Tuberculosis

Tuberculosis is an infection caused by a family of bacteria called mycobacteria. It turns up rarely in pet cats and dogs, but it matters more than the numbers suggest, both because some of the bacteria involved can infect people too, and because the disease is regulated by law in a number of countries.

Three members of the tuberculosis family, together known as the Mycobacterium tuberculosis complex, are relevant to cats and dogs. Mycobacterium bovis lives mainly in cattle and in wildlife such as badgers, and has also been found in rodents like moles and rats; it can infect both cats and dogs. Mycobacterium microti circulates mainly in field voles and shrews, and cats tend to pick it up through hunting. Mycobacterium tuberculosis, the main cause of human TB worldwide, mostly stays in people. It can infect dogs, usually caught from an infected person living in the same household, and only very rarely infects cats, because cats seem to be naturally resistant to this particular species. That resistance is why feline TB cases are almost always M. bovis or M. microti rather than the human strain.

Routes of infection include hunting and eating infected rodents or wildlife, drinking unpasteurised milk, and eating raw meat. One well documented cluster of M. bovis infections in UK pet cats was traced to a single brand of commercial raw pet food, and several of the affected cats never went outdoors at all, which shows that keeping a pet strictly indoors does not rule out this route on its own.

TB develops slowly and is easy to mistake for something else. In cats, the most common picture is skin disease: firm lumps, wounds that will not heal, or draining tracts, often with swollen lymph nodes nearby. If the lungs or gut become involved, or infection spreads through the body, you may also see coughing, faster breathing, weight loss, a poor appetite, fever or lethargy. Documented cases in dogs show a similar pattern of weight loss, coughing and general decline. None of these signs point specifically to TB, which is why a vet needs samples for microscopy, culture, PCR, or a blood test that measures the immune response, rather than relying on appearance alone.

Why the diagnosis is handled carefully

Treatment, where it is permitted, means combining several antibiotics for many months, and getting daily medication into a cat is genuinely hard work. In some countries M. bovis infection must be reported to the authorities, and infected animals may need to be euthanised, so local rules shape what happens after a diagnosis. The European Advisory Board on Cat Diseases advises vets to check their national regulations before starting treatment, and to weigh up whether anyone in the household, such as young children, older people, or someone with a weakened immune system, faces a higher risk.

Sensible prevention is straightforward: feed cooked or commercially heat-treated food rather than raw meat, avoid unpasteurised milk, and tell your vet if your pet hunts or has contact with cattle areas. If your cat or dog has a lump or wound that will not heal, or is losing weight and coughing over weeks rather than days, get it checked. This is general information, not a diagnosis, and only a vet examining your animal can say what is actually going on.