ZOO NEWS - Avian Disease

"The ABCs of Avian Disease" By Bruce Rideout DVM PHD, San Diego Zoo Blog

Like most wildlife veterinarians, I chose this profession because I love animals and wanted to make a difference. So, nothing makes me more frustrated than seeing a disease take a high toll on our animals and being unable to help.

Avian tuberculosis was one such disease – even though it is uncommon, it takes a high toll on innocent bystanders each time a case occurs, and until now, there wasn’t much we could do to help.

The problem with avian tuberculosis is that it has always been considered a highly contagious disease, but one that spreads slowly and is very difficult to detect, much like human tuberculosis. As a result, when a case of avian tuberculosis is identified, the traditional management recommendation was to humanely euthanize all exposed birds because some of them might go on to spread the disease even further.

Unfortunately, many of these exposed birds turned out to be perfectly healthy and were euthanized unnecessarily, but we had no way of knowing that beforehand. So we decided to make avian tuberculosis our top research priority several years ago. We wanted to find out the best way to prevent this disease, so we could avoid these devastating consequences for exposed birds.

As we investigated the transmission of this disease, we discovered something amazing and unexpected: contrary to 100 years of dogma, avian tuberculosis does not appear to be a highly contagious disease. Our results so far suggest that avian tuberculosis is acquired primarily from soil and water in the environment, not from other infected birds.

Apparently, it is an environmental disease and not at all like human tuberculosis. This means that an infected bird does not pose a significant risk of infection to other birds, so none of the exposed birds need to be euthanized.

We now recommend that the disease be called avian mycobacteriosis to avoid confusion with human tuberculosis, and we recommend that it be managed as a preventable environmental disease.

When I presented these results at the annual meeting of the American Association of Zoo Veterinarians, a zoo veterinarian later told me that she ran out into the hallway as soon as she heard the results and called her associate veterinarian to cancel the scheduled euthanasia of a very valuable bird that had been exposed to avian mycobacteriosis. That was one of the most rewarding moments in my career. Nothing makes a veterinarian feel better than saving a life.

The next phase of our research is taking us into new territory. Many physicians believe that their immunocompromised patients, such as those on cancer chemotherapy, should euthanize or get rid of their pet birds because of the risk that they will acquire avian mycobacteriosis from them.

But there is mounting evidence that human cases of avian mycobacteriosis are also acquired from the environment, not directly from birds. In order to confirm this, and thereby prevent the unnecessary euthanasia of healthy pet birds, we plan to obtain DNA fingerprints of mycobacteria from birds and humans to show that human infections are not acquired from birds. Stay tuned!