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More Bird Species Means Fewer West Nile Cases

Jessica Marshall, Discovery News

"American robins have even been termed the 'super-spreader' by a couple of people," he said.

His analysis showed that increased numbers of robins corresponded to increased cases of West Nile infection. "But it was not as significant as overall diversity," he added.

Greater numbers of bird species in a given area may decrease the relative number of good hosts to poor hosts, reduce the total number of good hosts, or reduce the probability that a mosquito will spread the virus from one good host to another. But which of these possibilities is the dominant factor is not yet known.

The work fits in to a bigger overall body of research showing increased biodiversity reduces disease transmission to humans. The idea first gained wide attention in 2000, when Felicia Keesing of Bard College in Annandale, N.Y., and colleagues reported that human Lyme disease infection correlated to reduced diversity of the small mammals that Lyme-spreading ticks feed on.

As with bird hosts for West Nile Virus, certain mammals, like mice, are better hosts for Lyme disease than others, like deer, Keesing said.

"There's little that would motivate people to protect biodiversity as much as protecting their health would," Keesing said. "From my point of view our default position should be protecting diversity because it's going to reduce disease transmission for us and other species."

Planning developments so that they maintain large, common green areas, rather than having individual parcels of land with disconnected patches of trees is one strategy for maintaining diversity of birds or mammals, she said.

Related Links:

Discovery News blog: Environmental Case

Discovery News blog: Born Animal

CDC on West Nile Virus

CDC on Lyme Disease

How Stuff Works: West Nile Virus