CSU to use clams to track bird flu

By Bill Scanlon, Rocky Mountain News (Contact)

Published April 7, 2008 at 12:45 p.m.
Updated April 7, 2008 at 4:14 p.m.

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Clams are fun to eat, but could prove invaluable in tracing the spread of bird flu.

This summer, scientists from Colorado State University will fly to Vietnam, place fresh-water clams in strategic waterways and see whether the mollusks have absorbed the H5N1 avian flu virus into their systems.

Using clams, rather than mechanical filters, to gauge the spread of bird flu is the idea of CSU's Department of Fish, Wildlife and Conservation Biology, and the Agriculture Department's National Wildlife Research Center.

CSU's Kate Huyvaert and USDA's Alan Franklin have found that freshwater clams accumulate bird flu viruses in their tissues when they filter water contaminated with the virus.

The clams could become an important weapon in tracing bird flu in the wild. Some epidemiologists worry that bird flu will be the next great pandemic, similar in scope to the influenza outbreak of 1918-19.

Avian flu is particularly prevalent in domestic foul, such as hens and ducks, in southeast Asia, and occasionally has infected humans who've either eaten poorly cooked infected birds, or who have been in close contact with the birds because they maintain backyard poultry.

Scientists have studied domestic flocks extensively for bird flu, but know much less about the extent to which avian flu has spread to wild birds that have the capacity to migrate across oceans and continents.

That's where the clams can be particularly effective.

"What is really neat is that we are harnessing nature to learn about a virus that affects humans and wildlife," Huyvaert said. "Not only are clams cost-effective, but we learn more about the ecological process of the virus interacting with other organisms."

This summer, CSU researchers will expose Asiatic clams to bodies of water in northern Vietnam where infections have been identified in local birds.

The Asiatic clams are widespread in Asia and previously have been used to monitor heavy metals and other contaminants.

The CSU scientists also will do a baseline survey of avian viruses carried by wild land birds in forests and in residential areas of northern Vietnam.

Thinh Vu, a doctoral student at CSU, will test his prediction that birds living in the forest's interior are less likely to carry the virus than birds that live at the forest edge and close to humans and other domestic birds.

Vu thinks health officials in southeast Asia may have underestimated the presence of the virus in land birds. He says land birds could play an important role in circulating the avian flu virus.

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