Seasonal Pasture Myopathy Warning
SEASONAL PASTURE MYOPATHY WARNING
Tragically, we have had two fatalities this week due to Seasonal Pasture Myopathy (SPM) (previously known as Atypical Myopathy) caused by sycamore poisoning (due to Hypoglycin A).
Both cases were in horses recently turned out on the same pasture where sycamore seedlings were growing – the three photographs are from their pasture, so that you can see what it looked like.
Recognition of this disease is relatively new to the veterinary profession, so we don't have all the answers yet, but there is a lot of ongoing research being conducted to help our understanding.
We do know that all parts of the sycamore tree are potentially dangerous, including the leaves, the helicopter seeds and the seedlings, whether alive or wilted. There seems to have been perfect climatic conditions this year to germinate a mass of seedlings within the last few weeks, so please be very careful about where your horses are turned out. The pasture where the two recent fatalities were turned out had been grazed by horses for many years without problems, but closer inspection revealed many sycamore seedlings, dry leaves and desiccated helicopter seeds mixed in with the grass.
There is lots of advice on this condition online now. Here is the link to our own advice page:
Try to remove as many of the seedlings as possible by picking them by hand (wear gloves), mowing your grazing with either a sweeper or collector behind or spraying the paddocks. Remember, the toxin will remain in the dead seedlings - horses will need to be kept off sprayed paddocks until there is no evidence of the dead seedlings in the grazing. Diluting out the grazing with hay or other supplementary feed will reduce the quantity of sycamore ingested.
If you have sycamore seedlings in your paddocks and would like to know how potentially dangerous they are, you can send samples to the Royal Vet College (RVC) who will analyse them and advise you of the concentration of Hypoglycin A within the sample. This will help to tell you how "dangerous" your paddock is. The test costs £60. Here is the RVC information sheet link:
A blood sample from your horse sent to the RVC can analyse the level of Hypoglycin A in the blood – this may be useful for those horses in contact with / on the same pasture as others suffering from sycamore poisoning, but it is too soon to know if this will help with early diagnosis or prevention of the condition – this is new and ongoing research. Speak to your own vet if you would like to arrange the submission of a blood sample to the RVC for this test.
If you are suspicious of sub-clinical / low-level sycamore poisoning, a blood sample from your horse can be analysed at Paton and Lee for the muscle enzymes AST and CK. Raised levels of these enzymes might indicate sub-clinical disease, prompting a change in management – again, the data on this is in its infancy. We know that in acute cases of sycamore poisoning a change in the blood AST and CK levels occurs AFTER clinical signs have already developed. Dark urine and other symptoms of the disease are therefore a more reliable test of poisoning and should be responded to urgently.
If you would like to blood test your horse, please contact the practice on 01376 513369 during normal office hours.