Apr 2, 2007 (CIDRAP News) – Officials in West Virginia yesterday planned to cull about 25,000 turkeys at a farm after routine tests indicated that some were probably exposed to a low-pathogenic H5N2 avian influenza virus, the US Department of Agriculture (USDA) announced yesterday.

Authorities discovered the virus 2 days ago during preslaughter surveillance conducted by a poultry industry group, the USDA said in a press release. The birds showed no signs of illness, and none had died. A West Virginia Department of Agriculture official said the farm is in Pendleton County in the east-central part of the state, according to a Reuters report.

"We can say for certain that this is not the highly pathogenic H5N1 virus that has spread through birds in Asia, Europe, and Africa," John Clifford, the USDA"e;s chief veterinary officer, said in the press release. He added that the test results suggested that the virus was a low-pathogenic strain, which poses no risk to human health but is common in birds and typically produces minor illness or no noticeable symptoms.

The USDA"e;s National Veterinary Services Laboratory will conduct sequencing and pathogenicity tests to further identify the virus, Clifford said.

The USDA"e;s policy is to cull birds that have H5 or H7 influenza viruses, because they can mutate into highly pathogenic strains, Clifford said. The poultry"e;s owner participates in the National Poultry Improvement Plan and therefore will be compensated for the loss.

The last H5N2 avian flu outbreak in the United States occurred in February 2004 at a chicken farm in Gonzales County, Tex. A flock of 7,000 broiler chickens was culled after the H5N2 outbreak, the country"e;s first in 20 years.

A genetic study of the 2004 Texas H5N2 outbreak strain showed it was highly pathogenic, though the clinical signs were consistent with a low-pathogenic strain. The findings led researchers to reexamine what avian flu viruses should be reported to the World Organization for Animal Health (OIE), according to a 2005 report in the Journal of Virology. Clifford said countries must now report all H5 and H7 detections to the OIE.