What owners need to know — based on a conversation with Dr Beth Wells
Horse owners across south-west Scotland are being urged to stay vigilant after vets confirmed a cluster of equine grass sickness (EGS) cases in Galloway and Wigtownshire. Multiple horses have already died, in a region where the disease is relatively rare.
The outbreak was reported in early September 2026 by Machars Veterinary Services in Newton Stewart. Vets there linked the cases to this year’s unusual weather, dry spells, temperature swings and sudden rain that appear to have created high-risk conditions.
This article draws on a conversation with Dr Beth Wells, an animal science consultant linked to the Moredun Research Institute and a long-standing contributor to Equine Grass Sickness Fund research. Dr Wells works on the weather patterns that coincide with outbreaks, and on how owners can use that knowledge on the ground. Her comments are combined here with confirmed details of the current cluster.
What is equine grass sickness?
EGS mainly affects horses, ponies and donkeys with access to grass. It damages a selective population of nerves, including those that control the digestive system, so the gut stops working properly. The result is intestinal paralysis and, in 80% of cases, death.
There is still no fully proven cause. Researchers believe that the gut pathology seen in cases suggest that a toxin, possibly produced by microbes in soil or on grass during certain weather, is involved. The disease is not contagious from horse to horse, but several animals on the same farm or in the same district can be affected at once.
Three overlapping forms are recognised:
- Acute – rapid onset, often fatal within 48 hours.
- Sub-acute – less rapid in onset (over a few days), yet ultimately fatal.
- Chronic – more insidious onset and milder signs, with a chance of survival if the horse is carefully nursed.
Overall, around 80% of affected horses die. Younger animals, especially those aged two to seven, are most at risk, though any age or breed can be affected.
Why now in south-west Scotland?
Within the UK, EGS is classically more common in eastern and central Scotland and England. A western cluster is unusual. Dr Wells says weather is the most plausible trigger. A prolonged dry spell, fluctuating temperatures, then a drought break with reasonably heavy rain is the pattern she and colleagues regard as high risk.
“In unusual weather like we have been having, we do see it much further west, not just in Scotland but in England and Wales,” she said. Cases in the current outbreak appear to be the true acute form, not a milder chronic picture or a different or new form of EGS
A weather-risk model and alert system has been developed so owners can be notified when high-risk conditions are forecast locally. Signing up for those alerts is one of the few practical steps available.
I asked Dr Wells about the real numbers of EGS cases versus those formally reported. The current outbreak included 5 horses and there have been 74 in the UK this year, including 10 reported on the EGSF case reporting system on one day. These seem relatively low numbers, although almost all have been fatal. But Dr Wells explained they believe this is “the tip of the iceberg” and the majority of cases are either not reported or not diagnosed as EGS.
What can owners do?
There is no vaccine and no guaranteed prevention. Dr Wells’ practical advice to owners is straightforward:
- Avoid sudden changes in diet or management, especially abrupt switches in feed or routine which are associated with higher risk.
- In a high-risk spell, do not assume 24-hour turnout is safest. Extra care at grass, and reducing continuous grazing when alerts are high, is worth considering.
- Watch the weather, not just the calendar. Dry weather, cold winds and then rain raise risk; a weather app is more useful than a fixed date.
- Watch horses closely for reduced appetite, difficulty swallowing, colic, sweating, muscle tremors or a sudden drop in condition.
- Call a vet at once if signs appear. Early intervention still only helps some milder cases, but delay helps none.
Myths, rumours and what the science does not yet say
Outbreaks always generate confident explanations online. Dr Wells was clear that several of the most repeated claims are not supported by science and some are simply wrong.
It is not one proven bug. EGS has not been proven to be caused by a single confirmed pathogen. Clostridium botulinum has been discussed for years. The older botulinum hypothesis has never been proven as the cause. Recent work on nerve junctions in affected horses does not support the involvement of botulinum nerve toxins. Treating EGS as “just botulism” is misleading.
There is no licensed vaccine. Historical vaccine trials in the 1920s, and later research interest in a botulinum-based jab, have not produced a product owners can request. Businesses or individuals asking for an “EGS vaccine” will not find one authorised for this disease. Claims that a shot is available “if you know who to ask” are misinformation.
It is not flu, and anti-vaccine stories do not explain it. There is no evidence linking EGS to influenza vaccination. Association is not proof. Social posts that fold EGS into wider vaccine arguments are not supported by the research Dr Wells described.
It is not only a “Scottish east-coast” disease. This cluster in south-west Scotland, and cases further west in England and Wales, show the disease can appear outside the textbook high-risk belt when the weather lines up.
It is not proven to be genetic and it is not only horses. One Hungarian study suggested a possible genetic predisposition, and some breeders believe there is a family link. That remains unproven. Similar dysautonomias have been described in dogs, cats and sheep; that does not mean owners should treat every species rumour as confirmed fact.
“White sauce”, miracle diets and gut-reset products are not treatments. Researchers are looking at the gut microbiome and novel viruses in EGS cases. Recent interest is focussed on potential microbial sources of the enzyme PLA2, the action of which aligns with the changes seen within the nerves at very high magnification. That is early science, not a shopping list. There is currently no specific treatment for the acute or sub-acute forms.
The honest position, as Dr Wells framed it, is uncomfortable but useful: weather and management change risk; the exact toxin is still being hunted; anyone selling certainty is ahead of the evidence.
Where the research is going
The Equine Grass Sickness Fund is the only UK charity dedicated solely to this disease. Other bodies, including the British Horse Society, have supported related work. Current lines include:
- Better diagnostics — laboratory antigen tests and tools that could be used closer to the animal.
- Comparing gut flora and novel viruses from EGS cases with healthy horses.
- Weather models that owners can actually act on.
- Community reporting of cases, so clusters are spotted faster.
None of that replaces a phone call to the vet when a horse looks wrong.
Looking ahead
This outbreak is a reminder of how quickly EGS can appear outside its usual map. Progress is real. Weather alerts, case reporting, and a more cautious reading of old theories remain important developments and activities, with the understanding that most affected horses still die.
Dr Wells’ message to owners is the same as the local vets’: know the signs, watch the weather, ignore tidy myths, and act fast. In a disease that still claims most of its victims, early awareness and honest information are the tools we have.
Further information and case reporting
Equine Grass Sickness Fund: www.grasssickness.org.uk
The Moredun Foundation Equine Grass Sickness Fund is the only registered charity in the UK raising funds specifically for research into grass sickness.
TO DONATE: https://www.justgiving.com/campaign/equinegrasssickness?utm_medium=CA&utm_source=CL
This article is based on notes from a conversation with Dr Beth Wells (Moredun Research Institute), Prof Scott Pirie (Royal (Dick) School of Veterinary Studies, University of Edinburgh) and on publicly reported details of the September 2026 south-west Scotland cluster. It is general information for owners, not a substitute for veterinary advice.
