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ORIGINAL RESEARCH article

Front. Microbiol.

Sec. Virology

Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1607204

This article is part of the Research TopicCross-Species Transmission of Viral InfectionsView all articles

Swine Influenza surveillance in Italy uncovers regional and farmbased genetic clustering

Provisionally accepted
  • 1Experimental Zooprophylactic Institute of the Venezie (IZSVe), Legnaro, Italy
  • 2Regional Center for Veterinary Pharmacovigilance, Experimental Institute of Zooprophylaxis of Umbria and Marche (IZSUM), Perugia, Umbria, Italy

The final, formatted version of the article will be published soon.

Swine Influenza is a respiratory disease endemic in pigs with implications for animal and public health. Pigs, as mixing vessels for human, avian, and swine influenza strains, contribute to viral reassortment and emergence of new strains. Influenza viruses can circulate and spread unnoticed between pig farms for extended periods, heightening the risk of reassortment events. This study aimed to monitor swine Influenza virus (swIAV) genetic diversity in Northern Italy and understand its evolution in the study area. Passive surveillance, conducted from 2013 to 2022, involved 253 farms located in three regions, collecting over 3,000 samples that were tested for swIAV. Eighty-five samples underwent full genome sequencing, and phylogenetic analyses were conducted for each segment. In addition, cross-reactivity of viral strains was assessed using hemagglutination inhibition (HI) tests with hyperimmune swine sera. Of the farms tested, 37.9% tested positive for swIAV on at least one sampling event. Twelve distinct genotypes were identified, including two novel genotypes in Italy, both detected in 2022. Phylogenetic analyses revealed the presence of strictly correlated viruses in farms sharing the same owner or geographical proximity and highlighted multiple introductions and reassortment events in some farms. Cross HI tests demonstrated minimal antigenic cross-reactivity between circulating swIAV strains. The study reveals a high genetic diversity in swIAV circulating in Northern Italy as a consequence of multiple virus introductions as well as new reassortment events with the identification of two new genotypes The findings highlight the importance of sustained surveillance and genetic monitoring to track viral evolution and reassortment, which are pivotal for early detection of strains with pandemic potential.

Keywords: swine influenza1, genotype2, diversity3, Italy4, antigenic5. (Min.5-Max. 8

Received: 07 Apr 2025; Accepted: 07 Jul 2025.

Copyright: © 2025 Cavicchio, Tassoni, Pastori, Carrino, Gagliazzo, Mion, Ustulin, Vio, Mantovani, Ceglie, Fusaro and Beato. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Maria Serena Beato, Experimental Zooprophylactic Institute of the Venezie (IZSVe), Legnaro, Italy

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