Q&A: Dog deaths investigated
Ten dogs have died in the East Midlands over the past two years from a mystery illness after walking in local woods.
Various theories have been put forward as to the possible cause of the deaths, but so far none have proved conclusive.
Where have the deaths happened?
All the dogs have died after walks in wooded areas in North Nottinghamshire. The areas include Sherwood Forest, Clumber Park, Haywood Oaks, Blidworth Woods, Sherwood Pines and Thieves Wood.
Other dogs have fallen ill in Sandringham Estate in Norfolk but have recovered.
When did the dogs die?
All the deaths have happened in the autumn, mostly in September, in 2009 and 2010.
What symptoms do the dogs have?
Vomiting, diarrhoea, lethargy and breathing difficulties.
Is a fungus or mushroom the most likely cause?
Natural England investigated the deaths in 2009 and tested for man-made poisons, but found no trace of them.
It suggested that fungi were a possible cause, but the owners of the dogs said they had not noticed them eating any unusual fungi.
Fungi enthusiast Beverley Rhodes said it was unlikely a mushroom was to blame for the mystery illness as the dogs would have had to ingest the poisonous mushrooms to become sick.
Veterinarian Janice Dixon said she had treated several ill dogs who had been taken for walks in the Sherwood Forest area and there was no sign of fungi in their vomit or faeces.
What have the investigators ruled out?
Natural England initially suspected a tick or mite could have caused the deaths, but none were found on the dogs who died.
Janice Dixon said ticks attach themselves to the dog's skin and stay on for several days. She had not found any sign of ticks or mites on the animals she treated.
Estate workers in Sandringham initially thought the symptoms could have been caused by the parvo virus.
But the virus is mostly found in dogs that have not been vaccinated and all of the dogs treated by Janice Dixon had been vaccinated.
Another cause ruled out by Natural England is poisoning from chemicals like strychnine or cyanide.
Tests done on some of the dogs that died in 2009 showed no signs of man-made poisons.
Are there any other possible causes?
Former dog trainer Ryan O'Meara, who edits K9 magazine, has suggested blue-green algae might be causing the deaths.
Dogs do not need to drink infected water to be affected but merely need to walk in a boggy area and lick their paws to get the toxin in their system.
Janice Dixon also suspects the algae might be the cause as only 20 parts per billion are needed to kill a dog.
It is difficult to test for the algae on live animals as samples are needed from the liver.
Who is responsible for investigating the deaths?
Natural England investigated the deaths in 2009 but ruled out man-made substances and blamed a natural substance. It did not investigate further as its remit does not include looking into natural poisoning.
The Forestry Commission is eager to find the cause but does not have the experts on staff to undertake an investigation. It has appealed for anyone with information to contact them.
The Environment Agency will test water in the area to see if blue-green algae is present. Results are expected at the start of October.
Animal Health Trust, based in Newmarket, Suffolk, has agreed to look at any evidence from veterinarians to try to track down the cause, but needs samples to start its work.
What action is being taken?
The Forestry Commission has put up signs at the affected forests to warn pet owners to keep their animals on leads.
Veterinarians are encouraging pet owners to contact them if they see any of the symptoms in their animals.
The Animal Health Trust has agreed to use its laboratory facilities to test samples from animals if they are collected and sent to them.