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H5N1 Bird Flu in Ohio
October 16, 2006
The U.S. Department of Agriculture (USDA) and Department of the Interior (DOI) today announced a detection of H5 and N1 avian influenza subtypes in samples from apparently healthy wild Northern pintails in Ottawa County, Ohio, that were killed by a hunter. Initial tests confirm that these wild bird samples do not contain the highly pathogenic H5N1 strain that has spread through birds in Asia, Europe and Africa.
The bird samples were collected on Oct. 8 through a partnership between USDA and the Ohio Division of Wildlife as part of an expanded wild bird monitoring program
Thirty five samples were collected directly from the birds and screened for H5 at the Ohio Dept of Agriculture Animal Disease Diagnostic Laboratory. Of those samples, two were sent to USDA's National Veterinary Services Laboratories (NVSL) in Ames, Iowa, for confirmatory testing and one screened by NVSL tested positive for both H5 and N1 subtypes.
The above comments indicate H5N1 is also circulating in Ohio near Lake Erie. Earlier reports described H5N1 mute swans in southern Michigan and mallards in Crawford County, Pennsylvania. H5N1 has also been found in mallards in Maryland and Green-winged teal in Illinois. In Montana, H5 and N1 were detected in Northern pintail, but only H5N3 was isolated. H5 has also been detected in Washington State, California, and New Jersey.
The detection of H5in general and H5N1 in particular in North America is unusual. Last year, Canada reported detection of H5N1, H5N2, H5N3, and H5N9 across southern Canada. H5N1 was only detected in Manitoba. This year Canada said results mirrored last years results.
Most of the announced detections in the United States has been H5N1. However, the frequency of other H5 serotypes has not been announced.
The H5N1 are of most concern. Although all H5N1 detected to date have tested as low path, the failure to detect H5N1 in the H5 N1 positive bird(s) in Montana indicates that the H5 isolated may not represent all H5 in the sample. In Montana, the failure was clear because the original positive was N1 positive, but no N1 serotype was isolated.
Isolation of low path H5N1 does not rule out high path H5N1, which is cause for concern. This concern is somewhat mitigated by the pathogenicity tests, but the values for those tests have also not been released.
The H5 in the United States has largely been from apparent healthy birds. Results in dead geese in California have not been released. Similarly, isolation of the confirmed H5 in a dead goose on Prince Edward Island was unsuccessful.
Although the above isolates have been said to be low path North American strains, high pah H5N1 in Asia has evolved by recombining with low path, and there is evidence for Asian H5 sequences in low path American isolates. In addition, the H5 isolates in North America have also picked up swine polymorphism.
Therefore, release of sequences from H5N1 in 2006 in the United States and Canada would be useful.