Epidemi-what?

Micronesian kingfishers are highly endangered and seemingly quite susceptible to the avian mycobacteriosis disease.

Whenever I am asked “What do you do for a profession?,” I am often confronted with a familiar, perplexing look followed by a request for clarification: “Epidemi-what?” Epidemiologist. The first thing that seems to enter people’s minds is “epidermis,” the top layer of skin. But, no, I don’t study skin. An epidemiologist studies causes and patterns of disease and health in populations (think epidemic). But what does that really mean, and what role does this funny word play in wildlife conservation?

The field of epidemiology has its roots in human health and is something that most of us are exposed to every day. All of those health-related statistics (such as the ones that say that if you have high cholesterol, then you are more likely to develop heart disease) are generated by epidemiologists. Basically, the epidemiologists look for differences in frequencies of heart disease between groups that do and do not have high cholesterol. As you can guess there are probably a lot of other things that could affect whether someone develops heart disease. The art of epidemiology is dealing with those “other” things through the use of special scientific study designs and analytical techniques. Instead of people and heart disease, my subjects are animals and their health issues.

Epidemiologist Carmel Witte studies causes and patterns of disease and health in zoo animal populations.

One of my first projects was investigating avian mycobacteriosis. This bacterial bird disease has long been thought of as highly contagious: if one bird in an aviary acquires the disease, the fear is that it will quickly spread to all of the other birds. The management implications are significant, causing a halt to breeding of all endangered species living in entire aviaries. So, we decided to ask the simple question, “Is this disease really super-contagious?”

I began tackling this question by using archived animal health data generated by San Diego Zoo Global’s pathologists and veterinarians. I searched records from the past 20 years to identify all of the cases of mycobacteriosis that we ever had. Then, I analyzed thousands of bird records to see what kinds of exposure all of the collection birds had to the relatively small group of 79 infected birds. What I found was rather interesting: up to 96 percent of all birds coming into contact with a disease-carrying bird never developed mycobacteriosis. The conservation implications for this are big: it is likely that mycobacteriois isn’t super-contagious, and zoos probably don’t need to halt breeding when a case is diagnosed.

This avian mycobacteriosis project is just one of many that I continue to tackle with the Wildlife Disease Laboratories’ team. Some other projects include studying feline herpesvirus infections in cheetahs and investigating transmission patterns of herpesviruses and mycobacterial infections in hoofed animals. In all of these projects, my mission is to use epidemiology to help remove disease as a roadblock to conservation and solve pressing health problems in animals. Now that you know exactly what a zoo epidemiologist does, the next time you hear that funny word, you will have the privilege of bypassing the “Epidemi-what?”!

Carmel Witte is a senior research coordinator at the San Diego Zoo Institute for Conservation Research.

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