Likely H5N1 Spread to Second South Korean Duck Farm
Recombinomics Commentary 15:55
April 5, 2008
A second and third possible outbreak of bird flu were reported at duck farms in southwestern Korea over the weekend, sparking fears that avian influenza might be spreading across the country, a government body said yesterday.
The Ministry for Food, Agriculture, Forestry and Fisheries announced yesterday that the two other suspected cases — at poultry farms in Jeongeup and Sunchang in North Jeolla — will mean more disinfecting operations in the region.
Preliminary tests showed the presence of bird flu in Jeongeup, but such tests were not conducted at the other site in Sunchang, 74 kilometers south of the initial outbreak on a chicken farm in Gimje, North Jeolla.
Government officials said about 500 ducks have died during the last 10 days at Sunchang. The owner has about 9,500 ducks.
I think the ducks died of other regular diseases, not bird flu, but we will conduct a test to confirm why they died, said an official of North Jeolla Province, declining to be named. The official said more birds probably would have died if it was bird flu.
The above comments describe the likely spread of H5N1 to another duck farm in South Korea (see satellite map). Ducks and other waterfowl usually have resistance to H5N1 and are not fatally infected. The Qinghai strain does produce an unusually high fatality rate in waterfowl, but frequently produces asymptomatic infections. The death of 500 ducks is highly suggestive of H5N1. The rate was closer to 50% for the other duck farm, but the fatality rate can vary widely, although rates can approach 100% domestic chickens.
These three outbreaks lie on a migratory bird pathway as seen by signals from whooper swans migrating between Mongolia and South Korea. In late 2006 H5N1 was widespread in this region, and recently released sequences clear demonstrated the Uvs Lake strain of H5N1 which evolved in Mongolia in the summer of 2006. The Uvs Lake H5N1 was isolated from domestic poultry as well as feces collected at sites frequented by migratory birds.
The new infections, which correspond in time and space with migration of birds back to Mongolia is not unexpected.
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