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. 2025 Apr 22;13(5):958.
doi: 10.3390/microorganisms13050958.

Virological Passive Surveillance of Avian Influenza and Arboviruses in Wild Birds: A Two-Year Study (2023-2024) in Lombardy, Italy

Maria Cristina Rapi  1 , Ana Maria Moreno Martin  2 , Davide Lelli  2 , Antonio Lavazza  2 , Stefano Raimondi  3 , Marco Farioli  4 , Mario Chiari  5 , Guido Grilli  1
Affiliations

Virological Passive Surveillance of Avian Influenza and Arboviruses in Wild Birds: A Two-Year Study (2023-2024) in Lombardy, Italy

Maria Cristina Rapi et al. Microorganisms. .

Abstract

Avian influenza (AI), caused by Alphainfluenzavirus (family Orthomyxoviridae), poses significant threats to poultry, biodiversity, and public health. AI outbreaks in poultry lead to severe economic losses, while highly pathogenic strains (HPAIVs) severely impact wild bird populations, with implications for biodiversity and potential zoonotic risks. Similarly, arboviruses such as West Nile virus (WNV) and Usutu virus (USUV) are emerging zoonoses. WNV can cause severe neurological diseases in birds, humans, and other animals, while USUV significantly affects blackbird populations and has zoonotic potential, though human cases remain rare. This study investigated avian viruses in 1654 wild birds from 75 species that died at the Wildlife Rescue Center in Vanzago, Lombardy, during 2023-2024. Necropsies were conducted, and virological analyses were performed to detect avian influenza viruses, WNV, and USUV. Among the tested birds, 15 were positive for H5N1 HPAIV clade 2.3.4.4b, all in 2023, including 13 Chroicocephalus ridibundus, one Coturnix coturnix, and one Columba palumbus. Additionally, 16 tested positive for WNV (15 for lineage 2 and one for lineage 1), one for USUV, and 11 co-infections WNV/USUV were recorded in 2023-2024. These findings underscore the importance of avian viral passive surveillance in identifying epidemiological trends and preventing transmission to other species, including mammals and humans.

Keywords: H5N1; HPAIV clade 2.3.4.4b; Usutu virus; West Nile virus; avian influenza; passive surveillance; wild birds.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Passive surveillance in wild birds. (a) Proportional distribution of collected wild birds during 2023–2024, categorized by the most represented taxonomic orders; (b) Proportional distribution of wild birds categorized by less represented taxonomic orders (“Others” in (a)).
Figure 2
Figure 2
Provinces of origin of wild birds analyzed. (a) Provinces within Lombardy region contributing to wild bird samples analyzed during 2023–2024, showing the most representative areas. (b) Geographic origins of wild birds analyzed during 2023–2024, including provinces from both Lombardy and neighboring Italian regions (“Other provinces” in (a))”.
Figure 2
Figure 2
Provinces of origin of wild birds analyzed. (a) Provinces within Lombardy region contributing to wild bird samples analyzed during 2023–2024, showing the most representative areas. (b) Geographic origins of wild birds analyzed during 2023–2024, including provinces from both Lombardy and neighboring Italian regions (“Other provinces” in (a))”.
Figure 3
Figure 3
Locations of avian influenza virus (H5N1 HPAIV clade 2.3.4.4b) positive cases in Lombardy, detected in wild birds during February and March 2023 (QGIS 3.34.3 map).
Figure 4
Figure 4
Geographic distribution of West Nile virus- and Usutu virus-positive cases in wild birds sampled in Lombardy during 2023–2024 (QGIS 3.34.3 map).
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References

    1. Jones K.E., Patel N.G., Levy M.A., Storeygard A., Balk D., Gittleman J.L., Daszak P. Global trends in emerging infectious diseases. Nature. 2008;451:990–993. doi: 10.1038/nature06536. - DOI - PMC - PubMed
    1. Vogt N.A. Wild birds and zoonotic pathogens. In: Sing A., editor. Zoonoses: Infections Affecting Humans and Animals. Springer International Publishing; Cham, Switzerland: 2022. pp. 1–31.
    1. Blagodatski A., Trutneva K., Glazova O., Mityaeva O., Shevkova L., Kegeles E., Onyanov N., Fede K., Maznina A., Khavina E., et al. Avian influenza in wild birds and poultry: Dissemination pathways, monitoring methods, and virus ecology. Pathogens. 2021;10:630. doi: 10.3390/pathogens10050630. - DOI - PMC - PubMed
    1. ENETWILD Consortium. Flavia O., Sascha K., Carola S.-L., Christoph S., Valerie A., Alina A., Sophia B., Hannes B., Caroline B., et al. The role of mammals in Avian Influenza: A review. EFSA Support. Publ. 2024;21:8692E. doi: 10.2903/sp.efsa.2024.EN-8692. - DOI
    1. Alexander D.J. An overview of the epidemiology of avian influenza. Vaccine. 2007;25:5637–5644. doi: 10.1016/j.vaccine.2006.10.051. - DOI - PubMed

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