Genetic characterization of equine influenza viruses isolated in Italy between 1999 and 2005.

The study involves the genetic characterization of four strains of equine influenza (EI) virus which caused respiratory disease outbreaks in Italy from 1999 to 2005. These events happened in physically isolated, flu-vaccinated horse populations. The results confirmed that current vaccines should be updated with the most recent strains to provide effective protection against the currently circulating American-based strains of EI.

Study Background

• The research was carried out due to the respiratory disease outbreaks that occurred in horse training stables in Rome and a stud horse farm in Bari from 1999 to 2005.
• All outbreaks happened in horses that had been vaccinated against the flu, indicating the possible emergence of new strains of the virus that can bypass the protection offered by the available vaccines.
• The investigators set out to genetically characterize the isolates from these outbreaks to determine their lineage and possible relationships with other known EI strains worldwide.

Research Methodology

• The researchers isolated four EI virus strains from the outbreaks and carried out genetic characterization.
• The analysis involved alignment and phylogenetic studies of the haemagglutinin amino acid sequences. This protein is present on the surface of influenza viruses and is often used as a marker for viral identification and classification.

Findings of the Study

• The isolated viruses from the Rome and Bari outbreaks were identified as members of the American lineage. They were found to be closely related to other recent strains isolated in America and Europe, including the vaccine prototype A/eq/SouthAfrica/4/2003.
• In contrast, the EI virus strain isolated in 1999 from a deceased foal was clustered within the European lineage.

Implications of the Study

• The findings suggest that the most recent outbreaks of EI in Italy have been caused by strains belonging to the American lineage, even in populations that had been vaccinated.
• This sheds light on the need to update existing vaccines to contain representatives of the currently circulating strains. It is crucial to update these vaccines to maintain their effectiveness in protecting horses against the influenza virus.
• The research highlighted the need for companies to expedite the process for registering updated vaccines. During the time of the study, no updated product was available on the market.