Thousands of seals were killed by the virus.

Staff at Natureland say they have taken in 50% fewer pups following the outbreak of Phocine Distemper Virus (PDV) in 2002.

Almost 3,000 seals were found dead on the Lincolnshire and Norfolk coastline as a result of PDV.

The disease which affects their immune system makes them weak and unable to dive underwater to catch their food.

Many of them die from Pneumonia.

Vaccinate seals

Duncan Yeadon, co-owner of Natureland said: "If there is half the number of seals out there, there is only going to be a small amount of pups.

"Mother's will only usually have one pup each year.

"Therefore a lower number need rescuing, this year we have only had four in, we would usually have double this.

"There is no way to vaccinate all the seals in the wild so we hope those that have survived have sufficient antibodies to resist it.

He added that he hoped they do not see the virus for a decade which will give the population a chance to recover.

The seals were last struck down by the disease in 1998 when 1,500 died off the Norfolk coast.