Vets are warning of East Anglia’s worst year on record for a mysterious and deadly dog disease.

One surgery recorded more cases of seasonal canine illness (SCI) in a week than in the two previous years combined.

Charles Bagnall, a partner at Orwell Vets, has warned dog walkers to avoid the woodland areas around Rendlesham, Sandringham and Thetford, where cases of SCI have been linked to the presence of harvest mites.

“We didn’t really see anything for a couple of years but this year seems to have been particularly bad,” he said.

“Whether it’s down to the weather conditions and the long dry summer, I’m not certain, but this appears to have been the worst year on record.”

The mysterious disease, which arises in woodland areas each year between August and November, causes symptoms of vomiting, diarrhoea and lethargy in its victims and in some severe cases even death.

One of Mr Bagnall’s patients, a dachshund who had visited Rendlehsam Forrest, died before arriving at the surgery.

Three others were severely dehydrated and required several days of intensive care.

“It’s concerning for the dog, concerning for the god and with that level of medical care it’s not inexpensive,” he said.

“My advice would be to avoid all woodland until the end of November.”

Neal Manning, whose partner Debbie Charman runs a dog grooming service, heard reports of 14 different dogs taking ill over one weekend in Sutton Heath.

“Nobody knows what’s causing it,” he said.

Highcliff Vets, however, has not seen any significant difference in the number of cases.

Richard Pettit, a veterinary partner, suggests the mysterious nature of the illness makes it hard to identify genuine cases.

“There’s a lot of unknowns about it and so the sensible thing to do is to avoid taking your dog anywhere you would expect to see it,” he said.

The Animal Health Trust, a veterinary charity, has been investigating a possible link between SCI and harvest mites.

It is advising dog owners to use fipronil spray, which treats external parasites, although vets have warned that the dangers of SCI may remain regardless.

The study runs until the end of November.