The emergence of West Nile virus (WNV) and Usutu virus (USUV) in addition to the autochthonous tick-borne encephalitis virus (TBEV) in Europe causes rising concern for public and animal health. The first equine case of West Nile neuroinvasive disease in Austria was diagnosed in 2016. As a consequence, a cross-sectional seroprevalence study was conducted in 2017, including 348 equids from eastern Austria. Serum samples reactive by ELISA for either flavivirus immunoglobulin G or M were further analyzed with the plaque reduction neutralization test (PRNT-80) to identify the specific etiologic agent. Neutralizing antibody prevalences excluding vaccinated equids were found to be 5.3% for WNV, 15.5% for TBEV, 0% for USUV, and 1.2% for WNV from autochthonous origin. Additionally, reverse transcription quantitative polymerase chain reaction (RT-qPCR) was performed to detect WNV nucleic acid in horse sera and was found to be negative in all cases. Risk factor analysis did not identify any factors significantly associated with seropositivity.

Clinical Unit of Equine Internal Medicine University of Veterinary Medicine Vienna Veterinärplatz 1 1210 Vienna Austria

Department of Basic Medical Sciences College of Medicine Mohammed Bin Rashid University of Medicine and Health Sciences Dubai Healthcare City Building 14 Dubai P O Box 505055 United Arab Emirates

Department of Mathematics University of Salzburg Hellbrunner Straße 34 5020 Salzburg Austria

Institute for Vertebrate Biology Czech Academy of Sciences Kvĕtná 8 60365 Brno Czech Republic

Viral Zoonoses Emerging and Vector Borne Infections Group Institute of Virology University of Veterinary Medicine Vienna Veterinärplatz 1 1210 Vienna Austria

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