Tuberculosis

Formerly known as “phtisia”,”consumption” or “white plague”, tuberculosis is an infectious disease mainly caused by the bacterium Mycobacterium tuberculosis (M.tb) that is transmitted through the respiratory tract. Some cases of tuberculosis also have a zoonotic origin (transmission from animal to human). Consumption of milk from cattle contaminated with Mycobacterium bovis is the source of these zoonotic infections.

Although there are few cases of tuberculosis in Belgium, this disease remains a major public health problem and requires continued vigilance. The introduction of eradication and surveillance programs has helped to control the infection of the bovine population.

What is tuberculosis?

Also known as the Koch bacillus, the bacterium responsible for tuberculosis is transmitted through the respiratory tract. People suffering from pulmonary tuberculosis are thus contagious. This form of the disease is the most common, but tuberculosis can also affect the kidneys, bones, lymph nodes or any other part of the body.
Tuberculosis, once a deadly disease, is now cured with antibiotics.

Latent tuberculosis and active tuberculosis

A person can be infected with the bacterium responsible for tuberculosis without necessarily developing symptoms of the disease and without being contagious.  This is called “latent” tuberculosis.

In a healthy person, the immune system is able to control the infection and keep it at an asymptomatic stage. In some cases, the organism can even kill bacteria. 
If the immune system weakens, the bacteria responsible for tuberculosis can then proliferate and cause symptoms to appear. 
When tuberculosis is accompanied by symptoms, it is referred to as “active” or “symptomatic” tuberculosis.

Only 10% of people with latent tuberculosis will actually develop active tuberculosis in their lifetime.

Bovine tuberculosis

In cattle, tuberculosis is caused by Mycobacterium bovis. It manifests itself in an inflammatory process leading to caseous necrotic lesions. The infection may be localized to a single organ or, if the immune system is failing, to generalized manifestations. The location of these lesions generally depends on the bacterial pathway of entry.
Post-mortem bacteriological diagnosis, mainly based on the detection of lesions in slaughterhouses. The varied presentation of tuberculosis lesions and the difficulties inherent in slaughterhouse work (including working speed) make this inspection difficult. In the laboratory, bacteriological analysis of lesions is also delicate because the growth of the bacterium is extremely slow. Diagnosis based on the ante-mortem immune response has so far been carried out by single or double tuberculination.
Bovine tuberculosis is a zoonotic disease of global distribution. An estimated 5 to 10% of human tuberculosis cases are due to M. bovis in developing countries. The fight against this disease is a priority for European health authorities. Belgium, like 19 other countries of the Union (Decision 2014/91/EU35), was officially declared free in 2003 (Decision 200¾67/EC; Directive 64/432/EEC). This status is acquired when the prevalence of tuberculosis in livestock is less than 0.1%. This status does not mean, however, that we are biologically unscathed. Since 2003, an average of four to five outbreaks of bovine tuberculosis have been reported each year in our country. 
In Belgium, the surveillance program for bovine tuberculosis is based on two pillars: surveillance of lesions at the slaughterhouse and tuberculination of animals. This program is currently undergoing a major revision.

Sciensano contributes to the fight against tuberculosis by providing rapid diagnosis, by monitoring the antibiotic resistance of bacterial strains, by detecting epidemics, and developing new and more effective vaccines and treatments. The Belgian Official Medicines Control Laboratory (OMCL) of Sciensano, together with the European OMCL network, is responsible for the quality control of the tuberculosis vaccine prior to marketing.

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