While recently treating a cow with milk fever in a paddock with numerous sycamore trees, I was reminded of the problems caused by sycamore tree poisoning last autumn.

Atypical myopathy in horses is caused by ingestion of sycamore tree seeds (helicopter seeds) and caused a large number of fatalities last October.

Atypical myopathy was first recognised in Europe in 1984 and is very similar to a disease in America called seasonal pasture myopathy.

Myopathy diseases in horses result in damage to muscle tissue and causes significant pain in affected animals. These horses are usually in overgrazed pastures in late autumn where they ingest the helicopter seeds, which contain a toxin called hypoglycin.

It would appear that the seeds remained on pasture for longer periods last October due to the unseasonably dry weather. Horses were left on these pastures without supplemented forage and went foraging among the fallen leaves, ate the seeds and thus became poisoned.

The toxin disrupts muscle fibres and this can trigger muscle tremors and sweating. Horses may be unable to move or get up. Dark red, muddy-coloured urine is also a symptom. Unfortunately, recumbency is usually followed quickly by death.

There is no specific treatment or antidote for this poisoning. Supportive therapy, such as fluids and pain relief, will help in mild cases where not many seeds have been ingested. Overall, prevention is better than cure in this case.

Minimising the threat of exposure for horses to these helicopter seeds is key to preventing the disease. This is easier said than done, as even paddocks free of trees may be exposed to windblown seeds. Thus apart from fencing the area under the sycamore trees, the main preventative measure is to provide sufficient supplementary feed to horses in late autumn so that they won’t go foraging among the dead leaves and seeds for sustenance.

Brian Ryan works at Mulcair Vet Clinic, Cappamore, Co Limerick. Mulcair Vet Clinic is part of XLVets, a group of progressive practices working together to achieve a better future for agriculture.