#15,454
In the 25 years since the emergence of HPAI (highly pathogenic avian influenza) H5N1 in China, we've seen 4 distinct waves of avian H5 sweep the world. The last big wave came in the fall of 2016, when a reassorted H5Nx virus emerged from Russia/China and sparked Europe's worst avian epizootic on record (see EID Journal: Comparison of 2016–17 and Previous Epizootics of HPAI H5 In Europe).
During the summer of 2017, China launched a massive H5+H7 poultry vaccination campaign, which appears to have helped subdue avian flu activity not only in China, but around the world.
But we've seen some cracks appear over the past year or two, and continued signs of evolution among HPAI viruses in the wild (see EID Journal: Evolution and Antigenic Drift of Influenza A (H7N9) Viruses, China, 2017–2019 and EID Journal: Genetic Characterization of Avian Influenza A(H5N6) Virus Clade 2.3.4.4, Russia, 2018).
Six days ago, in Russia's Worsening HPAI H5 Outbreak (in Poultry), we looked at a recent uptick in reported HPAI (highly pathogenic avian influenza) outbreaks in central Russia (in wild birds and in poultry), which appears to have started in late July or early August.
Once considered controversial, today there is little doubt that HPAI viruses are spread over long distances by migratory birds (see WHO: Migratory Birds & The Potential Spread Of Avian Influenza).
The 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.
Although past performance is no guarantee of future results, we've seen outbreaks of bird flu in Russia prior to their arrival in Europe, the Middle East, and Africa.
With migratory birds already on the move from their high latitude summer roosting spots to warmer climes, the UK's DEFRA has issued the following cautionary report:
Preliminary Outbreak Assessment
High Pathogenicity Avian Influenza (H5N8) in Russia
4 September 2020
Ref: VITT/1200 HPAI H5N8, Russia
Disease report
The Russian Authorities are reporting multiple outbreaks of highly pathogenic avian influenza virus (HPAIV) H5 with high mortality rates in poultry and also in wild waterbird carcases in southern central Russia close to the border with Kazakhstan at the end of August following initial reports of HPAIV H5N8 at the end of July.
Situation assessment
On 28 July, Russia detected two outbreaks of HPAI H5N8 in backyard birds on premises in villages in the Uvel’sky region, Chelyabinskaya Oblast, in the south near the border with Kazakhstan. Both premises reported having a mix of chickens, ducks and geese. The first, in Peschanoe, reported 99 cases out of 156 birds. The second, in Maloe Shumakovo, reported mortality of all 30 birds on the premises. Restriction zones were established and the birds culled. On 04 August, neighbouring Kazakhstan also implemented temporary restrictions on the import and transit of poultry and food products from Russia (Kazakh-TV, 2020). A wild duck carcass was also found during avian influenza passive surveillance on the lake near one of the villages just before the outbreak started. HPAIV H5N8 was detected in a sample of the wild duck carcass. The species of the wild duck is not known, nor is it known whether it is a migratory species.
In mid-August, three outbreaks of HPAIV H5 were detected in village/backyard birds in Omskaya Oblast with almost 50% of birds affected and dying. A further 17 outbreaks were then detected in the third and fourth weeks of August in Omskaya, Kurganskaya and Chelyabinskaya Oblasts. Most were in backyard or village birds although one huge farm with over 1.5 million birds in Omskaya Oblast was infected with over 10,000 birds reported dead. In late August and early September, eight outbreaks were detected in backyard birds in Tyumenskaya and Omskaya Oblasts with approximately 25% of birds affected and dying.
In late August, four wild mute swans (Cygnus olor) were found dead in Tyumenskaya Oblast and HPAIV H5 confirmed with PCR. Although mute swans do not migrate to the UK, the detection of H5N8 in wild birds and poultry in this region is significant, particularly at this time of year. Some waterfowl species which winter in western Europe, including the UK, also breed in this region of Russia and will migrate west in the coming weeks.
In summer 2016, HPAI H5N8 was reported in wild birds in south-central Russia, spreading to west Russia in the autumn. Subsequently, the virus was detected in a large number of outbreaks across Europe from autumn 2016, through to the first quarter of 2017. This was the largest known HPAI epidemic in Europe, affecting both poultry and wild birds. The H5N8 virus has evolved in the last 6 years since its first appearance and has frequently exchanged genetic material (reassortment) during its spread in wild birds across their migratory range and in domestic ducks, not only in China, but also in central Asia, Europe, Africa and North America. (Lycett et al., 2020).
The genotype of the current H5N8 viruses in Russia is not yet known, and importantly it is not known whether this virus is showing further genetic reassortment compared to the 2016/17 and 2019/20 forms of the virus that spread to Europe. Increased fitness of these viruses for wild birds through such exchange is possible.
The outbreaks in poultry in Russia confirm the virus retains HPAI properties with typical high mortality in chickens, ducks and geese. Therefore, if this H5N8 strain were to spread to Europe later this year, outbreaks in poultry should be detected relatively quickly, giving some warning of a potential increase in risk. Clinical impact on wild birds is more uncertain and so therefore is the utility of passive surveillance of wild birds but mortality events suggest this virus(es) results in fatal infection at least in some species.
Conclusion
The OIE/FAO international reference laboratory/UK national laboratory at Weybridge has the necessary ongoing diagnostic capability for these strains of virus, whether low or high pathogenicity AI and continually monitors changes in the virus.
In total in southern central Russia, 29 backyard/village bird outbreaks of HPAIV H5 have been reported with one very large poultry farm in addition to two detection events in wild waterbird carcases including four mute swans.
Currently the risk of HPAI incursion in wild birds in the UK is LOW (i.e. no change at present), and we are monitoring the recent outbreaks in Russia in terms of assessing the risk for further outbreaks over the coming months and increased probability of its spreading westwards during the autumn. The risk for poultry in the UK remains low for introduction of infection onto individual premises, but will depend on levels of biosecurity.
We recommend that all poultry keepers stay vigilant and make themselves aware of the latest information on www.gov.uk, particularly about recommendations for biosecurity and how to register their flocks.
We will continue to report on any updates to the situation in Russia and, in particular, any changes in disease distribution or wild bird movements which may increase the risk to the UK.
Further information is available here: https://www.gov.uk/guidance/avian-influenza-bird-flu
including updated biosecurity advice for poultry keepers for England;
https://gov.wales/avian-influenza for Wales and; http://gov.scot/avianinfluenza for Scotland.
While the events in central Russia have recently captured our attention, avian flu continues to make its mark around the globe. From the latest (Aug 20th) OIE Summary.
In the reporting period, 11 new HPAI outbreaks were reported in domestic birds in Asia and Oceania involving 3 different HPAI subtypes namely H5N1, H5N5 and H7N7.2 new outbreaks of H5N8 were reported in non-poultry in Europe. In addition, 89 HPAI outbreaks in poultry and non-poultry are still ongoing in Oceania, Europe, Asia andAfrica involving different subtypes, namely H5, H5N1, H5N5, H5N6, H5N8, H7N3, H7N7 and H7N9.
• Outbreaks of H5N1, H5N6 and H7N9 are still continuing in a few Asian countries with Vietnam reporting recurrence of new H5N1 outbreaks.• In Chinese Taipei, H5N5 subtype has continued to be reported since September 2019.• Australia experienced recurrence of H7N7 outbreaks after six years.• In South Africa ongoing outbreaks of H5N8 are continuing. The number of outbreaks of H5N8 which were reported in European countries in poultry and/or wild birds has decreased and only one outbreak of H5N8 is ongoing in Bulgaria. It is more likely that the source of infection in these outbreaks is contact with wild birds and followed by limited local spread.
Veterinary Authorities in the affected countries have responded to contain outbreaks in poultry with stamping out measures, heightened surveillance, and recommendationsto poultry owners to increase biosecurity.
The OIE Standards, and the transparency of reporting through the OIE’s World Animal Health Information System, provide the framework for Veterinary Services toimplement effective surveillance, reporting, and controls for avian influenza. Wild bird surveillance can indicate periods of heightened risk, and at these times measures toimprove on-farm biosecurity may reduce the likelihood of exposure of poultry.
While avian influenza is currently on the back burner due to our COVID-19 pandemic, the risks these (and other) viruses pose to agriculture and to human health remain genuine concerns.
