• This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

Atypical myopathy in horses (also known as seasonal pasture myopathy, sycamore myopathy or sycamore poisoning) is an often fatal illness, usually found in grazing equines — mostly in the autumn and spring.

With the first of the UK autumn storms of 2025 having passed, H&H has been contacted by owners who have lost horses to atypical myopathy after grazing around sycamore trees. This year is a mast year for many types of trees (including oak), which means there is a very large number of seeds being produced, which increases the risk. Periods of high winds can result in large dumps and carry the shedding seeds and leaves over long distances, so the risk isn’t limited to sycamore trees in or on the fence lines of paddocks.

The British Equine Veterinary Association (BEVA) has previously reminded owners of the dangers. “With leaves still on trees now is the time to identify sycamores in the vicinity of your horse’s fields and predict the future risk,” said Lucy Grieve, veterinary projects officer at BEVA. “Once the leaves start to turn and then drop it will be much more difficult to spot sycamores.”

This serious threat to horses’ health weakens the muscles of the horse’s body, including the heart, and can present with sudden stiffness, muscle tremors, collapse and colic-like signs, accompanied by a low temperature. Often dark urine is seen because the damaged muscle cells release the pigment myoglobin, which can damage the kidneys.

Atypical myopathy has a fatality rate of around 70% so should always be considered a veterinary emergency if it is suspected.

Atypical myopathy is not infectious and can affect horses of all ages and types, although young horses may be more vulnerable. Some horses appear to be more susceptible than others, which may be due to genetic differences.

Atypical myopathy: Causes | Risks | Signs | Diagnosis | Treatment | Prognosis | Prevention

What causes atypical myopathy in horses?

Studies have established that atypical myopathy is caused by ingestion of the hypoglycin A toxin from the seeds, seedlings and possibly flowers of certain trees of the genus Acer. The most common of this type in the UK is the sycamore tree, but different trees contain variable amounts of the toxin. It is important to note that the toxin is not present in every seed, seedling or tree.

The Royal Veterinary College provides a hypoglcyin A test that can be used on both plant samples and equine serum to identify the level of the toxin. This can vary within an individual tree from year to year, although a 2025 study found that trees in the same area typically have similar concentrations of hypoglycin A in their seeds. The study also found that toxicity could occur from water sources containing sycamore seeds and leaves.

Hypoglycin A prevents energy being produced within the muscle cells.

Much research has been done by the University of Liege and involved horses from Belgium, Germany and the Netherlands. High concentrations of hypoglycin A were found in all the sick horses. Botanists visited the pastures that had been grazed and the sycamore was found to be nearby in every case.

In the United States research has linked seasonal pasture myopathy (the US equivalent) to toxins from the box elder tree. Both trees produce seeds containing the agent hypoglycin A.

The “helicopter” wing-shaped seeds are thought to be the primary source of the toxin, but sycamore seedlings have also been found to contain the toxin, being a particular concern in the spring. It is recommended that seedlings are mowed and the cuttings collected and removed from the pasture afterwards as the toxic hypoglcyin A remains in the plant material after it has been cut.

When are horses most at risk?

Outbreaks of the fatal condition tend to be seasonal, with cases typically occurring in the autumn and spring. Victims are usually kept in sparse pastures, where seeds or seedlings are on the ground and are eaten when there is not much other grazing available. Windy autumn weather is particularly risky as it can deposit large numbers of sycamore seeds on to grazing land, which are then eaten. 

What are the signs of atypical myopathy in horses?

The onset of the disease can be extremely rapid, with some horses being found collapsed or dead in their fields. Signs include:

• Stiffness
• Weakness
• Reluctance to move
• Lethargy
• Muscle tremors
• Muscle pain
• Sweating
• Difficulty breathing
• Shivering
• Dark red or brown urine
• Fast, irregular heart beat
• Colic signs
• Unable to stand
• Sudden collapse and death

How is atypical myopathy diagnosed?

Your vets will be able to make a likely diagnosis based on the clinical signs as well as the horse’s environment, along with lab tests to confirm the levels of toxicity.

What treatment is available?

Horses diagnosed early will need treatment with intravenous fluids, pain relief and intensive care at an equine hospital, but once the signs are present it is already serious. Affected animals often deteriorate for the first 24 to 48 hours so should be moved to an equine hospital as soon as possible after the diagnosis is made as the period the horse is able to remain standing while in transit is going to be limited.

There is a compromise in that the horses do not want to be moved far, however effective intensive care is not really possible in the field, where they may be ingesting more toxin.

Supportive therapy including vitamins, minerals and antioxidants may be helpful.

A 2018 study showed that activated charcoal may bind the toxin, so your vet may consider stomach tubing with this following removal of any cases from pasture.

Atypical myopathy in horses: what is the prognosis?

With some 70% of cases proving fatal, the prognosis for horses with atypical myopathy is cautious at best. However, if a horse can survive the first few days of treatment, they can go on to make a full recovery over a period of some months with no long-term effects of the disease.

How can owners reduce the risk?

• Identify trees both around grazed fields as well as those in close proximity
• Fence off areas where sycamore seeds and/or leaves have fallen
• Regularly inspect fields to ensure seeds have not blown in from nearby sycamore trees
• Remove any seeds and leaves that have dropped into water troughs
• Mow areas where seedlings are growing and collect the cuttings
• Supply extra forage (hay or haylage), especially where pasture is poor
• Reduce stock density, so there is enough good grazing for every horse
• Turn out horses for short periods (ideally less than 6hrs.)
• Pick up and remove sycamore seeds, if possible
• Test for the presence of hypoglcyin A in your pastures
• Monitor horses carefully and if concerned, contact your vet immediately

If a case occurs and your horse is in the same field, ask your vet for advice and consider moving your horse.

Further reading:

Assessment of tree-associated atypical myopathy risk factors in Acer pseudoplatanus (sycamore) seeds and leaves – January 2025

Royal Veterinary College’s atypical myopathy fact sheet for horse owners [PDF] – 2022

Answers to the Frequently Asked Questions Regarding Horse Feeding and Management Practices to Reduce the Risk of Atypical Myopathy – February 2020

Equine atypical myopathy in the UK: Epidemiological characteristics of cases reported from 2011 to 2015 and factors associated with survival – April 2017

The Story of Equine Atypical Myopathy: A Review from the Beginning to a Possible End – November 2012

You might also be interested in:

The dangers of acorns to horses you need to know about

As autumn rolls on, confirmed cases of acorn poisoning increase. Sarah Smith MRCVS outlines the dangers for horses grazing in

5 common plants that could kill your horse

While many plants can be poisonous if eaten to excess, there are some poisonous plants that horses should avoid at

Are buttercups poisonous to horses? We ask the experts…

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

A heartbroken rider whose world fell apart when her two horses died within 10 minutes of each other said that if sharing her experiences saves one other horse, hers will not have died for nothing.

Laura Pache’s beloved thoroughbreds Pops and Nabs succumbed to atypical myopathy, or sycamore poisoning, in early January. She wants to raise awareness among horse owners who may have thought, as she did, that deep winter was a safe time.

“I want to raise as much awareness as I can as the thought of anybody else going through what I did – but more importantly what my boys went through – they were lovely boys,” she said. “They deserved to fall asleep in the field with the sun on their backs. They didn’t deserve this.”

Laura kept former racehorses Nabs, 16, and 17-year-old Pops on an “idyllic” private yard in Lincolnshire, which has some 40 acres of turnout. Both were fine on New Year’s Day, and the next morning when she checked them.

But on the afternoon of 2 January, neither came when she called them to the gate.

“Nabs was down; I actually thought he was dead,” she said. “I bellowed at him and he lifted his head, then got up and came over very slowly. I couldn’t find Pops, then spotted him standing completely still at the bottom of the field. I got to him and he didn’t want to move.”

Eventually, moving very slowly, Laura and a friend got both boys into the yard.

“I thought had they been charging around and got injured, or was it colic,” Laura said. “But they weren’t kicking their bellies or anything, just unsteady, heads down and moving slowly. I thought ‘This isn’t colic; something else is going on’.”

As the vet arrived, Pops urinated, and Laura saw his urine was dark red.

Warning, upsetting pictures

“I thought it was some sort of poisoning; had someone fed them something, or maybe sycamore, but I walk the fields all the time and as far as I knew there were no seeds left,” she said. “But slowly and surely, they started to go down. It became apparent that’s what it was, and over the next 48 hours, they got weaker and weaker.”

Laura praised all the local vets for their help; stocks of fluid were low but they all pulled together to provide what they had so she could nurse her boys at home with her vet’s help.

But despite the best efforts of all involved, she said, over the next 48 hours both horses’ condition deteriorated.

“I checked them at about 2am on the Sunday, went back in and dozed off on the sofa,” she said. “At 4am I sat bolt upright as the phone rang; it was my brother-in-law, who lives nearby, and he said ‘You need to come out, Pops has gone down’.

“He was on his side, shallow breathing. I phoned the vet, and god bless her, she came out and said we’d try to get his lungs working better but within 15 minutes, he had died.

“Nabs was next door and he was still up at that point but within 10 minutes of Pops passing away, the vet was checking him and she shouted ‘He’s going down’, and he collapsed and died too. It was unbelievable how it happened. Heartbreaking.”

Laura said she has always walked her fields, which have been grazed by horses for decades with no cases of myopathy, and raked up and removed sycamore seeds, seedlings and saplings that may have blown in, in spring and autumn, and had thought January was safe.

“We don’t seem to have a real winter any more, just a few days of frost but otherwise perpetual autumn,” she said. “The field they were in is quite a long ‘tunnel’ and I think with the strong winds, it just made a perfect sycamore bomb to dump all the seeds in there. I’ve spoken to so many horsey people, vets, people who work in the industry and no one thought it would be a problem at this time of year.”

Laura said some equestrians she has spoken to had not realised the dangers of sycamores at all, even in the traditional peak danger times.

“I know what the trees, seeds and saplings look like and I never saw this coming,” she said. “You think all the seeds have gone but it just takes them clinging on to one tree in a sheltered place and then a strong wind.”

Laura paid tribute to her boys, whom she took on about 10 months ago from a friend.

“I’m qualified as an instructor but hadn’t ridden for 15 or 20 years, then my friend asked if I wanted them and I thought ‘Yes, let’s do it again’,” she said. “I got on Pops and just sobbed; it was like my soul was back together again and I was back where I’m supposed to be, I was back home, back with horses.

“They say you find your heart horse and Pops was mine; 16.2hh but moved like he was 18hh, kind but fun and a bit of fire in his belly. But both of them were wonderful horses; kind and gentle. They’d been in the same racing yard and had spent their lives together, and they went at the same time.

“I can’t help but think that Pops knocked on Nabs’ door and said ‘We do everything together, come with me’. Because Nabs was still up at that point, then within 10 minutes he’d gone too. They have to still be together.

“I cremated them both and took some hair from their tails. My friend plaited them together so they will eternally be together now.”

Laura said the trauma and loss of her beloved boys has turned her world on its head.

“I find myself just standing in their field,” she said. “It’s bloody awful.

“It’s the trauma of it all too; three nights without sleep, trying to think they’re pricking their ears a bit more or moving better, and heartbreaking to see your adored horse with his head on the door to hold the weight of it. And even when I went out there at 2am there was that little whicker, and you think they give us everything.

“It’s heartbreaking and if I can save one other horse, their loss won’t have been for nothing.”

• To stay up to date with all the breaking news from major shows throughout 2025, subscribe to the Horse & Hound website

You may also be interested in:

Atypical myopathy: what you need to know right now to keep your horses safe

‘Grave danger’ of fatal equine illness from ‘explosion’ of toxic seeds

How to protect horses from atypical myopathy

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Many horse owners are worried about how to get sycamore seeds from their paddocks. Sycamore poisoning, or atypical myopathy, caused by the ingestion of sycamore seedlings or seeds can be fatal to horses, and while owners need to be on the lookout for any signs all year round, the disease is more common in the spring and autumn months.

Follow our guide to help ensure your paddocks are kept as low-risk as possible…

What is atypical myopathy?

Atypical myopathy is a often fatal muscle disease, thought to be caused by the ingestion of hypoglycin A, a toxin contained in sycamore seeds and seedlings.

Vets have recently reminded horse owners to take action to minimise the risks of atypical myopathy as spring is a common time for horses to suffer the potentially fatal condition, as sycamore seedlings start to emerge from the ground.

Young horses appear to be more susceptible, as are those being grazed on parched land.

What shall I do if I spot seeds or seedlings?

Getting rid of both the seeds and any fresh sycamore seedlings (depending on the time of year) is vital. If spotted in an area where horses are grazing, it is advised to remove the horses from the pasture immediately, by bringing them in or fencing off the infected area.

The seeds can carry some distance on the wind, so do not assume that if you don’t have sycamore trees in your horse’s field, your horses at not at risk.

If you are struggling to identify sycamore seeds, get in touch with an expert, such as a tree surgeon or someone from a local garden centre, who can help you confirm which tree the seed in question has come from.

It is possible to test seeds or seedlings to identify their levels of the hypoglcyin A toxin through the Royal Veterinary College.

How to get rid of sycamore seeds

Once you have identified you have sycamore trees in your local area, one of the of the most effective (certainly cost-wise) methods of removing the seeds is to hoover them up from the ground — usually by hand.

While time consuming, this is the only way you can guarantee the seeds have been effectively removed from the area. For a more long-term solution, employing someone to come and remove any sycamore trees on your own land is an option as long as the tree is not subject to a protection order.

Mowing areas of pasture is one way to trim the young seedlings, but the cuttings will need to be collected and this will not prevent them from growing again.

Using a certified weed killer (which is known to kill sycamores) can also get rid of the sycamore seedlings, but is less convenient for many due to the rest period the pasture will need following being sprayed. It is advised that you speak to a professional herbicide expert prior to purchasing a weed killer solution.

An example of a weed controller suitable for equestrians is Envy from Dow AgroScience — as with any chemical, it is vital to follow the resting and usage instructions.

What else can I do to protect my horse?

The Blue Cross education team has worked with veterinary experts at Bourton Vale Equine Clinic to provide the following advice to help horse owners prevent atypical myopathy:

• Feed forage, such as hay in parched fields, off of floor in haynets or feed racks
• Do not over stock fields so horses have access to good grass
• Limit turnout, ideally keeping horses in over night
• Section off areas around poisonous trees and collect and dispose of leaves and seeds safely away from horses
• Remove young sapling plants
• Be vigilant of the potential signs of this disease and act quickly if your horse becomes poorly
• Ensure you check your horse multiple times a day
• Check your insurance cover for veterinary care is up to date

You might also be interested in:

Atypical myopathy: what you need to know right now to keep your horses safe

Atypical myopathy: ‘Be vigilant this spring’ to protect your horse

Owners have been urged to take steps to combat this often fatal disease

‘Know your horse’: how simple actions can save your horse’s life

‘If you can prevent deterioration until the vet arrives, you're going to do such an amazing thing’

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

The owner of a mare who died from equine motor neurone disease (EMND) is sharing her story to try to help others.

Jade Wheeler’s time with Jazz was cut short, when ultimately the EMND meant she had to be put down in January, aged 15.

“Jazz quickly became my whole world, my heart horse, but it all ended in heartbreak,” Jade said.

She told H&H she took Jazz on full loan when the mare was 10, and it was a year later she started showing signs; she was tucked up, lying down more, and “couldn’t eat properly”, Jade said, quidding when she tried to have hay or grass.

Having first thought it was colic, the vets then suspected EMND but diagnosed vitamin E deficiency.

“We started her on a vitamin E supplement and she came back to full health within a couple of weeks,” Jade said. “I had my girl back for two years; long hacks together, learning dressage – we had the best time. Then, last year, she got sycamore poisoning.”

Jazz was one of the many horses who contracted atypical myopathy last year owing to a bumper crop of sycamore seeds. She spent 10 days in hospital, where she was diagnosed with EMND.

“It was my worst fear,” Jade said. “My whole world collapsed, again, but I wasn’t giving up on Jazz.”

EMND is strongly associated with vitamin E deficiency, and by the time the full test results came back, Jazz had been back on a high dose of the supplement, and was “getting stronger every day”.

Jade moved yards and once vets gave her the green light, started riding Jazz again.

“She was doing great,” Jade said. “We had three months of rides together, then we had our last one, without knowing.”

Jazz’s condition gradually deteriorated at first. But despite the fact she was still on the high dose of the supplement and a blood test showed normal vitamin E levels, she went downhill.

“She stopped eating on the Friday night; a part of me knew then that she was giving up,” Jade said. “On the Saturday she went downhill very fast, she could barely stand longer than a couple of minutes. We got the vet again and we had two options – [put her down or take her to hospital] – but she wouldn’t have survived the journey.

“It was clear that this was her motor neuron disease progressing quickly and there was nothing more we could do, apart from to make the hardest but kindest decision for Jazz.

“I had to say goodbye to my best friend. We called her owner, and she crossed the rainbow bridge doing her favourite thing, munching grass in her favourite field.

“I’ve been researching EMND and it’s extremely rare so I wanted to raise awareness, and if I can help one person have a few more years with their horse, like I did, that would help.

“She was my heart horse, and it was the best and worst four years of my life.”

You might also be interested in:

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The “grave dangers” of atypical myopathy have been highlighted as a bumper crop of seeds last autumn means an “explosion” in seedling growth – and more cases of the potentially fatal disease.

Atypical myopathy – a condition that weakens a horse’s muscles – can occur when toxin hypoglycin A, found in sycamore seeds, is ingested. It is thought the hot summer of 2022 had contributed to greater-than-normal production of the seeds, and a rise in cases of the condition.

The British Equine Veterinary Association (BEVA) said the huge number of toxic seeds are now sprouting in numerous places, including pastures and hay fields, “causing an alarming second rise in cases of atypical myopathy”.

Vet Phil Cramp lost his 13-year-old “gentle giant” Dermot to the condition last month.

“We’d been on a fun ride; he had a great time and was happy,” Mr Cramp told H&H. “But when we got home, he was quivering, he wasn’t right. We thought he’d tied up and treated him but he got rapidly worse.”

Mr Cramp took Dermot to his practice, where blood tests confirmed atypical myopathy and despite the vets’ best efforts, he had to be put down. Mr Cramp said the toxin is water-soluble, so the standing water from this wet spring has exacerbated the situation to a “perfect storm”. He added that the other horses kept in the same field were tested and had levels of the toxin but did not become ill.

“That tells us that some are susceptible and some aren’t,” he said. “They have to convert the toxin and none of them had done that.”

Mr Cramp advises spraying fields, and blood-testing horses who may have ingested seeds or seedlings.

“If the horse has the toxin, it needs to come out of the field, and be rested,” he said. “Exercise brings out the disease as the toxin inhibits ATP, the cells’ fuel, so the muscles run out of energy. There are things you can do to reduce the impact but rest is very important.”

Horse owner Amelia Shaw has started a petition calling for landowners to have an automatic right to fell sycamore trees on their land even if restrictions related to conservation areas or tree protection orders (TPO) apply.

Sign the petition

She told H&H she did get permission to fell a sycamore that was subject to a TPO on her land in 2016, but “it was a bit of a nightmare”.

“The whole process was difficult,” she said. “We were refused by the council but won on appeal. I was still at university so had time to do it but the condition is so prevalent this year and I’ve heard lots of people saying they want to fell trees but they’re protected. So I wanted to raise awareness, and also see if I could get support. It’s absolutely awful this year, we’ll be lucky if there are any horses left.”

BEVA is urging farmers cutting fields for hay to identify those at risk; not just those with sycamores nearby as the seeds can travel hundreds of metres, and avoid selling this hay to horse owners.

President David Rendle said: “By raising awareness of the risks of contaminated hay being fed to horses BEVA is hoping farmers will be able to identify any sycamore saplings within the crop while the grass length enables them to be seen. Sheep and cattle can also be affected by the toxin at very high levels but ruminants are more resistant to the toxin than horses. We are urging farmers to check their fields now and to discuss the risks from sycamores with their local equine veterinary practice if they need any further advice.”

You might also be interested in:

‘She was in unimaginable pain’: rider who lost dream horse to illness hopes to help others

‘They thought he wouldn’t make it’: owner of myopathy survivor speaks out on vital early treatment

Atypical myopathy: what you need to know right now to keep your horses safe

Sycamore seedlings — what’s the risk to my horse and how do I get rid of them?

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

A rider who lost her filly at 16 months old to atypical myopathy says that if her story saves one other equine it will be a fitting legacy to her dream horse.

Megan Carter’s part-bred appaloosa Dakota died last November, as did Finley, another yearling owned by a friend of Meg’s at the same yard.

Meg told H&H she wants to raise awareness of the risk factors of the often fatal condition to try to help others.

“I’d heard of it before last year but I didn’t know the severity, or how often it’s fatal, or that there’s no cure,” she said. “I sometimes still can’t believe what happened, because it was so quick, and so brutal.”

Meg bought Dakota last April, with the intention of eventually backing and producing the filly herself. At first she was kept on a livery yard, then she was moved to a sole-use yard with some other youngsters.

Meg said it was Finley who first showed signs of illness. He did not improve despite veterinary treatment so he was sent to Leahurst Equine Hospital.

“Dakota was absolutely fine,” said Meg. “No symptoms, eating and happy. I went to Leahurst with Finley and when we got back she was fine. Then I got a call the next morning to say she was unwell. When I arrived, she was almost dead already.”

Meg said Dakota could not stand, and was struggling to breathe and sweating.

“She was obviously in unimaginable pain,” Meg said. “My vet dropped everything but by the time he got there, all he could do was put her to sleep because she was so poorly. Finley was still in hospital but he died a few days later.”

Meg said Dakota was the first horse she had lost so her death was a huge thing to process.

“I’d planned to have her for the rest of her life; she was my dream horse in every way,” she said. “The best way to think about it is to be grateful for the time I had with her, and I want to raise awareness, and help people understand more about how the disease works.”

Issues Meg wants others to be aware of include the fact that sycamore seeds can travel a significant distance – there were no sycamore trees at the yard but after the horses died, they found a few seeds that must have blown there. At this time of year, tiny seedlings in fields can also cause issues; some owners deal with this by spraying them or running sheep on the land as they can eat them with no issues.

It is also possible to send samples of seeds or seedlings to the Royal Veterinary College to be tested, as they can have varying amounts of the toxin responsible for atypical myopathy.

“If one other person doesn’t have to go through what I did – if I can stop someone else experiencing this, I would feel I’d helped, and Dakota had helped,” Meg said. “It would be a good thing to remember her by.”

You might also be interested in:

Sycamore seedlings — what’s the risk to my horse and how do I get rid of them?

‘He saved me, now I want to save others’: heartbroken owner speaks out on fatal atypical myopathy

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The owner of a horse who is recovering from atypical myopathy has shared her story to highlight not only the often-fatal condition but the vital need for early veterinary treatment.

Karen Albutt’s part-Connemara sport horse Whittlie Burn Piccolo (Steve) spent a week at the Three Counties Equine Hospital, where he was given less than 25% chance of survival.

“The speed is what saved him, followed by the aggressive flushing treatment,” Karen told H&H. “The vets said it’s usually such a miserable prognosis with atypical myopathy so when they said he’d turned the corner, it was absolute elation.”

The Albutts bought Steve in January for Karen’s daughter Isla, 16, with the plan to event him and compete in working hunter classes. He was backed this summer and had been doing bits of work in preparation for his winter holiday.

But three weeks ago, he fell ill.

Karen said Steve is kept at home, living out, and that her daughter had found him lying down that morning.

“He neighed and got up, and she didn’t think anything of it,” Karen said. “We have a vet who lodges with us and he said the same; he looked fine.

“That was about 8 or 9am and by the time I got back at lunchtime, he was sitting in the field with his legs tucked under him. He’d eaten all the grass round him so he’d been there a while. I got his rug off and saw he was tucked up and had muscle trembling. I rang the vet and luckily, he was close by.”

The vet was not sure what the issue was but “knew something wasn’t right”. He ran bloods and by the time Karen arrived at the Three Counties with Steve, they had the results that confirmed atypical myopathy.

“Isla was at college and I had to ring her, then take her to see him in hospital and tell her he might not be coming home,” she said. “The vets said his [toxicity] levels were so high, they thought he wouldn’t survive.”

Every day, after Karen and Isla had visited Steve, vets told them they might still lose him.

“I think it was on Thursday they said he’d turned a massive corner and they thought he’d be ok,” said Karen. “They did all the checks on his heart and everything and they came back clear and they said there’s no reason he shouldn’t make a complete and full recovery, which is amazing.”

Karen said she wanted to share her experience to raise awareness of the condition. H&H reported last month that there has been a spate of cases this autumn.

“I think people need to be aware that it can happen,” she said. “We’ve got two other horses grazing the same paddock and their blood tests were fine; it’s just him who had the toxicity. He must have grazed on windblown seeds; people think it won’t happen to them but it can happen to anybody’s horse, and it doesn’t matter if you’ve had horses on that field for 30 years. I think this has been a really good season for seeds; each year is different so don’t think your trees are safe.”

Karen said Steve is now bright, happy and eating well, with just some weight and muscle loss to show for his brush with the fatal condition.

Three Counties intern Alice Addis agreed that it is vital horses with atypical myopathy have veterinary attention fast.

“Quick intervention and aggressive fluid therapy,” she told H&H, adding that horses are then usually kept comfortable with pain relief and monitored closely. “Those who make it to 72 hours and show improvement tend to be the ones who make it. Steve started showing signs of recovery at about the 48-hour mark, which was amazing.

“We’ve had a couple of cases where the horses go home, which is fabulous, and it’s the ones who get here quickly and are treated quickly.”

You might also be interested in:

‘He saved me, now I want to save others’: heartbroken owner speaks out on fatal atypical myopathy

Horse owners warned as vets report rise in atypical myopathy and acorn poisoning

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Owners have been urged to be aware of the risk of atypical myopathy and acorn toxicity following a rise in cases.

Atypical myopathy – a condition that weakens a horses’ muscles – can occur when toxin hypoglycin A, found in sycamore seeds, is ingested. It is thought the hot summer has contributed to greater than normal production of the seeds, and acorns, which can also cause fatal poisoning.

Sonia Gonzales-Medina, assistant professor of equine internal medicine at the University of Nottingham Vet School told H&H that Oakham Veterinary Hospital has had three cases, with two fatalities, and there are reports of cases from other practices.

“In studies we found there is a biennial increase in the production of seeds with more hypoglycin A, and when you put it towards the number of cases reported this year, it ties in well,” she told H&H.

“We found a variation in the amount of toxin in seeds when evaluating the same tree over different years, so some years horses are going to be more at risk. We weren’t able to pinpoint what those years will be like weather-wise, but we noticed warmer summers tended to mean more seed production.”

Dr Gonzales-Medina, who has led studies on atypical myopathy and is involved in ongoing research on treatments, reminded owners that seeds can travel more than 500 yards in strong winds, and paddocks should be checked. If a horse is suspected of being unwell, urgent veterinary treatment should be sought.

Kate Dawson’s gelding Bertie died from atypical myopathy on 16 October. Bertie was taken to Leahurst Equine Hospital where tests confirmed the diagnosis. But despite vets’ best efforts, he could not be saved.

I’d owned him 14 years but that was all taken away in 24 hours,“ Katie told H&H.

“Now I need to save others in Bertie’s name. The seeds can drift for miles, but so many people have messaged me who didn’t know it was a thing. We’ve heard of 14 horses who have died from it this last week.

“Everyone cared for Bertie; everyone who met him, loved him, and I need to turn this into something positive and save other horses, as if not, he’s died in vain.”

The Royal Veterinary College (RVC) testing service allows owners to submit seed samples to find out if the toxin is present. Vets can also send blood samples for testing.

“The lab has been especially busy with many confirmed cases. Some affected horses have unusually high levels of toxin in their blood and some horses have died. In others, there is milder disease, probably related to the horse eating less of the toxin,” an RVC spokesman said.

The British Equine Veterinary Association has reported a rise in cases of not only atypical myopathy but also acorn toxicity, a condition “less common and less well understood” than atypical myopathy – that needs urgent veterinary attention if suspected.

“Signs include moderate to severe colic or colitis, lethargy, dehydration and dark urine. Signs may develop extremely rapidly and death can occur within a further 12-24 hours.”

You might also be interested in:

‘He saved me, now I want to save others’: heartbroken owner speaks out on fatal atypical myopathy

Sycamore seedlings — what’s the risk to my horse and how do I get rid of them?

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The devastated owner of a horse who died from atypical myopathy is sharing her story in the hope her much-loved Bertie’s death will not have been in vain.

Kate Dawson had owned her coloured gelding for 14 years – but “that was all taken away in 24 hours”, she told H&H.

The 19-year-old gelding, who Kate credits for saving her life when she had anorexia, died on 16 October.

“He saved me from anorexia because he gave me a reason to get out of bed in the mornings,” Kate said. “Now I need to try to save others.”

Kate had a lesson on Bertie at her livery yard on Saturday (15 October). The pair had done a bit of everything in their 14 years together, including qualifying for the 2023 Northern Lights Championship in the working hunter class at their last event.

Kate said 14hh Bertie seemed as normal when she was grooming and tacking him up, but when she got on board, she thought he did not feel quite right.

“My trainer said he looked a bit stiff behind,” she said. “I stopped and he tried to go down and roll with me on him, and that’s not him at all. I untacked him and he looked really tucked up, and then he just went down.”

Kate called the vet, and mentioned the possibility of atypical myopathy, a condition also known as sycamore poisoning, and often fatal.

“The vet said they weren’t classic atypical myopathy symptoms and he thought it was colic,” Kate said. “He told me to walk him, which I did, but at about 8pm, he went down and I couldn’t get him up.”

Bertie was taken to Leahurst Equine Hospital, where vets agreed he was not showing classic signs of atypical myopathy, but ran the tests the next morning, confirming the diagnosis.

“We went to see him about 3pm and he perked up a bit, he had his head on my shoulder,” Kate said. “We stayed about an hour and a half, and I said to him ‘I’ll see you tomorrow’.

“Half an hour into the journey home, they rang and said he’d gone down. The vet said they couldn’t wait for us to come back as he’d be gone, they had no choice, so I didn’t get to see him again.”

Kate has shared her heartbreak on Facebook in hopes of raising awareness of the condition. There are no sycamore trees in Bertie’s field but the seeds that have been seen in it could have blown in.

“I need to save others in Bertie’s name,” Kate said. “The seeds can drift for miles, but so many people have messaged me who didn’t know it was a thing. We’ve heard of 14 horses who have died from it this last week.

“Everyone cared for Bertie; everyone who met him, loved him, and I need to make a difference, turn this into something positive and save other horses, as if not, he’s died in vain.”

You might also be interested in:

Atypical myopathy: what you need to know right now to keep your horses safe

Sycamore seedlings — what’s the risk to my horse and how do I get rid of them?

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Owners have been reminded to take action to minimise the risks of atypical myopathy as current conditions can make it more likely horses will contract the potentially fatal disease.

The British Equine Veterinary Association (BEVA) is advising taking practical steps to prevent horses eating sycamore seeds, which can cause atypical myopathy as they contain the toxin responsible, hypoglycin A.

Although horses do not usually choose to eat sycamore seeds, they are more likely to be ingested in barer fields. Windy weather can also spread them to fields in which there are no sycamore trees.

“The ‘toxic dose’ of sycamore seeds can vary from less than 100 to several thousand single seeds,” a BEVA spokesman said.

“With each tree potentially shedding more than 20,000 double-seeded ‘helicopters’, the amount on pastures can be considerable. In the spring, seedlings represent a risk to horses and can affect hay made from contaminated pasture. Seedlings at the edge of watercourses can also contaminate water supplies, especially when trampled as horses walk across them.”

BEVA is advising owners to identify sycamore trees, in and around grazed fields and those nearby, and collect seeds if possible, or fence off affected areas.

Feeding hay can prevent excess foraging for short grass, which can lead to accidental ingestion of seeds, although care must be taken to ensure the hay does not become contaminated with seeds.

“Don’t rashly fell trees when laden with seeds as this can cause a sudden and massive contamination of the pasture,” the spokesman said. “Consider local regulations, tree protection orders and tree ownership if felling is the only option.

“Monitor horses carefully even after they have been moved from affected pasture as disease can occur up to four days after exposure.”

The most consistent clinical sign of atypical myopathy is dark brown urine but other signs include reluctance to move and weakness.

“It’s imperative to contact your vet as a matter of urgency if you are concerned your horse may be suffering from atypical myopathy,” said BEVA president Huw Griffiths.

“We can use a special blood test, thanks to research funding from the Horse Trust, to diagnose and measure exposure to the toxin. The earlier we are able to intervene the more likely a favourable outcome for the horse.”

Atypical myopathy has a fatality rate of about 70% so should always be considered a veterinary emergency if it is suspected.

You might also be interested in:

Atypical myopathy: what you need to know right now to keep your horses safe

‘You don’t think it will be your horse’: owner’s atypical myopathy warning

‘He was very underneath himself at his back end and looked uncomfortable. At first I thought it was colic and

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

While many plants can be poisonous to horses if eaten to excess, there are some poisonous plants for horses that should be avoided at all costs.

In the UK, the most common form of poisoning is caused by the ingestion of ragwort over a period of time, but there are other plants which can cause severe problems — including death — if horses consume them.

Poisoning can take many forms in a horse, from ill thrift and photosensitisation to disease or disruption of the function of key body systems. There are seven different broad types of poison — alkaloids (as found in ragwort, yew, hemlock), glycosides, nitrates, photosensitisers, saponins and complex proteins. Within each category are many different active compounds.

Horses are most likely to consume poisonous plants if they have nothing else to eat as a result of a combination of poor grazing with a heavy infestation of such plants, or due to their undetected presence in hay or haylage.

Here is our guide to the fatal flora you need to know about to avoid a very sad and avoidable untimely end for your equine partner.

Poisonous plants for horses

1. Ragwort

Instantly recognisable from its frilly leaves and star-shaped yellow flowers, the deadly ragwort plant is common in British meadows. Once eaten, it attacks the horse’s liver. Horses will normally avoid eating ragwort because of the bitter taste, but it is palatable when dried and fed in hay. Under DEFRA regulations, landowners can be penalised for allowing ragwort to spread to grazing land, but horse owners should always remain vigilant and frequently check their hay.

Signs to look out for: One early sign of ragwort poisoning is weight loss, despite the horse eating normally. If detected in time, the effects can be treated with steroids; if not, the horse may go blind and eventually collapse.

What to do: Check your horse’s paddock regularly for ragwort, and dig it up at the roots and burn it when found. It is recommended to wear gloves when handling the plant. Use a reputable and trusted hay supplier.

More about ragwort:

• New research project launched
• Poisoned horse’s skin peels off
• Identifying liver problems

2. Sycamore

Historically, sycamores were not thought to be harmful to equines, but recently the often-fatal muscle condition Atypical Myopathy (AM) has become much more common in Britain. Triggered by the ingestion of sycamore seeds (also known as helicopter seeds), leaves and seedlings, AM is a fast killer with a mortality rate of between 75 and 90%. There’s no specific treatment for the condition, with affected horses given intensive veterinary care and IV fluids.

Signs to look out for: Lethargy, sweating, muscular stiffness, high heart rate, dark urine and difficulty standing. Affected horses are often found lying down.

What to do: The condition is more common in autumn, when the seeds and leaves are blown from the trees. Remove them along with any sycamore seedlings that appear in spring. Fence off sycamore trees from paddocks and ensure horses have access to sufficient supplementary feed to minimise the risk of foraging for alternative foods.

More about atypical myopathy

• What you need to know
• Family warns fellow owners
• Help with new research

3. Oak trees including acorns

Although some wild animals depend on acorns for their nutritional needs, the horse is not one of them. The tannic and gallic acids in acorns can cause severe damage to the equine gastrointestinal system and kidneys. It’s not just the acorns either – all parts of the oak are toxic to horses. Strangely, there’s anecdotal evidence that some horses get ‘addicted’ to acorns and will over-indulge in them to the point of making themselves ill.

Signs to look out for: Constipation, weight loss, colic, blood in the urine and fluid accumulation in the legs (edema) may indicate oak poisoning, but specific diagnosis can be difficult unless your horse has a history of consuming acorns.

What to do: Avoid grazing your horse in fields containing oak trees, or fence off the trees, particularly during autumn when the acorns fall. Activated charcoal (which absorbs toxins from the gut and allows them to be harmlessly excreted) is known to be an effective treatment if given immediately after ingestion; however, always seek the advice of your vet first.

4. Yew

The leaves, twigs and bark of the Yew tree are all toxic to horses and the lethal dose can be extremely small. The plant’s toxic alkaloids (taxine A and B) are extremely fast acting and horses have been found dead with the leaves of the tree still in their mouths. It is one of the most common causes of equine poisoning in France and Belgium. Luckily the bitter taste of the plant will put most horses off having a chew, but it’s not a plant to take risks with.

Signs to look out for: The horse dies from cardiac arrest. Prior to this muscle trembling, a lack of co-ordination, breathing difficulties, a slow heart rate and convulsions may be seen.

What to do: There is no treatment. Never graze horses in a field where they will have access to yew or where there is a risk that yew clippings might be tossed into their paddock. If neighbours have yew in their gardens, speak to them to explain the dangers.

5. Bracken

Found on moors and in meadows, horses will usually avoid eating bracken ferns unless grazing is particularly poor – although some do develop a taste for it. The good news is that it’s only harmful if digested in large quantities, such as ongoing consumption over a couple of months.

Signs to look out for: Bracken poisoning results in neurological (nervous system) symptoms that may include nervousness, circling, staggering, muscle spasms, blindness and convulsions. It can be treated with thiamine supplementation prescribed by a vet if caught early enough.

What to do: Horses usually avoid bracken, but if concerned, remove it from your horse’s field. Maintain good pasture management, regularly removing weeds to allow grass to grow, so your horse has no reason to consume it.

Other plants that are poisonous to horses include:

• Foxglove
• Deadly nightshade
• Buttercups
• Privet
• Rhododendron
• St John’s Wort
• Potatoes
• Meadow Saffron
• Horsetails/ Mare’s Tails
• Water Dropwort
• Hemlock

You may also be interested in…

23 ways to beat flies this summer

We might be excited about the prospect of some sun — but with it comes the pesky flies. So we

Are buttercups poisonous to horses? We ask the experts…

How to avoid your horse suffering from sunburn this summer

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The heartbroken owner of two yearlings who died within hours from atypical myopathy says if she can help save one other horse, at least something good will have come from the tragedy.

Rosie Wilcox lost her two rescues Denzil and Alfie, whom she had owned since they were foals, on Monday (14 October) and yesterday, despite vets’ best efforts.

“It’s so hard to lose one but both together is absolutely heartbreaking,” she told H&H.

“I got them together and they were inseparable — then they went together, bless them.”

Rosie found Denzil standing in the field with his head down on Saturday. Thinking he might have caught a chill, she brought him in overnight, but when she turned him out the next morning, his thighs started trembling.

“I wondered if he’d been kicked but then he lay down, and Alfie came and lay down next to him,” she said. “I called the vet straight away.”

When the vet arrived, it took four people to persuade Denzil to his feet, but he collapsed again in the stable.

“The vet said it sounded like sycamore poisoning and it wouldn’t be unreasonable to put him down then but that we could try to take him into the clinic,” Rosie said. “My friend, who’s a transporter, came out and we got him on the lorry but he collapsed on the way there.”

The vets treated Denzil, and Alfie, who stood for the journey to the clinic but collapsed overnight.

“They tried so hard to put up a fight but it was too much for them,” Rosie said. “Denzil died on Monday morning and we had Alfie put to sleep on Tuesday as his kidneys were breaking down and there was nothing the vets could do.

“Alfie hadn’t even shown any signs — we thought he might be lying next to Denzil as they were so close — and we think we caught his sooner but it was still too late.”

Rosie said her two older horses are fine, and that the owner of the land, in Hampshire, had used it to graze equines for some 14 years without problems. There are no sycamores in the field but there is one on a footpath that runs behind it, and they believe the seeds may have been blown in.

“We’ve gone round the fields and can’t find anything,” Rosie said, adding that she has fenced off parts of the field, the trees are going to be cut back, and her vet is going to run blood tests to ensure her other horses have not been affected.

Continues below…

Atypical myopathy: what you need to know right now to keep your horses safe

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

But she had never heard of atypical myopathy before and wants to raise awareness.

“I’ve posted about it on Facebook and have had so much support,” she said. “If spreading the word makes a few people have a look, or be aware of the symptoms, if I can do anything so no one else has to go through this, at least something good will have come from it.”

For all the latest news analysis, competition reports, interviews, features and much more, don’t miss Horse & Hound magazine, on sale every Thursday.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The owner of a horse who became seriously ill with atypical myopathy after grazing in a field with sycamore trees wants to raise awareness of the condition.

Viki Lees Martin of Newhaven in East Sussex moved her 19-year-old gelding Burt and seven-year-old mare Armida into a paddock edged with sycamore trees on 30 April. A week later she noticed Burt was unwell.

Vikki told H&H: “When I went to bring them in the following Wednesday (8 May) Burt looked lifeless – he was like a zombie.

“He was very underneath himself at his back end and looked uncomfortable. At first I thought it was colic and phoned the vet. I took his rug off and he had muscle tremors, his breathing and heart were racing.”

Viki’s vet attended and treated Burt for colic.

“When I checked him again at 11pm he looked more comfortable, but the next morning he wasn’t happy. I turned him out as he looked uncomfortable in the stable, but he just stood in the field shaking his head,” said Viki.

“I noticed I hadn’t seen him wee which I thought was quite a big thing. Another vet came out and took bloods and we discussed it being either grass sickness or atypical myopathy – I fell apart.”

Burt was taken to Cliffe Equine hospital in East Sussex, where he was put on a drip to get some fluids in to his body. A urine sample, which was dark brown, gave the vets a high suspicion of atypical myopathy and this was confirmed by blood test.

“Since then he has had 100 litres of fluids and pain relief. He’s very lucky we brought him in when we did,” Viki said.

“Burt is getting brighter every day and the vets are quietly positive. His muscle enzyme levels are getting better and he should get home this weekend. The vets are speaking about taking him off the drip and introducing turnout. We won’t know the full extent of the damage but his major organs seem ok.”

Viki had Armida blood-tested, but she has not shown any symptoms or been unwell. She now wants others to be aware of atypical myopathy and said previously she had thought of the warnings as “scaremongering”.

“I’d seen people online mention to be wary of sycamores and I didn’t really take that on board – you don’t think it will be your horse. I’ve had horses a long time and I’ve been beating myself up about it and feel like I was complacent. I have put a post on Facebook about what happened and I’ve heard good and bad stories. I think we all need to be more aware and check what’s in our fields,” said Viki.

“It can be a lottery for owners – Burt was ill, but Armida wasn’t. Fields often have mixed foliage so how do you eradicate the problem? I know you can pick up the seeds, but you can’t always cut every tree down. It can be the luck of the draw and I think Burt got the short straw that day but I can only be thinking positively now that he is on the road to recovery.”

Cliffe Equine vet Claudia Gilders said Burt will need careful monitoring for the next few months but has shown “massive” improvements.

“The chances of survival from atypical myopathy are quite low, around 25% therefore the fact that Burt has made it this far is amazing,” said Ms Gilders.

Owners concerned about atypical myopathy can test plant samples and horse serum levels for the toxin found in sycamores, hypoglcyin A, through the Royal Veterinary College (RVC).

RVC professor of comparative neuromuscular disease Richard Piercy told H&H: “Our evidence suggests that toxin levels fluctuate in sycamore material, but as yet we do not know why. Our data and that of others also suggests that other common acer species trees in European pastures do not produce the toxin, so providing this confirmation for some horse owners who are not sure about the tree species is very reassuring. Many horse owners make a decision and resort to felling trees, so being certain about whether a tree is a possible risk for their horses is very important for many people.”

Continued below…

Atypical myopathy: what you need to know right now to keep your horses safe

‘Don’t let it be your horse’: atypical myopathy warning after racehorse dies

Owners are being urged to check their fields for sycamore seedlings now as the often-fatal condition can affect horses in

Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Professor Piercy continues: “By testing horses for serum levels of the toxin, or its main metabolite, we can provide an accurate and rapid diagnosis. This allows appropriate preventative measures to be instituted, including avoidance measures for other horses on the same pastures. Negative results are also useful as they can redirect diagnostic investigation to other possible causes.”

Professor Piercy recommends owners take the following precautionary steps:

• If possible, remove horses from contaminated pastures
• Mow and remove cuttings from areas with seedlings
• Fence off areas with large numbers of seeds or seedlings
• Bring horses in at night if they are grazing sycamore-contaminated pastures
• Feed hay/haylage from reputable sources
• Consider testing horses for possible exposure if they might have been exposed and if they exhibit signs of lethargy, colic, weakness or muscle trembling – even if these signs seem mild. This should be done in consultation with your vet.
• Horses that have or might have been exposed, likely will benefit from B vitamin supplementation and other treatments. This should be done in consultation with your vet.

For all the latest news analysis, competition reports, interviews, features and much more, don’t miss Horse & Hound magazine, on sale every Thursday.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Experts are warning owners to take steps now to minimise the risks of atypical myopathy after conditions have created “the perfect storm”.

The British Equine Veterinary Association (BEVA) has said that bare pastures, potential hay shortages and transatlantic storms are to blame for the increased risk.

The cause of the disease is the toxin hypoglyxin A, which is found in the sycamore tree. The tree’s helicopter shaped fruit can distribute the seeds up to 4km with high winds causing more seeds to fall over a short duration of time.

BEVA member Adam Redpath said: “Horses do not typically choose to eat sycamore seeds, however when pastures are bare, there is a greater tendency for them to be ingested as horses are foraging for every last blade of grass.”

BEVA said a range of factors affect the amount of toxin found in sycamore seeds, meaning the ‘toxic dose’ can vary from less than 100 to several thousand seeds. It is urging owners to take early steps to prevent the disease by limiting access to any area containing sycamore seeds.

Owners should identify trees in grazing fields, as well as in close proximity, and collect seeds or exclude horses from affected areas. It is recommend that supplementary hay is fed to prevent horses from inadvertently grazing on seeds, but owners should ensure that hay has not been contaminated by seeds.

The disease can occur up to four days after exposure and typical signs include passing dark urine, reluctance to move, lying down and colic-like symptoms.

BEVA said in some horses the severity of muscle pain leads to euthanasia on welfare grounds.

Mr Redpath said: “Early veterinary intervention is essential to achieve a favourable outcome. You should contact your vet immediately if you spot any of the signs. Check your fields for sycamore seeds as this will help your vet to make a rapid diagnosis. Specific blood tests have been developed to both measure exposure to the toxin and to make a diagnosis, thanks to research funding from The Horse Trust.”

Atypical myopathy: what you need to know right now to keep your horses safe

Sycamore seedlings — what’s the risk to my horse and how do I get rid of them?

How to protect horses from atypical myopathy

For all the latest news analysis, competition reports, interviews, features and much more, don’t miss Horse & Hound magazine, on sale every Thursday.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Charcoal could help horses suffering from atypical myopathy, a new study has found.

Scientists have identified that the substance can help reduce the absorption of the toxin released by certain sycamore seeds, which can cause the condition.

There are hopes this could help horses in early stages of the illness and those who may have also eaten some affected seeds but are not yet showing signs of intoxication.

Atypical myopathy is an often-fatal condition in horses, usually seen in spring and autumn. It can be caused by eating sycamore seeds or seedlings that contain a high concentration of the toxin hypoglyin A.

Scientists at the University of Veterinary Medicine in Vienna set out to find a substance that could be given orally to horses to bind hypoglycin A and reduce the amount absorbed by horses.

They tested substances commonly used in equine veterinary medicine — activated charcoal composition, di-trioctahedral smectite, mineral oil and activated charcoal.

Jejunam (small intestine) tissue from six horses was used in the study and tested for the presence of the toxin after each of the substances was administered.

The scientists found activated charcoal composition and activated charcoal were “potent” binding substances for hypoglycin A.

“For the first time, this study identifies substances capable of reducing hypoglycin A intestinal absorption,” states the study.

“This might have major implications as a preventive measure in co-grazers of atypical myopathy-affected horses, but also in horses at an early stage of intoxication.”

Former British Equine Veterinary Association president Mark Bowen told H&H the research is “certainly interesting”.

“Vets have been using activated charcoal for all sorts of reasons, including atypical myopathy, for many years, but having some evidence is really useful,” said Mr Bowen.

“It suggests activated charcoal will be useful for treating horses that are starting to show signs of atypical myopathy.

“We need to remember this isn’t to be used lightly — we still need to do everything we can to avoid exposure [to sycamore seeds].”

The study was published in the March 2018 edition of the Equine Veterinary Journal.

H&H recommends owners contact their vet if they believe their horse could be showing signs of atypical myopathy.

You might also be interested in:

Atypical myopathy: what you need to know right now to keep your horses safe

Atypical myopathy: ‘Be vigilant this spring’ to protect your horse

Owners have been urged to take steps to combat this often fatal disease

‘Don’t let it be your horse’: atypical myopathy warning after racehorse dies

Owners are being urged to check their fields for sycamore seedlings now as the often-fatal condition can affect horses in

For all the latest news analysis, competition reports, interviews, features and much more, don’t miss Horse & Hound magazine, on sale every Thursday

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Horse owners have been urged to take extra precautions against atypical myopathy in the wake of storm Aileen.

The British Equestrian Veterinary Association (BEVA) is asking owners to be vigilant, as the last “big spike” in cases of the fatal equine disease, also known as seasonal pasture myopathy, came after major storms in 2014.

“High winds may cause the seeds to fall earlier than usual this year so BEVA is advising horse owners to take immediate steps now to identify sycamore trees on or near grazing land and prevent the seeds falling where they are in reach of horses,” said a BEVA spokesman.

Owners are advised to move horses off pasture at risk times, if possible, or to use temporary fencing to restrict access to sycamore seeds. Horses must have access to good quality, uncontaminated grazing, and providing clean hay or haylage also minimises the temptation to eat the seeds.

Sycamore trees should not be felled, BEVA added, as this can cause “massive pasture contamination”.

Owners should discuss risk and how to identify early signs of the condition with their vets, and be aware that even fields without sycamore trees can contain seeds spread by high winds or flooding.

BEVA senior vice-president Mark Bowen said: “In 2014 we saw a big spike in seasonal pasture myopathy in the aftermath of storms hitting the UK.

“It’s a terrible condition that can be fatal despite treatment. It’s easier to spot the sycamore’s maple-shaped leaves now while they are still on trees. Otherwise the seeds may be confused with ash keys. It’s best to speak to your vet for practical advice on how to keep your horse safe.”

The muscle disease is caused by toxin hypoglycin A, which is found in tree seeds including that of the sycamore.

Article continues below…

New research sheds light on atypical myopathy

British vets are welcoming new research that could explain the cause of the mysterious and fatal condition atypical myopathy

Atypical myopathy: is your horse at risk?

Autumnal grazing disease, atypical myopathy, has been on the increase but is your horse at risk?

Filly makes ‘miraculous’ recovery from atypical myopathy

'We were all crying our eyes out. If it had been an hour later she wouldn’t have been with us.'

Although sycamore seeds are not palatable to horses, those on poor grazing may eat large numbers of them.

Equines kept on sparse pasture with accumulated sycamore leaves and wood, and trees in or around the field, and without hay or feed are the most at risk.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

A racehorse trainer is warning owners to check their paddocks for sycamore seeds and seedlings after losing a talented racehorse to atypical myopathy earlier this week.

Take A Bow, an eight-year-old thoroughbred in training with Lawney Hill, died on Sunday (2 April) after the condition rapidly took hold.

The son of Norse Dancer had won over fences, hurdles and a bumper, and was set for a bright future.

He had been out grazing in a paddock (not pictured) with another horse, in a field where equines have been kept for more than 40 years.

There are no sycamore trees surrounding the field, but winter storms must have blown the seeds onto the patch of land.

Lawney wants to raise awareness of the condition and to make owners realise this can happen to anyone.

“This was a fit and healthy, big, strong horse. I was at a loss,” Lawney told H&H. “This is a freak accident and I want to highlight it and people to know about the condition.

“Don’t let it be your horse.”

Some sycamore seeds, leaves and seedlings contain a toxin called hypoglycin A, which is highly poisonous to horses. The condition has a very high mortality rate, of around 70%.

The condition is mainly associated with autumn, however it can — and does — affect horses in the spring.

Lawney told H&H that he seemed very lethargic and was showing signs of colic when she went to check on him on Saturday morning (1 April).

She immediately rang the vet, who arrived within 10 minutes. In that time he started sweating and was standing with his head in a bush at the edge of the field as if he “wanted to hide”.

He did not want to move and Lawney managed to gradually lead him in from the field to his stable. When the vet arrived she gave him a rectal examination and painkillers, but found no signs of impaction.

Once the pain relief kicked in, his condition appeared to improve for a short while.

The yard kept a close check on him and later that day Lawney rang the vet again as he began to deteriorate once more.

Both Bob Baskerville and Katie Robinson, of Hampden Veterinary Practice, examined the horse and did everything they could for him that day.

He was taken in to Donnington Grove equine hospital, who confirmed it was atypical myopathy. Sadly the vets could not save him and he had to be euthanised in the early hours of the following morning.

The other horse who was in the field with Take A Bow at a time has shown no signs of the condition.

Lawney and her husband Alan have consulted an agronomist, sprayed the paddock and have put up signs around the yard warning of the dangers of sycamore seeds and seedlings.

The couple are farmers and the fields are well maintained. This particular field had been rested over the winter and had plenty of fresh spring grass.

The National Hunt trainer has shared the news across social media to raise awareness of the condition.

Atypical myopathy: what you need to know right now to keep your horses safe

How to protect horses from atypical myopathy

H&H question of the week: ‘Seasonal pasture myopathy — what are the signs and prognosis?’

Nikki Pursey MA VetMB CertAVP(ESM) MRCVS of Farr & Pusey Equine Vets shares her expert advice on the deadly seasonal

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The owner of a filly who made a “miraculous” recovery from atypical myopathy wants to share her story to help raise awareness of the condition.

Dartmoor-based Dannie Williams’ coloured cob, Khaleesi (Kallie) and rescue pony, Bella, were found seriously ill on 6 December.

Two-year-old Bella was so bad that Dannie thought she was dead when she discovered her lying motionless on the floor in her field.

Kallie, also a two-year-old filly, was standing completely still and was not interested in food.

Dannie’s vet, from North Park Veterinary Equine, was called and at first they the vet believed the horses might have colic, but they were not showing the typical signs.

After urine and blood tests it was discovered that both horses had atypical myopathy.

Thankfully Bella’s condition improved quickly and she soon returned to good health but Kallie deteriorated and she was put on a drip.

By 8 December she could not stand.

Dannie and her friends manually turned her every six hours and hand-fed her, desperately hoping her condition would improve.

After 10 days Dannie decided that moving Kallie out to her field may encourage her to stand.

She was sedated and carefully pulled out to the field on rubber matting using a tractor.

Kallie remained lying down for another three days and Dannie began to question whether it was fair to keep her alive.

“It has been two weeks and she was skin and bone and she had pressure sores on her hip, shoulders and face,” she said.

“I wondered if I had done the right thing by keeping her going.

“The vet was going to come out later that day (21 December) and I rang to ask him to bring the injection to put her to sleep.”

However, that afternoon, while Dannie’s sister was sitting in Kallie’s field, she finally stood.

“It was a very emotional day,” said Dannie.

“We were all crying our eyes out. If it had been an hour later she wouldn’t have been with us.

“It was pretty miraculous. I still get tears just thinking about it.

“It was absolutely incredible, but I wouldn’t wish it on anybody.”

Kallie has since gone from strength to strength and Dannie is planning her show season.

“She is doing amazingly and she has put on all the weight that she lost,” said Dannie.

“You couldn’t ask for a better pony, I have such a strong bond with her.”

Continued below…

Atypical myopathy claims more horses’ lives

Owners of horses who have become fatal victims of seasonal disease come forward to share their stories and raise awareness

Warning over equine atypical myopathy after 20 horse deaths

Owners are calling for more research into the condition equine atypical myopathy after as many as 20 horses have died

Atypical myopathy: what you need to know right now to keep your horses safe

The horses are no longer turned out in the same place, as Dannie believes sycamore seeds had blown in from a tree next to the field.

“I would like to thank North Park Veterinary Equine for everything they did — they were out three to four times every day,” Dannie said. “I can’t thank them enough.

“I have been surprised how many people haven’t heard of atypical myopathy when I’ve spoken to people after what happened.

“It spurred me on to share Kallie’s story.”

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Could exercise and a regular vitamin and mineral supplement help protect grazing horses from the devastating effects of atypical myopathy? Andrea Oakes reports

Autumn traditionally sees a peak in cases of the rapid-onset condition atypical myopathy (AM), now known to be linked with trees from the Acer family. This acute muscle disease, sometimes termed atypical myoglobinuria or seasonal pasture myopathy, is caused by the ingestion of some species of Acer tree seeds (such as the sycamore) that contain the toxin hypoglycin A. The consequences can prove distressing and frequently fatal — muscle groups break down, both skeletal muscles and potentially those linked to cardiac and respiratory function, and renal failure can follow.

While intensive treatment can sometimes be successful, if started sufficiently early, unfortunately the prognosis is typically bleak.

Management clues

Early findings from the first UK-based AM study are helping to shed further light on this potential killer in the paddock. Owners and vets were encouraged to report confirmed cases through a surveillance website run by the University of Liège, in Belgium, and supported by the Animal Health Trust (AHT). This yielded 224 horses, with an average age of six. The breeds most commonly affected were cobs and part-bred cobs. Of the pastures they grazed on, 96% were affected with sycamore seeds and a further 68% with seedlings.

The overall survival rate was 38.6% (12% more than in a previous European study). Of notable interest, however, were potential clues about management of horses and their chances of recovery. “Those horses that had performed light to moderate exercise in the 48 hours prior to the onset of the disease, as well as having received regular supplementation with vitamins and minerals, seem to have overcome AM better,” said Dr Sonia Gonzalez-Medina, who presented the findings at the recent British Equine Veterinary Association congress. “In contrast, horses that had been grazing on pastures used all year round for equine grazing were less likely to survive.”

Certain signs — recumbency, hypothermia, a distended bladder palpable on rectal examination and an increased heart rate — also indicated less chance of survival.

Toxin risk

Also at the same congress, a Royal Veterinary College researcher, Alex Draper, critically appraised the evidence available as to whether the removal of all Acer trees should be undertaken. H&H vet Karen Coumbe MRCVS explained: “There are many different types of Acer tree in the UK. Accurate botanical identification is vital, since Acer pseudoplatanus, the sycamore, poses the highest risk.

Ingestion of the seeds and seedlings of this type of Acer has been shown to be linked to the greatest risk for AM development in horses, across four mainland European countries, due to the high levels of toxin they contain.

“It makes sense to prevent horses grazing pastures contaminated with material from sycamores,” added Karen. “The risk of eating the leaves alone is likely to be lower than that from seed or seedling ingestion, as there has been shown to be less of the toxin present in the leaves. Having said that, the likelihood of there being leaves and no seeds

is pretty improbable.

“It is really best to keep horses away from all sycamore material, ideally with fencing and other measures.”

Take action this autumn

• Avoid pastures surrounded by Acers during autumn and early winter.
• Collect and burn any winged “helicopter” seeds, which can travel a considerable distance in windy conditions.
• Supplement horses with forage if grazing is scarce.
• Call your vet immediately if your horse displays mild to moderate colic signs, depression, reluctance to move or weakness, dark urine or inability to raise his head. The sooner treatment can be initiated, the greater the chance of recovery.
• Be vigilant for Acer seedlings next spring, removing any you find.

Q: “Are sycamore seeds poisonous to horses? What signs should I look out for, how can I help avoid the issue of seasonal pasture myopathy and what is the prognosis for a horse who is poisoned by it?”

A: In recent years, sycamore seeds and, to a lesser extent, their leaves, have been found to contain the toxin hypoglycin A which, when eaten, causes seasonal pasture myopathy, which is also known as atypical myopathy. The toxin prevents energy being produced within muscle cells, causing muscle cells to die; the toxin particularly affects the muscles that enable the horse to stand and breathe, as well as the heart muscle. The amount of toxin present varies between seeds, even those from the same tree, and also from year to year, making it difficult to predict which horses will be affected.

Continued below…

Related articles:

• H&H forum: find out what H&H readers suggested
• Find out more about seasonal pasture myopathy
• Seasonal pasture myopathy: what you need to know NOW

The onset of the disease can be extremely rapid and, in some cases, horses may be found dead on the pasture. In the earlier stages of the condition, signs can include:

• lethargy
• dullness
• mild weakness or stiffness
• increased heart rate
• increased respiratory rate and difficulty breathing
• sweating
• muscle tremors
• difficulty swallowing
• choke
• excessive whinnying
• increased time lying down and difficulty rising
• dark red urine (due to muscle pigments being excreted in the urine)
• sudden collapse/death

The most important step is to prevent your horse from eating the sycamore seeds. To achieve this, you can:

• avoid grazing horses on high-risk during high-risk periods (autumn and spring)
• if complete avoidance is not possible, fence off areas with high numbers of seeds. Remember,
  seeds can spread up to three times the height of the parent tree or even further in extreme
  weather conditions
• pick up/remove sycamore seeds from pastures
• provide supplementary feed and forage, especially if the pasture is poor
• decrease the amount of time horses are turned out for
• reduce the stocking density
• ensure horse have access to fresh drinking water and water troughs are not under sycamore
  trees
• ensure horse are vaccinated and regularly dewormed
• if a case of seasonal pasture myopathy is suspected/confirmed, grazing cohorts should be removed from the pasture and undergo further tests

Unfortunately, even with aggressive treatment, the survival rate for horses with seasonal pasture myopathy is only 20-25%. Once a horse becomes recumbent, the prognosis is very poor but those more mildly affected and those remaining alive five days after diagnosis can make a full recovery.

The severity of seasonal pasture myopathy cannot be overstated. If you have any concerns or suspect your horse may have the condition, contact your vet immediately.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Horse owners have been urged to be vigilant for sycamore seedlings this spring, to help prevent a fatal equine disease.

The BHS has urged riders to check fields regularly for seedlings, removing any they find, to help prevent cases of atypical myopathy.

Also known as seasonal pasture myopathy, the disease can debilitate horses quickly, and is fatal in more than 75% of cases.

Research has identified the presence of toxin hypoglycin-A in sycamore seeds as a cause of atypical myopathy. But now scientists at the Universite de Liege, Belgium , have identified that seedlings also contain the toxin.

A spokesman for the BHS said: “For horse owners, the challenge of removing sycamore seeds and seedlings can be a daunting and onerous task.

“One of the preventative measures is to ensure horses have sufficient grazing available to help deter their need to search for additional food.

“At this time of year, some horses will have to be kept on restricted grazing to help control their weight and prevent laminitis; therefore it is vital to regularly check such pasture for sycamore seedlings and the first sign of ragwort rosettes.”

Atypical Myopathy is a muscular disease, which can appear rapidly and without warning.

Clinical signs include the horse appearing weak and having breathing difficulties as well as signs similar to those of colic.

Affected equines often progress quickly; many have been found dead in the field, owing to the speed at which the disease can develop.

Related articles:

• Atypical myopathy: what you need to know NOW
• Atypical myopathy kills 75%: owners and vets warned to be alert
• Atypical myopathy: is your horse at risk?

To help avoid horses developing the disease, owners are also advised to provide supplementary feed in fields, ensure paddocks are not over-stocked, stable horses overnight if possible, manage land appropriately to ensure weeds do not affect grass growth and fence off any sycamores if moving the horses is not an option.

Anyone concerned should contact the vet immediately.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

As the season changes vets are urging horse owners to be on alert for signs of the often-fatal condition seasonal pasture myopathy (SPM), formerly known as atypical myopathy.

A horse in the East Midlands has already died in recent weeks of the condition, which is related to the sycamore tree (pictured, top).

The illness weakens the muscles and can present with sudden stiffness, muscle tremors, collapse and colic-like signs.

The fatality rate is around 70% and it is most frequently seen in autumn and spring.

Victims are usually kept in sparse pastures, where seeds on the ground are eaten when there is little grazing.

Mark Bowen, president of the British Equine Veterinary Association, said: “In the past two years our understanding of this awful condition in horses has increased considerably. We now know that sycamore seeds contain the highly toxic agents that cause SPM and there are practical things that we can advise owners to do that minimise the risk to their animals.”

High winds in 2014 spread the seeds, and the National Equine Health survey recorded four times as many cases as the year before.

H&H vet Karen Coumbe added: “Now is the time of year that problems with this condition are likely to occur. It is too early to know how serious it will be [this year], but hopefully with publicity, owners will be more aware of the condition and how to avoid it.”

Seeds should be cleared from pasture, areas with seeds on the ground should be fenced off and additional forage should be supplied to reduce the chance of horses eating seeds.

Signs of seasonal pasture myopathy

• Weaknes
• Muscle trembling
• Lethargy
• Pain
• Dark urine
• Sweating/shivering

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Speed is of the essence when treating a horse with the potentially fatal seasonal condition, atypical myopathy. Andrea Oakes finds out why owners should be vigilant for cases this spring, and how best to plan ahead for autumn

The rapid-onset condition atypical myopathy (AM), which is now known to be linked to trees from the acer family, claimed dozens of equine lives across the UK last autumn as reported cases reached an unprecedented high.

While acers — most notably the sycamore tree — may have stopped shedding their seeds, animals at pasture remain at risk. Studies have shown that small spring outbreaks tend to follow those autumns in which a large number of cases have been reported.

In an attempt to raise awareness of the dangers of AM, vets have urged owners to take precautionary measures and to learn to recognise the most common signs. As H&H reader Jenny Crouch discovered, a little research about this mysterious condition can be a life-saver.

Warning signs

It was autumn 2009 when Jenny’s five-year-old New Forest gelding Peppercorn failed to come to the field gate for his breakfast.

“I knew immediately that something was wrong by the way he was standing,” says Jenny, who called the vet immediately.

“It was a laminitic-type stance. His gut was noisy and he was able to eat and pass droppings, but his head was lowered and he was obviously in pain.”

Jenny’s vet mentioned the possibility of a condition called atypical myoglobinuria, but felt that pelvic, neck or shoulder problems were more likely causes. Peppercorn was given a muscle relaxant while a blood sample was taken for analysis.

“Peppercorn was soon struggling to stay on his feet,” says Jenny. “He hit the ground and within 10 minutes was dead. It all happened within just two-and-a-half hours of us finding him. It was a huge shock.”

Blood test results revealed extremely high levels of the muscle enzymes creatine kinase (CK) and aspartate aminotransferase (AST), confirming AM. But the cause of the condition was at that time unknown.

“It was thought that a bacterium might be a cause, possibly in the pasture, leaves or air,” says Jenny, who closed off the field for winter. “We were focusing on bad weather as a contributing factor.”

A lucky escape

Jenny reopened the field the following spring, but one morning in May spotted her new youngster, Poppy, in a similar stance.

“I shouted for my husband to get the lorry,” says Jenny. “Between us and the vet we manhandled Poppy into it. She could barely take a step.”

Once at hospital, Poppy’s bloods were taken and she was stabled under a heat lamp and placed on an intravenous drip.

“Poppy was a remarkable case,” recalls Richard Parker MRCVS of Endell Veterinary Group.

“Her CK levels were 1,000,000iu/l and AST 400,000iu/l on admission [normal levels should be just a few hundred units]. Thanks to Jenny’s quick action in bringing her in, we were able to stabilise her and gradually nurse her back to health,” says Richard.

“We learnt a great deal from treating Poppy, especially that intensive treatment, if started early enough in the disease process, can be successful. We have since seen many further AM cases, and our survival rates are more than 60%.”

Jenny was able to take Poppy home 10 days later. The mare had lost considerable condition, but with field rest and time made a complete recovery.

Pasture management

Studies at the University of Liège in Belgium and Minnesota University in the US have since confirmed that toxins from the seeds of acer trees are to blame. Armed with this knowledge, Jenny is able to manage her pasture appropriately.

“We’re based in the New Forest national park and have both giant and mid-sized sycamores on our land,” she says.

“By taking them down we will be able to greatly reduce the risk and encourage native trees to grow.

“The predominant westerly wind brings sycamore seeds all the way across our five acres, so keeping the fields clear of them is a nightmare. While there’s no method I know that picks them all up, using a field sweeper on dry grass seems most effective.

“Walk around your paddocks and look at the plants and trees nearby. Be cautious of any acer. Go out in bad weather, too, to learn how the wind affects your pasture — some areas are worse affected with seeds, depending on prevailing wind direction.

“Most importantly, learn the signs and act quickly if you see them. Knowing what we did about Peppercorn helped us save Poppy’s life.”

Jenny has set up an open Facebook page called Equine-Atypical-Myopathy (myoglobinuria) to share information.

To find out more and help with research, go to Liège university’s site, www.myopathie-atypique.be

Ref: Horse & Hound; 5 March 2015

With increased warnings about atypical myopathy, vets are warning owners to take extra care in identifying potentially dangerous trees — but not to panic and cut them down.

The seasonal disease — which is fatal in 70-80% of cases — has surged this year and is caused by a toxin in sycamore seeds.

Last week the RSPCA put out a further warning.

“It appears that vets have seen more cases of this debilitating and sadly often fatal condition this autumn than in previous years, and that risk is likely to be carried through to the spring,” said RSPCA chief inspector Cathy Hyde.

“We would urge horse owners not to graze horses near sycamore trees from the autumn through until late spring, and to check their horses at least twice a day.”

The British Equine Veterinary Association (BEVA) said the weather is to blame for the rise in deaths.

“The recent high winds and heavy rain have resulted in large numbers of seeds falling from trees in a very short period of time posing a risk to horses grazing on surrounding fields,” said a spokesman for BEVA.

“BEVA encourages horse owners to walk around their pasture to identify any sycamore trees within or adjacent to grazing land, so they can take steps to reduce the risk of this disease.”

Don’t rush to chop

Some readers have said they have cut down trees already.

But H&H vet Karen Coumbe said she is “very reluctant” to encourage people to do this — though it is vital to identify the trees correctly.

“Trees are important on many levels, not least for shade in summer for horses,” said Karen.“If you have lost a horse, it must be very hard not to think of chopping trees, but I would plea not to rush now as the trees will be appreciated next summer.”

Lee Hackett from the British Horse Society added: “There is much to consider before any trees are chopped down, you must check they do not have a preservation order on them.

“It is also worth remembering that while chopping down the tree removes the immediate source of the risk, it does not remove the risk completely. Owners need to remain vigilant as the seeds can travel great distances by wind or water.”

Also beware acorns

Karen added readers should also be reminded that acorns can be poisonous to horses.

“Vets from Royal Veterinary College (RVC) and Bell Equine have just published a very relevant scientific paper in the Equine Veterinary Journal that reviews suspected acorn toxicity in nine horses. This showed that recovery is possible in mildly affected cases, but was sadly fatal in two thirds of the cases reviewed,” she said.

“Similar to the situation with sycamores, the disease is only seen in a small proportion of the population exposed to acorns and there seems to be an increased occurrence in certain years. Further investigation into factors predisposing to disease is required, but limiting exposure to acorns in the autumn seems prudent.”

Securing your land

Readers are also reminded trees might not be on their land.

Horse owner Andy Whelan contacted H&H due to seeds blowing onto his grazing.

“The fields in which our horses are kept are next to the M1 embankment. There are several sycamores and seeds fall into our fields,” he said.

“We endeavour to take precautions: removing any stray seeds from our pasture. However, it is becoming impossible to manage.”

They informed the Highways Agency, but were told “no action was needed”. H&H contacted the Highways Agency, which said it would look into it.

“It is worth reporting your concerns to the landowner, the Highways Agency in this case, however, they are under no obligation to remove the trees,” added the BHS.

This news report was originally published in H&H magazine on Thursday November 20, 2014

Read more articles on atypical myopathy:

More atypical myopathy deaths: family issues warning to fellow horse owners

A family are urging other owners to be on their guard as the fatal disease atypical myopathy continues to claim

Atypical myopathy claims more horses’ lives

Owners of horses who have become fatal victims of seasonal disease come forward to share their stories and raise awareness

Atypical myopathy: what you need to know right now to keep your horses safe

Vets urge owners to be aware of atypical myopathy signs

As autumn progresses, vets are calling for greater awareness of the often fatal seasonal condition

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

More owners are coming forward to share their stories following a spate of deaths caused by seasonal disease equine atypical myopathy.

Following last week’s news story (24 October) several H&H readers have been in touch urging others to be aware of signs of the fatal and rapid-onset disease.

Signs include dark urine, colic-like signs, muscle weakness, trembling and sweating.

Jackie Stevens from Warwickshire lost her five-month-old foal Sable on 15 October.

“I am devastated,” she told H&H. “I knew nothing about this disease before. It kills so fast she had no chance.”

Jade Kephalas’ seven-year-old gelding Oliver died on 17 October. He was grazing in a field in Chelmsford, Essex.

“We thought it was colic to start with but he was spiralling downhill, and it was terrifying to watch. He was soaked with sweat and there was nothing we could do to save him,” she told H&H.

“It was horrific and not something I’d been aware of in my 33 years of owning horses.”

The condition is believed to be caused by the toxic hypoglycin A, which is found in sycamore seeds.

The seasonal disease — which weakens the muscles in the horse’s body — is more common in autumn when seeds are falling, with high winds carrying them.

“It’s been so windy recently,” added Jade. “And Oli was a bit of a pig, he’d rummage through anything to eat, even though there was plenty of grazing.”

Last week Bell Equine in Kent and Royal Veterinary College confirmed they had both had cases of the illness. RVC reported five cases in 72 hours.

“It seems more common than it used to be but there’s no good reason that sycamores should suddenly be producing more toxins, though it could be to do with climate change,” said the RVC’s equine atypical myopathy expert Dr Richard Piercy.

“Much more research is needed. But the more people that are aware the better. You should give supplementary feed, especially after storms when the wind and rain carry the leaves and seeds further.”

There is currently no antidote to the condition, which has a 70-80% fatality rate. Horses diagnosed early can be treated with intravenous fluids.

H&H vet Karen Coumbe added that it was essential to raise awareness.

“We need to spread the word as equine hospitals have seen a depressingly large number of cases recently,” she said.

This news story was first published in Horse & Hound magazine (30 October, 2014)

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

As autumn progresses, vets are calling for greater awareness of the often fatal seasonal condition atypical myopathy.

On 16 October, RVC Equine said they had seen five cases of the condition in 72 hours and urged owners to be aware of the signs.

The onset of the disease can be extremely rapid, with some horses being found dead in their fields.

Signs include muscular weakness and stiffness, dark urine, fatigue, colic-like signs, shivering, sweating and trembling.

H&H vet adviser Karen Coumbe said her surgery saw its first case of the autumn disease last week.

The illness weakens the muscles of the skeleton and heart.

Aisha-Lee Jackson’s three-year-old Welsh section D Nevaeh was in good health before she died from atypical myopathy last November. She contacted H&H to raise awareness of the disease.

“At first Nevaeh appeared to show signs of colic, however on attempt to move her it became very clear there was something very wrong; she was unable to move her legs,” said Ms Jackson.

“I can only wish that I had heard of this disease before, and hope that by sharing my story, I can prevent the heartbreak and suffering of another horse/owner.

“I feel there is not enough awareness of it. As we are in autumn, when more leaves are on the ground, I want to highlight it to other owners.”

Last year, research by the University of Liege linked the mysterious fatal condition to the sycamore tree.

And last autumn, British vets put out a warning to keep horses away from these trees after a rise in cases.

The university recorded 415 cases across Europe between last autumn and this spring.

Earlier this year, experts in Belgium warned cases were on the rise, and the National Equine Health Survey (NEHS) included a question on the condition for the first time in response to an increase in reports.

Run by the Blue Cross, data was collected from 11,002 horses across the UK in May. Vets were asked to record the number of confirmed cases they had had in the previous year.

Thirteen cases were recorded — meaning the first estimate of the prevalence of atypical myopathy in the UK is 0.1%.

But more research is needed. Prof Josh Slater, who analysed the data, said: “The number of cases of this disease that occur each year are not known. Though NEHS has provided a snapshot, we need to capture data from a much larger number of horses to know how common this disease truly is across the UK as a whole.”

In the meantime owners need to be vigilant.

“Owners need to be aware of the possible risk of grazing near suspect trees, such as sycamores,” added Karen Coumbe. “Where possible they should be avoided completely.”

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Horse owners are urged to be on the look out for signs of the fatal condition atypical myopathy this spring, as experts in Belgium anticipate more cases across Europe.

The often fatal illness weakens the muscles of the skeleton and heart and can present with colic-like signs.

“From the retrospective studies we have learned that, when a large number of cases of atypical myopathy was recorded in the fall [autumn], many new cases are encountered in the following spring,” said a spokesman from the University of Liège.

“Unfortunately, spring 2014 could record a large number of deaths.”

The university recorded 415 cases across Europe between last autumn and this spring, and has recently been told of 3 more cases.

Last year, research by the university linked the mysterious fatal condition to the sycamore tree (news, 27 June 2013).

In the autumn, British vets put out a warning to keep horses away from these trees, after a rise in cases (news, 5 December 2013).

And now, with the current climatic conditions, seeds have begun to germinate. Victims are usually young horses, often kept on sparse pasture where dead leaves are on the ground.

“Owners need to be aware of the possible risk of grazing near suspect trees, such as sycamores,” said H&H vet adviser Karen Coumbe.

“It appears that the chance [of picking up the condition] is lower if there is good grazing, when horses are less likely to eat tree seeds or leaves. These may contain the toxin hypoglycin-A — which has been linked with atypical myopathy.

“This toxin is not always present in every seed, or in seeds from every tree. This makes it difficult to predict whether a particular horse will become ill when exposed.

“As the weather improves, the chance of cases occurring may diminish, but care must still be taken.”

Signs of atypical myopathy include:

• Shivering
• Sweating
• Collapse
• Fatigue
• Colic-like symptoms

Research for the condition is not subsidised. To help the University of Liège with funding for research visit: www.myopathieatypique.fr

This article was first published in Horse & Hound magazine (10 April 2014)

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

The mysterious fatal condition atypical myopathy has been linked to the sycamore tree.

A new study published in the Equine Veterinary Journal has revealed that toxins from the seeds of the sycamore is the likely cause of the condition in horses in Europe.

Earlier this year, research in America linked seasonal pasture myopathy (the US equivalent) to toxins from the box elder tree. Both trees produce seeds containing the agent hypoglycin A.

The new research was done by the University of Liège and involved 17 horses from Belgium, Germany and the Netherlands.

High concentrations of hypoglycin A were found in all the horses. The pastures of 12 of the horses were visited by botanists and the sycamore was found to be present in every case.

Outbreaks of the disease tend to be seasonal, with most cases occurring in the autumn. Signs include muscular weakness and stiffness, dark urine, fatigue, colic-like signs and trembling.

Victims are usually kept on sparse pasture, where dead leaves are on the ground.

Professor Celia Marr, editor of the Equine Veterinary Journal, said this was “an important advancement” in understanding and preventing the condition.

“Where grazing is near sycamores, it is imperative horses have sufficient feed, as this will minimise the risk that horses might be tempted to ingest seeds,” she said.

H&H vet adviser Karen Coumbe recommeds concerned owners talk to their vets. She also warns against “rushing to cut down trees” without consulting experts, as trees can be a vital source of shelter.

This news story was first published in Horse & Hound magazine (27 Juen 2013)

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

British vets are welcoming new research that could explain the cause of the mysterious and fatal condition atypical myopathy.

Scientists in the USA have found a link between toxins from the box elder tree and seasonal pasture myopathy, the American equivalent of atypical myopathy.

In 2011, UK vets put out a warning, sparked by an increasing number of cases of atypical myopathy (news, 17 November 2011). The year before, around 20 horses in Cornwall died from the disease.

Outbreaks of both diseases tend to be seasonal, with most cases occurring in the autumn. Symptoms in horses with the condition include muscular weakness and stiffness, dark urine, fatigue, colic-like signs and trembling.

Victims are usually kept in sparse pastures, where dead leaves are on the ground.

The research identified that seeds from box elder trees were present in the grazing of all 12 US horses in the study.

“This is a really important step forward,” said British vet Professor Celia Marr, who edits the Equine Veterinary Journal.

“We don’t know for sure that the causes are the same, but the clinical signs are identical and both conditions have a high fatality rate. Identifying a specific cause for atypical myopathy will be significant, as it is only when we know the causes that this condition can be prevented.”

Box elder is an American tree, but the toxic chemical it contains is found in other plant species. Early test results show that the European condition may be linked to similar trees, which could have an important bearing on future prevention of the disease.

H&H veterinary adviser Karen Coumbe said she welcomed the news.

“It sounds quite probable as the disease is known to occur on poor pasture and near wooded areas, often where there are dead leaves on the ground,” she said. “It would be useful if more research can be done, especially in the UK.”

This news story was first published in Horse & Hound magazine (14 February 2013)

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

A warning has been issued for owners and vets to be extra-vigilant this season as cases of an often-fatal muscular condition appear to be on the rise.

Liphook Equine Hospital in Hampshire issued an alert after diagnosing five cases of atypical myopathy in a few days at the end of October. Three of the horses died.

And they are aware of a further four deaths in the Hampshire/Sussex/Surrey area.

Atypical myopathy weakens the muscles of the skeleton and heart and can present colic-like signs. Horses may shiver, sweat or collapse. They will appear weak and have dark red-brown urine.

The condition often occurs at this time of year in horses that are at grass.

Vets are not sure of the cause but it is thought to be due to an ingested toxin – possibly from a fungus or bacteria – which is triggered by the change towards winter weather.

“We’ve seen a rise in cases from previous years,” said Victoria Copas from Liphook.

“And there are some less-recognised earlier signs to look for – lethargy, vigorous head shaking and choke-like signs. If you’re concerned, contact a vet.”

And H&H vet consultant Karen Coumbe, of Bell Equine in Kent, said she has seen two cases since the beginning of the month – one died and one recovered. H&H is also aware of cases in Berkshire and Suffolk.

“It’s always a problem at this time of year but we’ve seen more this season. The main thing is to catch it early,” Karen said.

Horses diagnosed early by blood and urine tests can be treated with intravenous fluids but it has a rapid onset.

This news story was first published in the current issue of Horse and Hound (17 November 2011)

• For all your insurance needs, contact KBIS

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Veterinary research suggests the following conditions can be linked to the often-fatal muscle stiffening disease, atypical myopathy:

It can affect all types of horses, but tends to target youngsters who are grazing permanent, old or even bare pasture.

The grazing conditions appear to be important: the paddocks are usually poorly drained with low nutritional value.

There are usually trees with fallen leaves on the ground and there is often a river or other watercourse nearby.

The affected horses are often not in work, may be in poor condition, unvaccinated and not regularly dosed for worms.

We can be certain that atypical myopathy is not infectious per se, but it can affect groups of horses, with numerous animals falling victim at the same time on the same grazing.

Atypical myopathy is a disease of the autumn, but it can occasionally occur in the winter and spring. It is almost certainly linked to periods of cold, damp or wet weather and a subsequent frost appears to stop an outbreak.

Read more about atypical myopathy in today’s issue of Horse & Hound (25 November ’10)

Looking for an equine vet?

Find out about grazing diseases

Owners are calling for more research into the condition equine atypical myopathy after as many as 20 horses have died in Cornwall in just a few weeks.

Sam Grange, who lives near St Austell, lost her 14-year-old ex-racehorse Haughty Lady to the disease on 27 October.

Alistair Todd from Churchend vets treated the mare and it was the first time he had seen the condition.

Atypical myopathy weakens the muscles and can present like colic. Horses may be shivering, sweating or collapse. They have a high heart-rate, look weak and have dark red-brown urine.

The mortality rate is around 70%. Horses diagnosed early can be treated with intravenous fluids, but it has a rapid onset. It is not contagious and can affect horses of all ages.

Mrs Grange has donated tissue from Lady to Dr Richard Piercy, head of comparative neuromuscular disease at the Royal Veterinary College, who has been researching atypical myopathy for three years.

“She was a fit, healthy mare,” said Mrs Grange. “We hope her death can save others with research.”

Dr Piercy told H&H: “Cases are not area specific and it often occurs at this time of year in horses that are outside. We have confirmed it is due to an ingested toxin — possibly from a fungus or bacteria.

“We seem to be seeing more cases now, but I don’t think that’s just because we’re recognising it more.”

The owner of a yard near Penzance, who did not wish to be named, has had two horses die over the past month.

The first, three weeks ago, was a four-year-old coloured pony. The second, on 26 October, was a three-year-old thoroughbred.

She said the pony had been “peeing Guinness”, adding: “He just collapsed in his field and was very unresponsive.”

Graham Sherwin from Rosevean vets in Penzance hadn’t seen the condition before. He advises owners to avoid low-lying paddocks surrounded by trees, or those with streams through them, and to stable horses overnight.

“Stay vigilant and if you see changes contact your vet. Horses can go downhill fast,” he warned.

Watch out for a vet feature on atypical myopathy coming soon in H&H.

This article was first published in Horse & Hound (4 November, ’10)

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now