Assessing effects from four years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle, 2013–2017

Abstract

The objective was to measure the association between badger culling and bovine tuberculosis (TB) incidents in cattle herds in three areas of England between 2013–2017 (Gloucestershire and Somerset) and 2015–2017 (Dorset). Farming industry-selected licensed culling areas were matched to comparison areas. A TB incident was detection of new Mycobacterium bovis infection (post-mortem confirmed) in at least one animal in a herd. Intervention and comparison area incidence rates were compared in central zones where culling was conducted and surrounding buffer zones, through multivariable Poisson regression analyses. Central zone incidence rates in Gloucestershire (Incidence rate ratio (IRR) 0.34 (95% CI 0.29 to 0.39, p < 0.001) and Somerset (IRR 0.63 (95% CI 0.58 to 0.69, p < 0.001) were lower and no different in Dorset (IRR 1.10, 95% CI 0.96 to 1.27, p = 0.168) than comparison central zone rates. The buffer zone incidence rate was lower for Gloucestershire (IRR 0.64, 95% CI 0.58 to 0.70, p < 0.001), no different for Somerset (IRR 0.97, 95% CI 0.80 to 1.16, p = 0.767) and lower for Dorset (IRR 0.45, 95% CI 0.37 to 0.54, p < 0.001) than comparison buffer zone rates. Industry-led culling was associated with reductions in cattle TB incidence rates after four years but there were variations in effects between areas.

Temporal and spatial Mycobacterium bovis prevalence patterns as evidenced in the All Wales Badgers Found Dead (AWBFD) survey of infection 2014–2016

“…The Krebs Randomized Badger Culling Trial (RBCT) remains the key source of empirical information on this issue; the resulting report concluded that in areas where there was high incidence of bTB there was compelling evidence that badgers were a significant source of infection in cattle 1 . Recent evidence suggests that industry led culling of badgers in England was associated with reductions in cattle TB incidence rates after four years but there were variations in effects between cull areas 7 .…”

Mycobacterium microti: Not Just a Coincidental Pathogen for Cats

“…However, wildlife reservoirs play an important and sometimes unpredictable role in disease transmission to farm animals, e.g., badgers in the UK ( 4 ), possums in New Zealand ( 5 ), or wild boars in Spain ( 6 ). The control of such animal reservoirs can directly influence the prevalence of human TB, as seen in New Zealand ( 7 , 8 ) or the UK ( 9 ).…”

Open letter to the prime minister regarding badger cull licences

“…Badger killing is ineffective. Downs and others1 used mathematical modelling to claim that, up until September 2017, the bovine tuberculosis (bTB) situation in cattle in their studied areas of the Gloucestershire pilot cull zone had improved after four years of culling – and this was much trumpeted as a success story by ministers. However, analysis of subsequent data released by APHA2 demonstrated that both the prevalence and incidence of disease in cattle herds in the Gloucestershire pilot cull zone were higher following five full years of culling than before culling began 3.…”

“…While incidence had fallen in the Somerset pilot cull zone, prevalence among cattle herds remained static over this period, and in the Dorset pilot cull zone the prevalence increased by 20 per cent over three years of culling. If the analysis performed by Downs and others1 were to be repeated to include the more recent data, very different conclusions would ensue.…”