Infectious Diseases 2006

Infectious Diseases 2006

USA: Low pathogenic avian influenza

15 August, 2006

A low-pathogenic strain of avian influenza was found in two wild swans as the result of the expanded avian influenza surveillance program.
The U.S. Department of Agriculture (USDA) and U.S. Department of the Interior (DOI) announced the discovery of two wild mute swans infected with a low-pathogenic H5N1 of the avian influenza virus. The two swans were found in Michigan as part of the recently expanded avian influenza surveillance program. Preliminary results have ruled out the possibility of this being the highly-pathogenic H5N1 strain that has spread through wild birds in Asia, Europe, and Africa.
USDA chief veterinarian Dr. Ron DeHaven said during a news conference that the swans did not exhibit signs of illness nor were any other birds in the area showing any signs of illness. This suggests that the swans were infected with low-pathogenic avian influenza. Additionally, genetic analysis of the virus conducted at USDA’s National Veterinary Services Laboratories (NVSL) in Ames, Iowa, suggested that it is similar to a low-pathogenic strain that has been found in North America -- in the United States in 1975, 1986, and in Canada in 2005.
DeHaven said it is possible that the swans were not infected with an H5N1 strain, but instead, with two separate avian influenza viruses, one containing H5 and the other containing N1.
The confirmatory testing underway at NVSL will clarify whether one or more strains of the virus are present, the specific subtype, as well as pathogenicity. These results are expected within two weeks.
The swans were sampled August 8 at the Mouillee state game area located on the coast of Lake Erie in Monroe County, Michigan. The samples were taken by USDA Animal and Plant Health Inspection Service personnel as part of an expanded wild bird monitoring program. USDA and DOI are working collaboratively with the states to sample wild birds throughout the United States for the presence of highly-pathogenic avian influenza.
DeHaven also emphasized that under World Animal Health Organization rules, the presence of low-pathogenic avian influenza does not warrant trade sanctions.