Leaky Drain Led To Foot And Mouth Outbreak

The Health and Safety Executive (HSE) has today published its final report into potential breaches of biosecurity at the Pirbright site. The report concludes HSE’s investigation following the outbreak of Foot and Mouth Disease (FMD) in Surrey on 3 August. The report can be viewed at: hse.gov.uk/news/archive/07aug/finalreport.pdf HSE Chief Executive Geoffrey Podger said: "During our investigation we established that it was possible for the live virus strain - O1BFS - to enter the site effluent drainage system. We judged it likely that waste water containing the live virus, having entered the drainage pipework, then leaked out and contaminated the surrounding soil. This conclusion is supported by evidence of long term damage and leakage, including cracked pipes, tree roots breaching pipework, and unsealed manholes. We also believe that excessive rainfall in July may have increased the potential for virus release from the drain. "Our report shows that during the period of our investigation both human and vehicle movements at Pirbright were not adequately controlled. We conclude that failure to keep complete records was not in line with accepted practice and represents a breach in biosecurity at the site. In particular, vehicles associated with ongoing construction work had relatively unrestricted access to the site. In our opinion, these construction activities - very near to the effluent drainage system - are likely to have caused disturbance and movement of soil in a way that contaminated some of the vehicles with the live virus. We established that some of the vehicles, probably contaminated, drove from the site along a road that passes the first infected farm. We conclude therefore that this combination of events is the likely link between the release of the live virus from Pirbright and the first outbreak of FMD. "We have drawn our concerns about the breaches of biosecurity, together with a number of recommendations, to the attention of the Pirbright site regulator - Defra - so that they can be rectified." HSE and Defra have today issued a co-ordinated safety alert to employers conducting work on pathogens in hazard groups 3 and 4 as a reminder of the measures needed to ensure primary and secondary containment. Geoffrey Podger continued: "This safety alert is to draw employers’ attention to issues arising from our investigation which need wider dissemination and action. Although these issues already form part of the basis on which such sites are permitted to operate, the purpose of the alert is simply to remind operators of their obligations. Both HSE and Defra will be reviewing these issues during their usual regulatory visits with the priority attention focused on sites handling hazard group 4 pathogens." HSE led the investigation given its investigatory expertise and parallel experience as the biosecurity regulator of human pathogen laboratories. HSE does not regulate any part of the Pirbright site in this respect. Three organisations operating at the site – the Institute for Animal Health (IAH), Merial Animal Health Ltd (Merial) and Stabilitech Ltd (Stabilitech) - all worked with varying amounts of the live virus strain - O1BFS - that caused FMD in the first infected herd in Surrey. Results of sequencing tests commissioned as part of the investigation indicate that this strain is highly likely to have originated from the Pirbright site. However, due to very small differences in the strains used by the three organisations, it has not been possible to pinpoint precisely the exact origin of the virus found in the infected animals. The HSE final report also addresses lines of enquiry that had focused on other containment arrangements at Pirbright, namely solid waste disposal, airborne routes through the fabric of site buildings or faults in filtration, and human movements. HSE concludes that there was no evidence of:

• any breakdown of containment systems for solid waste disposal at Pirbright;
• a biosecurity failure that could have led to the virus strain being released from the site to the atmosphere; and
• biosecurity arrangements having been breached through the malicious intent of staff.

This has been a complex, thorough and exhaustive investigation carried out and completed within four weeks.

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