Synonym: zoonotic tuberculosis

What is it?

Bovine tuberculosis is caused by Mycobacterium bovis, a bacterium closely related to the causative agent of human tuberculosis (Mycobacterium tuberculosis). M. bovis is found in many animal species, including livestock, wildlife and human beings, where it causes an illness very similar to that of M. tuberculosis in humans. Cattle are the main source of human infections. M. bovis is transmitted through the aerial or the digestive routes causing pulmonary and extra-pulmonary tuberculosis, respectively. M. bovis is mostly transmitted to humans through the consumption of contaminated milk. Transmission to humans through the aerial route is also possible when people have close contacts with animals. Whereas M. tuberculosis is mostly transmitted among humans through the aerial route causing proportionally more pulmonary tuberculoses, tuberculoses caused by M. bovis and M. tuberculosis are clinically undistinguishable.

Wildlife is also affected by M. bovis in different countries. Severe outbreaks were reported in South-African buffaloes and lions whereas badgers are an important wildlife reservoir of the disease in the UK.

Simplified text

OIE disease card (English, French and Spanish)

Simplified video

A farmer explaining the issues in BTB in the UK (7'52; English)

Technical text

Bovine tuberculosis, Iowa State University (English only)

OIE Terrestrial manual (English only)

Relative importance of zoonotic TB (English only)

Tuberculosis: a re-emerging disease in animals and humans (English only)

How to recognize it

Mycobacteria are slow-developing pathogens causing chronic diseases. Tuberculosis can remain localized to organs or draining lymph nodes. Symptoms will depend on the organs that are affected. Pulmonary tuberculosis causes a cough whereas extra-pulmonary TB may cause abscesses at the back of the throat (retro-pharyngeal abscesses) or abscesses along the digestive tract. Tuberculosis may generalize and impact severely the general condition of the individual.

In humans, the diagnosis of clinical tuberculosis can be done through observation of the mycobacteria in sputum or in biopsy. Mycobacteria can also be cultivated in the lab. In terms of appearance and structure M. bovis and M. tuberculosis are undistinguishable. Biochemical or molecular tests are needed to identify them at species level.  Such tests are costly and not routinely available in most African medical facilities.

Sub-clinical cases can be identified using the skin test. The test is based on the localized reaction of infected individuals 3 days after the inoculation of antigen in the skin. This method, again, does not make it possible to distinguish between M. bovis and M. tuberculosis. Furthermore, people vaccinated with the BCG vaccine will also give a positive skin test, as will exposed but healthy individuals. Alternatively, the interferon gamma test can be applied on whole blood in the laboratory.

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Association between zoonotic TB and extrapulmonary disease (English only)

Tuberculosis: a re-emerging disease in animals and humans (English only)

Finally, meat inspection at the abattoir may contribute to the surveillance of tuberculosis in livestock. Whereas most infected livestock are infected by M. bovis, there are reports of animals becoming infected by M. tuberculosis. The epidemiological relevance of this is questionable.

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Body condition scores: camels (English only)

Body condition scores: cattle (English only)

Body condition scores: goats (English only)

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FAO chapter on tuberculosis at meat inspection ( English only)

FAO manual on meat inspection for developing countries (English only)

Technical illustrations

Iowa State University (English, Spanish and Thai)

Technical text

Bovine tuberculosis, Iowa State University (English only)

OIE Terrestrial manual (English only)

Tuberculosis: a re-emerging disease in animals and humans (English only)

How to control it

Bovine tuberculosis is ‘cosmopolitan’ meaning that virtually all countries of the world have been exposed. Most developed countries eliminated M. bovis from their livestock using the “test and slaughter” method. In these countries, severe conditions are put in place before animals from endemic countries are imported. Surveillance networks are also put in place to detect TB infections as early as possible.

In Africa, many areas have developed a state of endemic stability in livestock whereby, in the absence of control measures, the prevalence of infection and the incidence of clinical cases are low. Controlling the movement of infected animals in such a context is probably not useful.

In areas where wildlife is not affected, contacts between large wild and domestic ruminants should be avoided. In livestock, elimination strategies are based on the detection and the slaughtering of animals that are positive at the skin test. In endemic areas where elimination of all positive animals cannot be implemented, the detection and slaughter of shedders (animals suffering from severe tuberculosis and ‘shedding’ germs in the environment) is probably a useful alternative since shedders represent a high transmission risk to humans and other animals.

The transmission to humans through milk and milk products is controlled when the milk is pasteurized or sterilized (e.g. boiled). The meat and the blood of infected animals are not considered to be very infective. Butchers are, however, at risk because they handle organs and lymph nodes containing tuberculosis lesions. Abattoir workers should therefore wear appropriate protective clothes and have access to disinfectants.

Finally, humans can be vaccinated against tuberculosis using the BCG vaccine. This live attenuated vaccine protects against both M. tuberculosis and M. bovis. Specific antibiotics can be used in humans. Yet, M. bovis is naturally resistant to pyrazinamide, unlike M. tuberculosis.  This has important implications for treatment.  In patients who are not responding to the standard treatment for M. tuberculosis, M. bovis should be suspected and a differential diagnosis performed.

Simplified video

A farmer explaining the issues in BTB in the UK (7'52; English)

Technical text

Capacity building for surveillance and control of tuberculosis (English only)

Development of a vaccine for cattle (English only)

Tuberculosis: a re-emerging disease in animals and humans (English only)

Cultural and geographical specificities

The impact of bovine tuberculosis on animal production and public health should be carefully evaluated before imposing control strategies to the communities.

Pastoralist communities

In addition to cattle, camels are commonly infected by M. bovis. Infected animals can infect humans (and other animals) by the aerial route, through the consumption of infected milk or during the butchering process.

The contamination of the milk can only occur if the animal suffers from severe tuberculosis (shedders). Such animals are easily detected as emaciated and unhealthy animals by their owner. Objective criteria could also be used to estimate a body score. Owners should be advised to discard shedders to avoid transmission to human beings. Such animals should not butchered either due to the risk of infection during the process.

Butchers should be able to detect TB lesions and protect themselves accordingly.

In case of high incidence of zoonotic extra-pulmonary tuberculosis in people, milk should be systematically boiled. Apart from logistical problems, this poses cultural problems related to changing the traditional methods of preparing milk products. On the other hand, the communities consuming raw blood are probably not prepared to cook it.

These measures will only protect people against M. bovis. In areas where human tuberculosis is abundant, the use of the BCG vaccine in infants will significantly protect people against the two species.

Technical text

Zoonotic transmission of tuberculosis between pastoralists and their livestock in South-East Ethiopia (English only)

Communities in northern Africa and the Sahel region

European cattle breeds are much more receptive to tuberculosis than local breeds. This should be taken into account when bringing such animals into an endemic area.

In addition to cattle, camels are commonly infected by M. bovis. Cattle can infect humans (and other animals) by the aerial route, through the consumption of infected milk or during the butchering process.

The contamination of the milk can only occur if the animal suffers from severe tuberculosis (shedders). Such animals are easily detected as emaciated and unhealthy animals by their owner. Objective criteria could also be used to estimate a body score. Owners should be advised to discard shedders to avoid transmission to human beings. Such animals should not butchered either due to the risk of infection during the process.

Butchers should be able to detect TB lesions and protect themselves accordingly.

In case of high incidence of zoonotic extra-pulmonary tuberculosis in people, milk should be systematically boiled. Apart from logistical problems, this poses cultural problems related to changing the traditional methods of preparing milk products.

These measures will only protect people against M. bovis. In areas where human tuberculosis is abundant, the use of the BCG vaccine in infants will significantly protect people against the two species of bacteria.

Technical text

Mycobacterium bovis isolates from tuberculous lesions in Chadian zebu carcasses (English only)

Mixed farming communities in more humid zones

European cattle breeds are much more receptive to tuberculosis than local breeds. This should be taken into account when bringing such animals into an endemic area.

The contamination of the milk can only occur if the animal suffers from severe tuberculosis (shedders). Such animals are easily detected as emaciated and unhealthy animals by their owner. Objective criteria could also be used to estimate a body score. Owners should be advised to discard shedders to avoid transmission to human beings. Such animals should not butchered either, due to the risk of infection during the process.

Butchers should be able to detect TB lesions and protect themselves accordingly.

In case of high incidence of zoonotic extra-pulmonary tuberculosis in people, milk should be systematically boiled. Apart from logistical problems, this poses cultural problems related to changing the traditional methods of preparing milk products.

These measures will only protect people against M. bovis. In areas where human tuberculosis is abundant, the use of the BCG vaccine in infants will significantly protect people against the two species.

Technical text

Bovine tuberculosis and brucellosis in traditionally managed livestock in southern Zambia (English only)

Cattle owners' awareness of bovine tuberculosis in Zambia (English only)

Zoonotic tuberculosis and brucellosis in Africa (English only)