First Reported Circulation of Equine Influenza H3N8 Florida Clade 1 Virus in Horses in Italy.
Authors: Ricci Ida, Tofani Silvia, Lelli Davide, Vincifori Giacomo, Rosone Francesca, Carvelli Andrea, Diaconu Elena Lavinia, La Rocca Davide, Manna Giuseppe, Sabatini Samanta, Costantini Donatella, Conti Raffaella, Pacchiarotti Giulia, Scicluna Maria Teresa
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Equine influenza remains a substantial biosecurity concern across European studs and competition yards, with antigenic drift potentially rendering current vaccination programmes ineffective if circulating strains diverge from vaccine antigens. Italian researchers characterised equine influenza virus (EIV) isolates from PCR-positive respiratory samples submitted through clinical diagnostic channels rather than formal active surveillance networks, allowing them to identify which H3N8 lineages were actively circulating without targeted sampling protocols. Their genetic analysis revealed the first documented detection of the Florida Clade 1 H3N8 variant in Italian horses, a finding that suggests either recent introduction via imported animals or undetected endemic circulation—both scenarios with significant implications for regional herd immunity and vaccine strain matching. The identification of this clade variant raises questions about the currency of vaccination protocols across European yards, particularly given that vaccine formulations may not adequately cover emerging sub-lineages within the H3N8 group. Practitioners should consider this emerging epidemiological data when risk-assessing incoming horses, particularly those with respiratory signs despite vaccination records, and may wish to discuss vaccine strain currency with their veterinary colleagues as part of comprehensive influenza prevention strategies.
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Practical Takeaways
- •Monitor vaccination status of your horses against equine influenza, as new viral clades may escape existing vaccine-induced immunity
- •Report suspected equine influenza cases (fever, respiratory signs) to your veterinarian promptly for PCR testing, as surveillance is incomplete in many regions
- •Coordinate with your veterinarian on vaccine strain recommendations, which may need updating as new EIV clades emerge in your geographic region
Key Findings
- •First reported detection and genetic characterization of H3N8 Florida clade 1 equine influenza virus in horses in Italy
- •Study identified EIV strains in PCR-positive samples from suspected cases without formal active surveillance systems
- •Findings highlight potential vaccine strain mismatch risk due to antigenic drift and shift in circulating EIV
- •Genetic characterization data support need for updated vaccine strains to maintain immunity protection