Every year on March 24th, the world marks World TB Day. While many people are fortunate to only know of tuberculosis only through their required Charles Dickens reading in high school, it’s a disease that impacts humans around the world today… and it infects cats, too.
Tuberculosis describes disease where there is a formation of inflammatory nodules, called granulonomas, in the body. Cats are naturally resistant to the organism that causes most tuberculosis in humans, Mycobacterium tuberculosis. However, cats can become infected with tuberculosis with other bacteria, including Mycobacterium microti, which is primarily found in rodents but can be transmitted to cats who hunt them. Cats are also susceptible to another strain of bacteria, Mycobacterium bovis. This infection usually comes from consuming unpasteurized cow’s milk, or from infected animals such as deer, badgers, ferrets, dogs, and other cats.
Most tuberculosis infections of cats have been reported in the UK, but the disease has been seen in cats other places, too.
Symptoms of TB in cats include coughing, wheezing, and/or weight loss. TB can also cause lumps or abscesses in cats, or bite wounds may fail to heal. These clinical signs of infection may look like other infections, so it requires laboratory testing to identify the cause as TB.
Just after last year’s World Tuberculosis Day, Public Health England and Animal Health and Veterinary Agency announced the first documented case of cat-to-human transmission of tuberculosis. Two people in England developed tuberculosis after contact with a cat infected with M. bovis, and two more people were diagnosed with latent tuberculosis, meaning they were exposed to TB at some point but did not have active disease. Although there were infected cattle in the area, there were signs that the cats had been infected by bites from local wildlife or by other cats.
In the US, M. bovis is uncommon in cattle, but it is found in white-tailed deer in northeastern Michigan and northern Minnesota, which has infected cattle herds in the same range. Raccoons and opossums in the area have also tested positive for tuberculosis as a result. Outdoor cats in the area could come into contact with wildlife exposed to TB, so be safe and be sure not to feed cats unpasteurized milk from herds which may be infected.
International Cat Care, Mycobacterial diseases in cats – tuberculosis
Veterinary Record, Feline tuberculosis caused by Mycobacterium bovis
The Veterinary Record, Unusual cluster of Mycobacterium bovis infection in cats
Journal of Wildlife Diseases, Epizootiloogic Survey of Mycobacterium Bovis in Wildlife and Farm Environments in Northern Michigan
Animal Health and Veterinary Laboratories Agency/Public Health England, Bovine Tuberculosis in domestic pets
Barn cats – depositphotos/modfos
Cat and mouse – depositphotos/AGorohov