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

The Canine Parvovirus, commonly known as Parvo, kills 50 per cent 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 said they have identified a number of cases on Teesside.

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

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

"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 healthy to ill in 12 hours.

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

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

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

Councillor Barry Coppinger, of Middlesbrough Council, 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 cases had been noted this year in Middlesbrough, Stockton and Hartlepool.

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

"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."