Tests were taking place in West Sussex this weekend after vets found possible signs of a pig disease wiped out in the UK 13 years ago.

The discovery was made at the same Essex abattoir where the first case of foot-and-mouth was detected in last year's devastating epidemic.

The Department for the Environment, Food and Rural Affairs (Defra) said routine testing in pigs resulted in serological positive tests for Aujeszky's disease in six pigs.

Further tests will be carried out this weekend at premises in West Sussex and Lancashire, Cheshire, West and North Yorkshire and Lincolnshire for other signs of the disease.

The State Veterinary Service will visit the six premises where the pigs either came from or had contact with.

Defra said the alert might yet be a result of a false laboratory reading or a contamination of samples.

Aujeszky's is mainly a disease in pigs but is not in the same league as foot-and-mouth. It is not as contagious and is generally spread from pig to pig.

The first British case of the disease - which is also known as pseudorabies - was in 1979.

Slaughtering affected animals wiped out the disease within ten years and the country was declared Aujeszy's-free in 1991.

Pigs are the natural host for the Aujeszky's virus, although it can infect cattle, sheep, cats, dogs and rats.

Symptoms in pigs include shivering, lack of co-ordination and hind leg weakness. It can prove fatal in piglets under seven days old.