Risk of the Introduction of High Pathogenic Avian Influenza (H5N1)
Into Ireland By Wild Birds – July 2007
Background
Following recent confirmation of the presence of H5N1 HPAI in the Czech Republic, Germany and France and the publication of a comprehensive risk assessment by the Department of the Environment, Food and Rural Affairs (Defra) of the likelihood of the introduction of H5N1 HPAI into Great Britain by wild birds[1], the Department of Agriculture, Fisheries and Food (DAFF) requested the National Parks and Wildlife Service (NPWS) of the Department of the Environment, Heritage and Local Government and BirdWatch Ireland to assess the risk posed to Ireland from migratory birds from or passing through that those affected parts of Europe.
DAFF wishes to express its appreciation for the ongoing support and ornithological expertise provided by both the NPWS and BirdWatch Ireland.
Recent Developments in the EU
Following the cases of H5N1 HPAI in Hungary and England (Suffolk) in January and February, respectively, the spring and early summer months were stable and no further cases/outbreaks were reported in the European Union until an outbreak was reported in a commercial turkey flock in the Czech Republic in June 2007. Subsequent outbreaks were confirmed in the Czech Republic and in southern Germany in June and in north-eastern France in July.
Since these initial outbreaks, there have been 5 cases in the Czech Republic, 296 in Germany and 2 in France. The most recently confirmed cases in the Czech Republic, Germany and France were on 21 June, 18 July and 29 July, respectively. The wild birds that have tested positive to H5N1 to date are Mallard Anas platyrhynchos, Mute Swan Cygnus olor, Canada Goose Branta canadensis and Black-necked Grebe Podiceps nigricollis.
Migratory Patterns
The months of July and August mark the period when the breeding season comes to an end and the autumn migration commences for most bird species in the Canada, Greenland and Iceland, and NW Europe flyways. There are many factors that determine when birds migrate or the rate at which particular elements of a population will migrate as well as when or which routes they will take. Some of these factors can be accounted for, such as weather effects, while others cannot, such as the proportion that fails to breed and hence the extent and timing of any early migration brought about by this failure to breed.
Some migratory waterbirds are known to arrive into Ireland as early as July, for example Curlew Numenius arquata and Redshanks Tringa totanus. Curlew Numenius arquata have been arriving at Irish coastal wetlands since early July along with Redshank, Oystercatcher Haematopus ostralegus and Black-headed Gulls Larus ridibundus. Some of these birds breed in Ireland and have simply moved from their inland breeding sites to the coast, hence the numbers present in coastal wetlands may comprise a combination of Irish-breeding as well as immigrant birds.
Some of the migratory species are on passage and use Ireland as a stop-over point en route to southern Europe and Africa for the winter. Generally though, Ireland tends to receive most birds from the north and north-west, i.e. Canada, Greenland and Iceland, during the early autumn. Britain, however, receives birds from northern Europe and further east to Siberia. Later in the autumn period – September/October – migratory birds from northern Europe and further east will also arrive to Ireland to winter here.
Assessment of Risk to Ireland
The report prepared by the NPWS and BirdWatch Ireland aimed to clarify, on the basis of the information available, the risk posed to Ireland by the fifteen species identified in the Defra report as posing some threat of introducing H5N1 to Britain. A summary of the risk posed to Ireland by those species, describing the breeding origins, wintering distributions and the numbers breeding (pairs, where appropriate) and wintering (where appropriate) in Ireland, is set out in the accompanying table. The table also includes a threat category ranging from highly unlikely to those species that may be considered to pose the greatest threat.
The assessment of risk is based on a combination of the numbers expected to come to Ireland over the coming months and the likelihood of them coming from currently affected areas. This information on the known temporal occurrence of these species, their numbers and breeding origins has been gathered largely from previously published material.
Conclusion
Of the fifteen species listed in the Defra report, most are considered to pose little or no risk of introducing H5N1 HPAI into Ireland at the present time and based on the current situation elsewhere in Europe. Based on breeding origins and total numbers expected to migrate to Ireland over the coming weeks, Northern Lapwings Vanellus vanellus and Black-headed Gulls which, according to the Defra report, began to arrive in Great Britain in July, might be expected to pose the greatest potential risk. Both are likely to be distributed very widely in Ireland on both wetland and non-wetland sites throughout the autumn and winter.
It is worth making the point that neither species have been implicated in the most recent episodes in central and western Europe and have not, on the basis of the best information available to the NPWS and BirdWatch Ireland, featured in previous outbreaks or been detected through EU-wide surveillance programmes. Consequently, it is concluded that the risk to Ireland of the introduction of H5N1 HPAI through wild birds remains low at this early stage of the autumn migration.
In view of the early stage at which the migration season currently is and the magnitude of the migration yet to come, particularly from late August onwards, the situation will be kept under review and the risk reassessed, if appropriate, taking account of the most up-to-date information available to DAFF, the NPWS and BirdWatch Ireland.
Ends.
[1] Defra (2007). Highly pathogenic avian influenza – H5N1: Recent developments in the EU and the likelihood of the introduction into Great Britain by wild birds (Authors: Sabrovic, M., Hall, S., Wilesmith, J., Coulson, N.), 1A Page Street, London, SW1P 4PQ, United Kingdom. Version 1, Released 12 July 2007.