A new analysis of the spread of Britain’s Foot and Mouth disease epidemic shows that extended culling programmes were essential for bringing the epidemic under control.
The study by researchers from Imperial College, London, which is fast-tracked to publication in the latest issue of the scientific journal Nature (4 October), also shows that the number of cases could have been reduced by 16 per cent (saving 30 per cent of animals culled) if the infected premises and contiguous premises cull policy had been fully implemented from 1 April.
The authors of the report call for continued vigilance in order to speed the elimination of the disease from Great Britain.
Professor Neil Ferguson, first author of the report, said:
"This is the most thorough analysis yet of the epidemic. It has enabled us to evaluate the different policies in turn and it clearly shows the need for a rapid and complete contiguous culling policy for disease control and eventual elimination."
The study also helps to explain why some regions were harder hit than others.
The researchers used geographical data representing the number of animals, the species of animal on the farms, and the fragmentation of the farms around the country to make highly predictive Foot and Mouth ‘risk maps’ of Great Britain.
The farm risk factors the maps identified include:
* large farms with many animals are significantly more infectious and susceptible than smaller ones
* cattle farms are most susceptible, sheep farms less so, and pig farms least susceptible
* fragmented farms - made up of scattered fields - are at much higher risk of transmission
Fragmentation, say the authors, is one reason why Cumbrian farms were so hard hit compared to those in Devon or Wales. Farms in Cumbria are significantly more fragmented and this led to increased transmission in the area, probably as a result of greater movement of people and vehicles between land parcels.
The analysis also leads to calculation of a new median distance of transmission of 4km, which, the authors say, "suggests that most transmission probably occurred through the movement of animals, personnel or vehicles, rather than through animal contact or windborne spread."
The UK risk maps also highlight areas of predicted high transmission risk such as the Derbyshire Dales and southwest Wales, which have not yet been affected.
"These areas in particular warrant heightened surveillance and continued vigilance in maintaining movement controls and biosecurity measures," said Professor Ferguson.
The Imperial team does not predict an end date for Britain to be clear of the epidemic. However they say that as colder conditions take hold, farmers need to be alert to the risks of relaxing controls in the coming months.
Dr Christl Donnelly, an author of the research, said:
"We would be very concerned if in the cooler months ahead there were a relaxation of movement restrictions and biosecurity controls."
"We will not have learnt the lesson of 1967 if restrictions are relaxed. As the weather gets cooler and the virus is able to survive longer, we are in danger of seeing significant outbreaks of the epidemic again," she said.
Materials provided by Imperial College Of Science, Technology And Medicine. Note: Content may be edited for style and length.
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