West Nile Virus and Usutu Virus Monitoring of Wild Birds in Germany

Abstract

By systematically setting up a unique nation-wide wild bird surveillance network, we monitored migratory and resident birds for zoonotic arthropod-borne virus infections, such as the flaviviruses West Nile virus (WNV) and Usutu virus (USUV). More than 1900 wild bird blood samples, from 20 orders and 136 different bird species, were collected between 2014 and 2016. Samples were investigated by WNV and USUV-specific real-time polymerase chain reactions as well as by differentiating virus neutralization tests. Dead bird surveillance data, obtained from organ investigations in 2016, were also included. WNV-specific RNA was not detected, whereas four wild bird blood samples tested positive for USUV-specific RNA. Additionally, 73 USUV-positive birds were detected in the 2016 dead bird surveillance. WNV neutralizing antibodies were predominantly found in long-distance, partial and short-distance migrants, while USUV neutralizing antibodies were mainly detected in resident wild bird species, preferentially with low seroprevalences. To date, WNV-specific RNA has neither been detected in wild birds, nor in mosquitoes, thus, we conclude that WNV is not yet present in Germany. Continued wild bird and mosquito monitoring studies are essential to detect the incursion of zoonotic viruses and to allow risk assessments for zoonotic pathogens.

Keywords: Germany; Usutu virus; West Nile virus; monitoring; network; wild bird.

Figure 1

Location of sampling sites with zoological orders of wild bird blood samples from 2014–2016 (big red stars = main collectors, small red stars = minor collectors). The samples highlighted in the pie chart represent the total of all samples collected by all minor and major collectors in each region of Germany.

Figure 2

Detection of USUV in dead birds in 2016 (red dot = one USUV positive case/bird in 2016, grey areas = USUV positive areas before 2016).