Sep 7, 2007 (CIDRAP News) – Britain's recent outbreaks of foot-and-mouth disease (FMD) were likely caused by faulty wastewater drains at a laboratory facility, which contaminated soil that was then spread by trucks to a nearby cattle farm, British authorities announced today.
The United Kingdom's Department for Environment, Food, and Rural Affairs (DEFRA) today released two final investigative reports on FMD outbreaks in late July at two farms in Surrey, which led to the slaughter of 570 animals. The outbreaks were the first in Britain since 2001, when widespread FMD outbreaks devastated the country's cattle industry.
DEFRA officials had previously linked the outbreaks to a leak from FMD laboratories near Pirbright where a commercial vaccine producer and a government-funded research institute share a facility.
The reports released today were produced by the government's Health and Safety Executive (HSE) and independent consultant Brian Spratt, a professor of molecular microbiology at Imperial College in London. DEFRA today also published its response to the reports, outlining several steps it will take to remedy problems at the Pirbright facility and prevent similar problems at other facilities that work with pathogens.
Though officials said faulty drain pipes were probably to blame for the FMD virus leak, investigators also found other problems at the Pirbright facilities, including several biosecurity breaches, such as inadequately monitored worker and vehicle movement and incomplete recordkeeping.
Hilary Benn, secretary of state for Environment, Food, and Rural Affairs, said in a press release today that the reports reveal that experts aren't absolutely certain about how the outbreak occurred and haven't identified a single cause.
"Even in these extraordinary circumstances, this should not have happened and must not happen again," Benn said. "That is why we are taking every possible precaution to prevent this from happening again."
In an epidemiologic report that accompanied the findings, DEFRA officials wrote that a surge of rainfall on July 20 and two of the following days could have compromised the drainage system. "This effluent might have contained 'packets' of virus contained in the cellular debris, which was discharged from the vaccine production containment facility," the report states.
Construction trucks at the Pirbright site, which were not washed or disinfected before leaving the area, could have picked up contaminated soil on their tires and wheel wells and transferred the FMD virus to roads near the first farm that reported FMD cases, the report said.
Genetic sequencing tests on virus samples from both of the affected farms suggested that the infection at the second farm came from the first farm, the investigators found.
The existing drain has been relined and manhole covers have been sealed, pending the construction of a new drainage system for the laboratories, DEFRA reported.
The HSE report recommended that DEFRA review the practice of using chemical treatments to sterilize liquid waste containing high-risk pathogens. Investigators reported that when the Pirbright lab workers dispose of liquid waste, they flush it into a discard tank with citric acid wash, then pump the fluid into an effluent tank where it is mixed with sodium hydroxide to kill the virus.
However, DEFRA said in the press release that it would go beyond the HSE recommendation and require the laboratories to use additional heat treatment systems and other preventive measures to sterilize the waste within a high-containment area. The department said it would not remove licensing restrictions from the labs until such systems are in place.
DEFRA also announced it ordered a review the government's regulatory framework for animal pathogens and advised other laboratories to ensure they are following procedures already in place to avoid similar pathogen leaks.
Debby Reynolds, the UK's chief veterinary officer, said in the press release that she was satisfied that FMD had been eradicated from Surrey and that the 10-km surveillance zone and other remaining restrictions would be lifted at noon tomorrow.
Sep 7 HSE press release on final FMD report
Final HSE report on FMD outbreak
Aug 7 CIDRAP News story "Report: Lab leak likely caused UK foot-and-mouth outbreak"