There have been a spate of reports of pet dogs falling ill with diarrhoea and vomiting after walks in Yorkshire and the North East. The mystery bug was first linked to beaches but has since spread inland.
David McCreadie, a former senior lecturer in marine biology and oceanography, believes dredging could be to blame.
Mr McCreadie started to find dead lobsters and crabs on the South Gare near Redcar after seeing a vessel dredging off Teesmouth last September.
He believes the process unearthed historical toxins which he is “99 percent certain” is responsible for the crab and lobster deaths, and could also be the cause of the mystery illness in dogs.
Mr McCreadie told Teesside Live: “I am 99.9 percent certain that this week-long dredging operation unearthed some historical toxins.
“It dumped the spoil about three to four miles off – fishermen found hundreds of dead seabirds floating at the site.
“We have asked Defra to take samples from the dredged area and the recent animals and if necessary send samples to Porton Down for analysis specifically cyanide and dioxins.
“As we all know the Tees has been an industrial sewer for 100 years.”
However, the Environment Agency has ruled out dredging as the cause of the dead crustaceans.
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It comes as the British Veterinary Association last week urged dog owners not to panic about the mystery illness and to talk to their vet if they have concerns.
BVA President Justine Shotton told BBC Radio 4’s Today programme: “We are aware of a recent spike in cases of dogs falling ill from gastroenteritis-like symptoms in several parts of Yorkshire and North East England.
“Vets see gastroenteritis cases relatively commonly in practice, but numbers seem to be increasing and more widespread than usual.
“At this time, we can’t speculate on what might be causing the symptoms, and there is currently no evidence to suggest a direct link between the illness and the dogs visiting the beaches.
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“We’ve heard reports from vets in the area who are really far inland and they are also seeing an increase in these kinds of cases in dogs that have never been to the beach, so I’m not sure yet if we have enough information to make that link.
“With gastroenteritis, most cases are mild, but some dogs may need hospitalisation with a drip. In the worst situations, it can become haemorrhagic leading to secondary complications or even death, but that is very rare.”
On a possible seasonal link to the cases, she added: “While pet owners are understandably worried, the cases may be part of a normal increase in gastroenteritis that vets see during the colder months.
“We saw something similar a couple of years ago, and the latest data from the University of Liverpool’s veterinary surveillance database points to the spike being part of normal seasonal variation at the moment.
“Our advice to concerned owners is to contact their local vet for prompt treatment if their dog shows any signs of illness, such as vomiting and diarrhoea.”