Pathology and Epidemiology in Action! Part 2 – The research

In Part 1 of this blog, our pathologist diagnosed avian mycobacteriosis in a green imperial pigeon. (Read here.) But what is this disease and why is it important?

Avian mycobacteriosis is a bacterial disease of birds. It was discovered in the late 1800’s around the same time as the cause of human tuberculosis, Mycobacterium tuberculosis. Unlike the human form of the disease, however, avian mycobacteriosis is caused by different mycobacterial species that are found commonly in the environment and which do not generally infect people.

Nevertheless, it was assumed that avian mycobacteriosis, like human TB, was a contagious disease spread easily from bird to bird. Thus, historically, when cases were identified in zoological collections, it could potentially lead to elaborate diagnostic testing, strict quarantine procedures, and halting breeding programs due to concerns about contagious disease spread. More recent studies have questioned this response and suggest that the disease may not be as contagious as we thought.

Thankfully, we do not have very many birds become infected with this disease, fewer than 1%, but when we do diagnose a bird with mycobacteriosis, as we did in this imperial pigeon, the primary concern is that the pigeon could have silently spread its infection to other birds that it contacted.  Being a 25 year old pigeon means that this particular bird spent a lot of years in our Zoo and could have shared enclosures with many other birds.  If this pigeon was infected for months or years before we detected it, are the birds with which it was housed over time at risk for developing mycobacteriosis, too? 

This is just one of the epidemiologic questions we are trying to answer in our ongoing research in Disease Investigations. We are using state of the art techniques that include looking at whole mycobacterial genomes and social network analysis to better understand to what extent the disease may (or may not!) be contagious.