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.
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.”
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