Terry Leadbetter, who runs Welsh Marine Life Rescue in Milford Haven, hopes the colony of grey seals living in waters off Pembrokeshire will be spared from the disease, which is spreading across northern Europe.

The distemper virus is spreading quickly

The illness - caused by the phocine distemper virus (PDV) - was confirmed to have reached the UK's shores on Wednesday after tests on five seals in south east England.

It has already claimed the lives of 2,000 seals in Denmark, Sweden and Norway since it was first spotted in May.

The disease was last seen in Europe in 1988, when more than 18,000 seals were wiped out.

We are mildly optimistic that the distemper virus won't affect the seals in the waters around Pembrokeshire

Terry Leadbetter

The west Wales coast is home to one of the largest populations of grey seals in Europe.

"During the last outbreak, the breed of seals most affected was the common seal," said Mr Leadbetter.

"Out of 18,000 seals which died as a result of the virus in 1988, only 350 were grey seals.

"The common seal is much more susceptible to the disease than the grey seal.

"We are mildly optimistic that the distemper virus won't affect the seals in the waters around Pembrokeshire because no common seals live here.

The disease is highly contagious to seals

"Only grey seals inhabit the waters in this area.

"So far out of the 2000 seals which have died from the virus this year, we are not aware of any evidence to say that any grey seals have been infected," he added.

The virus, which is not harmful to humans, causes symptoms of lethargy and runny eyes and nose in seals who contract it.

It is a highly contagious disease - similar to dog distemper - and attacks the immune system of the animal, usually leading to death by pneumonia.

"Naturally we are very concerned and will be monitoring the situation, particularly with the pupping season approaching.

"But we are remaining hopeful," said Mr Leadbetter.