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Report: Biodiversity can slow the spread of pathogens

The last living boreal toad found 2006 in the Cucumber Gulch wetlands in Breckenridge, Colorado. BOB BERWYN PHOTO.

Healthy ecosystems with all species present can slow the spread of deadly disease like the chytrid fungus that’s killing boreal toads

By Summit Voice

SUMMIT COUNTY — Species diversity may play a key role in slowing the spread of pathogens like the chytrid fungus that’s killing amphibians all over the world.

“With greater diversity of species, you get a dilution effect that can reduce the severity of disease,” said Catherine Searle, an Oregon State University zoologist and lead author of a recent study that looks at the role of biodiversity in slowing the spread of deadly diseases. “Some species are poor hosts, some may not get infected at all, and this tends to slow disease transmission,” she explained.

“This has been shown in other systems like Lyme disease which infects humans, mice and deer,” she said. “No one has really considered the dilution effect much in amphibians, which are experiencing population declines throughout the world. It’s an underappreciated value of biodiversity.”

The findings add to the evidence that biodiversity is important to many ecosystems. The study will be published this week in Proceedings of the National Academy of Sciences. The researchers worked in a  laboratory to show that increased species richness decreased both the prevalence and severity of infection caused by the deadly chytrid fungus, Batrachochytrium dendrobatidis.

“Emerging infectious diseases are on the rise in many ecosystems,” said Andrew Blaustein, a co-author on this study, professor of zoology at OSU and leading researcher on the causes of amphibian declines.

“Protection of biodiversity may help reduce diseases,” he said. “It’s another strong argument for why diverse ecosystems are so important in general. And it’s very clear that biodiversity is much easier to protect than it is to restore, once it’s lost.”

The dilution effect can occur in plants and animals, but also in human diseases. In a different report published last year in Nature, researchers noted an increased risk of West Nile encephalitis in the U.S. in areas with low bird diversity. And in more diverse communities, the infection of humans by schistosomiasis – which infects 200 million people worldwide – can be reduced by 25-99 percent.

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One Response

  1. Habitat destruction. One thing is abundantly clear, the decline of species is directly in concert with the increase of the human population expansion. Equilibrium is out of whack. As the story goes, it’s much easier to protect, than it is to restore, once it’s lost. Food for thought.

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