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.
Highlights
IntroductionMigratory avian species of the Western Palearctic (Europe, Middle East and Northern Africa) have developed countless seasonal North-South routes represented either by movements within the region itself (short-distance or intra-Palearctic migrants) or by reaching sub-Saharan Africa (long-distance or trans-Saharan migrants)
We provided a descriptive assessment of potential flavivirus dispersal through migratory birds crossing Italy
The low prevalence of West Nile virus (WNV) positive birds found in this survey, not excluding, definitely indicates that long distance migratory birds played a marginal role in introducing new WNV strains from Africa as well as from Central and Northern European countries
Summary
Migratory avian species of the Western Palearctic (Europe, Middle East and Northern Africa) have developed countless seasonal North-South routes represented either by movements within the region itself (short-distance or intra-Palearctic migrants) or by reaching sub-Saharan Africa (long-distance or trans-Saharan migrants) These birds leave the breeding sites and move southward in the late boreal summer/autumn for flying back northwards in spring for the following breeding season. The migratory behavior is context dependent and it is just triggered by specific habitat conditions at the breeding grounds (irregular migrants) During their journey, migratory birds can vehicle and spread zoonotic pathogens, including viruses, and they are thought to be responsible for the wide geographic distribution of some important arboviruses. In Europe, their circulation is mainly associated to a Received: 30 December 2021
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