March 20, 2014

Biologists Still Searching For Answers In Bald Eagle Deaths and other wildlife health news stories


Fish-Eating Ducks Hard Hit By Severe Winter, Ice

The Niagara River corridor from Lake Erie to Lake Ontario is renowned as a spectacular winter haven for hundreds of thousands of water birds. But this year's bitterly cold season has made it notable for something else: dead ducks.

Biologists say carcasses began piling up by the hundreds in early January after the plunging temperatures started icing over nearly the entire Great Lakes, preventing the ducks from getting to the minnows that are their main source of food. Necropsies on dozens of birds have confirmed the cause: starvation. "All have empty stomachs. They're half the weight they should be," said Connie Adams, a biologist in the state Department of Environmental Conservation's Buffalo office who has personally seen 950 dead birds.

"This is unprecedented. Biologists who've worked here for 35 years have never seen anything like this," she said. "We've seen a decline in tens of thousands in our weekly waterfowl counts." It's a phenomenon that has been seen elsewhere along the Great Lakes, with news reports of diving ducks and other waterfowl turning up dead by the hundreds along the southern part of Lake Michigan. They've also been found in Lake St. Clair between Lakes Erie and Huron.

... Necropsies and toxicity analyses showed many of the Michigan ducks were subsisting on invasive zebra mussels, which caused the birds to have potentially toxic levels of selenium in their bodies, Mason said. Zebra mussels filter toxins from the water and pass them up the food chain.

Most of the dead ducks seen in the upstate New York are red-breasted mergansers, which breed in northern Canada and Alaska and come south for the winter to the Great Lakes region. In most years, there are periods of freezing and thawing, providing enough breaks in the ice for them to dive for minnows.

Monroe News
15 Mar 2014
Location: Canada

Experimental infection of house sparrows (Passer domesticus) with West Nile virus isolates of Euro-Mediterranean and North American origins

...North American WNV outbreaks are often accompanied by high mortality in wild birds, a feature that is uncommon in Europe. The reason for this difference is unknown, but the intrinsic virulence of the viruses circulating in each continent and/or the susceptibility to the disease of Palearctic as opposed to Nearctic wild bird species could play a role.

To assess this question, experimental inoculations with four lineage 1 WNV strains, three from southern Europe (Italy/2008, Italy/2009 and Spain/2007) and one from North America (NY99) were performed on house sparrows (Passer domesticus), a wild passerine common in both continents. Non-significant differences which ranged from 0% to 25% were observed in mortality for the different WNV strains.

... Consequently, albeit being pathogenic for house sparrows, some Euro-Mediterranean strains had reduced capacity for replication in -and transmission from- this host, as compared to the NY99 strain. If applicable also to other wild bird host species, this relatively reduced transmission capacity of the Euro-Mediterranean strains could explain the lower incidence of this disease in wild birds in the Euro-Mediterranean area.

7th Space
19 Mar 2014

Cited Journal Article

Avian Botulism

Deer Health News
One Health News Corner
Huh?! That's Interesting!

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