A report in the latest newsletter from the University of Guelph Animal Health Laboratory describes a case of tuberculosis (TB) in a pet dog. The dog was a seven-year-old Bichon Frise that had an abdominal mass, low-grade fever, nasal discharge and pneumonia. Tuberculosis was diagnosed by testing a sample of the mass that was obtained during an exploratory surgery. The dog was euthanized because of the poor prognosis and because of concerns about transmission to people in the household.
Tuberculosis has historically been one of the most important infectious diseases in people and has re-emerged as a huge problem in human medicine, particularly because of the development of highly drug-resistant strains. The disease is caused by the organism Mycobacterium tuberculosis. It can be spread through the air over short distances by minute droplets when someone with active TB coughs, sneezes, speaks or sings. Other individuals become infected by breathing in the bacterium.
Tuberculosis is primarily a human disease. It has been reported in various animal species, but only rarely. Dogs are considered relatively resistant to TB, even so there are several reports in the scientific literature of TB in dogs. The source of the dog’s infection in this case was not discussed. Presumably, the dog was infected by close contact with an infected person.
One of the reasons for euthanasia of the dog in this case was the risk to household members. At this point, we have little information about the risk that infected animals pose to their human contacts. This makes providing evidence-based advice difficult. Many people may err on the side of caution by euthanizing the animal to prevent transmission. Important aspects that need to be considered include whether the owner can afford to attempt treatment of the animal (with no clear evidence of what works and longterm treatment being required), whether the disease is potentially treatable (i.e. what are the chances the animal will recover if it is treated), and the status of other household members with respect to TB disease or exposure. Of course, these consideration are all in addition to that of the animal’s condition and quality of life, which may warrant euthanasia regardless – tuberculosis can be a devastating disease, and it is often not detected until it is quite advanced.
There’s no correct answer. Our poor understanding of this disease in dogs and the significant health risks of TB in people unfortunately make euthanasia a reasonable decision.