Tuberculosis
Tuberculosis in pets is a slow, hard-to-spot infection with mycobacteria that can affect cats and dogs, carries a risk to people, and is regulated in many countries.
Tuberculosis (TB) is an infection caused by a group of slow-growing bacteria called mycobacteria. In pets it is uncommon, but it matters out of proportion to how often it turns up, because some of the bacteria involved can also infect people and because the disease is regulated by law in many countries.
Three members of the tuberculosis family are relevant to cats and dogs. Mycobacterium bovis lives mainly in cattle, badgers and rodents, and can infect both cats and dogs. Mycobacterium microti circulates in field voles and shrews, and cats pick it up while hunting. Mycobacterium tuberculosis, the main cause of human TB worldwide, mostly affects people, can infect dogs (usually caught from an infected human in the household), and only very rarely affects cats. Because cats are quite resistant to the human strain, feline cases are almost always M. bovis or M. microti. Routes of infection include hunting and eating infected rodents or wildlife, unpasteurised milk, and raw meat. A well-documented outbreak in UK pet cats was traced to a single brand of commercial raw venison food, and several of those cats were indoor-only, which shows that a pet with no outdoor access is not automatically safe.
TB is slow and easy to mistake for something else. In cats the most common picture is skin lesions: firm lumps, non-healing wounds or draining tracts, often with swollen lymph nodes nearby. When the lungs or gut are involved, or the infection spreads through the body, you may see coughing, faster breathing, weight loss, a poor appetite, fever or lethargy. Dogs more often show weight loss, coughing and general decline. None of these signs are specific to TB, which is why diagnosis relies on the vet taking samples for microscopy, PCR, culture or a blood test that measures the immune response, rather than on appearance alone.
Why the diagnosis is handled carefully
Treatment, where it is allowed, means several antibiotics together for many months, and getting that into a cat every day is hard work. In some countries M. bovis infection must be reported to the authorities and infected animals may have to be euthanised, so the rules where you live shape what happens next. The European Advisory Board on Cat Diseases advises vets to check their national regulations before starting any treatment, and also to consider whether anyone in the household is at higher risk, such as young children, older people or anyone with a weakened immune system.
Sensible prevention is straightforward: feed cooked or commercially heat-treated food rather than raw meat, avoid unpasteurised milk, and mention hunting habits or contact with cattle areas when your vet asks. If your pet has a lump or wound that will not heal, or is losing weight and coughing over weeks rather than days, get it looked at. This is general information, and only a vet examining your animal can say what is actually going on.