Tuberculosis in Dogs

Overview of Canine Tuberculosis

Tuberculosis, commonly referred to as TB, is a bacterial infection that affects dogs, cats and people. There are two primary bacteria responsible for tuberculosis in dogs and cats, Mycobacterium tuberculosis (human tuberculosis bacteria) and Mycobacterium bovis (cattle tuberculosis bacteria). Tuberculosis is most commonly thought of as a respiratory disease but the intestines can also be affected.

Dogs can be infected with either type of bacteria but cats have been found to be quite resistant to M. tuberculosis and are primarily infected by M. bovis.

Tuberculosis can be spread by inhalation of the bacteria or by ingestion of infected animal products. The route of exposure to the bacteria determines the type of infection. Dogs typically acquire infection through inhalation so the lungs are the primary targets and respiratory disease develops. Cats, unlike dogs, usually are exposed to tuberculosis by ingesting infected animal products (usually infected milk) and their disease is associated with the gastrointestinal tract.

Tuberculosis is a contagious disease and a zoonotic disease, which means it can spread from animals to humans. Extreme caution is recommended if you suspect your pet has tuberculosis. Most cases of canine tuberculosis are due to a spread of the bacteria from an infected person to the dog. Sometimes, the pet is the first one in the family diagnosed with tuberculosis. After testing the humans in the family, several may be found to be positive for tuberculosis and not yet showing signs of infection.

What to Watch For

Signs of tuberculosis in dogs may include:

• Coughing
• Depression
• Weight loss
• Increased thirst and increased urination
• Diarrhea
• Jaundice (yellow tinge to the gums)
• Vomiting
• Dehydration

Diagnosis of Tuberculosis in Dogs

Tuberculosis can be difficult to diagnose in dogs. Diagnostic tests may include:

• A complete blood count is usually done for most ill dogs. The results of this test may reveal an elevated white blood cell count.
• Biochemical profile can indicate the function of the organs and electrolytes and determine the overall health of the dog.
• For those pets with respiratory difficulty, chest radiographs (x-rays) can indicate if pneumonia is present but does not confirm the diagnosis of tuberculosis. Frequently, tuberculosis may be confused with lung cancer since both have similar x-ray signs.
• Organ biopsy is necessary to diagnose tuberculosis definitively. Unfortunately, biopsy of the lung or intestines is invasive and the pets are typically quite ill. There is significant concern that the pet may not survive the anesthesia and procedure.
• Culture and cytology (microscopic exam) of any discharge may reveal tuberculosis bacteria.
• Most cases of tuberculosis are diagnosed at autopsy.
• The skin test, which is commonly used in people, is not reliable in animals and is not used to diagnose tuberculosis.

Treatment of Tuberculosis in Dogs

Due to the high potential for transmission of tuberculosis from the infected dog or cat to people, especially children, treatment is not recommended. Most animals diagnosed with tuberculosis are euthanized.

Treatment can be attempted in some pets with long term use of drug therapy. Therapy can be unsuccessful and associated with potential toxicities.

Home Care and Prevention

There is no home care for tuberculosis. Tuberculosis is an uncommon disease but, due to antibiotic resistance, is slowly becoming more common. If you suspect your dog may have tuberculosis, or someone in the family has tuberculosis, consult your veterinarian immediately.

Any person with tuberculosis must be very careful around dogs. Coughing can result in spread of the bacteria through the air and nearby dogs may be exposed.