1 March 1996

Three bacteria at centre of blame

TUBERCULOSIS is caused by three bacteria: Mycobacterium bovis, tuberculosis and avium.

Many cattle are infected with avium from migratory birds, but they seem to have become sensitised to it. It does, however, cause a cross reaction during routine TB testing.

Mycobacterium bovis can affect human beings. Cattle carrying tuberculosis react positively to a TB test, although it doesnt infect them.

The first symptoms of TB infection in cattle are stock not "doing". They loose weight, develop a soft cough and lumps appear around the lymph nodes on the neck. Abscesses can develop in the udder, although this is very rare.

The air-borne bacteria are breathed in. They cause abscesses in body organs, lungs and lymph nodes. Once the body is infected the disease is spread via the blood to other organs.