What is bovine TB?

Bovine TB is a chronic, debilitating, infectious disease caused by the Mycobacterium bovis (M. bovis) bacteria. Following infection it may be many months or years before illness becomes apparent. Infected cattle can spread infection long before they show any sign of being unwell. For this reason the control and eradication of disease relies on the early detection and removal of infected animals before they become ill. An effective treatment for infected cattle does not exist.

The disease mainly affects the lungs and lymph nodes of the chest of cattle. It is thought to be easier to infect cattle by the respiratory route. Disease can also be spread less easily by the oral route and affect the lymph nodes of the head and alimentary tract. In the early stages of infection the disease is localised. Only in the later stages of the disease does infection become generalised and spread throughout the body. Clinical signs, although rarely seen, include chronic coughing, weight loss and mastitis (when the udder is infected). 

There is evidence that bovine TB can be transmitted from badgers to cattle and vice versa. There has been evidence of a link between cattle, badgers and bovine TB since the initial discovery of an infected badger carcass in Gloucestershire in 1971.  The final report of the Randomised Badger Culling Trial concluded that there was compelling evidence that badgers had a role to play in spreading bovine TB.  The Badger Found Dead Survey concluded that the badger is an important component in the epidemiology of bovine TB in areas of high cattle incidence.

Although the disease primarily occurs in cattle and badgers, it also affects other domesticated animals and wildlife such as:

• Camelids (such as llamas, alpacas, guanacos and vicunas).
• Deer.
• Goats.
• Sheep.
• Pigs.
• Wild boar.
• Cats.
• Dogs.

Bovine TB is a notifiable disease which can affect humans. The risk to human health is very low as a result of meat inspection at abattoirs and pasteurisation of milk (which kills M.bovis). As well as this cattle are regularly tested and removed if infected.