Why are we vaccinating badgers?
Bovine Tuberculosis (bTB), caused by the bacteria Mycobacterium bovis (M. bovis) is a major disease of cattle in many countries around the world. It is one of the most difficult and intractable animal health challenges the livestock sector in England faces today, causing considerable trauma for farmers and costing taxpayers over £100 million every year.
One of the many challenges with controlling M. bovis is the fact that the bacteria can also infect a wide range of wild mammal species. In the UK, it is the badger (Meles meles) which is the principal wildlife host for M. bovis, although wild deer may also play a role in some locations. Badger vaccination uses the BadgerBCG vaccine and aims to control the disease in badger populations, leading to healthier badger populations and reducing onward disease risks to cattle.
How do we vaccinate badgers?
The first important point to note is that badgers are a protected species, so vaccination requires a licence from Defra and Natural England with all trappers and vaccinators required to undertake specific training. As with most wildlife management, the first step is to undertake a survey, to map areas of activity (badger setts; latrines and runs) which provides data on badger distribution and abundance. Vaccination takes place during the season (1st May -31st Nov), with the vaccination process itself taking 2-3 weeks at each farm or vaccination site. The first stage of the process is burying bait (peanuts) in a series of ‘bait points’ close to areas of activity mapped in the earlier survey. Once this bait is being taken by badgers, cage traps are deployed and then pre-baited for several days, effectively training the badgers to enter the traps and take the bait. Once cages are regularly being hit, the traps are set to catch and checked at first light the following morning. The welfare of any trapped badgers is assessed to ensure the badger is safe to vaccinate, the vaccine is then administered via intramuscular injection into the back leg. All vaccinated badgers are given a fur clip and a spray of stock marker as a temporary mark to indicate they have been vaccinated. After another brief welfare assessment (to ensure there are no adverse reactions) the animal is released. Badgers are not knocked out or anaesthetised, instead the whole process is conducted through the bars of the cage trap. Some animals can become agitated in the trap, but often the badgers are quite calm or even asleep during the vaccination process.
What does the science say about badger vaccination?
There is good scientific evidence that vaccination significantly reduces the likelihood that badgers will become infected with M. bovis. In rigorous captive trials, vaccination has been shown to reduce the progression and severity of infection, leading to fewer TB lesions and reduced excretion of the bacteria. Field trials demonstrate that a large proportion of the badger population can be trapped and vaccinated. This will act to disrupt transmission, reducing the number of animals which are susceptible to infection and the likelihood they will spread the disease further. Vaccination of more than one third of adult badgers has also shown to reduce the likelihood that unvaccinated cubs become infected, which is evidence of ‘herd immunity’. Badger vaccination programmes typically run for four years such that coverage (the percentage of badgers vaccinated) will gradually increase over time. The vaccine therefore helps to keep TB free badger populations and also will drive down disease in populations where the disease already exists.
Fewer infected badgers in the landscape is good for badgers, and it can only be a good thing for cattle. Mathematical models looking at different options for wildlife control confirm that badger vaccine leads to fewer TB outbreaks in cattle, but proving this in the field is a challenge, partly because vaccination programmes in the UK so far have been relatively small scale. However, badger vaccination is steadily increasing in England with several large initiatives, including APHA delivered vaccination in several post-cull areas and a Defra funded project in East Sussex, supporting the local farming community to deliver vaccination over an area of 250km2. Large scale badger vaccination trials have also been conducted in Ireland and the results look quite encouraging. Badgers have been culled for many years in Ireland, but in several counties they conducted a trial to compare badger vaccination and badger culling over large areas. Both culling and vaccination were deemed to be equally effective at maintaining low TB rates in cattle and this has led to an increase in badger vaccination across the country. In England, we are moving to the next phase of our long-term strategy which will focus on widescale badger vaccination as the primary TB control measure in badgers. There are challenges to making this change, relating to the logistics of the process and to how badger vaccination is often perceived. Badger vaccination provides another tool in the toolbox of controls to reduce TB in cattle. As vaccination increases in the UK this will lead to more data, more evidence and increased awareness of the role it can play.
To learn more about badger vaccination visit www.TBhub.co.uk
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