New research published on badger TB spread
New data released by Imperial College London suggests that herd-to-herd transmission of bovine tuberculosis (bTB) is responsible for 94 per cent of cases.
Scientists from the college say that in areas where prevalence of bTB is high, badgers could ultimately be responsible for around 50 per cent of cases in cattle.
However, only 5.7 per cent of cattle infected with bTB caught the disease directly from badgers, according to a paper published in the journal PLOS Currents: Outbreaks. The remaining spread comes from cattle infected by badgers passing the disease on to other herds.
These new estimates are based on data from the Defra-funded Randomised Badger Culling Trial (RBCT), which ran from 1998 to 2005. This trial found that culling could reduce bTB within herds in the areas where culling took place, but increase prevalence of the disease in nearby areas.
Using mathematical models based on data from the RBCT, scientists previously estimated the proportion of TB in cattle that could be attributed to transmission from badgers. Researchers at Imperial College London say they have carried out a more in-depth analysis.
Whilst the research team says that badgers ultimately account for around 50 per cent of bTB in cattle in high prevalence areas, they note that "considerable uncertainty" surrounds this figure. Authors of the research paper give 38 per cent as a robust minimum estimate.
Professor Christl Donnelly from the college said: "These findings confirm that badgers do play a large role in the spread of bovine TB. These figures should inform the debate, even if they don't point to a single way forward."
The role of badgers in spreading bTB is widely debated and pilot culls in Gloucestershire are ongoing. After a similar pilot in Somerset recently failed to meet the target of reducing the badger population by 70 per cent, it has been announced that Natural England has granted a three-week extension of the cull.
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