The combination of broken drainage pipes, heavy rain and an absence of biosecurity measures combined to cause the recent outbreak of foot and mouth disease in Surrey, a report by the Heath and Safety Executive has concluded.

The HSE said it could not say with any certainty which of the two laboratories connected with the outbreak were responsible.

But it does conclude “that it is likely that live virus of the O1 BFS strain entered the effluent drainage system from the Merial facilities during the period covered by our investigation”.  However, while the HSE noted that Merial was compliant in its responsibility to pre-treat waste before sending for fianl treatment at the IAH’s facility, DEFRA should request Merial take further measures to ensure the virus is fully inactivated.

Published on Friday (7 September), the Final report on potential breaches of biosecurity at the Pirbright site 2007, concludes that an effluent pipe connecting the Merial facility to the final treatment plant which had been breached by tree roots is the most likely source of the outbreak.

This breach allowed effluent, carrying the live virus, to seep into the surrounding sub-soil before heavy rain brought the virus to the surface where it was picked up by the tyres of vehicles belonging to a construction firm working at the site.

The failure of the IAH to ensure these vehicles were subjected to any biosecurity measures being applied to these vehicles as they left the site allowed the virus to be carried along roads near the farms later to be infected.

DEFRA secretary of state Hilary Benn said it was unacceptable that the foot and mouth virus should escape, but stopped short of attributing any blame.

“What these reports do show is that the most likely explanation for this outbreak is a unique and unhappy combination of circumstances.

“The weaknesses in the drains, the heavy rain and floods, the building work taking place on the site, and the movement of vehicles.”

He added: “There can be no excuse for the fact that foot and mouth escaped from the Pirbright facility.

“It should not have happened, even in these extraordinary circumstances and it must not happen again.”

Asked who was responsible for the effluent pipe connecting the Merial facility to the final treatment work Mr Benn said that was an issue that had been disputed for many years.

“It may be that it has to be resolved by legal means,” he said.

The report made five basic conclusions regarding the condition of the pipework and its suitability to contain potentially hazardous material.  They are:

  • The existing effluent drainage system is not considered adequate as a containment against the release of animal pathogens.
  • The existing effluent drainage system does not meet the requirements for Defra Level 4 containment.
  • There is a strong possibility that contaminated material has leaked from the buried pipework, and into the surrounding ground. The subsequent transmission of this material may have been exacerbated by the porous nature of the surrounding
    medium.
  • The arrangements for discharge of the Merial sump into manhole FM1 leave the potential for overtopping of the manhole and release of material, dependant on the extant flow rate in the discharge line, and the number of pumps operating.
  • There is some evidence that some foul drainage may be discharging into the surface water lagoon, and this should be further investigated.