National Wildlife Health Center

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Wildlife Health Bulletin #06-06

To: Natural Resource/Conservation Managers  
From: Leslie Dierauf, Director, USGS National Wildlife Health Center
Title: Low-path Avian Flu H5 and N1 Found in Northern Pintails in Montana
Date: September 25, 2006

On September 21, 2006, the U.S. Departments of Agriculture and Interior announced the detection of H5 and N1 avian influenza subtypes in samples from wild Northern pintail ducks in Montana. Initial tests confirmed that these samples do not contain the highly pathogenic H5N1 strain that has spread through birds in Asia, Europe and Africa. These samples were collected from apparently healthy ducks and initial test results indicate the presence of low pathogenic avian influenza (LPAI) virus, which poses no threat to human health.

The samples were collected at the Benton Lake National Wildlife Refuge (NWR) in mid-September by Montana Fish, Wildlife and Parks and US Fish and Wildlife Service as part of the expanded interagency wild bird avian influenza surveillance program. Sixty-six samples were collected directly from the birds using cloacal swabs. Samples were initially screened at the Colorado State University Veterinary Diagnostic Laboratory. Sixteen of the 66 samples were sent to USDA's National Veterinary Services Laboratory (NVSL) in Ames, Iowa, for confirmatory testing.

One of the 16 samples screened by NVSL tested positive for both H5 and N1. However, this does not mean these birds are infected with an H5N1 strain. It is possible that there could be two separate avian influenza viruses, one containing H5 and the other containing N1. Confirmatory testing underway at NVSL will clarify whether one or more strains of the virus are present and the identity of the specific subtype(s), as well as confirm the pathogenicity. These results are expected within two to three weeks and will be made public when completed.

Benton Lake NWR is located on the western edge of the northern Great Plains, 50 miles east of the Rocky Mountains and 12 miles north of Great Falls, Montana. The Refuge’s 12,383 acres are dominated by native shortgrass prairie and surrounded on three sides by mountain ranges. During spring and fall migrations, up to 150,000 ducks, 2,500 Canada geese, 40,000 snow geese, 5,000 tundra swans, and as many as 50,000 shorebirds use the marsh.

The Refuge is also home to the largest breeding colonies of Franklin's gulls and white-faced ibis in Montana. Bald eagles are commonly seen in the spring and fall, and chestnut-collared longspurs, grasshopper sparrows, and burrowing owls nest in Refuge uplands.

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For additional information on avian influenza, please go to:

For information about the federal government’s overall efforts related to avian influenza and human pandemic preparations, go to

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