In 2001 a foot and mouth epidemic in the UK crippled farms across the country, costing the economy an estimated £8.5 billion (US$17.3 billion).

The clean-up was extensive and heartbreaking for farmers, requiring the slaughter of between 6.5 million and 10 million animals. The long-term effect was an incalculable loss of trade and confidence in the UK farming community.

In 2007, with farmers still haunted by the last outbreak, the disease was again detected in cattle at several farms in Surrey, south-west of London. The government immediately acted to isolate the disease with a ban on the movement of livestock across the country – at a time when farmers were likely to be transporting animals in preparation for autumn and winter conditions.

National Farmers Union spokesman Anthony Gibson told the BBC the new outbreak would have severe financial implications.

“The longer we keep getting these outbreaks, the longer it will take to get the export ban lifted. And that’s costing at least £2 million (US$4 million) a day. Since the foot and mouth outbreak was confirmed in August, we think the total cost to the farming industry is about £250 million (US$510 million). That’s in terms of lost exports and lower meat prices.”

A recent report by the Health and Safety Executive (HSE) was able to isolate the source of the outbreak and investigate likely causes. Poor plumbing installations at the nearby research facility Pirbright may have contributed, and the occupants of the facility were potentially in breach of strict biosecurity Standards.

The report was triggered when the Department of the Environment, Food and Rural Affairs (DEFRA) established that the foot and mouth virus that infected the cattle in Surrey was not naturally found in the environment. It was a laboratory strain and was not known to be in circulation anywhere else in the world.

This was the strain being researched at Pirbright by three occupants of the facility at the time – a government agency and two private companies.

The report investigated various ways the disease could have leaked from Pirbright, including airborne release, human movement, solid waste removal and liquid waste disposal. It found no evidence to suggest the disease was leaked from the site into the atmosphere or through solid waste disposal, as the appropriate bio-control systems were in place. But liquid waste disposal was a different matter.

Most liquid waste from the facility passed through two chemical effluent inactivation treatment processes on site before joining the public sewer. However, the report notes that wastewater from human showers was not treated before it entered the site drainage system. It was therefore possible for small quantities of live virus to enter the plumbing from workers.

It was also possible that one on-site operator, which was testing the virus in much higher volumes than the other two, flushed waste containing the virus into the effluent sump and this passed into the drainage system. Waste in the drainage system was routinely given a final effluent treatment before release into the public sewer, and these incidents in isolation were not considered to be in breach of biosecurity regulations.

However, at some stage in the drainage process before the second and final treatment phase (where caustic soda should have neutralised any live viruses), infected wastewater leaked out of the pipework, contaminating the surrounding soil. In other words, the report concludes, the site’s plumbing network failed to contain the virus.

In its assessment of the condition of the ageing drainage system, the report noted weaknesses in the containment standard of effluent drains across the Pirbright site.