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H7N3 Isolation in Arkansas Increases Surveillance Concerns
Recombinomics Commentary 15:59
June 11, 2008
A new “virus isolation” test — in which technicians try to grow the virus from a sample — confirmed the H 7 N 3 virus was still alive in at least one of the sampled birds.
Five Canada geese — most likely resident to the area — were harvested for the samples. Four wood ducks met the same fate. The samples were taken to the National Veterinary Services Laboratories in Ames, Iowa. Results could be available late this week.
Bannerman said it isn’t likely that any more waterfowl will be tested.
The above comments describe the isolation of H7N3 from the poultry outbreak in Arkansas (see satellite map). Initial reports described the detection of H7 and N3 antibodies, but failed to detect the virus in PCR testing. The above comments and the associated OIE report confirm that H7N3 has been isolated, in spite of negative PCR test results at the National Veterinary Services Laboratory (NVSL) as well as the Arkansas Livestock and Poultry Commission (ARLPC).
The test failures increase surveillance concerns. A recent report indicated that the primers used in PCR tests for H7 did not match H7 in wild birds and therefore would yield false negative results. The above data suggest that such mis-matched primers are still in use in national and state surveillance programs. It is unclear if the limited number of waterfowl will be tested with the same flawed reagents, but the failure to detect H7 in wild birds prior to the outbreak on the farm is cause for concern.
Recent sequences from H7 in the northeast have been made public. However, all isolates are from live markets or poultry farms in northeastern United States raising additional concerns about the ability of the US surveillance program to detect H7 in circulation in wild birds. Similarly, Canada also failed to find any H7 in their wild bird surveillance program, suggesting flawed H7 surveillance is common in North America.
Recombinomics Paper at Nature Precedings