Scottish wild bird highly pathogenic avian influenza response plan

Background

The 2021/2022 outbreak

11. The 2021/22 Highly Pathogenic Avian Influenza (HPAI) outbreak was the largest in the UK at that time, affecting poultry, other captive birds and wild birds, notably seabirds and wildfowl. Data collected by the Animal and Plant Health Agency's (APHA) GB-wide programme, which carries out year-round surveillance and testing of avian influenza in dead wild birds on behalf of Scottish Government and the other GB administrations, recorded a total of 603 wild birds across 34 species and 153 locations in Scotland as testing positive for HPAI between 1 October 2021 and 30 September 2022. These figures are the number of wild bird samples that tested positive and, is not an indication of the total level of mortality in the populations.

12. Scotland supports nationally and internationally important wild bird populations. A provisional assessment of evidence gathered by NatureScot and partners during the 2021/22 outbreak, shows that some species have been significantly affected by HPAI with a total of approximately 20,500 dead seabirds across 160 locations reported to NatureScot between 4 April and 11 September 2022. This is likely an under representative figure, as not all dead birds will have been reported and it cannot be stated equivocally that all mortalities were as a result of avian influenza. The species most reported were northern gannet, great skua, common guillemot, kittiwake, terns and large gulls, with some colonies recording particularly large losses. Presumed impacts of HPAI were recorded across Scotland, and were seen in both adults and chicks, with the timing of the HPAI spread differing across both regions and species.

13. Alongside seabirds, Scotland is also home to important wintering populations of wildfowl some of which were severely affected by HPAI during the winter of 2021/22, where an estimated 13,200 Svalbard barnacle geese died (around one third of the migratory or "flyway" population). HPAI also appeared to impact other important wildfowl species and a variety of raptor species such as golden and white-tailed eagles during this period, but to a lesser extent.

14. The 2021/22 outbreak of avian influenza virus was due to a H5N1 high pathogenicity avian influenza virus (HPAIV) (clade 2.3.4.4b), which was first detected at low levels during the previous outbreak in 2020/21. The first occurrence of this strain recorded in Europe was detected in 2020/21 in northern Europe (albeit at moderately low level) through the summer, including detections in great skuas on the Outer Hebrides and Northern Isles of Scotland.

15. Whilst the 2021/22 H5N1 viruses are related to those detected during 2020/21, three UK genotypes have been identified that can be distinguished based on their genetic composition, suggesting a new incursion in GB. Many of the UK H5N1 cases in 2021/22 epizootic are due to viruses that have their origins in migratory waterfowl that arrived in the UK in late 2021 (some of these can be distinguished genetically from viruses over-summering in northern Europe). It is not possible to exclude that some of the current H5N1 HPAI cases originated from the indigenous wild bird population carrying over-summering virus.

16. The continued detection of infection in wild birds through 2022/23 demonstrated that the virus was still circulating in wild bird populations and the probability of HPAI H5 still being present in wild birds in GB, in early February 2023, was very high. Direct and indirect contact with wild birds was deemed the most likely risk pathway for introduction of the virus into poultry holdings. Hotspots of infection remain a definite possibility, although these are difficult to predict. Evidence from surveillance, genetic sequencing of the virus and scientific risk assessments, conducted by government, indicate that infected poultry premises are very unlikely to be the cause of disease spread into other kept bird premises in the absence of links such as very close proximity, movement of infected birds or shared personnel. These activities are tightly controlled, particularly during any outbreak, when strict protocols are followed as set out in the Notifiable Avian Disease Control Strategy for Great Britain.