Jul 12, 2007 (CIDRAP News) – The US Department of Agriculture (USDA) confirmed yesterday that turkeys from a Virginia farm carried antibodies indicating possible past exposure to a mild form of H5N1 avian influenza virus.
Virginia's agriculture department had announced Jul 9 that samples collected during routine preslaughter testing initially showed the birds had antibodies to an H5 virus. In a press release yesterday, John Clifford, the USDA's chief veterinary officer, said tests at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa, indicated that the antibodies correspond to an H5N1 subtype.
"There have been no signs of illness or death in the birds, indicating that this is not the highly pathogenic H5N1 virus that has spread through birds in Asia, Europe, and Africa," Clifford stated. The NVSL will run further tests to better identify the virus the birds may have been exposed to, Clifford said.
So far, tests suggest that the antibodies detected correspond to the low-pathogenic North American strain of H5N1, which usually causes only minor illness or no noticeable signs in birds, the USDA said.
Several thousand poultry samples collected from other poultry operations near the affected Shenandoah Valley turkey farm have all tested negative for avian influenza, which further suggests that the antibodies found in the turkeys involve a common avian flu virus that poses no threat to humans, Clifford said.
When the USDA expanded its avian flu testing program for wild birds beyond Alaska in 2006, several birds, such as a green-winged teal in Delaware and mallard ducks in Illinois and Michigan, tested positive or were presumed positive for the mild North American H5N1 strain.
In a fact sheet on the low-pathogenic H5N1, the USDA said the strain was detected in apparently healthy wild birds as long ago as 1975. In 2002, antibodies to the same strain were found in samples from Michigan turkeys, but the virus could not be isolated.
After Virginia officials announced the antibody findings, Richard Wilkes, the state veterinarian, banned all bird sales and exhibitions until Jul 30 and restricted the application of poultry litter on fields in 17 counties, according to a Jul 9 press release.
In other avian flu news, veterinary officials in the Czech Republic announced today that tests have confirmed the lethal H5N1 strain at two more poultry farms, bringing the number of outbreaks in the country to four, Reuters reported today.
The farms are in the eastern part of the country, within a 3-kilometer protective zone around another farm where H5N1 was recently detected, the Reuters report said.
Josef Duben, a state veterinary authority spokesman, told Reuters veterinarians were preparing to cull all 71,000 birds on the farms.
The Czech Republic reported its first poultry outbreak in late June, though wild swans in the country had tested positive for H5N1 in the spring of 2006. Since the Czech poultry outbreak, Germany has reported H5N1 in wild birds and in one domestic bird, a pet goose, and France has announced positive findings in wild birds.
Meanwhile, animal health officials in Vietnam said 2 days ago that two more provinces had reported H5N1 findings in ducks, according to a report yesterday by Xinhua, China's state news agency. The disease has struck 500 ducks owned by six households in Dien Bien province in northern Vietnam, where several other provinces have also reported recent outbreaks.
USDA fact sheet on low-pathogenic H5N1