October 26, 2006

 

US researchers identify potential bird flu transmitters

 

 

University of Georgia researchers Tuesday (Oct 24) said in a release that the common wood duck and laughing gull are very susceptible to highly pathogenic H5N1 bird flu viruses and have the potential to transmit them.

 

The findings demonstrate that different species of North American birds would respond very differently to infection.

 

David Stallknecht, associate professor in the department of population health at the UGA College of Veterinary Medicine and co-author of the study, said knowing which species are likely to be affected by highly pathogenic H5N1 viruses is a vital component of efforts to quickly detect the disease should it arrive in North America.

 

"It was very interesting that in some species that you normally think of as influenza reservoirs--the mallard, for instance--the duration and extent of viral shedding is relatively low," Stallknecht said. "This may be good news since it suggests that highly pathogenic H5N1 may have a difficult time surviving in North American wild birds even if it did arrive here."

 

The species studied were: Mallards, which are often infected with commonly circulating, low-pathogenic bird flu viruses in North America and Eurasia; Northern pintails and blue-winged teal, which migrate long distances between continents; redheads, a diving species; and wood ducks, which breed in Northern and Southern areas of the US The laughing gull is a common coastal species ranging from the Southern Atlantic to the Gulf Coast.

 

Stallknecht said in low-pathogenic bird flu, most of the virus is shed in the faeces. The virus then spreads as other birds drink contaminated water. The study found that in highly pathogenic H5N1 bird flu, however, the birds shed most of the virus through their respiratory tract.

 

Stallknecht said that with this knowledge, scientists can detect the virus in live birds more effectively by swabbing the birds' mouths and throats.

 

In a related study scheduled to be published in the December issue of the journal Avian Diseases, the researchers quantified how long the virus persists in water. They found that highly pathogenic H5N1 bird flu viruses don't persist as long as common low-pathogenic strains. In some cases, persistence times were reduced by more than 70 percent.

 

This could affect transmission and supports the idea that these viruses may not have much of a chance of becoming established in North America.

 

Stallknecht said the finding is encouraging, but cautioned that it's difficult to put it into context without results from a study his team is currently working on that will assess the minimum amount of virus it takes to infect a bird.