VETS fear a contagious killer bug could decimate the North-East's dog population unless immediate action is taken to control the outbreak.

The dreaded Canine Parvovirus, known commonly as Parvo, kills 50pc of dogs which contract it.

In Britain the disease has been tightly controlled by a vaccination policy which has been in place since the 1970s.

But experts say they have identified a number of cases on Teesside.

"We think there are between 10,000 and 15,000 dogs in Middlesbrough," said council dog warden Paul Robertson.

Experts fear dogs could be at risk if they use the same parks as infected dogs.

Mr Robertson warned: "This bug can be devastating and we do see odd cases every now and then.

"But at the moment there is a risk this could spread right through Middlesbrough."

The bug last took hold on Teesside in the 1970s when hundreds of dogs died.

The virus causes diarrhoea and intestinal bleeding and even with treatment dogs can go from being very healthy to very ill in just 12 hours.

Parvo also stays active and potentially infectious in the home for up to a year.

Experts say the number of unsupervised dogs which have not been recently vaccinated, means the risk of the bug spreading is high.

Now vets and dog wardens are urging owners to make sure their animals' inoculations are up to date and warning them not to let their dogs out alone.

Councillor Barry Coppinger, Middlesbrough Council's Executive Member for Public Protection, said: "One infected stray dog could spread the disease to many others and contaminate a wide area in a very short period of time".

Lloyd Oxley, senior partner at the Bridge Veterinary Group in Middlesbrough, said this year cases had been noted in Middlesbrough, Stockton and Hartlepool.

"This appears to be a big problem in dogs that are unvaccinated and with lapsed boosters," he said.

"Parvovirus is virulent and infectious.

"Owners must act in a responsible way and have their dogs vaccinated and boosted annually, both for their pets' welfare and that of other animals in the region, or we will repeat the decimation seen in the 1970s."