Avian malaria marches northward as climate warms

7:38 AM, Sep 25, 2012   |    comments
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By Susanne Rust

Super-hot summers, explosive storms and melting ice caps are the usual images that spring up when discussing climate change.

But researchers at San Francisco State University are bringing the conversation to the birds.

These scientists have found that as the climate changes and the northern latitudes heat up, avian malaria - a devastating bird disease - is steadily creeping toward the North Pole.

And when it gets there, it could prove to be devastating to arctic birds that have no immunity to the virus.

"Right now, there's no avian malaria above latitude 64 degrees," said Ravinder Sehgal, an SFSU associate professor of biology. "But in the future, with global warming, that will certainly change."

Sehgal and his team took blood samples from birds in three Alaskan cities: Anchorage, Fairbanks and Coldfoot.

They found that of the 676 birds they sampled, slightly more than 7 percent were infected. These included Boreal chickadees, black-capped chickadees and fox sparrows.

Claire Loiseau, lead author on the study and an SFSU postdoctoral student, could not be reached for comment; she is in French Guiana doing field work.

The research appeared in the journal the Public Library of Science.

"In general, the parasite can affect the fitness of the birds, meaning how many eggs the birds may lay," Sehgal said. "Of course, it can kill many birds, too, such as penguins, and many birds in Hawaii went extinct in large part because of avian malaria."

Evidence of the disease was found in samples taken from the two more southern Alaska cities, but not in Coldfoot.

The researchers, who were also from UCLA, UC Davis, the University of Alaska Fairbanks and the federal Bureau of Land Management, then built a predictive map, using current data and future predictions on temperature and precipitation.

They found that the malaria parasite can survive and reproduce in a thin band just south of 64 degrees north latitude. But if current projections for climate are correct, that band will move north.

Sehgal said the disease is likely to push south, too.

"Penguins in zoos die when they get malaria, because far southern birds have not been exposed to malaria and thus have not developed any resistance to it," Sehgal said. "There are birds in the north, such as snowy owls or gyrfalcons, that could experience the same thing."

Sehgal and his team still are uncertain how the parasite is being spread in Alaska, but they now are collecting mosquitos to see which ones are responsible and to get a better sense of how the disease is being transmitted.

They also are hoping their research will shed light on human malaria and its interaction with climate change.

"Human malaria used to be common in the Northern Hemisphere, but modern medicine and eradication of mosquito vectors limited the spread," he said. "We believe that global climate change may lead to an increase in malaria at higher elevation - in mountainous regions - where human malaria is endemic."

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