“I was talking with a fisherman in a bar in Anchorage…” Thus began a lecture on “Amphibian Abnormalities and their Environmental Linkages: Observations and Musings after a Decade of Research” by ecologist Mari K. Reeves, with the U.S. Fish and Wildlife Service in Alaska. Reeves was speaking at Oregon State University on April 3, 2015, as part of the One Health Seminar Series that veterinarian/PhD-candidate Rhea Hanselmann has been promoting on campus (http://vetmed.oregonstate.edu/one-health-seminars ).
The final talk in the series, “Tales from the Public Health Division: investigations of zoonotic disease outbreaks,” by Paul Cieslak, MD with the Oregon Department of Human Services, takes place on May 1, 2015 at ALS 4001.
One Health is “the concept that the health of humans, animals, and the environment are directly linked, and that the condition of one can affect the health of the others.” It is a global movement endorsed by the World Health Organization (WHO) and many other national and international organizations seeking to unite healthcare efforts for more comprehensive prevention and treatment of disease. Given that 70% of new and recurring human diseases are related to animal carriers or environmental stressors, it makes sense to address well-being in this more holistic way. Hanselmann, who is researching the effects of environmental change on the incidence of Hanta-virus infections, is working with Luiz Bermudez in the Department of Biomedical Sciences to develop One Health courses. They hope that OSU will begin to offer integrative classes and eventually a One Health credential program for undergraduate students.
In Reeves’ talk, the fisherman with whom she had been talking had a surprising analogy for “Mother Nature.” He argued that nature is not a mother, but rather a baby. Babies are resilient, he pointed out, but they need a great deal of care. While they may heal from some injuries quickly, seemingly minor trauma can have long-term consequences that may not be immediately apparent. Connecting the fisherman’s insight with her One Health perspective, Reeves showed a modified graph based on C. S. Holling’s 1973 visualization demonstrating a threshold for resilience that takes into account the accumulation of stressors. While an animal, human, or ecosystem may be able to recover from an insult readily if it is already in a relatively healthy state, recovery is more difficult when stressors accumulate. Multiple stressors and low- level stressors can have significant impacts, but are very difficult to study.
To demonstrate the effects of small, non-toxic doses of a contaminant, Reeves showed a video of an experiment in which one could see that when an uncontaminated (control) fish smells a predator, it immediately sinks to the bottom of the tank to hide. In contrast, fish exposed to minute amounts of copper seemed fine, but were not able to smell the predator signal the same way that the uncontaminated fish did. When the predator smell was released into the tank, these exposed fish did not sink to the bottom and hide, and not smelling danger, they quickly became prey.
What does this have to do with studying frogs? When studying stressors affecting the health of frogs, it can be difficult to pinpoint relatively small changes in their environment. However, as for the fish in the experiment above, even minute stressors such as barely measurable levels of pesticides or heavy metals can have significant impacts on frog populations, especially when combined with other stressors. As advocates of the One Health perspective have argued, this is true for other creatures as well, including humans.
Frogs have historically been a favorite creature for biological studies, because so much of their development is visible as they change from egg to tadpole to frog. Because they then migrate to totally different habitats, they are also exposed to a wider variety of environmental hazards than most other species. When a frog population starts declining rapidly, or includes many frogs with deformed or extra limbs as was noticed in the Midwest several years ago, how can one tell what is going on? Pollutants, parasites, predators, climate change – any of these could be driving the demise of a frog population. In a large-scale study published by Reeves and her colleagues in Ecological Monographs (August 2010), the researchers found that the most important factor in frog survival was where they lived. The quality of their habitat proved to be a mitigating factor for other stressors, contributing to better health and survival rates. Again, the corrolary lesson for humans seems clear: protecting our habitat is the best way to protect our health.
Unfortunately for frogs, clean habitat is hard to come by. A 2013 study by the U.S. Environmental Protection Agency showed that over half of U.S. streams and rivers are in poor condition. Reeves ended her talk with a call for help in cleaning up our waterways. Her descriptions of frogs inspire a deep sense of delight and wonder in these amazing creatures. Furthermore, in helping frogs, we very likely will be helping ourselves in ways we don’t yet understand.