The Randomised Badger Culling Trial (RBCT) was the first robust scientific evaluation of the effect of badger culling on cattle TB. It lasted 10 years and cost in excess of £50 million. It was overseen by an Independent Scientific Group (ISG).
Two culling treatments were undertaken: reactive culling where localised culls were carried out on farms that had recently experienced a TB outbreak in cattle, and proactive culling where larger scale areas were culled. Both these treatments were restricted to regions where the historical incidence of TB in cattle was high. In addition to culling, there were matched "control" areas where no culling was carried out. The principle is the same as we see in medical trials, where one segment of the population receives a treatment drug and another receives a placebo, the idea being that, at the end of the trial, any significant effects can be reliably ascribed to the treatment.
There were ten treatment areas for both the reactive and proactive culls, and ten matched controls. Each of the 30 experimental areas were about 100 square kilometres in area.
Reactive culling was stopped by government ministers when it was found that TB in cattle was getting significantly worse compared to the control sites. At the end of the proactive culls it was found that there were both positive and negative effects, whereby farms in the core of the culling area experienced a relative decrease of around 25% and farms on the edge of the culling area experienced a relative increase of around 25%, compared to the control areas.
The negative effects of both reactive and proactive culling were thought to be due to the disruptive effects of culling on the badger population, causing increased dispersal and movement by the remaining badgers and thereby exacerbating the spread of TB.
Taking account of the cost of culling, as well as the compelling results of the trial, the ISG concluded that badger culling can make no meaningful contribution to the control of TB in cattle in Britain. They recommended that the best way to combat the disease was to improve the detection and removal of TB in cattle themselves, mentioning that this would also improve the TB situation in badgers, since transmission can be both ways. They also recommended improvements in farm biosecurity to reduce the risk of transmission and continuing work to develop vaccines for both badgers and cattle.
Since the end of the proactive culling trial, the negative edge effects have waned and the positive effects have continued for longer. However, it is notable that the ISG have not changed their advice on culling. Indeed, the distinguished scientist Lord Krebs, who designed the RBCT, has dismissed the government's best estimate of their hoped for decrease in cattle TB of just 16% over nine years, as “not a very effective way of controlling the disease.”
"The vast majority of scientists with knowledge of the TB issue agree that culling badgers is not the solution to controlling TB in cattle."
Links to research papers
- DEFRA SCIENTIFIC INVESTIGATION REPORT
- BADGERS AND BOVINE TB
- TB CONTROL MEASURES ANNEX A
- TB CONTROL MEASURES ANNEX B
- FINAL REPORT
- DEFRA VACCINATING CATTLE
- INFORMATION ON KREBS AND RBCT
- DIVA REPORT AND STUDY BY WHELAN