We saw the UK's last RRA on avian flu only a week ago (see DEFRA: Rapid Risk Assessment On H5N6 In Wild Birds In Dorset), but since then more wild birds have been detected in the middle of England with the H5N6 virus (see UK: DEFRA Expands Bird Flu Prevention Zone As More Infected Birds Are Found).
In light of those developments, today DEFRA (Department for Environment, Food & Rural Affairs), has released an updated risk assessment which increases the likelihood of finding more infected wild birds in England and Wales.I've reproduced the summary and conclusion below, but follow the link to read the full 19 page PDF report in its entirety.
Rapid Risk Assessment on the finding of H5N6 HPAI in wild birds in England and Wales
22nd January 2018
This document is an update of a rapid risk assessment made on the 14th January in response to a finding of H5N6 HPAI in Dorset and follows new findings in wild birds and a revision to the original risk question. The same strain of virus has now been detected in wild water birds in Warwickshire and Hertfordshire and this changes the risk assessment. All updates made on the 22nd January are shown in red for ease of reference.
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.
On the 11th January, a second site was reported to the authorities. A large wild bird die-off involving nearly 70 birds was observed by the site warden and 17 of the assemblage were sent to the EU/OIE/FAO AI Reference Lab for testing. Thirteen birds of mixed species tested positive for H5N6 HPAI and this was confirmed on the 16th January. The site is a known gull roost in the Midlands, with several thousand gulls roosting at the site over the winter months. Other migratory and resident wild waterfowl are also regularly reported from the site.
On the 19th January another submission of wild birds found dead at a third site in Hertfordshire tested positive for H5N6. The submission included 19 wild waterfowl and gulls. The site is in one of the Higher Risk Areas (European Implementing Decision 2017/263), identified by the high number of migratory wild waterfowl that overwinter there.
This rapid risk assessment is to gather the evidence and assess the likely source of infection and the risk of spread of the virus to poultry or to wild birds in England and Wales, in the context of the background risk level from migratory wild birds.
The assessment suggests that there is now an increase in the likelihood of finding more cases in wild birds in England and Wales as a result of this finding, which increases this risk level to HIGH in comparison to the previous national risk of incursion level (MEDIUM). At a local level, around the site in Dorset, there would be a slight increase in the risk of spread for poultry on poultry farms in the immediate area, where poultry mix with wild birds, but there is some uncertainty around the role of bridging species and the modes and risk of fomite spread into the local environment.
The new site in Warwickshire is the roost of many gulls of various species, several of which are migratory and local ornithological expertise suggests they will travel long distances as part of their migration and relatively long distances on their daily commute between feeding sites and roosting sites.
The third site hosts a substantial number of waterfowl and other water birds including gulls which were amongst those tested positive for H5N6. Infected gulls may act as bridging species for poultry farms or through transmission to other water birds and waterfowl. The uncertainty around the length of time disease has been present and the probability of a greater geographical spread of infection in wild birds has increased the risk level for the direct and indirect exposure to poultry to MEDIUM although this will depend on the biosecurity level at the holding level. Where strong biosecurity is implemented, the risk may be mitigated to low.
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. However the new assessment suggests there is now an increase across the whole of England and Wales, because of the large number of gulls detected at these two places, their behaviour and flight patterns and the significance of one site along a migration flyway for east to west movement of waterfowl.
There may be some unquantifiable increase in risk to poultry premises nearby the site in Dorset, 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.
The wider risk to poultry across England and Wales because of gull behaviour may not have changed substantially with these findings; it does reduce our level of uncertainty though and increases the geographic area known to be at risk with greater certainty. Therefore the overall likelihood of a poultry incursion occurring in the wider region has increased and is highly dependent on the level of biosecurity at the holding. There is uncertainty around whether the virus can transmit readily to gallinaceous poultry, if previous exposure of wild birds to H5N8 will change the transmission dynamics of the new strain and what the extent of the geographic bound is for the new strain. We will keep this under review.
Our previous statement on the 15th January that “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” is not relevant now.
More birds have tested positive and the two new sites together with the species of bird involved has changed the risk level to “HIGH” for further incursions in wild birds, meaning the event will occur often, or at least once in the next year. The exposure assessment for poultry has also increased as a result of this new finding. There is still uncertainty around the transmissibility from gulls to poultry therefore where there are no additional biosecurity measures on the holding, the likelihood of a new poultry outbreak has increased to MEDIUM. Where biosecurity is implemented well, the risk would be mitigated to LOW.(Continue . . . .)
While subdued compared to the spread of H5N8 in Europe last year, there are new media reports today of another outbreak of H5N6 in the Netherlands (see Highly pathogenic avian influenza variant fixed hobby holder Rhoon) and media reports picked up by FluTrackers.
During its first incursion into Europe, over the winter of 2014-15, H5N8 made a similarly unspectacular debut, so it is too soon to know how much of a factor HPAI H5N6 will be in Europe going forward.