Fall 2020 Avian Flu In The Netherlands
#15,534
Yesterday, in UK: 2nd Farm Reports Avian Flu & DEFRA Outbreak Assessment #2, I highlighted one potentially significant statement in the DEFRA report which suggested Europe's fall's crop of HPAI H5N8 viruses are genetically distinguishable from the H5N8 viruses that were circulating in Europe last spring.
While lacking specifics, the report stated:
Preliminary analyses available indicates strong similarity amongst these viruses across a broad region and they can be distinguished from other contemporaneously circulating viruses including those associated with widespread infection in the first six months of this year across Europe
Whenever we talk about an influenza subtype (whether it be human, swine, avian, etc.) we are actually talking about an array of genetically similar viruses, which may be further divided up into different clades, subclades, and genotypes.
As the following WHO chart illustrates, different subclades of HPAI H5Nx subtypes circulate around the world, but even within each subclade, individual viruses can demonstrate considerable genetic variance.
In the past, abrupt upticks in avian flu activity have often been linked to the emergence or arrival of new genotypes (or subclades) of existing avian subtypes - which may have different qualities (virulence, host range, replication, and/or transmissibility) - or against which local wild and migratory birds may have less existing immunity.
- In May of 2005 the first major expansion of H5N1 beyond Southeast Asia began when suddenly and unexpectedly, waterfowl (brown headed gulls, cormorants, ducks, geese, etc.) died en massd at Qinghai Lake, China- and quickly spread via migratory birds into Europe, Africa, and the Middle east signaling the emergence of clade 2.2 (aka QH05) of the H5N1 virus.
- In 2009 researchers found evidence of another emerging clade - (2.3.2) - (see 2011 EID Journal New Avian Influenza Virus (H5N1) in Wild Birds, Qinghai, China), at Qinghai lake. In short order this emerging 2.3.2 clade began to show up in migratory birds, and poultry, from Japan to India, supplanting the old 2.2 clade in many regions.
- In January of 2015 we saw another `Qinghai-like' die off of birds, this time in Henan Province, China which was subsequently identified as clade 2.3.2.1c (see Novel H5N1 Reassortment Detected In Migratory Birds - China). Within months this new sub clade was seen in Nigeria.
- In June of 2016, in OIE: Russia - HPAI H5 In Wild & Migratory Birds, we saw a report of a number of birds taken by hunters earlier that month in and around Ubsu-Nur Lake in Russia that had tested positive for HPAI H5. Three months later it was confirmed by FAO/EMPRES to be H5N8 Clade 2.3.4.4., which by November of 2016 had sparked Europe's largest avian epizootic on record.
Today we've a pre-print article from researchers at Wageningen Bioveterinary Research (WBVR) in the Netherlands which provides us with the first genetic characterization of HPAI H5N8 viruses isolated this fall in the Netherlands.
This study finds these latest incursions have more in common with HPAI H5N8 viruses seen in Egypt in 2018-2019, than with those recently reported in Europe.
I've only posted the link, abstract, and an excerpt from the discussion. So follow the link to read the paper in its entirety.
Nancy Beerens, Rene Heutink, Frank Harders, Marit Roose, Sylvia Pritz-Verschuren, Evelien Germeraad, Marc EngelsmaThis article is a preprint and has not been certified by peer review [what does this mean?].AbstractThe HPAI H5N8 virus detected in mute swans in the Netherlands in October 2020 shares a common ancestor with clade 2.3.4.4b viruses last detected in Egypt in 2018-2019 and has a similar genetic composition. The virus is not directly related to European H5N8 viruses detected in first half of 2020.
(SNIP)
Conclusions
A novel HPAI H5N8 virus was detected in the Netherlands in October 2020 in mute swans found dead. The virus is not closely related to H5N8 viruses causing outbreaks in Eastern Europe, Germany and Bulgaria in the first half year of 2020, but shares a putative common ancestor with viruses last detected in Egypt in 2018-2019, which dates around March 2017. The virus was likely introduced by waterfowl migrating to wintering sites in the Netherlands. In October, wild bird migration is ongoing and millions of wild birds will reach their wintering sites in Europe in the coming months. This early detection of HPAI H5N8 virus in the Netherlands predicts a high risk for the poultry industry in Europe for the 2020-2021 winters season.
The HPAI H5N8 virus that sparked Europe's 2016-2017 avian epizootic proved to be better adapted for long-term carriage by migratory birds than had previous H5N8 incarnations, and reassorted easily with other LPAI viruses, unleashing a number of new subtypes (H5N5, H5N9, etc.) as it spread across Europe.
The HPAI H5N6 virus that replaced it in 2017-2018 fared less well, and for the past couple of years HPAI H5 activity has been fairly subdued (with a few exceptions) around the globe.
Right now, we don't have any information about the capabilities of this new variant, other than it appears to be spreading reasonably efficiently by migratory birds, making it too soon to begin to guess how much of an impact it will have this fall and winter.
Although surveillance of avian influenza in the Middle East - including Egypt - is spotty at best, a few recent blogs include:
Viruses: PA From Recent H9N2 AIV Enhances H5N1 Infection In Mammalian Systems
Study: Genotyping & Reassortment Analysis of HPAI H5N8 and H5N2 viruses from Egypt
EID Journal: Novel Reassortant HPAI A(H5N2) Virus in Broiler Chickens, Egypt
Emerg. Microbes & Inf.: Active Surveillance & Genetic Evolution of Avian Influenza Viruses in Egypt, 2016–2018
