What is the situation with TB in the UK?
Bovine Tuberculosis (bTb) is a disease that is highly infectious and effects the respiratory abilities of cattle. The disease is spread by the bacterium Mycobacterium bovis, and leads to lesions growing in the lungs of the infected cattle or any of the other of the wide range of mammals that are susceptible to the disease. At this stage there is no known cure for bTb and no legal or useful (more on that to come) vaccination. When a cow is found to have been infected with Tb it is killed, as the disease is highly infectious farmers and cattle suffer greatly from an outbreak. Since January 1st 2008 278,263 cattle have been culled in Great Britain because of bTb.
Badgers, Cattle And TB.
Aside from Cattle bTb can also infect a wide range of mammals, including Badgers. As the research stands now we know that bTb does pass between populations of Badgers and Cattle, though we know little about how this infection is actually happening. It appears now that Cattle can contract bTb from both direct and indirect contact with infected Badgers. It is very unclear how many outbreaks of bTb amongst cattle are due to Badger contact, the most up to date studies estimate that roughly 50% of outbreaks can be related to Badgers, but the number directly caused by Badgers is closer to 6%(1). The pathogen being dealt with here has a very complex biology which makes dealing with, understanding and preventing outbreaks of bTb very difficult and very complicated.
Vaccination- there is currently no legal vaccine against bTb, the only current Vaccine is called the BCG vaccine- Mycobacterium bovis Bacille Calmette-Guérin. As you may understand most vaccination involves partially infecting the patient with an amount of the very disease that you are trying to prevent it getting as often a disease can only infect an animal once, meaning that if you can infect it whilst preventing the effects of the disease some how you can stop it getting the disease proper. The problem with Mycobacterium bovis Bacille Calmette-Guérin is that though it is seemingly effective the tests we use to identify bTb in cows cannot differentiate between a cow infected with bTb and a cow who has been given the version of bTb in the vaccine. This renders it effectively useless as it would leave us unable to detect if the animal has been infected with bTb and hence unable to stop an outbreak. Work on an effective test that could tell us what we would need to know is ongoing, but even if/when it is achieved it will have to go through years of testing and EU approvals. All this means that even good estimates say it will be ten years before vaccination is a realistic solution to the bTb problem.
More, next time…