A bird specialty store owner wrote me recently, concerned about potential tuberculosis (TB) exposure. A client’s bird had been diagnosed with "human TB" and that person had spent a lot of time with the bird. The source of the TB hadn’t been identified, and the store owner was worried about the risk that he/she had been exposed as well.
Is it really TB?
The first thing to consider in a case like this is whether TB was really present. "Human TB" is caused by Mycobacterium tuberculosis. Birds can be infected by M. tuberculosis, but are more often infected by Mycobacterium avium complex (MAC), a related group of bacteria. Based on what the store owner wrote here, it seems that M. tuberculosis was the cause of disease.
Can TB be spread from birds to people?
Probably, but the evidence is sparse. Tuberculosis can be spread from people to birds, and it’s likely it can go the opposite direction. However, close and prolonged contact is typically required for TB transmission. Human-to-bird cases tend to be birds owned by people with active TB who have close mouth-to-mouth contact with their birds (e.g. mouth-beak feeding).
What is the likelihood of transmission?
Being in the same room as a bird with TB is probably pretty low risk (just like casual contact with a person carrying TB is low risk). The risk also depends to a degree on the type of disease the bird has. If it has respiratory tract disease it is probably more likely to be shedding the bacterium in its respiratory secretions, which poses a greater risk of transmission than other forms of the disease.
Is there cause for concern?
I guess there’s always some degree of concern when it comes to TB, but I assume the likelihood of transmission of TB from the bird to the store owner is quite low. The source of TB wasn’t known, but most likely the bird was infected by its owner, and if so, being around the bird’s owner is probably as (or more) risky.