a huge number of dissection cases involving this particular issue, all unaided and unfunded by outside bodies, Sharon has consistently met with brick walls and skeptical responses when she has put the information forward to relevant authorities.

Why? It’s not as if she’s new to this. She has previously identified congenital malformations in the caudal cervical vertebrae of thoroughbreds, and in the atlas of Spanish Mustangs, as well as asymmetries in the femur structures of racehorses due to racing (published in the Australian Veterinary Journal).

She isn’t looking for funding (although she obviously wouldn’t say no), but would like to have this research taken up for the benefit of all ridden and driven horses. The sooner the problem is recognized and investigated, the sooner that episodic pain in the horse can be recognized, with appropriate joint support or rest given where appropriate.

And the sooner we can all learn more in our great drive towards improved equine health, the better. As Sharon says,

“In truth, we are still in the dark. Seeing it is one thing, analyzing it and providing a preventative program is something totally different.”

 

Questions, thoughts or comments? Join us at The Horse’s Back Facebook group. 

 

More Information

Shop for the Best Discounted Pet, Equine, & Livestock Supplies!Sharon May-Davis, PhD, M. App. Sc. (Ag and Rural), B. App. Sc. (Equine), ACHM, EBW, EMR was the Equine Therapist for the Modern Pentathlon Horses and the Australian Reining Team at the Sydney 2000 Olympics. She has worked with the Australian Champion from seven differing disciplines and has a particular interest in researching the musculoskeletal system. She also conducts clinics and seminars in relation to her work and regularly presents in the Northern and Southern hemisphere.

 

 © All text copyright of the author, Jane Clothier, 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!

 

10 Ways to Seriously Mess Up When Buying a New Saddle

by

saddle-shop-header

Not long ago, I was having a think about the reasons that people buy saddles that so obviously don’t fit their horses. This is a regular spell of head-scratching that occurs when I’ve worked on a few horses with back and postural issues stemming from saddle misfit.

Now, in my view, a saddle fit session is a pretty critical part of buying a saddle.

It goes without saying, surely, that there’s a living, breathing horse out there in the paddock or stable and that the new saddle needs to fit onto his back – and that this suitability really does need to be established before the saddle is purchased.

Yet, many people still buy a saddle and only afterwards try to establish whether it will fit their horse or not.

It’s all a bit of a gamble – not only with their money, but with their horses’ comfort and back health.

All text (c) Jane Clothier, https://thehorsesback.com No reproduction without permission. Thanks!

What on earth is going on here?

Good question. Either people are genuinely unaware of the reasons for fitting saddles, or they do know but are marching to a different, louder drumbeat when they go shopping.

To make more sense of this, I decided to apply the psychology of consumer buying behavior. At the simplest level, there are five stages involved in a purchase:

  1. Need recognition (we feel the need for a new saddle),
  2. Product research (we learn what’s out there),
  3. Evaluation (we consider everything learned through our research),
  4. Purchase decision (we carefully select the most suitable saddle), and
  5. Post-purchase behavior (we react positively or negatively to our choice).

english-saddlesWell, how tidy is that? Too tidy, maybe. The problem is that we all behave erratically when shopping, being influenced by our  personal biases.

These are preferences, beliefs and thought processes that hold up our personal view of the world – and our illusions. Biased behavior includes:

  • Cherry-picking information by being selective over what we see, hear and read,
  • Yielding to peer pressure,
  • Favoring someone’s viewpoint because we like them (whether we know them or not – take celebrity endorsement),
  • Supporting our self-image (actually how we think other people see us),and
  • Being totally inconsistent in our behavior, just because we do that.

We’re none of us exempt from this. Being emotionally charged, biases are very motivating.

What happens is that they can leapfrog us from need recognition straight to purchase decision, making us ignore the research and evaluation findings or leave them out altogether. (And this forms the basis of every advert you’re ever likely to look at.)

10 Emotional Saddle-buying Decisions

Here are 10 ways that you can succumb to biases that skew your saddle purchase decisions.

"I could be that good too...where's my credit card?"
“I could be that good too…where’s my credit card?”

1. Your instructor or trainer uses that saddle

Whoah… this could cause some shouting, but instructors, trainers and clinicians don’t always know all there is to know about saddle fit, even though they know HUGE amounts about riding and training.

No offence meant, honestly, but some riding instructors give their students terrible advice about saddles. They say one fits, when it doesn’t. Horse owners just follow this well-meant advice, because they really believe in and admire their instructor.

Some trainers and clinicians even use a favorite saddle on all their own and their clients’ horses. It suits the rider, so… Some of these cause damage and the clients often don’t realise until someone else points it out at a later date.

(There’s a variation on this one, too: attend clinic or do course, then buy saddle. No further comment.)

2. Your knowledgeable friend owns that saddle

A lot of horse-related knowledge is passed between friends. When it’s good, it’s good, but when it’s bad, it can be very bad.

No matter how much you like your friend, there’s a high chance that their physique and their horse’s is likely to be different to yours. And your friend will very likely ride differently too. These three points are frequently overlooked.

Saddler who learned from his father, who learned from... Photo (c)Nicola Valley Museum
Saddler who learned from his father, who learned from… Photo (c)Nicola Valley Museum

3. There’s a local saddle maker in town who makes that saddle

He lives close by and tells the local horse community all about what he does and what he makes. He’s knowledgeable, he loves his work and, dang it, he’s such a nice guy.

It’s possible, just possible, that he may know more about producing beautiful hand-crafted saddles than equine anatomy and biomechanics, having learned more from his father and other craftsmen than from modern schools of equine thought.

And, obvious as it sounds, there’s a difference between a saddle-maker and a saddle-fitter, although there are definitely plenty of saddle-makers who are also great saddle-fitters.

But at small town level it can, and does, go either way. (You can probably tell I’m trying not to offend anyone here.)

Can the buyer tell the difference? Frequently not, as so many people buy an expensive, custom-made saddle that doesn’t fit, but which can’t then be returned. (If this isn’t the case with your locally made saddle, then brilliant – I’m genuinely pleased for you.)

A famous rider's name doesn't doesn't make this saddle fit
A famous rider’s name is on the saddle, but it still doesn’t fit

4. That saddle is named after a famous rider

There are many saddles out there named after a top-of-their-game rider – it’s celebrity endorsement with bells on.

It’s a funny thing how what works for them makes that style of saddle suitable for hundreds of thousands of other riders and their horses, of all shapes and sizes.

And the buyer’s riding will improve to an unfathomable degree… won’t it?

Aspirational shopping aside, some of these saddles are amazingly good, but (no naming names now) not all of them are. This is particularly true if they’re occupying what we can call the ‘value end’ of the market.

This saddle fits all arabians - and is a bargain too
This saddle fits all arabians – and look, it’s a bargain too!

5. Your friend with the same breed of horse as you has that saddle

Some people constantly draw parallels between their own horse and that of a friend or acquaintance who has a horse of the same breed.

The prospective saddle buyer sees which saddle their friend has and decides it must be good for their horse too.

This is so much the stronger if the owner is much admired or is winning in competition with that saddle.

Yes, breeds obviously have prevalent conformational traits. But it’s not a given, as horses – and their riders – can be very individual.

Images of dream-like perfection
Images of dream-like perfection…

6. You’ve seen a stunning photo of that saddle in a magazine

And it really was beautiful. The horse was beautiful, the saddle was beautiful, and the rider was stunningly beautiful. An image of dreamlike perfection… in an advert. It always works, doesn’t it?

We’ll all look just like the stunner in the paradise-like photo once you buy the saddle.

No, I don’t think so either.

7. A Facebook regular recommends that saddle

We all know them and recognize them: the person who is very vocal on Facebook, being big in their own lunchtime with strongly held opinions. A queen bee, they hold forth at the center of a community of regulars who mutually reinforce one anothers views.

To the less informed reader, this verbiage may sound like unassailable fact. So when the queen bee says a certain saddle is the best and how it’s right for certain horses, her view may be perceived as being expert opinion.

(Hey, she may indeed be right, but not above and beyond someone who is standing look and assessing fit on actual, living horse – with a rider on board.)

Big brand saddle - but the design has had its day
Big brand saddle – but the design has had its day

8. When you were a kid, everyone craved that saddle

Times change, the knowledge-base grows and designs evolve. The industry moves on (although some companies don’t) and what was great back then may not be so now.

Brand names rely on consumer loyalty, but over long periods of time your loyalty may be misplaced. Formerly great brands may now be merely good, which is OK if the price reflects that change, but…

Have you noticed that people will buy used, 25-year-old spine-pinchers just because they were made by that company?

9. Your horse went better when you tried out that saddle

What? Surely this one’s a no-brainer? You’ve borrowed a saddle and your horse went better in it than in your old saddle, which was causing problems – that means the borrowed saddle is a good fit, doesn’t it?

Nope. It’s a sure-fire indicator that your horse is showing relief at not experiencing the same old pokes and pressure points when ridden, because at last somebody has taken the offending piece of leatherwork off his or her back.

What we aren’t seeing at this stage are the new problems that may emerge from this replacement saddle that may not fit, but in a different way.

It’s like repetitive strain injury – it can take time for signs of problems to become visible (although in endurance riding, problems can show up within a single day’s ride.)

10. You’ve never seen a better price attached to that saddle

In an online world, we’ve never been more able to shop around for that super-bargain.

And when we find it, it’s all so much easier to ignore any possible shortcomings. This is even more so when time pressure is involved, for instance in an online auction.

Try to bring in reason over emotion

Oh I know, it’s hard to do. We’re never going to escape the emotional side of shopping, particularly with new – or new to us – saddles.

The bigger the purchase, the more rewarding it’s likely to be.

Yet that’s all about us. Our horses are happily unaware of the thrill of shopping. To the horse, a saddle that fits will minimize the negative effects of bearing our weight on its back – while one that doesn’t fit won’t.

We owe it to our horses to make informed and well-considered decisions.

I realize that it can be hard to know if you’ve got a good saddle fitter, but involving a trained professional in the research and evaluation stage of your buying decision will certainly decrease the chances of making a catastrophic error that will cause pain and damage to your horse.

Alternatively, in this online world where you can find those superb saddle bargains, hop onto YouTube and take look at some of the excellent videos posted by professional saddlers. It really couldn’t be much easier.

 

Questions, thoughts or comments? Join us at The Horse’s Back Facebook group. 

 

 

How to Fight the Big Fight against Neck Threadworms

by 108 Comments

fight-header-2

This follow-up to ‘The Disturbing Truth About Neck Threadworms and your Itchy Horse’ discusses how to manage the parasites, once you know your horse has them.

The original article was aimed at my Australian bodywork clients here in NSW, yet it quickly worked its way through other networks – I haven’t a clue what or where, but it started running and it’s still running today.

All text (c) Jane Clothier, https://thehorsesback.com No reproduction without permission. Thanks!

Astonishingly, five years later, it’s been read by over 500,000 people in nearly every  country in the world.

I make no claim to be the first to write about neck threadworms. For making it a more widely known issue, the forum members of The Chronicle of the Horse website must take credit (and I recommend anyone with specific questions about their horse to head over there).

I guess my post succeeded in bringing the available information together in one place – in that it simply reflected my own experience of researching the subject on behalf of my newly itchy, increasingly unhappy horse.

‘The Disturbing Truth’ has certainly offered a possible answer to many owners whose horses are besieged by the living hell that is variously known as Sweet Itch, Summer Itch, or Queensland Itch.

That’s because in a certain percentage of cases – not in all of them – the cause is onchercerciasis, a hypersensitive reaction to the larvae of the Onchercerca cervicalis parasite.

Ignore the nay-sayers – it’s an international battle

Imagine your itchy horse with a regrown mane...
Imagine your itchy horse with a regrown mane…

One thing that’s become really, really clear from responses to the first article is that onchercerciasis is a problem for horses worldwide. It’s obviously worse in some climatic areas than others, but that doesn’t mean it doesn’t exist in cooler zones.

Reading the comments triggered by the article tells us all we need to know. Horses travel within countries and internationally – the larvae can then be transmitted to new host horses in the destination region, providing there are enough local culicoid flies to transmit them.

As another reader pointed out, warmer and wetter winter and summers are giving the flies a better hit at it than ever before.

Research has shown the presence of neck threadworms in horses in such non-tropical countries as Canada, the UK and Poland. In fact, the UK research was conducted in the early 1900s, showing that air transport of horses has little to do with it and that this parasite has been in cooler climes for a long time.

Dragging neck threadworms into the daylight

The comments at the bottom of ‘The Disturbing Truth’ are illuminating. Some people have battled their horses’ itch, often so bad that it prevents their horses from being ridden, for a decade or more.

They have struggled with different diagnoses, with various medications, with investigations into suspected colon disorders and testing for allergen sensitivities, all to no avail. Everyone involved certainly meant well, but the problem still remained.

Astonishingly, more than one person has previously mentioned neck threadworms to their vet, only to have it dismissed out of hand, because “that’s not a problem around here”.

Despite this, some of those same horse owners have started treating their horses and are already some way down the road to reducing the larval population and are resolving the issue. Some are seeing manes grow back on their horses for the first time in years.

This isn’t to say that all itching is caused by the larval stages of Onchocerca cervicalis. I don’t want to be grandiose about this. But it’s certainly affecting enough horses for it to be worth ruling out. For the price of a couple of tubes of ivermectin wormer, why on earth not do just that?

Culicoid fly in close-up
Culicoid fly in close-up

It’s baffling that this problem has ceased being common knowledge and so often slips under the radar. It’s true that the companies producing wormers certainly know about neck threadworms, but quite naturally focus on promoting their products’ effectiveness against far more serious gastrointestinal worms.

(And let’s be honest, many horse owners feel distrust towards drugs companies, whether involved in human or veterinary medicine.)

Even so, in regions such as the Australian tropical and subtropical zones, you’d think there’d be a bit more awareness, wouldn’t you? But then perhaps we’ve all been so hung up on Queensland Itch, we’ve been unable to see the wood for the gumtrees.

[Article continues after advert.]

Down to business: How to win at worming

With your initial burst of worming, either on a fortnightly or monthly basis, single or double dose (as described in ‘The Disturbing Truth’), you’ll have established that your horse does indeed have neck threadworms.

Using ivermectin, you’ll have seen a temporary worsening of the problem and, possibly, the increased itching and/or eruption of pus-filled lumps in the mane.

Moving on from that point , it’s important that you establish a strategy for dealing with the ongoing presence of the neck threadworms in future months and years.

Regretfully, when I say ‘win at worming’, what I actually mean is ‘win at managing the worms’. As we know, you can’t kill off the adults, only the microfilariae. Hence you can only strive to bring it all under control.

That’s why tackling neck threadworms in your horse is a numbers game. It’s safe to assume that most horses can deal with a relatively small number of microfilariae, so it follows that the more you can bring those numbers down – and keep them down – the more likely it is that your horse will be able to deal them without experiencing hypersensitivity.

In other words, the itching will ease.

A calcified lump in a dissected nuchal ligament
A calcified lump in a dissected nuchal ligament

Just to repeat: you can’t bump off the adults. Once they’re in your horse’s nuchal ligament, they’re there to stay for 10 years or more. And then even when they die, they remain present, entombed in a small calcified lump in the ligament.

You can see one in the picture on the right. ‘M’ marks the center of a lump nearly 2x4cm in a veteran horse’s nuchal ligament.

How frequently should you worm?

At different times of the year, the microfilariae being introduced to your horse will vary in numbers, depending on the level of culicoid flies around. This means that with evenly spaced wormings, you’re going to have different results at different times.

As the warmer months are going to see faster increases of the population, it makes sense to worm more frequently in Spring and Summer. The microfilariae are picked up from a horse by the biting fly, after which they develop in the fly for 15-21 days (research seems to differ on this point).

The flies are the vectors that take the larvae through an additional life stage. After this time period has lapsed, they deposit them back into a horse. This is going to happen faster with horses that live in herds within a kilometer or so of standing water.

  • Some owners feel that monthly worming during Spring and Summer is sufficient to interrupt the pre-adult lifecycle. Check with your equine vet if you’re not sure (although one reader’s vet suggested worming at 6-monthly intervals, for some mysterious reason).
  • Once the microfilariae numbers are down, possibly after the first year, some owners come down to 6-weekly and 8-weekly wormings.
  • Others prefer to leave the horse from mid-Autumn until mid-Spring, following only a ‘normal’ worming schedule during this time, before worming more frequently during the fly season.

In the end, it’s a matter of individual choice. All you can do is observe your horse and keep at it until you see a significantly reduced reaction in terms of itching.

The longer your horse has been living with neck threadworms, the longer it’s likely to take. And the more tropical and humid your regional climate, the more biting flies there are going to be. Even so, you might be pleasantly surprised by the speed of the positive change.

Include gastrointestinal worming in your plan

Once you’ve used an ivermectin wormer to identify the presence of neck threadworms in your horse (see ‘The Disturbing Truth‘), it’s sensible to also worm intermittently with moxidectin, found in Quest/Equest. The reason is that this is the only wormer to hit Onchocerca microfilariae AND encysted small strongyles.

Encysted small strongyles in the colon. (c) Vetnext.com
Encysted small strongyles in the colon. (c) vetnext.com

While neck threadworms can make life highly unpleasant for your horse, encysted small strongyles can kill him or her if they suddenly erupt.

They would have to build up to a high level first, but if your horse has been malnourished before coming to you, or is a rescue horse, or if you’ve only used ‘natural’ wormers for some years, you have the perfect conditions for such an event.

The best approach is to address the intestinal worms before moving onto the neck threadworms. So if it’s unlikely your horse has had Quest/Equest or Panacur for some years, use one of these first.

In my region, Strategy is also valuable in addressing pinworms, which are resistant to many other products.

Support your horse’s intestinal tract

Shop for the Best Discounted Pet, Equine, & Livestock Supplies!Worming for neck threadworms is always going to be a necessary evil. None of us would wish to be following such a rigorous worming schedule if we had the option, so we must do our best to mitigate any negative effects.

If you’re following a heavy worming schedule, you should also be supporting your horse’s gut, which is going to be taking a chemical hammering.

The best place to start is with probiotics, either added to the feed or administered through a plunger tube (although your horse may be a little off plungers at the moment…).

The reason for using a probiotic, which is essentially a supply of beneficial flora for the hind gut, is that the existing ‘beneficial bacteria’ will have been reduced by the wormer. It’s then more likely that pathogens (‘bad bacteria’) will proliferate, potentially leading to intestinal inflammation and diarrhoea.

This is not only uncomfortable and painful for your horse, but the affected digestive processes will reduce nutritional uptake, which in turn leads to an impaired immune system.

And what happens with an impaired immune system? The horse will be itchier.

Using probiotics means that in supporting your horse’s intestinal function during worming, you will also be supporting your horse’s immune system. It’s a double-win .

You can also help to restore damaged mucosal lining. Various plant sources are ‘mucilages’, meaning that when mixed with water, they form a slippery substance that lines and soothes the intestine. You can consider using aloe vera juice, slippery elm, marshmallow root, liquorice root and chia seeds.

Itching elsewhere on the body

Some owners are saying that their horses, which have had all the signs of neck threadworms, have also started itching on the tail head and along the back. This doesn’t fit with the usual oOnchocerciasis locations of head, neck, chest and ventral areas, and could be due to:

  • Pinworms, which lay eggs around the anus and cause itching of the tail head,
  • The horse reacting to dying microfilariae previously delivered by culicoid flies biting in ‘atypical’ areas of the body (it’s interesting to note that bite locations may vary according to the particular species of fly, which differ from country to country),
  • The horse reacting to the saliva of all culicoid flies, having become hypersensitive to microfilariae that have entered their current life stage within the flies’ saliva. In other words, the horse has developed the Itch.

It’s worth noting that there are two different types of Onchocerca worms also affecting horses and donkeys, and that these cause problems in other areas of the body.

  • Itching on the legs can be due to Onchocerca reticulata, as the adult worms are found in the connective tissue of the flexor tendons and suspensory ligament of the fetlock, mostly in the forelimbs.
  • In donkeys, Onchocerca raillieti are also found in the nuchal ligament but also, nastily, in subcutaneous cysts on the penis and in the perimuscular connective tissue. 

Can neck threadworms lead to the dreaded ‘Itch’?

Itching along the topline
Itching along the topline

Now, this is where things get a bit curly. Once your horse has started reacting to Onchocerca microfilariae, they may develop The Itch – aka Queensland, Summer or Sweet Itch (take your pick).

If their system is reacting to the microscopic larvae carried in saliva, why not react to the saliva itself? The immune system is nothing if not intelligent: it learns and it acts on the information it receives.

I’ll be honest here. I’ve not read any research into this, but hooray for Dr Carl Eden BVM&S MRCVS of Virbac, who writes:

Internal parasites such as Onchocerca cervicalis… may also cause pruritus and in the case of O. cervicalis, its involvement in cases of Queensland itch must not be underestimated.

Let’s look at this for a moment.

The Itch is a clinical syndrome, being a hypersensitivity to certain allergens. When the allergen is the saliva of the culicoid flies, the outcome is an inflammatory response.

This in turn leads to a pruritic (itching) skin condition. We’ve all seen its awful progression from hair loss, bumps and wheals, to alopecia, crusting, broken skin and worse.

So I’m speculating here: some of the horses with neck threadworm symptoms develop the Itch as they develop a heightening, acute sensitivity.

The thing is, whether this supposition is right or wrong, you can do no wrong by managing your horse as if it has both neck threadworms and the Itch.

Managing the itching side of neck threadworms

Furiously rubbing the tail head leads to hair loss (c) hyfeed.com.au
Furiously rubbing the tail head leads to hair loss (c) hyfeed.com.au

While you’re working on reducing the microfilariae numbers, there’s plenty you can do to make your horse more comfortable. There’s nothing worse than seeing your horse breaking his or her skin while rubbing an itch that won’t ease, whether it’s caused by neck threadworms alone, by the parasite and a developing itch problem, or by the parasite and a pre-existing itch problem.

I’m not going to go into lots of detail as to what you can do, but here, in no particular order, is a starter list.

  • At the heavier end, a short course of glucocorticoid therapy (ie, steroids) will reduce the inflammatory response. Some owners have used oral prednisolone – Preddy®-granules –  to support their horses during the initial stages of ivermectin worming. It’s not good for pregnant mares, suspected or actual laminitics (steroids can trigger an onset) and horses with internal issues.
  • Antihistamine preparations work on the chemical response, but may lead to occasional behavioral changes or even have a sedative effect.

There are changes you can make to your horses diet and nutrition:

  • Supplementing your horse’s diet with Essential Fatty Acid (EFA) – Omega 3s – has been shown to reduce insect hypersensitivity. This can be a shop-bought product, or cold pressed linseed oil, or cod liver oil added to the feed.
  • Improving mineral supplementation helps to boost the immune system. This doesn’t mean using an off-the-shelf standard product, although that is better than none. Ideally, identify the deficiencies or imbalances in your horse’s forage and diet, and then supplement accordingly.
  • Some people are using a combination of chondroitin sulphate, spirulina, and ground linseed (flax) in the daily diet, with some success.
  • Probiotics also help to boost the immune system by improving gut function, as we saw earlier.

There are also measures you can take to keep the culicoid flies away from your horse in the first place:

  • A fly rug keeps the carriers, the culicoid flies, away from the horse (c) sweetitchtreatments blog
    A fly rug keeps the carriers, the culicoid flies, away from the horse (c) sweetitchtreatments blog

    External and topical protection can help to keep the culicoid flies at bay: fly rugs, wipe-on insecticides, and oil-based creams and lotions, especially those containing camphor, menthol or thymol, act as barriers while providing relief and repelling flies.

  • If you stable your horse, try to do so between 4pm and 8am, when the biting flies are most active in subtropical and tropical zones. Fans will help circulate air and discourage flies, while mosquito netting on windows will also help.
  • Bathing in dermatological shampoos containing chlorhexidine gluconate bring relief while working against localized bacterial infection.

Do it your way: it’s an individual fight

Ultimately, the line you take when tackling neck threadworms in your horse is going to be an individual one.

You’ll be taking into account the severity of your horse’s reaction to the microfilariae, the duration of the problem, and the intensity of the fly presence in your area. And in managing the itching side, different treatments will work with different horses.

Let’s not forget, there’s also the matter for what you can do in practical terms – eg, if you’re never home from work before 6pm, you’ll be unable to stable your horse from 4pm every day.

And then there’s what you can afford to do on a financial level, especially if you have multiple horses affected (one reader of ‘The Disturbing Truth’ had four).

Please feel free to add your comments and share experiences below. We’re all learning and the contributions are fantastic. Meanwhile, if you’re after specific advice for your individual horse, I recommend talking to the guys over at the Chronicle of the Horse forum.

 

Queensland Itch, Dr Carl Eden BVM&S MRCVS

Studies on Onchocerca cervicalis Railliet and Henry 1910: I. Onchocerca cervicalis in British Horses* Philip S. Mellora1 p1 , J Helminthol. 1973;47(1):97-110.

Prevalence of Onchocerca cervicalis in equids in the Gulf Coast region. Klei TR, Torbert B, Chapman MR, Foil L.  1984 Aug;45(8):1646-7.

 

Questions, thoughts or comments? Join us at The Horse’s Back Facebook group. 

 

The Disturbing Truth About Neck Threadworms and Your Itchy Horse

by 284 Comments

disturbing-truth-feature

Look on any ivermectin or moxidectin-based wormer packet and you’ll see a long list of parasites. Tucked in neatly at the end – it’s nearly always at the end – you’ll see the words Onchocerca cervicalis, otherwise known as neck threadworms.

Also known as neck threadworms, these critters vary in length from 6cm to 30cm (think the length of a regular ruler). Astonishingly, they live in the horse’s nuchal ligament.

Yes, the nuchal ligament. It runs the full length of the neck, from poll to withers, with a flat ligament part connecting with the cervical vertebrae.

Apparently, most horses have Onchocerca. For many they’re not a problem, but some horses develop a reaction to their microscopic larvae (the microfilariae). This is known as Onchocerciasis. The horses become itchy, mostly around the head, neck, chest, shoulders and underside of the belly. That’s why owners often make the understandable assumption that their horse has Queensland itch or sweet itch.

 

A quick introduction to neck threadworms

Original article by Jane Clothier, posted on https://thehorsesback.com, June 2013. All text and photographs (c) Jane Clothier. No reproduction without permission. Links to this page are fine.

Onchocerca is what’s known as a parasitic filarial worm (nematode). One reason these worms get relatively little attention is that they never live in the intestines. The microscopic larval form live in the horse’s skin, mostly around the head, neck, shoulders, chest and underside of the belly. It is the adult worm that later makes its home in the nuchal ligament.

The problem is global and horses in most countries have been found to have this parasite. Unfortunately for those of us who keep horses in warmer, humid climates, it’s more frequent here. The biting insect that serves as a carrier is the Culicoides fly, which is also connected to Queensland Itch (aka Sweet Itch, Summer Itch, etc.).

It’s an unfortunate coincidence of environment that leads to many cases of neck threadworms being missed, because they’re assumed to be Itch.

 

Does your horse have “the itch” – or neck threadworms?

It’s a humdinger of a thought. If your horse is itchy, something different could be happening to what you think is happening.

  •  Your horse has the ‘regular’ itch (ie, Queensland, sweet, whatever it’s called in your region) and are reacting to midge spit – and nothing else. (The point of this article certainly isn’t to try and say that all itch cases are due to neck threadworms. Just some.)
  •  Your horse has neck threadworms and its inflammatory reaction to them has increased its sensitivity, so it’s now reacting to fly bites everywhere – in other words, Queensland/sweet itch has been triggered as a secondary response.
  • Your horse only has neck threadworms, in which case they’re probably rubbing along the mane and particularly the base of mane, around the neck and face, under the chest and down the ventral line (under the belly), but not on the tail head – or at least, relatively little.

Are you by any chance now thinking other horses you know? If so, they might be suffering from Onchocerciasis. There’s a lot of it about.

 

So how do we identify neck threadworms?

Neck threadworms have a distinctive life cycle, but as is so often the case, the problem presents in  different ways, depending on the individual.

In my brumby Colo, it started with him scratching the underside of his neck on posts. That was about 3 months before I had an inkling it might be neck threadworms. How I wish I’d known  what it was at that point, so that I could have nipped the problem in the bud…

A pony with the Itch and neck threadworms. It's Autumn and she's stopped rubbing out her entire mane, but is still itching that tell-tale area in front of the withers. Her coat has raised in a temporary histamine reaction to the ivermectin wormer.
A pony with the Itch and neck threadworms. It’s Autumn and she’s stopped rubbing out her entire mane – it has grown back – but is still itching that tell-tale area in front of the withers. Her coat is raised in a temporary histamine reaction to the ivermectin wormer.

I’ve also seen it manifest as a new, previously unseen itchy and scurfy patch on the lower part of the neck of a horse who’d never been itchy. And I’ve heard of a local horse who suddenly started furiously itching his face, bang in the middle of the forehead, to the point that it bled. He had never been itchy before.

These are the classic early signs, usually recognised by the owner only through miserable hindsight. Other signs include small lumps forming along the underside of the horse and on its neck and face, weeping spots, and a scaly crest to an area of the mane through rubbing.

The base of the mane, just in front of the withers, seems to be party central where neck threadworms are concerned.

 

 

The real nastiness of neck threadworms

The microscopic larvae can travel to the eye, although this is rare.
The microscopic larvae can travel to the eye, although this is rare.

It just gets better: the larvae can travel to the horse’s eyes, where they can cause untold damage. This cheering sentence from Scott and Miller’s Equine Dermatology sums it up: “O. cervicalis microfilariae may also invade ocular tissues, where they may be associated with keratitis, uveitis, peripapillary choroidal sclerosis, and vitiligo of the bulbar conjunctiva of the lateral limbus.”

Oh heck. Nobody’s sure how common this is. All I know is that I don’t want to find out the hard way.

Consider this: in humans, a slightly different strain of Onchocerca infestation is known as River Blindness.

Please remember this detail when you’re deciding whether to worm for neck threadworms or not.


The very strange lifecycle of the neck threadworm

These worms have a complicated existence. They’re among the shapeshifters of the parasitic worm world, developing through several larval stages before reaching adulthood.

The first stage microfilariae live in the horse, close to the skin. Their numbers are highest in the spring and decrease to their lowest point in mid-winter. They live in clusters, which is why you may first notice patches of scurfy skin where the horse has started itching. This is a reaction to the dead or dying larvae.

Itching down the midline. Mine have itched neck and shoulders only - so far. (Photo courtesy of blog, Baba Yaga's Mirror)
Itching down the midline. Mine have itched neck and shoulders only – so far. (Photo courtesy of blog, Baba Yaga’s Mirror)

At this point, our good friends the culicoid flies make a contribution, by biting the horse and ingesting a good number of microfilariae along with blood. Within the fly, the larvae then develop through a further stage (or two). They are then deposited back into a horse when the flies bite. The flies can do this for an impressive 20 to 25 days after first hoovering up the larvae.

Back in a host horse, the larvae then make their way via the bloodstream to the connective tissue of the nuchal ligament, which runs along the crest of the neck. Here they moult and develop into adult worms. The adults live for around 10 years and in this time, the females release thousands of microfilariae (larvae) very year.

Original article by Jane Clothier, posted on www.thehorsesback.com, June 2013. All text and photographs (c) Jane Clothier. No reproduction without permission, sorry. Links to this page are fine.

No matter where the adult worms settle, the itchiness is caused by the microfilariae that aren’t lucky enough to be consumed by a fly and are instead left to die off.

The next part’s really not fair. The more the horse itches and breaks the skin, the more the flies will bite exactly where the microfilariae are located, before transporting them to the same or another horse, to start all over again.

Unsurprisingly, horses with most lesions have higher microfilariae counts – it’s a perfect ascending spiral of parasite-induced discomfort.

The Onchecerca life cycle lasts for 4 to 5 months.

 

Can we test for neck threadworms?

The microfilariae can be identified in the living horse through a biopsy of the nuchal ligament. Published veterinary research shows you won’t get any indication within 34 days of worming, so the timing is critical.

Worming with ivermectin can lead to weeping spots in the mane. This was after they'd cleared.
Worming with ivermectin can lead to weeping spots in the mane. These can be painful. This photo was taken after they’d cleared, leaving bald areas. Sometimes the hair grows back white.

A dose of ivermectin-based wormer is the quickest way to tell if your horse has them. If the microfilariae are present, the horse usually responds with intense itching – and I mean, manically intense, demented itching – around 48 to 72 hours after worming.

It may develop weeping, gunky spots at the base of the mane. (If you live in a paralysis tick area, it’s similar to the localised reaction you see in response to the ticks.) These are very specific spots around 1cm in diameter, with hair loss after they’ve erupted.

My brumby responded this way, rolling furiously and rubbing vigorously against posts. Unsurprisingly, he was also hard to handle for a few days. He was definitely sore at the base of the neck, where the weeping eruptions came out, and didn’t want to be touched there. I have to say that the scale of his reaction came as a shock to me, so take heed and be prepared with some soothing salves.

 

What can we do about adult neck threadworms?

Here’s the depressing answer: not much. But we can manage them.

The nuchal ligament runs from poll to wither and links with the vertebrae. Yellow = funicular part, home to neck threadworms.
The nuchal ligament runs from poll to wither and links with the vertebrae. Yellow = funicular part, home to neck threadworms. (Image copyright Sustainable Dressage.)

The adults live for 10-12 years and happily inhabit the nuchal ligament. What often happens is that the horse’s body throws down calcification around the adult worms in an attempt to isolate the foreign body. In some horses, you can feel a collection of  pea-like bumps in the nuchal ligament. In the ones that I’ve checked, this was just in front of the withers.

The slightly better news it that the worms are so fine and the lumps so small that it doesn’t seem to affect the function of the ligament, which is tough and fundamentally taut anyway. However, I’ve not yet knowingly seen a horse with a long history of neck threadworms – I’d be interested in doing so.

Heavier calcification is usually most prevalent in horses in their late teens. It figures, as the adult wormers are older, and longer. Apparently they intertwine and live in small clumps. Mid-aged horses have mainly shown inflamed tissue around live parasites.

In horses less than 5yo, the parasites can be present but there’s relatively little immunological response. So if your horse has suddenly developed itchiness at the age of 5 or 6, you could be looking at the presence of this parasite.

Original article by Jane Clothier, posted on www.thehorsesback.com, June 2013. All text and photographs (c) Jane Clothier. No reproduction without permission, sorry. Links to this page are fine.

 

Managing the initial outbreak

Do you worm your horses? Do you want to reduce the itching at the cost of having to worm more? I know I do, but I realise that some people can’t abide the thought of chemical wormers, or their increased use. But here’s what you can do if you want to reduce that dreadful itching and virtually eliminate the possibility of eye damage.

Unfortunately, there’s no single recommended protocol for worming against neck threadworms, so you’re in fairly uncharted territory.

  • wormerTo address the initial outbreak, the advice ‘out in the field’ is to use a regular dosage of an ivermectin-based wormer, multiple times until symptoms subside. The recommended interval I’ve seen is a week, but do check with your *equine* vet first.
  • I’ve also read forum posts by US horse owners stating that a double dosage at fortnightly intervals is the most effective treatment. It’s usually around three doses, or until symptoms subside. One reason is that lower doses do not kill off enough larvae, allowing resistance to develop amongst those that remain. Wormers are certainly tested as safe at higher dosages, but again, horses are individuals, so always check with your *equine* vet first.
  • I’ve read that an injection of ivermectin can be more effective, with off-label use of a product such as Dectomax being recommended as the heavy artillery when all else has failed. Again, do check with your *equine* vet.

Some say that an ivermectin and praziquantel wormer is more effective. One small comfort is that these wormers are available in the lower price ranges. It’s a consideration, because if you’re worming multiple horses, this won’t be a cheap time. It may even be worth looking at the large bottles of liquid wormer used by studs for greater economy.

Published research has shown that moxidectin-based wormers are equally as effective in addressing the microfilariae (but don’t double-dose with this one – only with ivermectin).

Whichever option you follow, it’s worth following this worming protocol with prebiotics, probiotics and ‘buffers’ such as aloe vera to support a healthy gut lining.

Reducing the larval population

After the initial worming, it’s a matter of management. What you’re trying to do is keep the numbers of microfilaraie low, so that the horse’s itching is reduced. Remember, most horses show little reaction, although the parasites are present. The aim has to be to bring them down to levels the horses’ systems can deal with, while taking other measures to boost the horses’ immune system.

  • Some vets say a single dose every 6-8 weeks during the fly season.
  • Others say every 3 months, timed in accordance with the larval lifecycle, which is 4 to 5 months.
  • In humid sub-tropical zones, where all parasite burdens are dramatically higher, I’ve heard of people doing it as frequently as once a month.

Beyond that, you’re back to the barrier treatments – fly rugs, lotions and potions to deflect the flies and to insulate the skin, lotions to soften the skin and heal the lesions, fly screens on shelters during the day, etc. And don’t forget about boosting your horse’s immune system generally through sound nutritional approaches.

 

And if we do nothing?

If we don’t address the problem one way or another, we have very itchy horses, for their entire lives.

Researchers say that the calcification in the ligaments has no effect, but you’ve got to wonder. There’s no guarantee that those scientists had a highly developed understanding of equine biomechanics. Maybe they did, but… who knows. A lot of the small amount of research available is over 20 years old and the knowledge base has since grown.

There’s a small but serious risk of damage to the eyes.

On the plus side, Onchocerciasis hasn’t been found to have any association with fistulous withers.

How to put together a program of treatment for your horse with neck threadworms (and maybe the Itch) – How to Fight the Big Fight against Neck Threadworms

To recap…

Onchocerciasis is so often masked by the itch that awareness, even in the regions where it’s rife, is low.

And in those same regions, there are so many highly prevalent and deadly parasites – the worms that cause colic, that drag down the horse’s condition, that can kill through spontaneous mass emergence from encysted larval stages – that the neck threadworm larvae simply doesn’t get much of a look-in.

To repeat, I’m not saying that all cases of itch are neck threadworms. Just that these parasites may be involved and can be a contributory factor in a heightened immunological response that leads to Queensland itch (or sweet itch, or whatever you know it as).

However, some horses definitely have neck threadworms. The earlier we can identify and manage it, the better.

We can’t eliminate the neck threadworms, but we can certainly manage the effects and make our horses’ lives more comfortable.

(c) Jane Clothier – no reproduction without permission – jane@thehorsesback.com

 

Here are some of the links I’ve been accessing for this article.

 

Equine Onchocerciasis: Lesions in the Nuchal Ligament of Midwestern US Horses. G. M. Schmidt, J. D. Krehbiel, S. C. Coley and R. W. Leid. Vet Pathol 1982 19: 16.

Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses. Herd RP, Donham JC, Am J Vet Res. 1983 Jun;44(6):1102-5. http://www.ncbi.nlm.nih.gov/pubmed/6688162

Onchocerciasis, Submitted by EquiMed Staff. http://equimed.com/diseases-and-conditions/reference/onchocerciasis

Onchocerciasis, the Neck Thread Worms and Midline Dermatitis in Horses.

The Hypersensitivity of Horses to Culicoides Bites in British Columbia. Gail S. Anderson, Peter Belton and Nicholas Kleider. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1680856/pdf/canvetj00574-0044.pdf

Onchocerca in Horses from Western Canada and the Northwestern United States: An Abattoir Survey of the Prevalence of Infection, L Polley. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1790494/

Research of skin microfilariae on 160 horses from Poland, France and Spain. M.T. FRANCK et al. Am J Vet Res. 1983 Jun;44(6):1102-5. http://www.revmedvet.com/2006/RMV157_323_325.pdf

Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses. Herd RP, Donham JC. http://www.ncbi.nlm.nih.gov/pubmed/6688162

Equine Dermatology. By Danny W. Scott, William H. Miller Jr. via Google Books [link now unavailable]

Baba Yaga’s Mirror. Personal blog. [link now unavailable]