#15,514
For the past couple of months we've been following outbreaks of HPAI H5 in Western Siberia (see Russia's Worsening HPAI H5 Outbreak (in Poultry)) and Northern Kazakhstan, along with warnings from the ECDC, ESFA, FLI, and DEFRA that poultry interests along the Black Sea/ Mediterranean flyway (primarily Europe, the Middle East, and Africa) should remain alert.
These recent reports are reminiscent of the run-up to Europe's record setting 2016-2017 epizootic (see OIE: Russia - HPAI H5 In Wild & Migratory Birds), which saw a highly virulent reassorted HPAI H5N8 virus arrive in Germany in October, and spread rapidly across the continent.
Last week, in Israel: HPAI H5N8 Discovered At Poultry Farm In Kibbutz Ma'anit, we looked that first of several reports of avian flu in Israel this fall, which has included an infected swan at a zoo (see JPOST Two more cases of bird flu in Israel, ministry points to migrating birds).
Yesterday the Netherlands government issued the following brief (translated) statement regarding the discovery of 6 dead swans in Kockengen, two of which have tested positive for HPAI H5N8.Considerably more detail, and background, comes from the following (translated) report published yesterday from Wageningen Bioveterinary Research (WBVR).
Bird flu diagnosed in whooper swans in Kockengen
News release | 21-10-2020 | 15:42
Bird flu has been diagnosed in two wild mute swans in Kockengen (Utrecht). This is a highly pathogenic variant of avian influenza (HPAI of the serotype H5N8). Minister Schouten has asked the animal diseases expert group to assess this finding. The experts will today (October 21) map out the risk for a poultry farm to become infected with highly pathogenic bird flu. Minister Schouten will then determine whether - and if so, which - follow-up steps are necessary.
Highly pathogenic bird flu H5N8 in wild mute swans
Published on October 21, 2020
On Tuesday, October 20, 2020, Wageningen Bioveterinary Research (WBVR) demonstrated highly pathogenic H5N8 bird flu in two dead mute swans. The two swans entered were part of a group of six swans that were found dead in the green heart of the Netherlands, near Kockengen.
H5N8 virus and bird migration
In August, H5N8 virus was detected in dead mute swans in Western Russia, then also in tufted duck and mallard. The virus was then also detected in dead wild birds in Kazakhstan in September. In October, H5N8 virus was detected in swans at a zoo in Jerusalem, Israel. Wild migratory birds can bring the virus from these areas to Europe during their autumn migration. However, no H5N8 viruses have yet been reported on the migration routes to the Netherlands from countries east of the Netherlands.
It is striking that the H5N8 virus has been detected in dead swans in Russia, Israel, and now the Netherlands. Swans may be very sensitive to this specific virus, this will have to be investigated further. The wild mute swan populations in Russia are known not to migrate to Europe to hibernate. The virus was therefore probably introduced to the Netherlands by other bird species, after which local bird populations became infected. This suggests that the virus is circulating locally among wild birds in the Netherlands. No dead birds from other areas in the Netherlands have yet been tested, so it is unclear whether the virus has spread further.
Risk of introduction to poultry
The H5N8 virus can be introduced to poultry farms from the wild bird population. In particular through the faeces of wild birds infected with the virus. The risk of introducing highly pathogenic avian influenza into the poultry sector is therefore currently high, especially in areas with many wild waterfowl. Biosecurity and vigilance for clinical symptoms of avian flu in poultry farms are currently of great importance in preventing avian flu outbreaks.
Genetic composition of avian flu viruses
Highly pathogenic avian influenza viruses were previously introduced in the Netherlands by wild migratory birds, after which several poultry farms became infected. In 2014 this concerned an H5N8 bird flu virus, in 2016 also an H5N8 bird flu virus but with a genetically different composition. In 2017, the H5N6 virus was introduced in the Netherlands. WBVR will conduct further research to determine the sequence of the entire virus genome. This will reveal how this new H5N8 virus is related to other highly pathogenic avian influenza viruses currently circulating.
Dead wild bird monitoring program
The dead wild bird monitoring program is of great importance for the rapid detection of highly pathogenic viruses in the Netherlands. This program also makes it possible to monitor the further spread of the virus among wild birds in the Netherlands. Wild birds found dead can be submitted to be tested for bird flu infection.
The world's major migratory bird flyways (shown below) - along with scores of minor pathways not depicted - serve as a global interstate highway for avian influenza viruses. While primarily north-south conduits, there is enough overlap to allow for east-west movement as well.
A study, published in 2016 (see Sci Repts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1), suggests that waterfowl can pick up new HPAI viruses in the spring (likely from poultry or terrestrial birds) on their way to their summer breeding spots - where they spread and potentially evolve - and then redistribute them on their southbound journey the following fall.
It is unclear at this time whether the HPAI H5N8 viruses being carried south (and west) by migratory birds this fall have changed appreciably since last year, or if they pose any greater threat than usual. Hopefully we'll be getting some genetic analyses in the days ahead.
While avian flu activity has been fairly subdued around the world for the past three years, these viruses continue to evolve and adapt, and there is little to prevent another virulent strain from emerging in the future.
