Virus mutations reveal how disease has spread

The Veterinary Laboratories Agency, Addlestone, has rejected suggestions that it may have played a part in the second cluster of outbreaks.

The VLA site, which works in partnership with the Institute for Animal Health at Pirbright, has found itself at the geographical centre of the September foot-and-mouth cluster (see map above).

Staff who work with the foot-and-mouth virus transfer between Pirbright and Addlestone, where a number of farm animals are kept, Farmers Weekly has learned.

A spokeswoman for the VLA said: “We have farm animal units dotted about the site and there’s a small number of staff passing between the two sites.”

But the farm animals at the laboratory had not shown signs of the disease, the spokeswoman said.

“A rule prevents researchers who work in the so-called ‘hot zone’ at IAH from coming within 30m (100 feet) of farm animals.

“They can still visit the VLA site for meetings but for five days they cannot get within 30m of the animals at the site.”

“We believe this is sufficient to prevent the disease from passing to the livestock here,” the spokeswoman said.

A DEFRA official added that they had concerns over biosecurity at the site during a critical period in August when severe structural damage resulted from floods and high winds.

“We are looking into this but do not yet have enough information to suggest that the power cuts and flooding of the site may have any link to the foot-and-mouth disease outbreak.”

Meanwhile a process known as sequencing of the foot-and-mouth virus could hold the key to tracking down where the outbreak began and where it went next, according to IAH scientists.

A Pirbright spokesman explained the sequencing process, saying that every time a virus passed through livestock it mutated slightly.

“With each case we can examine the virus and tell how many mutations it has undergone.

“Comparing that with the original and with all of the other samples allows us to establish a pattern of progress of the disease that is more reliable than assessing the age of the lesions alone.”

Speaking ahead of the release of DEFRA’s report into the likely movement of the virus, a DEFRA scientist confirmed that the sequencing showed the first outbreak was in animals at the farm owned by Roger Pride in Elstead.

“It looks as though the August outbreak did indeed begin at Wolford’s Farm, Elstead, Surrey.

“Although we can track the disease, there is still some mystery as to how it jumped and infected the second cluster of holdings near Egham,” she conceded.

  • DEFRA’s epidemiology report was due to be published as FW went to press. Visit for updates


Accidental Transport Virus moved via transport on wheels or workers’ shoes

Livestock Movement Farm animals carried the virus in the brief break in movement bans

Wildlife Deer or some other live vector could have moved between farms

Sabotage Theft of samples spread maliciously