Evidence for West Nile Virus and Usutu Virus Infections in Wild and Resident Birds in Germany, 2017 and 2018.

Friederike Michel,Rebekka Schwehn,Dominik Fischer,Martina Schmoock,Volker Schmidt,Rüdiger Korbel,Patrick Wysocki,Monika Rinder,Kerstin Müller,Sylvia Urbaniak,Markus Keller,Christine Fast,Renke Lühken,Michael Lierz,Martin Eiden,Michael Sieg,Maximilian Reuschel,Ute Ziegler,Thomas W Vahlenkamp ,Martin H Groschup

doi:10.3390/v11070674

Abstract

Wild birds play an important role as reservoir hosts and vectors for zoonotic arboviruses and foster their spread. Usutu virus (USUV) has been circulating endemically in Germany since 2011, while West Nile virus (WNV) was first diagnosed in several bird species and horses in 2018. In 2017 and 2018, we screened 1709 live wild and zoo birds with real-time polymerase chain reaction and serological assays. Moreover, organ samples from bird carcasses submitted in 2017 were investigated. Overall, 57 blood samples of the live birds (2017 and 2018), and 100 organ samples of dead birds (2017) were positive for USUV-RNA, while no WNV-RNA-positive sample was found. Phylogenetic analysis revealed the first detection of USUV lineage Europe 2 in Germany and the spread of USUV lineages Europe 3 and Africa 3 towards Northern Germany. USUV antibody prevalence rates were high in Eastern Germany in both years. On the contrary, in Northern Germany, high seroprevalence rates were first detected in 2018, with the first emergence of USUV in this region. Interestingly, high WNV-specific neutralizing antibody titers were observed in resident and short-distance migratory birds in Eastern Germany in 2018, indicating the first signs of a local WNV circulation.

Highlights

Wild birds, especially migratory birds, play a key role in the transport of emerging pathogens and their vectors via their major flyways into Central Europe [1,2]
Not all organs could be collected from every bird, so number of liver samples from birds that either died or were euthanized at the Veterinary Clinic at the we focused on examining the brain, liver, and spleen
West Nile virus (WNV) seropositive birds were found occasionally in all geographic regions (Region A–Region C), displaying quite low neutralizing antibody titers generally ranging between ND50 1:10–1:20 and sporadically up to ND50 1:80

Summary

Introduction

Especially migratory birds, play a key role in the transport of emerging pathogens and their vectors via their major flyways into Central Europe [1,2]. Monitoring wild birds and arthropod vectors (e.g., mosquitoes, ticks, etc.) is best suited to reveal the entry of new emerging (in particular zoonotic) pathogens and is a prerequisite for the rapid implementation of public and animal health measures. WNV is a mosquito-borne arbovirus of the family Flaviviridae [7] and an important zoonotic pathogen worldwide. WNV is a single-stranded RNA virus [8] circulating in an enzootic cycle between ornithophilic mosquitoes as vectors and avian host species [9,10]. A transmission of WNV via bridging vectors (mosquitoes feeding on both avian and mammalian species) to a variety of other vertebrates is possible

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