Avian Influenza A Virus in Wild Birds in Highly Urbanized Areas

Josanne H Verhagen,Ron A M Fouchier,Job B G Stumpel,Albert D M E Osterhaus,Vincent J Munster,Roy Slaterus,Frank Majoor,Guus F Rimmelzwaan,Martin Schutten,Pascal Lexmond,Oanh Vuong

doi:10.1371/journal.pone.0038256

Abstract

Avian influenza virus (AIV) surveillance studies in wild birds are usually conducted in rural areas and nature reserves. Less is known of avian influenza virus prevalence in wild birds located in densely populated urban areas, while these birds are more likely to be in close contact with humans. Influenza virus prevalence was investigated in 6059 wild birds sampled in cities in the Netherlands between 2006 and 2009, and compared with parallel AIV surveillance data from low urbanized areas in the Netherlands. Viral prevalence varied with the level of urbanization, with highest prevalence in low urbanized areas. Within cities virus was detected in 0.5% of birds, while seroprevalence exceeded 50%. Ring recoveries of urban wild birds sampled for virus detection demonstrated that most birds were sighted within the same city, while few were sighted in other cities or migrated up to 2659 km away from the sample location in the Netherlands. Here we show that urban birds were infected with AIVs and that urban birds were not separated completely from populations of long-distance migrants. The latter suggests that wild birds in cities may play a role in the introduction of AIVs into cities. Thus, urban bird populations should not be excluded as a human-animal interface for influenza viruses.

Highlights

Wild aquatic birds are frequently infected with influenza A viruses
Wild bird sampling activities were intensified [6] after the emergence of highly pathogenic avian influenza (HPAI) H5N1 viruses in SouthEast Asia, and the detection of HPAI H5N1 viruses in migrating wild birds since 2005 [7,8,9]
The number of sampled hatch year (HY) and after hatch year (AHY) birds were distributed in high and low urbanized areas, with the exception of HY Black-headed Gulls that were intensively sampled in June and July at their breeding colonies in rural areas

Summary

Introduction

Wild aquatic birds are frequently infected with influenza A viruses. Wild birds are assumed to be the original source of influenza A viruses currently circulating in the animal and human population, as wild birds are often infected with all known influenza A virus hemagglutinin (H1–H16) and neuraminidase (N1–N9) subtypes [1,2]. In most cases wild birds are infected with low pathogenic avian influenza (LPAI) viruses that cause no or only mild disease symptoms in their natural hosts. Wild bird sampling activities were intensified [6] after the emergence of highly pathogenic avian influenza (HPAI) H5N1 viruses in SouthEast Asia, and the detection of HPAI H5N1 viruses in migrating wild birds since 2005 [7,8,9]. AIVs, including HPAI viruses, have sporadically been reported from wild birds in highly urbanized areas [11,12,13], but very little is known about the frequency of AIV infection in wild birds in cities and the risk these birds could pose to domestic animal and human health. We further hypothesized that wild birds sampled near closed water bodies (stagnant water, not connected to other water sources) will be infected with AIV, suggesting these birds play a role in the introduction of AIVs into

Methods

Results

Conclusion