Surveillance of Influenza Virus A in Migratory Waterfowl in Northern Europe

Anders Wallensten,Mia Brytting,Malin Karlsson,Thord Fransson,Ron A.M Fouchier,Albert D.M.E Osterhaus,Björn Olsen,Martin Stervander,Johan Elmberg,Paul D Haemig,Jonas Waldenström,Vincent J Munster,Neus Latorre-Margalef,Åke Lundkvist

doi:10.3201/eid1303.061130

Abstract

We conducted large-scale, systematic sampling of influenza type A virus in migratory waterfowl (mostly mallards [Anas platyrhynchos]) at Ottenby Bird Observatory, southeast Sweden. As with previous studies, we found a higher prevalence in fall than spring, and among juveniles compared with adults. However, in contrast to other studies, we found that prevalence in spring was sometimes high (mean 4.0%, highest 9.5%). This finding raises the possibility that ducks are capable of perpetuating influenza A virus of different subtypes and subtype combinations throughout the year and from 1 year to the next. Isolation of the H5 and H7 subtypes was common, which suggests risk for transmission to sensitive domestic animals such as poultry. We argue that wild bird screening can function as a sentinel system, and we give an example of how it could have been used to forecast a remote and deadly outbreak of influenza A in poultry.

Highlights

IntroductionWe conducted large-scale, systematic sampling of influenza type A virus in migratory waterfowl (mostly mallards [Anas platyrhynchos]) at Ottenby Bird Observatory, southeast Sweden
We conducted large-scale, systematic sampling of influenza type A virus in migratory waterfowl at Ottenby Bird Observatory, southeast Sweden
Influenza A virus has diversified into 2 separate avian lineages, North American and European [3,4], so it is reasonable to ask whether the ecology of influenza A virus in Europe differs from that in North America

Summary

Introduction

We conducted large-scale, systematic sampling of influenza type A virus in migratory waterfowl (mostly mallards [Anas platyrhynchos]) at Ottenby Bird Observatory, southeast Sweden. In contrast to other studies, we found that prevalence in spring was sometimes high (mean 4.0%, highest 9.5%) This finding raises the possibility that ducks are capable of perpetuating influenza A virus of different subtypes and subtype combinations throughout the year and from 1 year to the next. Current knowledge of influenza A virus ecology in wild birds is derived mainly from North American studies [1,2], which show seasonal changes and between-year fluctuations in prevalence and subtype distribution. We compare our data to other long-term systematic surveillance studies of influenza A virus in wild ducks, review geographic patterns and prevalence of influenza A virus subtypes, and discuss their modes of perpetuation in waterfowl

Methods

Results

Conclusion