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Wildlife and TB
From Department of Agriculture, Food and the Marine
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The bacteria which causes bovine tuberculosis, Mycobacterium bovis, can infect many different species of mammals including wildlife. In most cases, wildlife species are infected by spillover of disease from infected cattle and they do not play a role in maintaining the disease or passing it back to cattle.
Badgers, however, have been shown to play an important role in spreading TB to cattle in Ireland. In order to eradicate TB in cattle, it is therefore necessary to address the risk posed by TB in badgers. DAFM does this through:
- Removing badgers from areas where there are severe TB outbreaks in cattle which have an epidemiological link to badgers.
- Vaccinating badgers in areas where the risk posed to cattle by infected badgers has been brought under control.
- By reducing the risk to cattle, these policies help farmers and reduce the overall levels of bovine TB.
Research carried out on TB in deer in Ireland had found that in certain areas where there are high densities of deer, cattle and badgers living alongside each other, the same strains of TB can circulate between them. However, there is currently no evidence that deer play a significant role in the spread of TB to cattle in most parts of Ireland. Where significant outbreaks of TB occur in cattle and deer are suspected of playing a role, DAFM enables farmers to understand this risk by:
- Facilitating local farmers and hunters to work together to reduce deer numbers
- Testing a sample of deer carcases obtained through this approach for TB infection
Badgers were first identified as being susceptible to infection with Mycobacterium bovis (M.bovis), the bacterium that causes bovine tuberculosis (bTB), during the 1980s. DAFM funded research in the East Offaly area and other studies which concluded that badgers were likely to have been involved in the cycling of bTB in cattle and concluded that eradication of bTB from the national herd would not be feasible until TB in badgers was addressed and controlled.
DAFM funded studies which evaluated the effects of culling badgers, and these culminated in the Four Area Study (1997-2002) in which removals of different intensities were carried out and compared in areas in counties Cork, Donegal, Kilkenny and Monaghan. The study concluded that lowering badger densities in areas resulted in reduced incidences of bTB in those areas.
Informed by the research findings of the previous decades, and agreed as part of the 2000 partnership agreement, Program for Prosperity and Fairness (PPF), the Government agreed that all future serious occurrences of bTB in cattle w
ould be investigated by state veterinarians and where evidence was found that pointed to badgers being involved in the TB problem locally, then measures would be taken to reduce the risk from badgers. Government, through DAFM, also committed to supporting research aimed at testing available vaccines and vaccine delivery systems, with a view to advancing vaccination of badgers against bTB to a point where it could be delivered nationally and would be a feasible substitute for badgers requiring to be culled.
Commencing in 2002, systems were put in place in every Regional Office area in the country whereby serious breakdowns of bTB (i.e. breakdowns having 3 or more skin test reactors) were investigated by a state veterinarian. If evidence was established of infection being introduced by badgers , this would trigger a survey in the area adjacent to the diseased herd for signs of badger activity and seek to identify the location of badger’s underground burrows, called setts. A targeted removal program would follow the completion of these surveys which involved trapping/removing badgers within a 2Km radius of the affected farm, and by this means the local badger densities would be maintained at an average of 0.5 badgers Km2, which is below the 2-3 badgers Km2 normally found in the areas of Ireland where cattle are grazed/farmed. By 2016 roughly one third (33%) of the agricultural land of the country was part of DAFMs wildlife program area, and maintaining the local badger populations at the 0.5 badgers Km2 target resulted in roughly 6000 badgers being removed each year. While this policy was very successful in terms of contributing to the lowering of bTB levels in cattle, it isn’t sustainable in the longer term due to the risk that badgers numbers could become excessively low.
DAFMs badger vaccine research program, which commenced in 2002, has also been very successful, and the results have informed and supported the development of the current badger vaccine policy. It proved that Bacillus Calmette–Guérin vaccine (BCG) (which is used in humans) can be used in badgers to generate sufficient immunity to address the risk of TB. Since 2002 DAFM funded research has focused on establishing if BCG protects badgers and how it might be delivered most efficiently to badgers. BCG was first proven to protect badgers challenged with M.bovis in a laboratory setting, and this was followed up with a large field trail carried out in a 755 Km2 area in Kilkenny over the period 2009-2012. This trial showed that BCG did protect vaccinated badgers in the wild, and that it provided levels of protection (the scientific term is efficacy) of 60% (i.e. 6 out of 10 vaccinated badgers are protected by BCG). A complimentary trial (Non-Inferiority Trial) ran in areas in six (6) counties during the period 2014-2017, where capture/vaccination/release of badgers in areas was compared with capture/remove in other areas in the same counties and this trial has shown that vaccination/release can be substituted for long-term continuous culling of badgers once the densities of badgers in a bTB endemic area are first reduced by the targeted culling program which is implemented by DAFM.
The Minister of Agriculture, Food and the Marine, Michael Creed, announced in February 2018 that the policy of vaccination of badgers is now part of the TB eradication programme; this will eventually replace a majority of the current culling program. Beginning by expanding the vaccination areas in the initial counties where vaccine is used (counties Cork, Galway, Kilkenny, Longford, Louth, Monaghan, Tipperary and Waterford) substituting vaccination for culling will be a rolled out, on a phased basis, to every county over a period of years. The removal of badgers from areas with severe cattle TB outbreaks which are epidemiologically linked to badgers will continue where necessary to reduce the risk of TB to cattle and the level of TB in the badger population.
Converting the current unvaccinated population of badgers in bTB endemic areas to a predominantly vaccinated badger population will result in fewer TB infected badgers and fewer instances of badgers infecting other badgers or cattle, and so will ultimately facilitate the final eradication of bTB from Ireland’s cattle population.
