Wild animals as carriers

Bovine TB: Difficult to detect, transmission rare

(Bild: APA/BARBARA GINDL (Symbolbild))

In Vorarlberg, a person has been infected with the pathogen in the course of bovine tuberculosis cases. Although infection is rare, it is possible, as the current case shows. A classification.

Bovine tuberculosis is an infectious disease caused by bacteria that can be transmitted to humans and is therefore a zoonosis. It is caused by the two bacterial species Mycobacterium bovis - which occurs worldwide - and Mycobacterium caprae, which has been detected in western Austria and other European countries, as can be read in a leaflet from the Austrian Agency for Health and Food Safety (AGES).

Tuberculosis is usually only detected on the basis of conspicuous slaughter findings.

Die AGES

Risk of infection increases with prolonged contact
The good news is that the risk of infection for humans is not particularly high, especially in the case of Mycobacterium caprae, as German lung specialists write. However, it increases with prolonged contact with infected creatures. The greatest danger for humans comes from drinking unpasteurized milk.

Tuberculosis often goes unnoticed for a long time
One of the main problems with tuberculosis is that it progresses slowly and often goes unnoticed for many years. "It is usually only detected on the basis of conspicuous slaughter findings," writes AGES. Wild animals such as red deer, wild boar and badgers can form a reservoir of the pathogen, and tuberculosis remains permanently in these animals. From this reservoir, the disease can spread to domestic animals, for example when cattle graze on alpine pastures.

Wild animals, such as red deer, are considered to be carriers of tuberculosis. The pathogens remain permanently in these animals.

(Bild: ©Brais Seara - stock.adobe.com)

The transmission itself occurs through the inhalation of fine droplets containing the pathogen, which are coughed up by sick animals, or via contaminated feed. Tuberculosis bacteria that are excreted in milk, for example, can survive on feed for months.

These are the signs
Externally recognizable cases of bovine tuberculosis are very rare. Progressive coughing as a result of chronic pulmonary tuberculosis and a gradual deterioration in general condition with emaciation are the most likely signs of the disease. Tuberculous processes can also affect other organs. Because of the associated pathogen excretion, udder, uterine, intestinal and testicular tuberculosis are the most significant.

A total of five farms affected
In Vorarlberg, further farms are currently under lockdown due to suspected TB. On Friday, the state veterinary authority spoke of a total of five farms - three in Bregenzerwald, two in Montafon - with around 170 animals and provided information on the current status of the investigations: Of a total of 442 contact animals from the farm of origin, 437 tested negative. Of the eight animals initially killed for diagnostic purposes on the large farm, seven were positive. A final report on the possible chain of infection is still pending.

Four positive animals in the Bregenzerwald
Five suspect animals were killed on a contact farm in the Bregenzerwald, four of which were also positive. The tests of the remaining livestock were inconspicuous. The farm remains closed as a precautionary measure, according to the authorities. The pathogen was also detected in a calf that came from the original farm and was on a farm in Montafon after it was diagnostically killed.

The other animals on the farm were negative, but this farm also remains under lockdown. Independently of this, a farm in Montafon was also closed due to suspected TB, where nine animals reacted positively during tests in the special surveillance area and were killed. The results of their tests are still pending.