Q&A: The badger cull
- 23 October 2012
- From the section Science & Environment
The government has announced a delay to the timetable for the culling of badgers in England.
The proposals would have seen thousands of badgers shot by trained marksmen in two pilot zones in the South West this autumn.
But the plan has been beset by problems. Surveys found more badgers that expected in the two areas, increasing the cost of the cull and making it more difficult to complete before badgers go underground for the winter.
Wildlife campaigners launched a last minute legal challenge, while an e-petition signed by more than 150,000 people spurred a parliamentary debate set for Thursday.
The proposals are designed to tackle the problem of TB in cattle, which cost more than £90m last year and led to 26,000 cattle being slaughtered.
Q: What is cattle TB?
A: Bovine tuberculosis (TB) is an infectious disease of cattle. It presents a serious problem for the cattle industry, causing financial and personal hardship for farmers.
The disease is caused by the bacterium Mycobacterium bovis (M. bovis), which can also infect and cause TB in badgers, deer and other mammals.
Q: What happens to cattle with TB?
A: The clinical signs of bovine TB include weakness, coughing and loss of weight. However, these symptoms are seldom seen on farms as cattle are regularly tested for TB and then destroyed if they test positive.
Q: Why are badgers implicated in spreading TB?
A: Scientific evidence has shown that bovine TB can be transmitted from cattle to cattle; from badgers to cattle and cattle to badgers; and from badger to badger. Badgers are thought to pass on the disease to cattle through their urine, faeces or through droplet infection, in the farmyard or in cattle pastures. However, it is not clear how big a role badgers play in the spread of bovine TB since the cows can also pass the disease on to other members of the herd.
Q: What is the main scientific evidence for and against culling badgers?
A: The most extensive scientific evidence comes from a £50m study in England on whether culling badgers reduces bovine TB, known as the randomised badger culling trial or the Krebs trial. The data suggests that if certain conditions are met, culling could reduce disease incidence by an average of 16% over nine years, although it could be higher or lower.
This figure takes into account both decreases in the number of new cases of TB within the cull zone, and an increase in cases outside - the so-called perturbation effect.
The badger culling trial in England found that killing badgers disrupted their social groups, with badgers moving further afield to establish new groups, taking TB with them. This perturbation effect led to an increase in cases of bovine TB outside of the cull zone, although the impact diminished over time.
The pilot culls are attempting to use borders such as rivers and motorways to reduce the risk of badgers spreading TB to neighbouring areas, but this approach has not been fully tested.
Also, the Krebs trial trapped badgers in cages for the cull, while the main method planned for Gloucestershire and Somerset is free shooting. Any deviation from methods used in the original trial will decrease or increase the expected impact on bovine TB, say scientists.
As independent scientists have pointed out, "badger culling has positive and negative effects on bovine TB in cattle and is difficult, costly and controversial" .
Q: How will badgers be culled?
Trained marksmen will shoot the badgers at night after putting food such as peanuts outside their setts. This method has not been formally tested before. In Ireland, badgers are caught with a snare, before being shot. The badger culling trial in England trapped badgers in cages before shooting them.
According to one newspaper report, cage-trapping badgers for vaccination (or shooting) costs about £2,500 per hectare, whereas shooting them as they run freely costs about £200.
Q: How will the success of the pilot culls be measured?
The pilot culls will look at whether badgers can be killed effectively and humanely, not at any scientific data. A government agency will carry out some sample post mortems to see if the badgers have been shot humanely. The carcasses will not be tested for signs of TB infection. On the basis of this evidence, ministers will make a decision about whether or not to extend the pilots.
Q: What are the costs of TB?
TB has cost the taxpayer in England £500m to control the disease in the last 10 years. According to the UK Government Department for Environment, Food and Rural Affairs (Defra), each pilot cull will cost about £100,000 a year, with the costs met by farmers who want badgers to be killed on their land.
Policing costs have been estimated at £0.5m per area per year, according to a written answer to parliament.
Q: What is happening in Wales, Scotland and Northern Ireland?
Scotland is classified as free of TB. The Welsh Assembly Government has chosen to vaccinate badgers, with trials underway in north Pembrokeshire.
Northern Ireland is conducting research into an eradication programme involving vaccination and selected culling of badgers with signs of TB infection.
The Republic of Ireland has been culling badgers since the 1980s. One study, known as the Four Areas Trial, found reductions in cattle TB incidence ranging from 51% to 68% over a five-year culling period. Culling is still underway, so there is no data that can be compared with the study in England.
Q: What can we learn from TB outbreaks in other countries?
TB is not confined to the UK. Transmission between other wildlife species has been documented in Michigan, US, with white-tailed deer and cattle. In New Zealand the brush tail possum is thought to harbour bovine TB, and is killed using poison and traps.
Q: What other measures can be taken to combat TB?
Other measures to reduce transmission include improved bio-security, particularly stopping badgers from getting into farm buildings where they can come into contact with cattle, or feed stores. According to a recent review of scientific evidence: "Recent Defra data indicates that the average cost to farmers to improve bio-security is about £4,000. Considering the average cost of dealing with a TB herd breakdown in GB (about £27,000), these measures would appear to be a cost-effective way of attempting to reduce potential TB transmission between species."
Q: Can badgers or cows be vaccinated?
There is a vaccine for badgers - the BCG jab, which has been used by a number of wildlife and conservation bodies in England, including the Gloucestershire Wildlife Trust, the RSPB, the Wildfowl and Wetlands Trust and the National Trust.
Badger vaccination is also underway in Wales, and there are plans to introduce it in Northern Ireland.
According to the Food, Environment and Research Agency (Fera): "Vaccinating badgers is a risk reduction measure. It reduces the risk of badgers catching TB, resulting in fewer infected badgers. This in turn may reduce the risk of transmission from badgers to cattle."
Cattle can also be vaccinated with the BCG vaccine. However, vaccination of cattle against TB is currently prohibited by EU legislation, mainly because BCG vaccination of cattle can interfere with the tuberculin skin test, the main diagnostic test for TB.
Vaccination is not effective in badgers or cattle that are infected with TB.