Tracing the 2021 equine influenza Outbreak: First characterization and phylogeographic analysis of H3N8 Florida clade 1 virus in Tunisia.
Abstract: Equine influenza (EI) is a highly contagious viral respiratory disease affecting equids, with the potential of causing widespread outbreaks across Europe, the Americas, Asia, and other regions of the world. In Tunisia, in the spring of 2021, an EI virus outbreak occurred in a farm housing purebred Arabian horses that exhibited respiratory signs. This outbreak led to a national lockdown on horse movements and the cancellation of equestrian events. A total of 432 serum samples, collected from 2018 to 2021, were tested using ELISA competition assay. In addition, 100 Nasal swabs were collected during the 2021 outbreak and tested for the presence of EI via qRT-PCR. Five of these samples underwent full sequencing targeting hemagglutinin (HA) and neuraminidase (NA) genes. Phylogenetic and phylogeographic analyses were carried out on HA and NA gene sequences using Bayesian methods. Out of 432 serum samples, 80 tested positive, leading to an overall seroprevalence of 18.51 %, with the highest values recorded in 2018 and 2021. Complete sequences of the HA and NA genes identified the subtype as H3N8, belonging to the American lineage, Florida clade 1. Tunisian strains exhibited close genetic relationships with those from Algeria, the USA, France, Saudi Arabia, and the UK. Phylogeographic analysis reveals probable origin of the virus in Tunisia from the USA and France in 2017-2018. Our study highlights the critical need for continuous surveillance and molecular characterization of EI strains, particularly given their high transmissibility and potential for global dissemination.
Copyright © 2025 Elsevier Inc. All rights reserved.
Publication Date: 2025-08-12 PubMed ID: 40825254DOI: 10.1016/j.virol.2025.110655Google Scholar: Lookup
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- Journal Article
Cite This Article
APA
Badr C, Arbi M, Souiai O, Larbi I, Nsiri J, Elbehi I, Bouslama Z, Bennour MA, Essaied MS, Ines Khosrof , Chabchoub A, Ben Aoun B, Ghram A, Lachheb J.
(2025).
Tracing the 2021 equine influenza Outbreak: First characterization and phylogeographic analysis of H3N8 Florida clade 1 virus in Tunisia.
Virology, 611, 110655.
https://doi.org/10.1016/j.virol.2025.110655 Publication
Researcher Affiliations
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia. Electronic address: chaima.badr@pasteur.utm.tn.
- Laboratory of Bioinformatics, Biomathematics and Biostatistics (LR16IPT09), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Bioinformatics, Biomathematics and Biostatistics (LR16IPT09), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia; Higher Institute of Medical Technologies of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- General Directorate of Veterinary Services, Ministry of Agriculture, Tunis- Belvedere, 1002, Tunisia.
- Horse Clinic, EL Mbarka, Sidi Thabet, 2020, Tunisia.
- Horse Clinic, EL Mbarka, Sidi Thabet, 2020, Tunisia.
- Laboratory of Viruses, Vectors and Hosts (LR20IPT10), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- National Foundation for the Improvement of the Horse Breed, Sidi Thabet, 2020, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
- Laboratory of Epidemiology and Veterinary Microbiology (LR 16IPT03), Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, 1002, Tunisia.
MeSH Terms
- Animals
- Horses
- Horse Diseases / epidemiology
- Horse Diseases / virology
- Disease Outbreaks / veterinary
- Phylogeny
- Orthomyxoviridae Infections / veterinary
- Orthomyxoviridae Infections / epidemiology
- Orthomyxoviridae Infections / virology
- Phylogeography
- Tunisia / epidemiology
- Influenza A Virus, H3N8 Subtype / genetics
- Influenza A Virus, H3N8 Subtype / classification
- Influenza A Virus, H3N8 Subtype / isolation & purification
- Hemagglutinin Glycoproteins, Influenza Virus / genetics
- Neuraminidase / genetics
- Seroepidemiologic Studies
- Viral Proteins / genetics
Conflict of Interest Statement
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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