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Pieter Johnson, an assistant professor of ecology and evolutionary biology, 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, for instance, a team led by Johnson reported how human-induced ecosystem changes have helped spread diseases that affect multiple species.

The team’s research, reported in the Proceedings of the National Academy of Sciences, 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.

In the Proceedings of the National Academy of Sciences, Johnson’s team 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.

That’s because nitrogen and phosphorous from eutrophication promote the growth of algae, which increases the number and vigor of the herbivorous snails. Parasites, worms called trematodes, infect the snails.

Those more robust and numerous snails harbor more trematodes, which, in turn, infect more green frogs.

Frogs infected with parasitic trematodes frequently suffer limb deformities, such as the growth of extra legs or malformed legs. 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) are shared between human and wildlife 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 team aim to focus further on 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 the loss of biodiversity and increase in human alteration of natural ecosystems emphasize the importance of ecological research on emerging disease, he said.

Johnson has a record of ground-breaking research. In the 1990s, a spate of frog-limb deformities baffled scientists. A team led by Johnson published a paper in Science in 1999 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 whose results were 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 is the 10th ���������� faculty member since 1988 to win a Packard Fellowship.

Johnson has 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 has also won a $99,700 grant from the Colorado Division of Wildlife to study the possible causes of decline of amphibians, which are the world’s most threatened class of vertebrates.

“This is wonderful news,” notes ecology and evolutionary biology chair Jeffry B. Mitton. “EBIO is a great department.”