The culling of badgers in the UK has been a hotly debated topic over recent months. Many local governments are under the impression that these culls may, in fact, decrease the spread of Mycobacterium bovis from badger to cattle (Donnelly, et al., 2005). M.bovis is a bacterium that causes bovine tuberculosis (bTB) in cattle. Bovine TB is zoonotic and is easily transmitted from cattle to humans, the incidence rate of which is thought to have increased since the 1980’s (Woodroffe, et al., 2006). It is thought that the European badger (Meles meles), a protected species, is a reservoir for this disease (Woodroffe, et al., 2006).
Figure 1. Schematic diagram illustrating the transmission routes of bovine tuberculosis (Jack, et al., 2008).
Disease transmission
The disease in cattle is hard to diagnose as the symptoms mimic those found in many other diseases. Cattle infected with bTB will usually exhibit prolonged weight loss, present with a recurring light fever, and suffer fatigue with associated weakness and a lack of appetite (Pollock, et al., 2005). Other diagnostic symptoms include swelling of the lymph nodes (usually those located in the neck), a cough that is moist and appears worse in the morning or after exercise and chronic mastitis which is an infection of the udder in female cows that cannot be cured by administering conventional antibiotics (Department for Environment, 2014). Humans are at risk of catching bTB through consumption of unpasteurised milk products that have been obtained from infected cattle, the inhalation of bacteria that have been exhaled by infected cattle and also the inhalation of bacteria expelled from the carcasses of infected cattle or from their faeces and other excretions (O’Hagan, et al., 2010-2011). There has been a steady increase in geographical range of bTB since the foot and mouth disease (FMD) epidemic in 2001 (Vial, et al., 2013).
Detrimental Effects of bTB
Bovine tuberculosis has a major effect on the agricultural industry, with farmers losing thousands in revenue when infected cattle are culled. There are many control strategies in place to try and curb the transmission of this disease, although to date none have proven to be 100% effective (Moustakas & Evans, 2015) (Figure 2).. From around the 1950’s preventative methods included routine testing of cattle, with infected cattle immediately slaughtered and the movement of livestock on the farm restricted (Menzies & Neill, 2000). This method proved successful and most of the UK remained infection free, although sites of infection still persisted in some areas where European badgers were present (Donnelly, et al., 2007).
Figure 2.Figure highlighting the problem with badger culling and the knock on effects (BBCWildlife, 2015)
To cull or not to cull
Badger culling was then enforced despite public protest (Figure 3) and has been an element in the UK control strategy for a number of years. Despite many field trials on a large scale, badger culling has been linked to both an increase and decrease in the incidence of bTB in cattle. It is thought that repeated culling within the same boundaries can, in fact, increase the transmission rate of bTB. This is due to the disruption of the badger’s natural habitat, causing infected badgers to colonise new areas, with some badgers actually recolonising their previously culled habitats (Woodroffe, et al., 2006). Organisations such as the Royal Society for the Prevention of Cruelty to Animals (RSPCA) are against badger culling, calling it wrong and cruel, and it is thought that the cull will actually cost more money than the cattle it would save costing around £2500 per hectare, and it will only be successful in the short term (Ericson, 2013). Even with these culling efforts, the incidence rate of bTB continues to rise (Wilkenson, et al., 2003).
Figure 3. Photograph highlighting the local opposition to the badger cull in Gloucestershire (Moody, 2013)
Vaccine Development
Development of a vaccine for both cattle and badgers appears to be the most popular option, especially favoured by organisations such as RSPCA as it is a more humane way to deal with the current issue. An oral bait vaccine is preferred rather than trapping badgers and distributing the vaccine individually as this decreases the cost significantly (Wilkenson, et al., 2003). In a trial conducted in Cornwall by Prof. Rosie Woodroffe, the bTB vaccine proved to be effective.
Figure 4. A Badger receiving the BadgerBCG vaccine against tuberculosis (Case, 2015)
Through trials on badgers the vaccine has reduced the risk factor and is thought to also have the potential to reduce the spread of the disease. Within this trial eighty badgers were given the vaccination between September and November and there is hope that within the next few years up to 1,000 badgers will receive the vaccine. This project, which has been running 7 years, has cost around £1m and the funding has been provided by the Badger and Cattle Vaccination Initiative, The National Trust and also through fundraising. The Trials and vaccinations were provided for free by DEFRA (the Department for Environment, Food and Rural Affairs). A vaccine plan as outlined in EFRA Select Committee’s Tenth Report of 2007-08 showed the timescale as per Figure 5.
Figure 5. Schematic of the timescale vaccine plan as outlined in EFRA Select Committee’s Tenth Repost of 2007-08 (Jack, et al., 2008)
Conclusion
The estimated cost for the vaccination programme stands to be around £7-£8 million for badgers and around £10-£12 million for cattle (Jack, et al., 2008). Even with these high estimation costs for a preventative vaccination method it could still prove to be more economic in the long run to vaccinate rather than cull. BBC news reported that, on average, it costs approximately £4,121 per badger killed in a cull, with the culls that have already occurred in Somerset and Gloucestershire already costing £7 million. These culls aim to kill around 70% of the badger population (BBC, 2014). With recolonising still such a huge risk after a cull, the vaccine appears to be a more sensible approach to curbing the transmission rate of bTB and has the support of the general public and the majority of farmers.
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