Tuberculosis in Cats

The infection has a fast onset, spreading throughout the lymphatic system and the circulatory system where it can come into contact with many different organs. The bacteria often infect the respiratory system and cause pneumonia to develop. If the lungs are infected, the condition often become chronic, or ongoing. The gastrointestinal tract is also frequently affected in the feline manifestation of tuberculosis. If the infection has spread to multiple organs, the condition is often fatal. If cattle tuberculosis is not a problem in the general area, instances of cats contracting the bacteria are rare.

Mycobacterium is a type of bacteria that cause an infectious disease capable of affecting almost all animals. This bacterial infection is commonly known as tuberculosis (TB). There are three main types of tuberculosis, M. tuberculosis, M. bovis and M. microti. Cats are rarely affected by the most common human strain, M. tuberculosis, however, they are susceptible to the other two forms of the disease. Mycobacterium bovis, or cattle tuberculosis, is most often the cause of tuberculosis in cats. This form of TB is not often found in North America.

The symptoms of tuberculosis depend on where the infection is located in the body. Severe symptoms involving multiple body parts may indicate that the infection has progressed beyond the point of treatment. Signs to watch for are as follows:

• Weakness
• Lethargy
• Depression
• Anorexia
• Weight loss
• Dehydration
• Polydipsia (increased thirst)
• Polyuria (frequent urination)
• Fever
• Wet cough (may cough up blood)
• Labored breathing
• Shallow breathing
• Vomiting
• Diarrhea
• Jaundice
• Skin lesions

A cat has to come into direct contact with the bacteria to become infected. While cats often do not contract the common form of human tuberculosis, it is possible for a human to be infected with M. bovis or M. microti and pass those bacteria onto any cats they regularly are in contact with. Other possible routes of infection include:

• Ingesting milk or food that has been contaminated with the bacteria
• Inhalation of infected cough droplets from animals with the disease

If tuberculosis is suspected, a professional diagnosis is necessary as public health authorities may need to be notified due to the danger of human exposure to the harmful bacteria. Provide your veterinarian with the cat's full medical history and be prepared to answer questions about possible exposure to infected cattle or cattle by-products. The veterinarian will then complete a physical examination of the cat, looking to match all of the showing symptoms with the known signs of tuberculosis. Certain types of cancer and other diseases will have to be differentiated.

Full blood work will need to be run, including a complete blood count to look for elevated white blood cell levels and a biochemical profile to assess organ function and electrolyte levels. An x-ray of the chest will be needed to confirm the presence of pneumonia and to ensure lung cancer is not causing the symptoms. If the cat is stable enough to handle being sedated with anesthesia, a biopsy of the affected organs may be taken so that a microscopic examination may be performed to identify the bacteria. In some cases, lung aspirations can be collected by a bronchoalveolar lavage or gastric wash. These samples can also be sent to a lab for a cytological exam. In many instances, tuberculosis is only confirmed via post-mortem assessment.

Depending on the severity of the case and the region of the occurrence, some veterinarians may refuse treatment as infected cats cause a risk of tuberculosis development in humans. In these instances, the cat will be euthanized. 

Medication Therapy 

Although rarely reported, there has been success in treating cats that have tuberculosis with a long term antimycobacterial medication prescription. The dosage must be regularly monitored, as the prescription can cause adverse side effects and lead to toxicity of the cat. After several months of treatment, bacteria levels may be significantly lower. Treatment may need to be ongoing in some circumstances.

If your cat has been approved for treatment, it will need to be isolated until deemed clear of the infectious bacteria. If the cat goes into remission, recovery is still not guaranteed. If the infection is caught early enough, a full return to health is possible, though not probable. The cat will need to return to the clinic for ongoing checkups and blood work to see if the tuberculosis is dissipating.

Advanced cases of tuberculosis in cats may require immediate euthanization. Ensure that your veterinarian has contacted local health officials to report the infection. Any human that has been in contact with the cat should be tested for tuberculosis. To prevent tuberculosis exposure, do not allow your cat to drink unpasteurized milk. If a human has been diagnosed with tuberculosis, they should stay away from any pets so as not to pass on the infection.