03/11/2024
Disease Vigilance: ***Atypical Myopathy***
As the Autumn leaves are falling it is a really important time to be vigilant for sycamore seedlings which can travel surprisingly far in high winds.
Hypoglycin A, a toxin found in sycamore seeds is responsible for causing Atypical Myopathy, a disease which is fatal in around 70% of cases.
Signs of the disease can come on extremely quickly and include:
- Muscle soreness or stiffness
- Weakness
- Dullness and lethargy
- Muscle tremors
- Colic signs
- Prolonged recumbency (lying down significantly more than usual and reluctance to get up)
- Dark red or brown urine
The toxin indiscriminately breaks down the muscles of the horse down into products which have to be filtered through the kidneys. As the kidneys attempt to rid the body of these products they become heavily (and sometimes irreparably) damaged.
Initial signs are non specific with affected horses appearing quiet and lethargic but the disease will quickly progress with the horse showing muscle fasciculations (severe trembling), sweating, inappetence, colic–like signs and dark coloured urine. At this stage the horse will soon become recumbent and treatment is usually hopeless as the heart and lungs will start to fail.
Unfortunately the disease can progress so quickly that some horses are found dead in their fields with sycamore seeds still in their mouth.
Vets are more likely to be able to successfully treat the disease if:
* The horse has no other underlying systemic disease
* The horse has only ingested small amounts of the toxin
* The horse is still standing and able to walk
Treatment of the disease involves aggressive intravenous fluid therapy (this will require hospitalisation in almost all cases) and a combination of anti-inflammatory medication, sedation, strong painkillers and muscle relaxants. Blood samples are taken as often as twice daily to enable monitoring of the muscle enzymes in the blood as well as the response to treatment.
The vast majority of cases are seen in the Autumn when the seeds have recently fallen onto pasture but the prevalence varies greatly from one year to the next, probably due to differences in climatic conditions. Every Autumn, however, we would recommend the following guidance:
- Fence off space around sycamore trees in paddocks or manually collect fallen seeds
- Provide additional forage if needed to reduce overgrazing of pasture which may have seeds on
- Check the boundaries for sycamore trees if you have recently moved your horse to new pasture
- Signs can take up to four days to appear even once a horse has been removed from pasture contaminated with sycamore seeds so remain vigilant
- Contact your own practice immediately if you are concerned that your horse or pony may be showing signs of atypical myopathy - they will be available 24/7 to answer your call and to discuss your concerns
Photo shows a fantastic survivor of Atypical Myopathy thanks to one of our Equicall vets!
