Can culling be used to eradicate bovine TB?
Bovine TB is an infectious disease of cattle but can also be present in other mammals which are caused by the bacterium Mycobacterium bovis (M. bovis). This disease is also zoonotic which means it can be transmitted from animals to people and cause a similar disease to human TB but is not very common. Bovine TB takes place over a prolonged period of time and the clinical signs of the disease are: weakness, loss of appetite, weight loss, fluctuating fever, intermittent hacking cough, diarrhoea, large prominent lymph nodes.
The disease is more prevalent in most of Africa, parts of Asia however other countries such as the UK still have significant pockets of infection despite reducing Bovine TB. Areas of England that have high incidences of Bovine TB in cattle also tend to have high number of badgers. The disease is spread by contact between infected animals and non-affected animals. The usual route of infection is by inhaling infected droplets which are expelled from the lungs by coughing which makes it mainly a respiratory disease. Calves and humans can also become infected by ingesting raw milk from infected cows. As the course of the disease is slow it can take up to months or years before the animal dies but in that time the disease can pass to other herd mates before it begins to manifest the clinical signs.
The standard method for detection of TB is the tuberculin test, where a small amount of antigen is injected into the skin, and the immune reaction is measured. Cattle that react to the skin test are taken away for slaughter and the farmer compensated. The testing occurs every four years however can happen annually to those cattle at higher risk. The image below shows the number of cattle tested positive for bovine TB up to 2010. In addition to the skin testing, Gamma interferon blood testing is used along side