Sept. 22, 2012, 10:16 p.m.
ANCHORAGE, Alaska (Reuters) - Malaria is infecting birds as far north as Alaska's interior, and a rapidly warming climate may be the reason the mosquito-borne disease appears to be advancing northward, a new study shows.
It is the first time scientists have detected the transmission of avian malaria in local birds at such far-north latitudes anywhere in North America, said the study, published on Wednesday in the scientific journal PLOS One.
"We now have shown that malaria is being transmitted in Alaska," said Ravinder Sehgal, a San Francisco State University biologist and a lead researcher on the project.
While tropical birds that migrate to Alaska in the summer are known to carry the disease, there had never been any documented cases of it spreading to non-migratory Alaska birds or birds newly hatched in Alaska that had not yet flown south, Sehgal said.
Longer periods of warm weather in the summer may be allowing the malaria parasite to thrive in Alaska and be transmitted by mosquitoes, Sehgal said.
"The question was, how far north is it getting, and is it going to get to birds that have never expressed it?" he said.
The study notes that temperatures have been increasing in the Arctic at almost twice the average global rate, and that the warming climate has changed vegetation in the far north.
The study evaluated blood samples taken last year from birds in Anchorage, Fairbanks and Coldfoot, a community north of the Arctic Circle. The researchers found avian malaria in resident and hatch-year birds in Anchorage and Fairbanks, though not as far north as Coldfoot.
Of 676 birds tested, 7.2 percent were found to be infected. Some of the hardest-hit birds were black-capped chickadees, Sehgal said. Of the black-capped chickadees tested in Anchorage, about 30 percent were infected.
Further studies are underway to try to determine what type of mosquito might be spreading the disease, Sehgal said.
It is unclear what effect avian malaria might have on the Alaska birds. For some species elsewhere, malaria transmissions are devastating, Sehgal said.
Penguins, which have no natural defenses against malaria, die when they are infected in zoos, he said. Malaria also has seriously damaged bird populations in Hawaii, where non-native mosquitoes have been introduced to the habitat.
But Alaskans need not fear for their health, Sehgal said. The study detected only avian malaria, which is different from the type of malaria that afflicts mammals.
"Certainly, it is not going to spread to humans," he said.
(Editing by Cynthia Johnston and Xavier Briand)