Infectious Diseases 2006

Infectious Diseases 2006

Montana Wild Bird Samples Undergo Additional Avian Influenza Testing

21 September, 2006

The U.S. Departments of Agriculture and Interior today announced a detection of the H5 and N1 avian influenza subtypes in samples from wild Northern pintail ducks in Montana. Initial tests confirm 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 duck samples were collected on Sept. 15 in Cascade County, Montana, by Montana Fish, Wildlife and Parks as part of a cooperative, expanded wild bird monitoring 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. Of the 66 samples tested at the Colorado State University state lab, 16 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, the specific subtype, as well as confirm the pathogenicity. These results are expected within two to three weeks and will be made public when completed.
The Departments of Agriculture and Interior are working collaboratively with States to sample wild birds throughout the United States as well as in Canada and Mexico for the presence of highly pathogenic avian influenza (HPAI). As a result of this expanded testing program, USDA and DOI expect to identify additional cases of common strains of avian influenza in birds, which is not cause for concern.
Low pathogenic avian influenza commonly occurs in wild birds and can be found in a number of duck populations including the Northern pintail. It typically causes only minor or no noticeable symptoms. These strains of the virus include LPAI H5N1, commonly referred to as North American H5N1, which is very different from the more severe highly pathogenic H5N1 circulating overseas.
Duck populations, including Northern pintail ducks, are commonly hunted. There is no known health risk to hunters or hunting dogs from contact with low pathogenic forms of avian influenza virus (USDA).