Genetische Untersuchungen zur Migration zweier Vogelgrippe-Vektoren: Reiher- und Tafelente

• Forschungsstelle: BLV
• Projektnummer: 1.08.07
• Projekttitel Englisch: Genetic analysis of migration in two avian influenza vectors : tufted duck and common pochard

Schlüsselwörter (Englisch)

Avian influenza, Aythya ferina, Aythya fuligula, diving ducks, population genetics, migration.

Kurzbeschreibung (Englisch)

Wild birds probably played a role in the introduction of highly pathogenic avian influenza H5N1 into Europe. In Switzerland, the incidence of H5N1 was particularly high in the tufted duck (Aythya fuligula) and the common pochard (Aythya ferina). Both species are long distance migrants and, thus, prime candidates as vectors of avian influenza.
Here, we propose to infer the migration patterns of these two duck species using a population genetic approach. Feather samples will be collected from various locations throughout Eurasia and genetically analysed at nuclear and mitochondrial loci. This data will be used to assess the level of genetic differentiation among breeding populations and determine the origin of ducks on European and Asian wintering grounds. This will provide the first quantitative assessment of the extent of mixing among East Asian and European ducks. In particular, the project will provide information on the proportion of Swiss winter guests originating from areas with high incidence of H5N1 and the populations of origin of the H5N1-positive birds found in Switzerland. A better understanding of possible transmission pathways of H5N1 will help to ensure that protective measures for poultry are targeted and effective.

Projektziele (Englisch)

The primary goal is to provide a solid basis for assessing the risk of H5N1 introduction into Switzerland by migratory ducks. The two target species from the genus Aythya are prime candidates as long distance vectors because of the large number of birds migrating between Central Europe and Asia each year, the potential mixing of birds wintering in Southeast Asia and Europe on their Northern Asian breeding grounds, and the high incidence of H5N1 in Aythya in Switzerland. Detailed knowledge about the population of origin of infected birds, the time of arrival of birds from populations in high risk areas, and the relative proportion of such birds among the winter guests in Switzerland will allow the efficient monitoring of infection risks, and consequently a much more informed and sensible implementation of protective measures for poultry. The close interaction with existing projects on avian influenza like Constanze will ensure a comprehensive analysis of imminent risks caused by H5N1 and potentially other strains of avian influenza or other zoonothic pathogens.
In order to provide a detailed analysis of migration in Aythya and to determine the population of origin of infected ducks in Switzerland (and abroad), we aim to:
1. Identify the genetic population structure of tufted ducks (A. fuligula) and common pochards (A. ferina) across their distribution range. This will include extensive sampling of birds in Asian and European wintering and breeding areas.
2. Identify the breeding areas of tufted ducks and common pochards wintering in Switzerland and abroad. This will include comparative DNA sequence analyses and genetic assignment to populations. This approach will be extended to samples from different Swiss lakes and several winters to encompass spatial and temporal variation.
3. Genetically analyze the tufted ducks and common pochards found to be infected with H5N1 and other strains in Switzerland, and determine their population of origin. The resolution of this assignment will depend on the observed levels of genetic differentiation between populations of these species. The genetic analyses will also provide a means for reliable species identification of previously unidentified birds from the Swiss avian influenza surveillance programme (e.g. 8 positive cases from 2006).
4. Cross-validate the migration routes and population structure postulated from the analysis of ring recoveries.
5. Identify potential differences between the sexes in Aythya with respect to migratory behaviour and fidelity to particular breeding or wintering areas through the analysis of genetic marker loci with different modes of inheritance.
This project will be the first to analyze migration among populations of potential long-distance vectors of avian influenza in detail. Knowledge about population connectivity and, consequently, potential transmission pathways will not only allow decisive and timely reactions of the authorities to existing pathogenic strains but it will also provide a basis for targeted and effective measures against new strains or novel pathogens potentially emerging in the future.

Umsetzung und Anwendungen (Deutsch)

31.05.2007: Umsetzung:
Grundlagen zur Risikoabschätzung
Erkenntnisse für Monitoring der AI
effizientere Vorbeugemassnahmen
gezielte Hilfe zur AI-Bekämpfung in wichtigen Gebieten (Selektionssitzung 2007/mvo)

Umsetzung und Anwendungen (Englisch)

The assessment of the risk of H5N1 introduction into Switzerland and Europe is of high significance to veterinary and human health. Knowledge about the population of origin of infected birds in Switzerland, the time of arrival of birds from populations in high risk areas, and the relative proportion of such birds among the Swiss winter guests will allow the efficient monitoring of infection risks, and consequently an implementation of protective measures for poultry only in times of high risk. After all, such a targeted application of costly and laborious protective measures is also economically highly relevant.
In this context, the proposed project complements ideally the already existing projects within the Constanze framework because the establishment of laboratory protocols and genetic databases will allow the efficient species identification of duck samples and potentially their population of origin. Our existing contacts with the national reference laboratory of Germany should also allow us to extend the analyses to infected ducks from abroad. Once fully established, these procedures could be easily transferred to other institutions in Switzerland or abroad that will be involved in the monitoring of zoonothic pathogens in the future. If desirable, methods and protocols could be applied to other waterfowl species with only relatively minor modifications.
Besides the direct applicability of results in Switzerland, this project is likely to have a broad scientific impact overall. Various national and international research projects aim currently at predicting the transmission pathways and frequencies of H5N1 from the genetic analysis of detected viruses. Such predictions are hampered by difficulties of virus detection, the uncertainties about the mode of transmission among hosts, and the unknown role of vectors in the spread of viruses. The investigations proposed here directly address the latter factor by analysing movement patterns of the two most likely natural long-distance vectors for avian influenza from South East Asia to Europe. The results of the proposed project will undoubtedly be of high significance to all authorities, institutions and researchers concerned about the spread of current or novel highly pathogenic strains across Asia and Europe.
This project could also form the basis of a combined genetic analysis of viruses and hosts over time, which may help to identify transmission pathways in host populations directly. For example, the presence of the same virus strains in ducks from genetically distinct breeding populations would be highly suggestive of transmission during migration or on the wintering grounds. Genetic analysis of viruses over time and quantitative information about the exchange among host populations could allow the tracing of the origin of new virus strains (e.g. Drummond et al. 2006).
Apart from direct animal and human health considerations, it is of general interest in virology and evolutionary biology to understand how high pathogenicity evolves and spreads across populations, and under which conditions it can be maintained over time. Our analyses shall shed light on this co-evolutionary process as the extent of genetic structure among hosts populations and the local size of populations are likely to be the key factors (Schmid-Hempel & Ebert 2002).
Last but not least, we expect a significant impact of this project on bird migration research. Even after decades of work and tens of thousands of ringed Aythya birds, ring recoveries are more or less absent for very large areas of the distribution range (e.g. central and eastern Siberia). Our project shall provide important information to fill this gap, and demonstrate the utility of genetic investigations additional to other sources of information.

UMS 2011:
Diverse Publikationen sind erschienen, Massnahme der Risikogebiete ist auch international Standard und es zeigte sich aus den Reusltaten, dass kein Anlass besteht, diese Massnahme der Risikogebiete zu ändern. Status: erledigt.
Auflagen: Projekt ist erledigt, wenn Publikation erschienen ist. Jda erhält den Auftrag diese einzufordern (mvo)

Publikationen / Ergebnisse (Deutsch)

Liu, Y.; Keller, I.; Heckel, G. (2013) Temporal genetic structure and relatedness in the Tufted Duck Aythya fuligula suggests limited kin association in winter. IBIS The International Journal of Avian Science 155: 9, 499 - 507

Publikationen / Ergebnisse (Englisch)

Liu Yang, L. (2011) Genetic analysis of migration in two avian influenza vectors: tufted duck and common pochard. Dissertation, Institut für Ökologie und Evolution, Universität Bern.

Stovicek, O.;et al. (2011) Development of microsatellite markers for a diving duck, the common pochard (Aythya ferina). Conservation Genet Resour, DOI 10.1007/s12686-011-9407-6.

Liu, Y.; Keller, I.; Heckel, G. (2011) Range-wide genetic population structure of common pochard (Aythya ferina): a potentially important vector of highly pathogenic avian influenza viruses. Open access, doi: 10.1002/ece3.46.

Liu, Y.; Keller, I.; Heckel, G. (2012) Breeding site fidelity and winter admixture in a long-distance migrant, the tufted duck (Aythya fuligula). Heredity 00, 1–9.

Zugehörige Dokumente

• 1.08.07 Datenblatt MJB Heckel8429 [PDF] 84 kB
• Breeding site fidelity_2012_Yang [PDF] 592 kB
• Range-wide genetic_Yang [PDF] 848 kB