Search our Site

Atypical Myopathy/ Sycamore Poisoning

Sadly every year we see several cases of this horrid disease.​ Atypical myopathy is a frequently fatal disease of horses caused by eating Sycamore seeds/helicopters or seedlings. The toxin, hypoglycin A, in the seeds causes muscle damage which in turn leads to a wide range of clinical signs. Your horse might become dull, weak, stiff and trembly as the disease progresses but early signs include lethargy, quietness and a reluctance to work.

Cause of Atypical Myopathy
Hypoglycin A which is a toxin found in the seeds/helicopters and seedlings of the common maple sycamore tree (Acer pseudoplatanus) is the causative agent for atypical myopathy. This toxin prevents energy being utilised in the muscle cells resulting in damage. The more toxin the horse consumes the more damage occurs. As a result, the disease is common in the Autumn and early winter months (October/November) when the greatest number of sycamore helicopters are present and bad weather will trigger large numbers of the seeds to fall so often precipitating a rise in the number of cases. New cases can often occur in the spring when seedlings start to germinate.
Importantly the amount of toxin varies within the seeds and seedlings and some horses can become sick after eating only a few of them.

Clinical Signs of Atypical Myopathy
• Mild cases - depression, lethargy, weakness or stiffness, low head carriage
• More severe cases – Muscle tremors, difficulty breathing, colic, red/brown urine, collapse and possible death

Diagnosis of Atypical Myopathy
• A history of exposure to sycamore seedlings or seeds
• Clinical signs consistent with the disease
• The absence of an alternative somewhat more common diagnosis i.e. process of elimination
• Several horses possibly showing abnormal clinical signs rather than a single sick horse
• Elevated muscle enzymes on blood sample
• Dark brown pigment within the urine

Treatment of Atypical Myopathy
It is a common misconception that this condition invariably results in death but we are getting better at recognising this condition in the early stages and hence survival rates are increasing with potentially a 50:50 survival rate supported by some clinicians. Treatment is predominantly supportive as there is no specific recognised antitoxin.

Goals of treatment
1) Firstly and most importantly remove the horse from exposure to the sycamore seedlings.
2) Fluid therapy to support the damaged tissues and encourage elimination of the toxin
3) Analgesia. This is a painful condition due to the extensive muscle damage and good management of the horse's comfort level is crucial to a successful recovery.
4) Restrict movement. The muscles fatigue and rest is nutritional support with intravenous glucose
5) Vitamin E which is an antioxidant and can help support damaged muscle cells
6) Activated charcoal. In the acute stages of the disease when recent exposure to the toxin is likely there is some logic to giving the horse charcoal which will help eliminate the toxin from the body. Mineral oil would have a similar effect but would also empty the horse's guts and therefore deprive him of useful nutrients.
7) Carnitine and Riboflavin both have potentially beneficial effects and may be used by your vet.

If your horse survives the first 48 hours the prognosis increases considerably is essential. Cost of treatment can be anything from £1000-£3000 but severe cases could easily cost in the region of £5000 due to the intensive care required.

Prevention of Atypical Myopathy
• Be aware of the risks of sycamores so keep an eye out for seedlings or seeds/helicopters
• Remove horses from areas where sycamore exposure could be possible.
• Monitor 'in contact' horses with blood samples every 5 days if a horse on a yard displays clinical signs.
• Provide plenty of alternative forage so that horses don't go scavenging.

Please keep horses away from sycamore trees and seedlings.  
Eye, eye!
The trouble with haynets is...


No comments made yet. Be the first to submit a comment
Already Registered? Login Here
Wednesday, 27 October 2021

Our Location

Lingfield Equine Vets is situated in the beautiful Surrey Hills area. We are located just north of Felbridge on the A22 with easy access for all equine transport vehicles.

Contact Us Today
Lingfield Equine Vets
Chester Lodge, Woodcock Hill,
Felbridge, Surrey,
RH19 2RD
(01342) 300008