24 Hour Emergency Line: (01295) 670501

Equine Atypical Myopathy Symptoms


equine atypical myopathy symptoms

Equine atypical myopathy is a serious and, sadly, often fatal muscle disorder. It is usually caused by horses eating sycamore seeds, leaves and seedlings. However, other types of acer can contain the toxin that causes atypical myopathy. This blog article outlines the main equine atypical myopathy symptoms.


Equine Atypical Myopathy Symptoms


The onset of atypical myopathy is rapid, and it can affect individuals or groups of horses. Some horses are more susceptible to atypical myopathy than others.


The symptoms of equine atypical myopathy include:


  • Muscle weakness, soreness or stiffness - the hypoglycin A (HGA) toxin mainly affects the heart and muscles that help the horse to stand. 
  • Lethargy and fatigue. The horse may struggle to move, stand or breathe
  • Heart and respiratory problems
  • Muscle trembling
  • Colic-like symptoms
  • Brown or dark red urine


Atypical myopathy is not contagious, but care should be taken to assess and monitor other horses grazing in the same area. It is important to note that just because other horses have or have not suffered from atypical myopathy, it does not mean that all horses grazing on the same pasture will be affected in the same way. Genetic factors, grazing habits and weather conditions all appear to be factors. 


Treating and Preventing Atypical Myopathy


Suspected atypical myopathy cases require urgent veterinary treatment. The chances of survival are mostly dependent on the horse being treated quickly. Your vet will be able to advise you on the best course of action for your horse.


Other horses grazing the same pasture as the suspected or confirmed case should be moved to another pasture and monitored closely. There is no way of telling which horses are more or less susceptible to atypical myopathy.


There are a number of steps that can be taken to minimise the risk of equine atypical myopathy. Regularly checking for and removing acer leaves, seeds and seedlings (particularly sycamores) is the best way of preventing atypical myopathy. Remember that sycamore seeds are designed to travel by air (hence their propellor-like shape), so it’s worth keeping an eye on neighbouring areas. 


Seedlings tend to be the main concern in the spring, whilst seeds and leaves are a bigger problem in the autumn. You can mow the grass and collect the cuttings in the spring in order to remove the seedlings. Remember that the cuttings will still contain the HGA toxin, so they must be removed and disposed of properly.


Emergency Equine Vet


Avonvale Equine Vet Practice offer 24/7 emergency call-outs. Night or day, if you suspect your horse is suffering from atypical myopathy or any other veterinary emergency, call our emergency line on 01295 670 501. There is always an Avonvale Equine vet on-call and ready to help your equine companion. We are also happy to advise our clients, so if you would like to know more about how to spot and prevent equine atypical myopathy, register with us today. 


Share this post