The lives of British horses are at risk from a fatal disease linked to eating sycamore seeds.

There has been a surge in the number of horses being struck down by equine atypical myopathy, with 12 cases, six of which proved fatal, in Hampshire alone last week, the Daily Mail reported.

Experts have estimated that the spate of cases that began in the autumn could see more than 100 horses dead by the summer.

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Earlier this year, a study carried out by Faculty of Veterinary Medicine at the University of Liege, Belgium, linked toxins from sycamore tree seeds to the fatal condition, which causes substantial muscle damage and in 75 per cent of cases death within 72 hours. Occasionally, it is possible to save horses with intensive fluid therapy.

The study found that most horses that presented with atypical myopathy were kept in sparse pastures with lots of dead leaves and wood on the ground. In all cases investigated a sycamore tree was present in the area.

It is believed that horses only eat the tree's so-called helicopter seeds when other sources of food are meagre, so vets advise owners to ensure their animals have plenty of feed when they are out grazing.

But a large crop of seeds in the UK last autumn means that the risk has increased in recent months.

Dominique Votion, from the University of Liege, told the Daily Mail there had been more than 50 confirmed cases in the UK between September and December, but that figure was a huge underestimate as many were not reported and the number could well be more than 100.

Symptoms include dark coloured urine, muscle stiffness unrelated to exercise, muscle tremors, lethargy and colic like symptoms.