An outbreak of equine influenza at a harness horse racetrack.

The research presents a study of an outbreak of equine influenza at a standardbred racetrack. Roughly one third of the 1050 race horses contracted the illness, which caused a temporary cessation of racing activities. The researchers suggest that the large-scale outbreak may have been mitigated or prevented by a proper vaccination program.

Investigation of Equine Influenza Outbreak & Isolation of Virus

• The research was initiated after about a third of the horses at a standardbred racetrack fell ill with symptoms resembling influenza.
• Due to the outbreak, all racing activities had to be suspended for three days.
• To understand and confirm the disease, the research team collected samples from the affected horses. They successfully isolated the A/Equi-2 influenza virus from one horse.

Seroconversion & Absence of Threshold Protective Levels

• Following the isolation of the virus, seroconversion – a marker of infection or vaccination – was observed in eight of the 10 horses tested.
• Interestingly, horses that did not show symptoms lacked any demonstrable threshold protective levels of HI antibody against the A/Equi-2 influenza virus.
• These unaffected horses were nevertheless resistant to the disease, which was assumed to result from other factors related to previous exposure.

Vaccination Status & Need for a Vaccination Program

• In the backdrop of this outbreak, it was discovered that only a few of the horses had been vaccinated against equine influenza.
• The research team suggested that if a proper vaccination program had been implemented, the outbreak could have been contained to a smaller scale, or perhaps even prevented.
• Given the scale of this outbreak and its detrimental effect on racing activities, the study underscores the importance of a systemic vaccination program for horses to prevent such occurrences.