Avian influenza (bird flu): rapid risk assessment on infected premises near Inverurie - January 2022

Rapid risk assessment on infected premises near Inverurie, Aberdeenshire on 21 January 2022.


Rapid risk assessment – near Inverurie, Aberdeenshire, Scotland

Date: 21 January 2022, updated 24 January 2022

Author: Dominic Mellor

Reviewer: Lisa Boden, Harriet Auty

Introduction

  1. Total birds on site: 40 ducks
  2. Biosecurity and links to other premises: No evidence of significant risks of fomite spread between the infected premises and other premises with susceptible species
  3. Commercial activity on the premises: No commercial activity reported

New cases of HPAI H5 in wild birds and poultry continue to be reported in the UK and Northern Ireland. As of 21 January 2022, the UK had confirmed 81 total outbreaks in poultry, five (5) of which have been in Northern Ireland and five (5) in Scotland. Ongoing wild bird surveillance indicates that the virus is currently circulating across a range of species including gulls and raptors and will possibly continue over the next few months. Incursion into poultry is largely biosecurity dependent. As of 21 January 2022 the background risk of poultry exposure across GB is assessed as medium (with low uncertainty) where biosecurity is optimum and high (low uncertainty) where biosecurity is sub-optimal.

Data made available to EPIC indicate that there are 0 poultry premises registered within the 1km zone, 0 poultry premises registered within the 3km zone and 28 premises registered between the 3km and 10km zone. One of these is a moderate sized commercial enterprise and three are reported to have partridges and/or pheasants released for shooting. However, it is reported that there is not a high level of gamebird activity (i.e. free living gamebirds) in the local area at present. We cannot rule out the existence of smallholder or backyard premises (<50 birds) that have not registered their poultry in any of these zones, but there are not thought to be any high risk premises within 3km.

In terms of wild bird species present in the area, the wetland bird survey confirms moderate numbers of birds (low thousands) along the nearby coasts. During the current outbreak there have been a small number of wild bird findings of HPAI H5N1 reported from the vicinity of this premises including duck, geese and swans. Presence of open landscape and moorland means raptors are likely.

Regarding this particular suspect premises, the ducks present are the most likely to be of concern for spreading the virus.

This risk assessment is for the potential definition of the infected premise AIV2021/11, a “non-commercial special category premise” which allows disapplication of certain measures in the Avian influenza and Influenza of Avian Origin in Mammals Scotland Order 2006.

Risk question:

Is there an increased risk of HPAI infection in poultry premises within proposed zones (above that of the current background risk levels) as a result of identified infection on the infected premise? 

Risks pathways to other premises within the proposed zones from the identification of this infected premise are:

  1. a local increase in the background risk of disease in wild birds,
  2. through transmission from the infected premise to susceptible birds on another premise via fomites (human or equipment) or via an infected bird (either through movement or through free ranging).

The background risk of incursion in wild birds in Scotland is already assessed as high (with high uncertainty) and therefore the risk from wild birds to other local premises will not be increased by the occurrence of this IP compared to the background risk.

The risk to other premises within the proposed zones will be contingent on the links between those premises and the IP. This risk would be reduced by the Avian Influenza Prevention Zone measures in place, which include housing.

Potential links to other premises would include:

  • links via water courses or surface water
  • links via game bird ranging (bird to bird contact)
  • links via fomites (either carried on people or equipment)
  • links via personnel onsite
  • links via direct/close contact (contiguous premises)

Referring to table 13 in ‘Risk Assessment for the transmission of Highly pathogenic Avian Influenza from infected smallholdings to commercial poultry premises’ Version 2, 2017 (authors Gale, Horrigan and Kelly) all pathways were assessed as low, very low, or negligible (apart from where there are free ranging game birds in close proximity to the infected premise, in which case the risk is assessed as very high), although in some cases with high uncertainty. A number of the pathways are not relevant because of the provisions of the existing AIPZ. With existing AIPZ measures already in place, including housing, it is expected that biosecurity would be enhanced at other premises.

The background risk of infection to poultry premises on which the biosecurity is poor is currently categorised as high and with stringent biosecurity is currently medium (refer to defra risk assessment, on the day of assessment 21 January 2022). For all but one potential pathway of infection from a smallholder premises to another commercial premises, there is no increased risk from this infected premises to others within the proposed zones above the current background risk from wild birds, as all are assessed as low or very low.

However, this is contingent on an assessment of the risk from game birds. Three game bird premises are reported in the proposed zones. If there are game birds very close and with potential contact with the IP that may travel back to their holding of origin, then the risk of transmission to a new premises is very high. The pheasant shooting season is almost finished, which means that the population of birds will be substantially reduced (season finishes 1 Feb), and it has been indicated that there is not a high level of free-ranging game bird activity in the local area. Therefore, contact between the infected premises and free-ranging game birds is unlikely. This suggests there is no increased risk from this infected premises to others within the proposed zones above the current background risk from wild birds, although the uncertainty around the game bird route is medium.

The epidemiological investigation has not found any evidence of significant risks of fomite spread between the infected premises and other premises with susceptible species. However, if any dangerous contacts were identified, they would be assumed to be considered to be high risk.

Conclusion

In conclusion, the current assessment is that the risk to other poultry premises within the proposed zones would be no greater than the current background level of risk from wild birds and would therefore not be increased by confirmation of infection on the infected premises. However, this has medium uncertainty and this risk level is contingent on the geographic location of the infected premises in relation to other premises (particularly unregistered poultry premises within 1km or 3km zones), and on the assumption that no dangerous contacts are identified as described above.

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