Tuberculosis (TB) is the most common fatal infectious disease in humans worldwide. There are different tuberculosis pathogens, the most common pathogen of human tuberculosis is Mycobacterium (M.) tuberculosis. The bacterium can be inactivated by pasteurisation (heating to 72°C for a short time); however, it is insensitive to desiccation or cold.
Tuberculosis is widespread worldwide, especially in Africa, Asia and Latin America. According to estimates by the World Health Organisation (WHO), more than one third of the world's population is infected with tuberculosis (M. tuberculosis). Every year, 1.6 million people die from the infection and around 9 million become newly infected.
In Europe, the pathogen of bovine tuberculosis (M. bovis) was greatly reduced after the Second World War, as a result many countries received the officially recognised status "free of bovine tuberculosis". In 1999, Austria's cattle population was granted the status "officially free of bovine tuberculosis" by the EU. Since then, this tuberculosis pathogen has not been detected in any Austrian cattle population.
Humans are the only relevant reservoir for M. tuberculosis. For mycobacteria that can be transmitted from animals to humans, such as M. bovis and M. caprae, cattle, wild boars, goats or wild ruminants (especially red deer) are the pathogen reservoir.
Mode of transmission
Whether an infection occurs depends on the frequency and intensity of contact, the amount of inhaled or orally ingested pathogens and the physical condition of the affected person. Infection usually occurs through inhalation of fine droplets, which are released during coughing and sneezing by persons suffering from open tuberculosis. Open pulmonary tuberculosis refers to diseases in which pathogens can be detected in the sputum. Transmission through raw (unpasteurised) milk from infected cattle is in principle possible.
Infection from animal to animal occurs preferentially by the aerogenic route through inhalation of fine droplets containing the pathogen, which are coughed up by diseased animals. However, it can also occur through contact or orally, e.g. via contaminated feed in feed mangers and salt licks.
The time from infection to outbreak of the disease can range from a few months - especially in young children - to many years and decades.
Humans: After a droplet infection, small inflammation foci usually form in the lungs within the following three to six weeks, which encapsulate into nodules (tubercles). This form with locally limited signs of disease is called closed tuberculosis because it is not contagious and no pathogens are excreted. Active infection begins with general symptoms especially night sweats, increased temperature, fatigue, weight loss, lack of appetite, general feeling of illness. In pulmonary tuberculosis, tissue loss can lead to so-called caverns. Symptomatic for this is massive, often bloody, sputum. These patients are highly contagious. One speaks of a miliary tuberculosis when there is a spread via the bloodstream with diffuse infestation of several organ systems, usually also with lung involvement. Tuberculous meningitis (meningitis) may also develop.
Animal: Chronic pulmonary tuberculosis in cattle is mainly manifested by a progressive cough and a slowly deteriorating general condition. However, disease processes may also occur in other organs. In cattle, tuberculosis may remain latent or subclinical for years.
As the pathogens are difficult to reach with drugs, therapy takes several months and the risk of mycobacteria developing resistance is particularly high. In cases of confirmed tuberculosis, patients must therefore be treated with a combination therapy of several special antibiotics, so-called antituberculotics. The duration of treatment is correspondingly long (over months) in order to avoid possible relapses.Tuberculosis is a notifiable animal disease. Control is focused on the eradication of infected animals.
As there is no effective vaccine protection against tuberculosis, the most important measure is to detect diseased individuals as soon as possible and to treat them effectively.