Exotic pathogens and native wildlife

Those who have been following Zoo Atlanta’s activities may know that our Herpetology Department has been very active in the realms of research and conservation of amphibians, with regards to the catastrophic amphibian chytrid fungus. Our work has ranged from local field surveys to global policymaking. The take-home point on that issue is that non-native species can cause huge problems in foreign ecosystems. In this case, the non-native species happens to be a genetic strain of a pathogenic fungus that became an emerging infectious disease in wildlife (amphibians). While amphibians were the first example we had of such a phenomenon, in the last 15 years we have seen the precedent play out all over again, for example with the white-nose fungal syndrome in bats. Snake fungal disease is another example. Both of those pathogens recently have been found in Georgia. As in amphibians, where we learned the hard way that eradicating or controlling fungal diseases in the wild appears to be impossible, the situation for our bats and snakes is concerning.

Now let’s switch our attentions to the oceans. Just a couple of years ago, alert sports divers along the U.S. Pacific Coast began reporting large numbers of dead and dying starfish (or sea stars, if you prefer). The Monterey Aquarium maintains extremely healthy sea life by pumping in clean seawater from offshore, but suddenly lost all of its starfish to what is now called starfish wasting disease. Pacific ecosystems already are showing major changes in shellfish populations, upon which the starfish used to feed. This is a big deal, with massive ecological implications. Emerging infectious diseases in wildlife are more and more becoming major conservation concerns, and researchers are scrambling to characterize the pathogens and epidemics as best they can. Many of these situations have a single thing in common—exotic wildlife that release their native pathogens into new ecosystems. Lacking any evolutionary exposure to these new pathogens, the local host-species may explode into regional epidemics. With this information in mind, I was terrified to read a recent paper in the journal Science (Carlton et al., 2017) that described the massive numbers of non-native marine invertebrates (and even a few fishes) that have rafted to our Pacific Coast from Japan, attached to the millions of floating objects washed to sea during the deadly Fukushima tsunami. How many of these exotic species will become established on our coastline? What ecological effects will they have here? And, with all my experience with the amphibian chytrid fungus, when I hear about exotic species now, my thoughts go directly to the question: “What exotic pathogens might they be carrying?” Controlling established exotic species, such as Burmese pythons, is difficult enough, but exotic pathogens are even more insidious.

The original publication:
Carlton, J. T., et al. 2017. http://science.sciencemag.org/content/357/6358/1402

National Geographic Video Starfish Wasting Disease (warning: graphic images): http://video.nationalgeographic.com/video/news/150915-starfish-struggle-wasting-disease-vin

Natural History Magazine article on tsunami flotsam: http://www.naturalhistorymag.com/features/252279/tracking-tsunami-flotsam

Joe Mendelson, PhD
Director of Research