Since early December, more than two dozen bald eagles have turned up dead along the banks of the Great Salt Lake, and now wildlife officials in Utah have identified the killer: a rare wintertime outbreak of West Nile virus.
The 27 dead eagles contracted the virus after preying on infected waterfowl called eared grebes, which stop at the lake during their annual migration from Canada to Mexico. An additional five bald eagles are responding to treatment for leg paralysis and body tremors at local rehabilitation centers, officials said.
West Nile virus typically afflicts birds during warmer months, when the mosquitoes that carry it are active. But Utah had a very warm fall that extended the insects’ breeding season into late October.
The birds do not pose a risk to humans, but officials cautioned that people should not handle sick or dead eagles.
“People become infected with West Nile virus after being bitten by a mosquito that carries the virus,” JoDee Baker, epidemiologist with the Utah Department of Health, told "NBC News." “Since the mosquitoes that transmit West Nile virus aren’t active in the winter, there’s no risk to the public’s health." According to the U.S. Centers for Disease Control and Prevention, there were 2,318 confirmed cases of West Nile virus in the U.S. in 2013, with 105 deaths.
After soaring back from near extinction in the 1960s, bald eagles were removed from the federal endangered species list in 2007, though they are still protected under the Bald and Golden Eagle Protection Act. The U.S. Fish and Wildlife Service estimates more than 9,500 nesting pairs of bald eagles live in the contiguous U.S.
Habitat destruction and the contamination of the birds' food source, largely as a consequence of the insecticide DDT, decimated the population half a century ago. Officials estimate that only 475 breeding pairs existed in 1963, down from 100,000 in 1782 when America’s Founding Fathers designated the bird as the national symbol.
Officials are not worried that the virus will have long-term effects on the 750 to 1,200 bald eagles that migrate to Utah each winter to feed.
“Even though it’s difficult to watch eagles die, the deaths that have and still might occur won’t affect the overall health of the bald eagle population that winters in Utah or the overall population in the United States,” said McFarlane.
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Original article from TakePart