Wednesday, July 18, 2018

Denmark: HPAI H5N6 Reported In Dead Eider


Although news about HPAI H5N6 in Europe has been pretty much absent for the past couple of months (see latest DEFRA report), and the warmth of summer usually helps to suppress bird flu, we've a new report of the discovery of HPAI H5N6 in a wild bird in Denmark, north of Lolland.
This is the first HPAI detection in Denmark since mid-April - although LPAI H5 was reported in early May - and the 30th positive finding in wild birds of 2018.
This from Denmark's Veterinary and Food Administration, after which, I return with a bit more.

Avian influenza - current situation

There are 16 July detected highly pathogenic bird flu in a dead wild bird found Smålandshavet north of Lolland.

wild birds

Discovery of bird flu in wild birds

National Veterinary Institute have 16 July 2018 identified highly pathogenic avian influenza type H5N6 in a dead eider. Eider was found with several other dead birds Smålandshavet north of Lolland.
It is the first time since mid-April that gathered a dead wild bird in nature, which turns out to be infected with highly pathogenic avian influenza. The total number of cases this year has now reached 30. 
Previously, it has been especially sea eagles and buzzards, which are found to be infected, but the infection is also found in other species of birds such as crows, gulls, swans and one cormorant. The findings are gradually made many places in Denmark, including in North Jutland, Zealand, Lolland, Falster, Funen, Bornholm and Als.

The first findings of highly pathogenic avian influenza H5N6 was done in early March in an eagle found near Slagelse. For details about findings see map of Denmark here .

Sporadic finds of bird flu is not surprising, but usually it is rare to find highly pathogenic bird flu in mid summer. There have been no reports of human infection with the avian influenza virus type.
While H5N6  hasn't sparked the kind of large scale avian epizootic we saw over the winter of 2016-17 with H5N8 - both viruses have shown unusual persistence, and an expanded host range - in wild birds.
And that is a fairly recent change.
A 2015 study (see PNAS: The Enigma Of Disappearing HPAI H5 In North American Migratory Waterfowl) - conducted after the 2014-15 North American HPAI H5 epizootic - concluded that while migratory waterfowl can briefly carry HPAI H5, they were not a good long-term reservoir for highly pathogenic avian flu viruses.
HPAI viruses appeared to burn out fairly quickly in aquatic waterfowl populations - likely due to their long standing immunity to LPAI viruses - and would therefore have to be reintroduced periodically.
That changed in the fall of 2016 when H5N8 returned to Europe and brought with it a number of genetic and behavioral changes attributed to a reassortment event that likely took place sometime in the spring of 2016 (see EID Journal: Reassorted HPAI H5N8 Clade - Germany 2016).
Last summer we saw scattered reports of H5N8 across much of Europe, with the UK's DEFRA Warning Of A `Constant Risk' From Avian Flu in early  September.
While far less pronounced this summer, we've been watching widespread and persistent HPAI H5N8 outbreaks in Russia and Bulgaria the past few months.

Although the finding of HPAI H5N6 in a dead Eider (even in July) is far from earth shattering, it is a reminder that - despite the inhospitable summer season - some remnants of the HPAI H5N6 virus continue to circulate in European wild birds as well.

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