Five days ago we saw the OIE Notification: 1st Occurrence Of H5N6 In The UK which listed 3 sick swans recovered in Dorset, in the south of England. Two days later in UK: DEFRA Announcement On H5N6 In 17 Wild Birds In Dorset, we saw the number and types of wild birds expanded with a warning that more could expected over the coming days.
The UK now joins The Netherlands, Germany, and Switzerland in reporting this recently arrived reassorted H5N6 (from last year's H5N8 epizootic virus). H5N8, meanwhile, has recently been reported in Italy, Russia, Bulgaria, The Middle East and Africa.Although H5N6 isn't spreading across Europe at anywhere near the speed that H5N8 did during last year's record bird flu season, during its first foray in to Europe - during the winter of 2014-15, when North America was in the throws of their own epizootic - H5N8 activity in Europe was similarly subdued.
We've a lengthy Rapid Risk Assessment today from the UK's DEFRA, which provides us with considerably more background on this reassorted virus than we've seen so far, along with an assessment of the risk to the UK's poultry interests.
Rapid Risk Assessment on the finding of H5N6 HPAI in wild birds in Dorset
In December 2017, the Netherlands reported a new strain of H5N6 HPAI in a duck fattening farm in Flevoland; several cases in wild birds (mute swans, Cygnus olor) in the same region and cases in captive birds at a single site (mallard ducks, mute swans, greylag geese and guinea fowl) were reported in the following days.
In late December / early January two further cases in wild birds were reported, one in southern Germany and one in west Switzerland. In January 2018, three mute swans were found dead and tested positive for H5N6 HPAI in Dorset, on the South coast of England and initial analysis confirms this virus has the same characteristics as the Netherlands strain.
The current numbers, as of 12th January, are 15 mute swans, 1 Canada goose and 1 pochard, all found dead and all testing positive. There have been no reports in domestic poultry, either commercial or small holding premises.
H5N6 HPAI viruses of the clades 188.8.131.52c and d were detected first in China in 2014 and then continued to spread in poultry in China, Laos, Cambodia, South Korea, Vietnam and Japan and some viruses in clade 184.108.40.206c have zoonotic potential and caused a small number of human cases (EFSA Panel, 2017).
According to a Promed report on 13 December 2017, “The OIE/FAO/EU International Reference Laboratory at APHA-Weybridge, UK, working with the Animal and Plant Quarantine Agency of the Republic of Korea, characterized a novel emerging highly pathogenic avian influenza A(HPAI) (H5N6) virus isolated from both wild birds and domestic poultry in the Republic of Korea.
Phylogenetic analyses of a representative of these viruses showed that it was different from previously circulating Korean H5N6 viruses in the 2016-2017 winter season and which had caused a very limited number of human cases.
All genes of the novel HPAI virus except the neuraminidase were of the "European H5N8 HPAI lineage" that emerged last winter (16/17) and continues to be detected in some European countries. The neuraminidase N6 is most similar to the H5N6 reassortant virus isolated from chickens in Greece in early 2017, which had acquired a neuraminidase gene from the Eurasian low pathogenic avian influenza A virus lineage circulating in wild birds. These analyses demonstrate continued circulation of this H5 lineage in multiple geographic regions and likely wild-bird mediated spread.” See also Lee et al, 2017.
The current season (winter 2017/2018) has seen several outbreaks in poultry and cases in wild birds of H5N8 HPAI in Italy, Bulgaria and Germany (see Figure 1), but none in the northerly part of the EU; further outbreaks of H5N8 HPAI cannot be ruled out since the virus continues to circulate elsewhere including the Middle East and South Africa.
In December 2017, the Netherlands reported a single outbreak of avian influenza in fattening ducks in Flevoland region (OIE, 2017). Four week old ducks showed increased clinical signs and increased mortality. The birds tested positive at the National Reference Laboratory and the virus was confirmed as H5N6 HPAI; disease control measures were put in place, including a housing requirement for all commercial poultry. According to the Dutch laboratory, the sequence shows this was a reassortant between a low pathogenic HxN6 strain and the circulating Eurasian H5N8 HPAI strain (Wageningen, 2017).
Further cases in wild mute swans were reported during December and January (OIE, 2017). At the end of December, Switzerland reported a case of H5N6 HPAI in a wild mute swan and on the 8th January, Germany reported a case of H5N6 HPAI in a wild duck (species not known; OIE, 2017). The H5N6 HPAI currently in Europe therefore appears to be an emerging strain.
Overall, the finding of wild birds infected with H5N6 HPAI virus at the site in Dorset does not substantially increase the risk of incursion to poultry on poultry farms in GB. There may be some unquantifiable increase in risk to poultry premises nearby, because of the contact with bridging species or other wild water birds; this is only a marginal increase and will be time limited by the level of infection circulating in the wild bird population. This will depend on the biosecurity practices at the premises.
There is no increase in risk of incursions of avian influenza to wild bird populations in the rest of the UK, above MEDIUM which is the current level. Wild waterfowl are unlikely to move far from the area at this time of year, according to the observed behaviour of the birds in previous seasons; this site is a high risk site during any season for avian influenza in Europe; previous incursions here did not lead to any spread to poultry farms. More wild waterfowl may test positive in the coming weeks not only from this site but elsewhere in the UK or continental Europe and this will continue to inform our risk level.
(Continue . . . )