A dog owner has recalled the horror of nearly losing her two beloved pets to a mystery illness they picked up after walking in a Suffolk forest.

Caroline Peters believes the bug, which nearly killed Sparkie and Ruby, may have been a case of Seasonal Canine Illness (SCI), which has left several dogs unwell after walking in wooded areas or parkland during autumn months since 2009.

Ms Peters had been visiting her partner in Ipswich when she took her dogs for a walk in Rendlesham Forest earlier this month. Days later, the dogs were fighting for life in a specialist veterinary centre in Newmarket.

“We were there for about an hour-and-a-half,” said Ms Peters, from Felsted in Essex. “Ruby was off the lead but Sparkie was on the lead. We saw toadstools but they have been ruled out – there was nothing in their tests to suggest there had been any form of poisoning.”

Two days after visiting the forest, both dogs collapsed and were taken to a veterinary surgery in Great Dunmow before being referred to the specialist centre, where they were in intensive care for two nights.

Sparkie and Ruby are now recovering but Ms Peters wants to help prevent the same thing happening again.

“I’ve had dogs all my life and had never heard of SCI. I would never have dreamt something like this could happen. It seems to be isolated to pine forests. One thing common in cases is evidence of the dogs picking up harvest mites.”

Although harvest mite infestation has been identified in dogs affected by SCI, the cause has yet to be confirmed, despite investigations by the Animal Health Trust (AHT) charity.

SCI can be fatal, although in recent years there has been a fall in the number of deaths, and more common symptoms include sickness, diarrhoea and lethargy within 72 hours of walking in woodland.

Anyone who suspects their dog of showing signs of SCI is advised to contact a vet immediately. Owners can also talk to their vet about spray treatments which can be applied before walking in woodlands as a preventive measure against harvest mites.