Vaccination of badgers will prevent badgers from contracting Bovine TB from cattle and prevent them having the ability to infect other badgers, thus removing them from the chain.
Vaccinating badgers reduces the severity of the disease in those that become infected after vaccination. The only vaccine that is currently available for use against TB in any species, including humans, is Bacille Calmette– Guérin (BCG). The only difference between the human BCG and the Badger BCG (the UK licensed vaccine for badgers) is that the dose given to badgers is higher than that given to humans. Scientific research has been carried out which demonstrated that the BCG was safe for use in badgers.
This was necessary in order for the vaccine to be licensed for use by the Veterinary Medicines Directorate. Only a proportion of the susceptible population (that is, those that are not already infected with bovine TB) need to benefit from the protective effects of the vaccine in order to reduce the prevalence of infection in the population. This is known as herd immunity and works on the principle that if some of the population are protected from the disease, it is less likely that an infected individual will come into contact with a susceptible individual, therefore, the disease is less likely to be passed on. Obviously, the higher the proportion of protected individuals there are in a population, the lower the number of animals that could become infected.
Currently, the only available vaccine is an injectable one. Badgers are trapped in cages, injected with the vaccine then released. Cage trapping of badgers has been undertaken for over 30 years. Research has shown that, when trapping is carried out by properly trained and experienced personnel, the number of badgers injured in cage traps is very low, with the majority of those injured only suffering minor abrasions. Whilst the programme of work has been designed to minimise the time required on delivering licensed vaccines, research by its nature takes time and much of the work has to be carried out sequentially. There are defined steps in obtaining a licence, or Marketing Authorisation, from the Veterinary Medicines Directorate for vaccines, which include studies to demonstrate both vaccine safety and efficacy.
New diagnostic tests for badgers had to be developed initially, starting in 1999, to enable badger vaccine research to begin. Defra has been funding research into TB vaccines for use in cattle and badgers since 1998, and the total investment in vaccine development has reached more than £30 million. Defra has been working alongside the Veterinary Laboratories Agency, which leads the vaccine research on Defra’s behalf, and The Food and Environment Research Agency (Fera), which has over 30 years experience of trapping and injecting badgers. Defra also maintains close links with international researchers particularly in the Republic of Ireland and New Zealand.
Defra and the VLA are also working in close co-operation with researchers working on new vaccines for TB in humans. As with any vaccine, not all vaccinated individuals will be fully protected. However, laboratory studies indicated that in common with other species, BCG vaccination did significantly reduce the overall disease burden.
A recent field study of wild badgers showed that of the badgers that tested negative for TB at the outset, vaccination led to a significant reduction in the incidence of positive responses to a blood test that we know is a good indicator of the extent and severity of TB infection. They are currently carrying out research into oral vaccination of badgers in Ireland and injectable and oral vaccination of possums in New Zealand. There is research currently underway in the UK in developing an oral vaccine bait for use in badgers; the possibility of a usable oral badger vaccine is approximately two years away. The vaccine is as effective as the injectable one and is currently undergoing safety tests for its licence.
TB or not TB: an answer to the culling question - Irish Times Research has demonstrated that vaccination reduces the severity and progression of TB in badgers that were experimentally infected with Bovine TB after vaccination. BCG vaccination also reduced the amount of bacteria excreted in urine, faeces and other clinical samples. Badgers are not reservoirs for Bovine TB as they cannot self perpetuate the disease within their species. Bovine TB will naturally die out within the badger population.
Defra agreed that the badger contribution is at best small. It is hoped that improved cattle testing will reduce the incidents of bTB in the herd.