The recent outbreak of foot and mouth disease on two farms in Surrey was probably caused by leaky drains combined with heavy rain, building work and vehicles moving from a nearby laboratory, experts said today.
The Health and Safety Executive (HSE), which published its official report into the outbreak today, said it was "pretty clear" that the virus escaped from the Pirbright laboratories but said it was not possible to pinpoint whether the exact source was the Institute of Animal Health or Merial, which share the site.
HSE chief executive Geoffrey Podger said his team’s examination of the site showed "long-term damage" to the pipework of the effluent system, which could have allowed the disease to escape.
"It was absolutely essential that this pipework was fully contained, and it was not," he said.
He said the pipes showed damage from tree roots while unsealed manholes were also present.
In addition, building work and the movement of soil from the area of the damaged pipes were not being adequately controlled, and vehicles were able to move off site towards nearby farming land where the disease infected herds of cattle.
Mr Podger also said the drains were unable to cope with recent heavy rains, which could have helped the spread of the virus.
"It’s now pretty clear that the outbreak originated at Pirbright. It isn’t possible to pinpoint the exact source," he said.