Pieter Johnson, an assistant professor of ecology and evolutionary biology at the University of Colorado at Boulder, has won a highly prestigious David and Lucille Packard Fellowship, a five-year award that will support his study of emerging diseases in changing environments.
Johnson will use the $875,000 award to continue his pioneering research on emerging diseases. Last year, a team led by Johnson reported how human-induced ecosystem changes have helped spread diseases that affect multiple species.
Johnson is the 11th CU-Boulder faculty member since 1988 to win a Packard Fellowship.
Johnson found that aquatic environments with high levels of nitrogen and phosphorous, usually from fertilizer runoff or sewage effluent, precipitate a chain-reaction of parasitic infections in three species: birds, snails and amphibian larvae.
Johnson's team, which published its results in the Proceedings of the National Academy of Sciences, was the first to report the mechanism of cascading events from excessive nutrient enrichment, or eutrophication. Freshwater snails become larger and more numerous with eutrophication.
According to Johnson, nitrogen and phosphorous from eutrophication promote algae growth, which increases the number and vigor of the herbivorous snails. Parasites, worms called trematodes, infect these snails.
Those more robust and numerous snails harbor more trematodes, which in turn infect more green frogs, he said.
Frogs infected with parasitic trematodes frequently suffer limb deformities, growing extra or malformed legs, Johnson said. Frogs with limb deformities are easier prey for birds, which eat the parasitically infected frogs and whose waste perpetuates the cycle.
With the Packard Fellowship, Johnson hopes to expand upon such work. Many emerging diseases such as West Nile virus jump between wildlife and human hosts, and he notes the need to understand the relationship between an increasingly altered environment and emerging diseases.
"By combining experiments, field studies, long-term data and ecological monitoring, my lab seeks to identify how environmental changes affect disease, and reciprocally, how changes in disease feed back to influence ecosystems."
Johnson and his colleagues also will further investigate nutrient enrichment, the interaction between biodiversity loss and disease, and the relationship between climate change and disease.
Ecologists have not traditionally studied disease, Johnson said. But biodiversity loss, often from human alteration of natural ecosystems, emphasizes the importance of ecological research on emerging disease, he said.
Johnson is known for groundbreaking research. In the 1990s, a spate of frog-limb deformities baffled scientists. A team led by Johnson published a 1999 paper in the journal Science reporting compelling evidence that the deformities were caused not by pollution, as was widely suspected, but by parasitic trematodes.
Johnson was an undergraduate at Stanford University when he and his team did the experiments reported in Science. At that time, "most of the scientific community had ignored or even ridiculed the idea that parasites could create deformities," The New York Times noted in its coverage of Johnson's 1999 paper.
Johnson also just won a $107,764 grant from the Morris Animal Foundation to study amphibian declines in Colorado. And with EBIO Research Associate Val McKenzie, Johnson also won a $99,700 grant from the Colorado Division of Wildlife to probe the causes of the decline of amphibians, the world's most threatened class of vertebrates.
"This is wonderful news," said ecology and evolutionary biology Chair Jeffry B. Mitton. "EBIO is a great department."