West Nile and Usutu Virus Introduction via Migratory Birds: A Retrospective Analysis in Italy

Abstract

The actual contribution of migratory birds in spreading West Nile (WNV) and Usutu virus (USUV) across Europe and from Africa to old countries is still controversial. In this study, we reported the results of molecular and serological surveys on migrating birds sampled during peaks of spring and autumn migration at 11 Italian sites located along important flyways, from 2012 to 2014. A total of 1335 specimens made of individual or pooled sera, and organs from 275 dead birds were tested for WNV and USUV RNA by real time PCR (RT-PCR). Furthermore, sera were tested by serum neutralization assay for detecting WNV and USUV neutralizing antibodies. Molecular tests detected WNV lineage 2 RNA in a pool made of three Song Thrush (Turdus philomelos) sera sampled in autumn, and lineage 1 in kidneys of six trans-Saharan birds sampled in spring. Neutralizing antibodies against WNV and USUV were found in 5.80% (n = 72; 17 bird species) and 0.32% (n = 4; 4 bird species) of the tested sera, respectively. Our results do not exclude the role of migratory birds as potential spreaders of WNV and USUV from Africa and Central Europe to Mediterranean areas and highlight the importance of a more extensive active surveillance of zoonotic viruses.

Arbovirus persistence in North-Western Europe: Are mosquitoes the only overwintering pathway?

“…As observed in other countries, repeated outbreaks of WNV and/or USUV may in part be explained by the occurrence of virus reintroductions and/or maintenance of the viruses without vector activity. Repeated introductions of WNV and USUV may occur via infected migratory birds, despite the lack of conclusive evidence [ 31 , 54 ]. Additionally, bird-to-bird transmission in winter has been observed for both USUV [ 55 ] and WNV [ 56 ], and as such, this also remains a potential overwintering mechanism for WNV and USUV.…”

Evolutionary dynamics of Usutu virus: Worldwide dispersal patterns and transmission dynamics in Europe

“…The results of our phylogeographic analysis suggested that the evolution of USUV has been shaped by long-distance migration routes between continents. Migratory birds are known as viral hosts and reservoirs, hence viral dispersion, including arboviruses such as WNV and USUV, has been associated with migratory birds' flyways (Zhang et al, 2014 ; Mancuso et al, 2022 ). Eight major migratory birds' flyways have been established: Pacific Americas, Mississippi Americas, Atlantic Americas, East Atlantic, Black Sea-Mediterranean, West Asia-East Africa, Central Asia, and East Asia/Australasia (CMS Technical Series No.…”

Expedited retrieval of high-quality Usutu virus genomes via Nanopore sequencing with and without target enrichment

“…To date, USUV epidemiological surveillance programs have focused primarily on the molecular (RT-qPCR) and serological detection (virus neutralization tests and enzyme-linked immunosorbent assays) of USUV-specific genome and antibodies, respectively. Passive and active surveillance efforts of wild birds and captive zoological birds are regularly performed, among others in Austria ( Bakonyi et al, 2007 ; Chvala et al, 2007 ; Meister et al, 2008 ; Rubel et al, 2008 ), Belgium ( Rouffaer et al, 2018 ; Benzarti et al, 2020 ), France ( Vittecoq et al, 2013 ; Roesch et al, 2019 ; Constant et al, 2020 ), Germany ( Ziegler et al, 2015 , 2022 ; Michel et al, 2018 , 2019 ), Hungary ( Bakonyi et al, 2007 ; Weidinger et al, 2020 ), Italy ( Manarolla et al, 2010 ; Savini et al, 2011 ; Tamba et al, 2011 ; Giglia et al, 2021 ; Lauriano et al, 2021 ; Scaramozzino et al, 2021 ; Zecchin et al, 2021 ; Mancuso et al, 2022 ), the Netherlands ( Lim et al, 2018 ), Spain ( Jurado-Tarifa et al, 2016 ; Marzal et al, 2022 ), and the United Kingdom ( Buckley et al, 2003 ; Horton et al, 2013 ; Folly et al, 2020 ). Nonetheless, a genomic surveillance of USUV is rare, with a limited number of available full-genome sequences.…”