Isolation and characterization of the equine influenza virus causing the 2006 outbreak in Chile.

The research article discusses the identification, isolation and analysis of the equine influenza virus that caused an outbreak in various regions of Chile in 2006.

Virus Isolation and Identification

• The researchers involved in this study investigated an outbreak of influenza in horses that occurred in July 2006, affecting regions across Chile. The symptoms in horses were severe, including fever, serious nasal discharge, dry cough, lack of appetite, and depression.
• The virus responsible for this outbreak was successfully isolated and identified. Through haemagglutination inhibition testing, the virus was confirmed as the equine influenza virus H3N8. This method of testing used serum (a blood component) that was designed to specifically interact with the H3N8 strain of the virus, thereby inhibiting haemagglutination – a reaction that causes red blood cells to clump together.
• Interestingly, this virus strain did not react to serum designed for the H7N7 strain of the equine influenza virus, confirming its H3N8 identity. Consequently, the isolated virus was officially named A/equi/2/Lonquén/06 (H3N8).

Gene Sequencing and Comparison

• Following virus identification and isolation, key genes of A/equi/2/Lonquén/06 (H3N8) were sequenced. Specifically, the genes for haemagglutinin, neuraminidase, and nucleoprotein were isolated and their sequences were determined. These genes are significant as they determine the virus’s capability to infect host cells and replicate.
• The isolated H3N8 genome sequences were then compared with other known equine influenza virus sequences. Results showed notable contrasts with the Santiago/85 isolate, another strain of the equine influenza virus found in Chile during a previous outbreak.
• Intriguingly, the A/equi/2/Lonquén/06 (H3N8) strain demonstrated a closer genetic relationship with North American equine influenza isolates, particularly with the Florida lineage. Additionally, the sequenced genes also showed significant similarities with Argentinean isolates from the 1990s.

Implications

• The findings of this study have significant implications for understanding the origins, evolution, and potential control strategies for equine influenza viruses. Specifically, they provide insight into the genetic diversity of these viruses, which is vital information for developing effective vaccines.