Bovine Tuberculosis (Mycobacterium bovis) RT-PCR

Bovine tuberculosis (TB) is a slow, long-lasting disease of cows and buffaloes, caused mainly by Mycobacterium bovis. It most often affects the lungs and lymph nodes, which are small glands, but it can spread to other parts of the body, including the udder. Many infected animals look healthy for a long time. Others slowly lose weight, become weak, have a fever that comes and goes, cough, breathe with difficulty or give less milk. The germ spreads between animals mainly through the breath, especially in crowded sheds.

This test uses PCR (polymerase chain reaction), a lab method that copies a germ's genetic material, called DNA, many times until it can be detected. It looks for DNA of the Mycobacterium tuberculosis complex, the group of closely related TB germs that includes M. bovis. Depending on the case, the sample is a nasal swab, milk or tissue. Tissue usually comes from a post-mortem, an examination after death, when a veterinarian finds lumps that look like TB. Because the test looks for the germ itself, vets often use it alongside other TB tests, such as the skin test done on the farm or a blood antibody test.

Infected animals do not pass the germ all the time, so a negative PCR does not always mean an animal is free of TB. A registered veterinarian reads the result together with the animal's signs, history and other tests, and advises on next steps for the herd. Tuberculosis can pass to people, mainly through unboiled milk and close contact with sick animals, so wear gloves when handling animals or samples, wash your hands well and see a doctor if you have a long-lasting cough or feel unwell. The lab handles these samples under safety rules.