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AI incidences continue in the US

New cases of avian influenza cases are emerging in the US, this time in north-central Washington, where highly pathogenic avian influenza has swept through another mixed-bird backyard flock, creating the third quarantine zone in the state.

The Washington State Department of Agriculture has established a quarantine zone 6 miles around where about 100 birds, raised primarily as a youth project, were infected in Okanogan County near the Canadian border.

First outbreak in commercial flock

This follows the first H5 N8 HPAI outbreak in commercial birds (domestic turkeys) which was reported last week in California.

Reports of H5N8 HPAI began in a backyard flock in Oregon and was followed by an outbreak of H5N2 HPAI in backyard poultry in Washington State as well as four wild bird cases of H5N8 HPAI – two in California, (a gadwall Anas strepora, and a green winged teal Anas carolinensis), one in Utah (American wigeon, Anas americana) and one in Idaho (mallard, Anas platyrhynchos).

First incidence of H5N1 HPAI

In addition, as part of enhanced surveillance activities, a case of H5N1 HPAI has also been reported in a green winged teal in Washington State. This is the first time H5N1 HPAI has been reported in the USA but can be clearly differentiated from other contemporary H5N1 HPAI viruses since genetic analysis has revealed that this virus is a re-assortant virus between the Eurasian lineage H5 gene of the H5N8 HPAI virus already identified in the USA and the N1 gene of North American LPAI wild bird lineage.

This is suggestive that the introduction of the Eurasian H5N8 virus into the Pacific flyway in late 2014 has resulted in mixing with North American lineage viruses leading to the emergence of H5N2 HPAI and now H5N1 HPAI viruses in USA and Canada (OIE, 2015d).

Source: Department for Environment, Food and Rural Affairs, Animal & Plant Health Agency

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