Avian influenza (bird flu): Rapid risk assessment on infected premises in Dumfriesshire -15 December 2021

Rapid risk assessment on infected premises near Gretna, Dumfriesshire, Dumfries and Galloway on 15 December 2021.


Rapid Risk Assessment – near Gretna, Dumfriesshire, Dumfries and Galloway, Scotland

Date: 15th December 2021

Authors: Andrew Bremang

Reviewers: Harriet Auty, Lisa Boden, Sibylle Mohr and Dominic Mellor

Introduction

  1. Total birds on site: 10 mixed poultry- cockerels (2), chickens (2), ducks (2) and geese (4).
  2. Biosecurity and links to other premises: TBC
  3. Commercial activity on the premises: None

New cases of HPAI H5 in wild birds and poultry continue to be reported in GB and Northern Ireland. As of 14th December 2021, the UK had confirmed 52 total outbreaks in poultry six (6) of which are in Northern Ireland and four (4) in Scotland. It is expected that the infection pressure both on wild birds and poultry will increase as migratory wild water birds are peaking. 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 14th December 2021 the background risk of poultry exposure across GB was medium (with low uncertainty) where biosecurity is optimum and high (with low uncertainty) where biosecurity is sub-optimal.

Mapping and data made available to EPIC indicate that there are 2 poultry premises within the 1km zone (1 with <50 birds and 1 >=50 birds), 7 premises in the 3km zone (5 with >=50 birds) and 22 premises within the 10km zone (15 with >=50 birds) including a number of large premises. However we cannot rule out the existence of smallholder or backyard premises (<50 birds) that have not registered their poultry in any of these zones.

In terms of wild bird species present in the area, the wetland bird survey confirms the presence of a large number of geese at the Solway Estuary (5-year average: Barnacle Goose - 40,958; Pink-footed Goose - 11,346). There has been a number of wild bird findings of H5N1 reported from the area mostly including geese and swans. Presence of open landscape and moorland means raptors are likely.

Regarding this particular suspect premises the ducks and geese are the most likely species to be of concern for spreading the virus; they were not housed until recently and would possibly have had contact with wild birds.

This risk assessment is for the potential definition of the infected premise AIV2021/61 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 GB is already assessed as very high (refer to defra risk assessment) 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 impacted by the Avian Influenza Prevention Zone measures in place, which include housing. It must also be noted that of the 33 registered premises within the 10km zone, 28 fall within the 3km and 10km zones of an existing infected premises which would likely improve biosecurity awareness and likelihood of detection of these premises.

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)

Although contact between wild birds and unhoused ducks and geese may have occurred prior to December 4th the risk is no greater than the VERY HIGH wild bird risk already assessed across GB.

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 14th December 2021).  For all but one potential pathway of infection from a smallholder premises to another commercial premises, then 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. 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. Therefore, local assessment concerning the proximity and  contact between the infected premises and game birds is necessary before the overall risk can be assessed accurately. Until such assessment confirms that there is no high-risk contact with free ranging game birds the uncertainty remains very high and the risk could increase to very high.

This risk assessment has been carried out with high uncertainty about any fomite links (equipment, bird, and human links between the infected premise and other susceptible premises).  Any dangerous contacts 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 identification of infection on the infected premises.  However, this has high uncertainty and this risk level is contingent on the geographic location of the infected premises in relation to other premises (particularly poultry premises within 1km or 3km zones), confirmation from the field that there has been no commercial activity at the site and that there are no game birds in close proximity to the site, and that no dangerous contacts are identified as described above.

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