ENSURING non-essential vehicles do not go on to farms is a key factor in preventing the spread of foot-and-mouth, says a respected vet.

Mr Jim Wight, son of the late Mr Alf Wight, better known as author James Herriot, urged farmers not to relax stringent precautions as the virus continued to devastate parts of North Yorkshire.

Mr Wight, of Sutton, Thirsk, said other important moves included keeping stock as far away from roads as possible.

"Movement of animals, people and vehicles spreads this disease; I do not think that it travels far on the wind," he said.

"The most important thing is not to let vehicles on to the farm. Milk tankers and feed wagons have to visit farms, but they should be thoroughly disinfected. Any other vehicle that isn't necessary should be banned from the farm."

He said many outbreaks had occurred among animals grazing close to roads. "Farmers should try to keep animals inland, away from the roads," he said.

Mr Wight agreed to come out of retirement to carry out 48-hour surveillance on a farm at Felixkirk, near Thirsk, which was served with a D-restriction because it was within 3km of infected premises.

Farmers Mr Robin Bosomworth and his son, Trevor, were wary of ministry vets carrying out the inspections because of their contact with other farms.

They also hoped the involvement of James Herriot's son would raise national public awareness that the foot-and-mouth crisis was far from over.

Mr Wight, who helped tackle the 1967 foot-and-mouth outbreak as a junior practising vet, said the large number of sheep involved in the current outbreak complicated the situation.

Movement of stock thousands of miles had led to a greater spread of the disease than 34 years ago.

While researching his father's biography, Mr Wight learned that he had been involved in a foot-and-mouth outbreak in the Thirsk area in 1944.

"When foot-and-mouth was confirmed in a pig herd, the farmer was dreadfully upset because some pigs had been taken to a butcher a mile away," he said. "It threw the whole place into panic because they had travelled a whole mile. In the current outbreak, animals have travelled thousands of miles."

The only way to control the virus was by what had recently been termed biosecurity.

"The virus survives a long time in slurry and muck, but not outside in dry sunlight," he said.

Efforts to tackle the disease over the last five months had also been hamstrung because of what Mr Wight called "draconian" cuts in the number of ministry vets.

He said the reopening of about 75pc of footpaths in North Yorkshire, planned from today, increased the risk of spreading the disease. "I am a keen walker, but I am the first to accept that we have got to make sacrifices," he said. "We walkers should be prepared to at least hang up our boots for a short while more."

It was also important to learn from the current situation in case there were further outbreaks in the future.