Sep 13, 2006 (CIDRAP News) – Final tests confirmed that a mild strain of H5N1 avian influenza virus, not the deadly type, was found in wild mallard ducks in Maryland last month, the US Department of Agriculture (USDA) said yesterday.
In August, investigators found the virus in fecal samples from resident mallards on the state's eastern shore that showed no signs of illness. The samples were sent to the USDA National Veterinary Services Laboratory (NVSL) in Ames, Iowa, where nine tested positive for an H5N1 virus. Subsequent genetic analysis suggested that the virus was a mild strain, but more tests were slated to characterize the pathogenicity.
In yesterday's announcement, the USDA confirmed the samples contained the "North American strain" of low-pathogenic H5N1 virus. Low-pathogenic strains commonly occur in wild birds and cause only minor sickness or no noticeable disease. However, they can evolve into lethal strains.
The same low-pathogenic form of the virus was confirmed in Michigan swans in late August. Also, test results are pending on samples recently taken from Pennsylvania ducks, which tested positive for the mild strain on initial screening tests in early September.
The rash of positive tests for the mild strain of H5N1 avian flu comes amid expanded wild bird testing programs spearheaded by the USDA and the Department of the Interior in collaboration with state game personnel.
In other news, chickens in southern Sudan have tested positive for the lethal form of H5N1, according to a Reuters report today. A Sudanese agriculture official said the samples were taken in August. He also said his department had received more reports of deaths and sickness in domestic birds last week and that test results are pending.
According to data from the United Nations Food and Agriculture Organization (FAO), Sudan's last report of avian flu outbreaks in poultry was in April.
A health official in Egypt, Sudan's northern neighbor, reported last week that H5N1 had resurfaced at a chicken farm in the southern part of the country.
Sep 12 USDA press release on H5N1 test results in Maryland ducks
Sep 5 CIDRAP News story "Tests indicate mild H5N1 virus in ducks in 2 states"
Dec 30, 2005, CIDRAP News story "H5N1 avian flu viruses: What's in a name?"