Keeping Native Breeds Animal Health and Welfare Silent Killers: Atypical Myopathy Sycamore poisoning is a toxin derived disease which affects the muscle metabolism in horses which can be rapidly fatal. The mortality for sycamore poisoning can be as high as 75-90% and early, intensive veterinary intervention is key for increasing survival rates. There is a new test available at the Equine Neuromuscular Lab at the Royal Veterinary College for testing a blood sample for the toxin and testing the plant material too. However variable amounts of HGA can be found at different times in different parts of the plant/tree so this is not necessarily a reliable indicator of risk. The blood sample, however, is used for diagnosis. Sycamore poisoning also called Atypical Myopathy, is caused by a toxin called hypoglycin A. Concentrations of Hypoglycin-A (HGA) can vary from tree to tree. When eaten, HGA is converted into a toxin within the horse’s body. This toxin is typically found in sycamore seeds and saplings. The toxin has a rapid negative effect .The toxin acts by damaging the striated muscle (the muscles allowing the horse to stand and breathe), preventing energy being produced, and can also affect the muscle of the heart. Atypical Myopathy can affect individual horses or several horses within the same group. It is currently unknown why some horses remain unaffected by HGA and others develop this life threatening condition. Diagnosis is often based on clinical suspicion, a history of exposure or potential exposure to sycamore seeds or saplings, increased levels of muscle enzymes in the blood, dark red/brown urine and the absence of evidence of other issues such as colic. Symptoms of Sycamore poisoning may include the following: Depression Stiffness and reluctance to move Muscle tremors Sweating Weakness Lethargy Difficulty breathing Reluctance to work Red or brown urine Choke Colic Low head carriage Fast or irregular heart beat Sudden collapse and death In the case of Sycamore poisoning prevention is key. There are may ways you can help safeguard your equine friends. Feed sufficient forage, such as hay or haylage in fields where grazing is short. Feeding off of the floor helps to minimise the risk of ingestion. Do not over stock your grazing, and limit turnout where necessary. The length of exposure to the toxins appears to play a role in the risk of AM. Where sycamore trees are present near horse’s pasture, it is recommended to limit grazing time to less than six hours a day Section off areas around poisonous trees and collect and dispose of seeds and saplings Be vigilant, seeds may be blown in from neighbouring pasture or woodland. Be vigilant of the potential signs of this disease and act quickly if your horse becomes unwell. Ensure you check your horse regularly Be aware that the harrowing of pastures has found to increase the risk of Sycamore poisoning. This practice may disperse the sycamore material throughout the pasture SYCAMORE POISONING IS A VETERINARY EMERGENCY. IT REQUIRES IMMEDIATE ATTENTION. IF YOU SUSPECT YOUR HORSE IS SHOWING SIGNS OF SYCAMORE POISONING CONTACT YOUR VET IMMEDIATELY