A MYSTERY illness which has killed dogs taken for walks in Notts woodland has struck for the fourth year in a row.
Seasonal canine illness has led to the deaths of several dogs being walked at Sherwood Forest or Clumber Park every autumn since 2009.
An exact cause of the illness has never been found.
This week, one Notts owner spoke of how the condition nearly killed her one-year-old pet after a walk this week.
And an animal health group is warning it has detected new cases in both Sherwood Forest and Clumber Park in recent weeks.
Kath Roberts said her shitzu cross Sophie rapidly succumbed to illness two days after walking in Clumber Park last Friday. By Sunday the dog had started vomiting a yellow and brown substance and by Monday was gravely ill.
Mrs Roberts, 56, of West Bridgford, said: "She was on her last legs and having trouble with her breathing and still vomiting. We rushed her in to the vets and she was on a drip all day on Monday."
After painkilling injections and antibiotics at Gamston Vets4Pets, Sophie began to recover and was at home and eating again by Wednesday.
"It was very frightening. Sophie was so poorly on Monday I didn't expect her to pull through. I think there should be warning signs up in the park but we didn't see any, unless we missed them."
The Animal Health Trust has been running an investigation into the mystery illness since September 2010.
The charity said yesterday it was aware of seven suspected cases at Clumber Park and nine at Sherwood Forest since the end of August.
However, no fatal cases have been reported so far this year.
At least one dog died of the illness in Notts last year and at least two were killed in 2010 while eight died in 2009, all after being walked in Sherwood Forest or Clumber Park.
Charlotte Robin, who is coordinating research into the illness for the trust, said: "There could, of course, be more cases that are occurring that have not been reported to us."
A year ago the trust ruled out plants as the cause of the illness and more studies are still being carried out. Other theories have included natural toxins from fungi and algae blooms.
Trevor Pressley, visitor experience manager at Clumber Park, said: "We've had posters on seasonal canine illness at Clumber over the last three years and will be putting up more posters as a result of this most recent outbreak."
"Covering a 3,800 acre site is difficult, and we welcome thoughts from dog walkers in the area as to how we can continue to get the message out to other dog owners."
Dog owners are advised to look out for vomiting, diarrhoea or lethargy which usually appears within 24 to 72 hours of dogs having walked in woodland in autumn.