Which animals can get bovine TB?

Although cattle are considered to be the main hosts of M. bovis, the disease has been reported in many other domesticated and non-domesticated animals. These include:

buffaloes, bison, sheep, goats, horses, camels, pigs, wild boars, deer, antelopes, dogs, cats, foxes, mink, badgers, ferrets, rats, primates, llamas, kudus, elands, tapirs, elks, elephants, sitatungas, oryxes, addaxes, rhinoceroses, possums, ground squirrels, otters, seals, hares, moles, raccoons, coyotes and several predatory felines including lions, tigers, leopards and lynx.

Where in the world is it found?

TB is found throughout the world. The disease is more prevalent in most of Africa, parts of Asia and the Americas. Many developed countries have reduced or eliminated bovine TB from their cattle population; however, significant pockets of infection remain in wildlife in Canada, the United Kingdom, the United States and New Zealand. Until the 1920s when control measures began in developed countries, TB was one of the major diseases of domestic animals throughout the world. Today it remains a major disease of cattle and wildlife.

What is being done to control bovine TB?

Control of bovine TB in cattle herds

For many years the control of bovine TB has focused on the control of bovine TB in domestic cattle herds. This has been through whole herd skin testing, slaughter surveillance and monitoring the movement of animals between herds.⁶ Vaccinating cattle for the control of bovine TB is not currently used within any international control program and it is illegal within the E.U.⁷ This is because vaccines based on the TB bcg vaccine, all interfere with the action of the tuberculin skin test which is used for the diagnosis of TB in cattle. If the bcg vaccine is used then it is impossible to differentiate between cattle that have TB and cattle that have been vaccinated. In addition in 2016 there started to be a worldwide shortage of the bcg vaccine.

Pasteurization of milk

The pasteurization of milk and other dairy products has been important in preventing the spread of the disease to humans. Pasteurization means heating the milk to a sufficient temperature that any bacteria in the milk will be killed.

Wildlife reservoirs

In recent years it has become clear that the disease in certain countries has become established in “wildlife reservoirs” of infection in different host animals. These are as varied as:

• cervids, particularly deer & elk, in North America,
• mustelids, particularly badgers, in Europe,
• swine, particularly pigs, in Europe,
• marsupials, particularly possums in New Zealand,
• and bovids, particularly buffalo in Africa.

In these instances it has been assumed that livestock, usually cattle, served as the initial source of infection for different wildlife species. It has however been unclear when this may have happened. The wildlife were then able to maintain the disease in their free ranging populations until contact between livestock and infected wildlife allowed the disease to be transmitted back to the livestock. So this allows the disease to continue whatever action is taken with infected cattle herds.

Controlling bovine TB in wildlife populations

The control of bovine TB in wildlife is complex as there are limitations to what can practically be achieved, and a variety of stakeholder interests that need to be taken into consideration. A range of actions to address the disease risk have been adopted in various countries and with different wildlife populations. These include:⁸

• Wildlife population reduction or depopulation and replacement with disease free animals,
• Effective on-farm biosecurity to protect livestock and feed from contact with wildlife,
• Continued participation in surveillance and testing efforts to protect livestock from potentially diseased wildlife,
• Vaccination of wildlife to reduce transmission to livestock,
• Wildlife free buffer areas to prevent contact between wildlife and livestock.