Background information: the science of badgers, cattle and TB

What is the most reliable and up-to-date evidence on this subject?

The most comprehensive study into badgers, bovine TB and cattle was conducted by an independent research group, the Independent Scientific Group (ISG), who were funded by DEFRA. The ISG were a group of expert scientists chosen for their specialist knowledge of badgers, ecology, epidemiology, and statistics. They devised a large scale experiment to assess the effects of badger culling on the spatial distribution of bovine TB infection in badgers and cattle. This experiment took place between over 7 years (1998 – 2005) and cost in the region of £50 million.

How did they study the effects of culling badgers on bovine TB incidence in cattle?

They measured the effects of three different treatments on the incidence of bovine TB in cattle:

• Widespread ‘proactive’ culling (as many badgers as possible were killed to maintain low badger densities across the area every year),

• Localized ‘reactive’ culling (badgers were only killed in areas where there were outbreaks of bovine TB in cattle locally),

• No culling (no badgers were killed in these areas).

To ensure that the experiment was reliable, each treatment was replicated ten times in areas covering approximately 100km2, giving a total of 30 trial areas covering 3000km2.

They recorded badger activity and the number of road killed badgers in each trial areas and all culled badgers were examined and tested for bovine TB. Cattle were also tested for bovine TB during routine veterinary surveillance. A total of 11 000 badgers were killed during this experiment.

What did they find?

Proactive culling significantly reduced badger density in all 10 trial areas, and also reduced the incidence of bovine TB in cattle in these areas. However, in the areas adjacent to culled areas the incidence of bovine TB actually increased (Woodroffe et al. 2007. Journal of Animal Ecology. 78, 818-827). Importantly, even in the pro-active culling areas bovine TB was not fully eradicated in cattle despite the continued removal of badgers over many years (Jenkins et al. 2007Journal of Applied Ecology. 44, 897-908).

 What did the Independent Scientific Group finally conclude?  

“The ISG’s work, much of which has already been published in peer-reviewed scientific journals has reached two key conclusions. First, while badgers are clearly a source of cattle TB, careful evaluation of our own and other’s data indicates that badger culling can make no meaningful contribution to cattle TB control in Britain. Indeed, some policies under consideration are likely to make matters worse. Second, weaknesses in cattle testing regimes mean cattle themselves contribute significantly to the persistence and spread of the disease. Scientific findings indicate that the rising incidence of disease can be reversed and geographic spread contained, by the rigid application of cattle-based control measures”

Bourne et al. 2007. Bovine TB: the Scientific Evidence. A Science Base for a Sustainable Policy to Control TB in Cattle. Final Report of the Independent Scientific Group on Cattle TB

A further study, carried out after the cull, stated that any ongoing benefits of the cull were still only “modest” (Jenkins et al. 2008.International Journal of Infectious Diseases. 12, 475-465). This study also states publicly that significant proactive badger culling prevented only 12 confirmed breakdowns over 6 years (there would be expected to be 130 herd breakdowns per year in the absence of a cull). From a business point of view, the costs of culling exceeded the savings achieved through reduced incidence of herd break down derived from culling badgers (Bourne et al. 2007; Jenkins et al. 2008). This is clearly unsustainable from an economic point of view. Further data published in 2010 still found "reductions in cattle TB incidence achieved by repeated badger culling were not sustained in the long term after culling ended and did not offset the financial costs of culling" (Jenkins 2010). These data on the longer term impacts of the RBCT continue to be gathered and future trends may alter our understanding of the impacts of culling.

Other Important Information

It has been highlighted many times that many other British wildlife species including red deer, fallow deer, fox, polecat, wood mouse and rat can also all carry bovine TB. Eradicating badgers cannot eradicate bovine TB as it is present in other species. Fallow and red deer are considered to present the highest risk when you take into account disease pathology and likelihood of transmission, and then only when they are in high densities. Less is known about the epidemiology of the disease in other mammals but it is likely that in some cases they are end hosts, and not transmitting the disease back to cattle.

The Wildlife Trust of South and West Wales (WTSWW) knows that bovine TB (bTB) in cattle is a significant problem for farming in Wales, and that urgent action is required to combat the disease. The Wildlife Trusts, as a stock owners and managers, recognise the serious disruption and anxiety caused to farmers experiencing a herd breakdown. We particularly recognise the important role that the livestock industry can play in the environmentally-sensitive management of the countryside.

What is the most reliable and up-to-date evidence on this subject?

The most comprehensive study into badgers, bovine TB and cattle was conducted by an independent research group, the Independent Scientific Group (ISG), who were funded by DEFRA. The ISG were a group of expert scientists chosen for their specialist knowledge of badgers, ecology, epidemiology, and statistics. They devised a large scale experiment to assess the effects of badger culling on the spatial distribution of bovine TB infection in badgers and cattle. This experiment took place between over 7 years (1998 – 2005) and cost in the region of £50 million.

How did they study the effects of culling badgers on bovine TB incidence in cattle?

They measured the effects of three different treatments on the incidence of bovine TB in cattle:

• Widespread ‘proactive’ culling (as many badgers as possible were killed to maintain low badger densities across the area every year),

• Localized ‘reactive’ culling (badgers were only killed in areas where there were outbreaks of bovine TB in cattle locally),

• No culling (no badgers were killed in these areas).

To ensure that the experiment was reliable, each treatment was replicated ten times in areas covering approximately 100km2, giving a total of 30 trial areas covering 3000km2.

They recorded badger activity and the number of road killed badgers in each trial areas and all culled badgers were examined and tested for bovine TB. Cattle were also tested for bovine TB during routine veterinary surveillance. A total of 11 000 badgers were killed during this experiment.

What did they find?

Proactive culling significantly reduced badger density in all 10 trial areas, and also reduced the incidence of bovine TB in cattle in these areas. However, in the areas adjacent to culled areas the incidence of bovine TB actually increased (Woodroffe et al. 2007. Journal of Animal Ecology. 78, 818-827). Importantly, even in the pro-active culling areas bovine TB was not fully eradicated in cattle despite the continued removal of badgers over many years (Jenkins et al. 2007Journal of Applied Ecology. 44, 897-908).

 What did the Independent Scientific Group finally conclude?  

“The ISG’s work, much of which has already been published in peer-reviewed scientific journals has reached two key conclusions. First, while badgers are clearly a source of cattle TB, careful evaluation of our own and other’s data indicates that badger culling can make no meaningful contribution to cattle TB control in Britain. Indeed, some policies under consideration are likely to make matters worse. Second, weaknesses in cattle testing regimes mean cattle themselves contribute significantly to the persistence and spread of the disease. Scientific findings indicate that the rising incidence of disease can be reversed and geographic spread contained, by the rigid application of cattle-based control measures”

Bourne et al. 2007. Bovine TB: the Scientific Evidence. A Science Base for a Sustainable Policy to Control TB in Cattle. Final Report of the Independent Scientific Group on Cattle TB

A further study, carried out after the cull, stated that any ongoing benefits of the cull were still only “modest” (Jenkins et al. 2008.International Journal of Infectious Diseases. 12, 475-465). This study also states publicly that significant proactive badger culling prevented only 12 confirmed breakdowns over 6 years (there would be expected to be 130 herd breakdowns per year in the absence of a cull). From a business point of view, the costs of culling exceeded the savings achieved through reduced incidence of herd break down derived from culling badgers (Bourne et al. 2007; Jenkins et al. 2008). This is clearly unsustainable from an economic point of view. Further data published in 2010 still found "reductions in cattle TB incidence achieved by repeated badger culling were not sustained in the long term after culling ended and did not offset the financial costs of culling" (Jenkins 2010). These data on the longer term impacts of the RBCT continue to be gathered and future trends may alter our understanding of the impacts of culling.

Other Important Information

It has been highlighted many times that many other British wildlife species including red deer, fallow deer, fox, polecat, wood mouse and rat can also all carry bovine TB. Eradicating badgers cannot eradicate bovine TB as it is present in other species. Fallow and red deer are considered to present the highest risk when you take into account disease pathology and likelihood of transmission, and then only when they are in high densities. Less is known about the epidemiology of the disease in other mammals but it is likely that in some cases they are end hosts, and not transmitting the disease back to cattle.

The Wildlife Trust of South and West Wales (WTSWW) knows that bovine TB (bTB) in cattle is a significant problem for farming in Wales, and that urgent action is required to combat the disease. The Wildlife Trusts, as a stock owners and managers, recognise the serious disruption and anxiety caused to farmers experiencing a herd breakdown. We particularly recognise the important role that the livestock industry can play in the environmentally-sensitive management of the countryside.

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