Anatidae migration in the western Palearctic and spread of highly pathogenic avian influenza H5NI virus

Abstract

During the second half of 2005, highly pathogenic avian influenza (HPAI) H5N1 virus spread rapidly from central Asia to eastern Europe. The relative roles of wild migratory birds and the poultry trade are still unclear, given that little is yet known about the range of virus hosts, precise movements of migratory birds, or routes of illegal poultry trade. We document and discuss the spread of the HPAI H5N1 virus in relation to species-specific flyways of Anatidae species (ducks, geese, and swans) and climate. We conclude that the spread of HPAI H5N1 virus from Russia and Kazakhstan to the Black Sea basin is consistent in space and time with the hypothesis that birds in the Anatidae family have seeded the virus along their autumn migration routes.

Figure 1

Map showing the spread of highly pathogenic avian influenza (HPAI) H5N1 virus and its environmental context. The background color indicates the month when the first frost was observed, from July through December 2005. The distribution of the main wetlands is indicated (dark blue; west Siberian lowland [WSL]). The reported presence of HPAI H5N1 virus from July 2005 to January 16, 2006, is indicated by squares with color coding for the first report of HPAI H5N1 virus in the country, and by green dots for other records.

Figure 2

Distribution overlay of migratory flyways of Anatidae bird species in the western Palearctic: each pixel of gray shading indicates the number of species that include the area as part of their flyway. A) All species with an equal weight (indicative of species diversity by pixel). B) Flyways weighted according to their population (indicative of anatid populations). Population-weighted distribution overlay for flyways intersecting highly pathogenic avian influenza (HPAI) H5N1 virus records are shown for C) July through August and D) July through December. E) The maps displayed present the product of map B by the overlay of anatids wintering distribution and by the log₁₀ of poultry density, as an index of the risk for transmission of HPAI H5N1 virus from anatids to domestic poultry in their wintering sites under the affected flyways.

Figure A1

Population of Anatidae in the western Palearctic (7).