August 15, 2006

 

USDA: Michigan bird flu case not deadly Asian strain

 

 

The strain of bird flu, announced by the US Department of Agriculture apparently is H5N1, but it is a low-pathogenic version and is not similar to the deadly Asian strain, according to a USDA official Monday (Aug 14).

 

The discovery of the H5N1 strain in wild mute swans in Michigan is the North American version and is likely similar to the one that was found in Canada earlier this year, the USDA said.

 

The highly pathogenic H5N1 Asian strain of bird flu is deadly to many avian species including domestic chickens, turkeys and other poultry. The disease is carried by migratory birds and typically spreads along their flyways.

 

Bird flu comes in many forms, most of which are low pathogenic variants that may not even result in symptoms in infected birds, according to Carol Cardona, extension poultry veterinarian at the University of California, Davis, in a press release earlier.

Earlier this year, the USDA announced plans to expand its search for bird flu into the lower 48 states from its focus on Alaska.

 

"Bird flu is caused by type A influenza virus and can vary from a mild disease with little or no mortality to a highly fatal, rapidly spreading epidemic (highly pathogenic bird flu) depending on the infecting virus strain, host factors and environmental stressors," Cardona said in the release.

 

Most bird flu viruses have been isolated from ducks, although most free-flying birds also may be infected, she said. Waterfowl are more resistant to bird flu than are domestic poultry. Viruses can cause no obvious disease in waterfowl but can be highly pathogenic (rapidly fatal) in domestic poultry.

 

Trade sources have said the main US chicken and turkey flocks are relatively insulated from the disease because they are raised indoors, minimising the chance of contact with wild birds or their faeces. Most veterinarians and trade sources in the US say the chances of widespread transmission in the US, therefore, is much lower than in other countries where contact with live and dead birds by families is much greater.

 

Meanwhile, neighbouring Canada said the discovery of the low-pathogenic strain of bird flu in Michigan should have no impact on its trade relations with the US.

 

"According to the World Organisation for Animal Health (OIE) guidelines and our understanding with the US, a finding of this kind in wild birds is something that isn't unexpected and has no impact on cross-border trade between Canada and the US," said Dr. Jim Clark of the Canadian Food Inspection Agency.