Management of an Equine Herpesvirus-1 Outbreak During a Multi-Week Equestrian Event.

The research details how an outbreak of Equine Herpesvirus-1 (EHV-1) is managed during a multi-week equestrian event, highlighting that isolating and testing horses and regular maintenance of biosecurity protocols is crucial for preventing the spread of the virus.

Objective of the Research

• The objective of this research was to record and scrutinize the management tactics in response to an EHV-1 breakout that took place in a large, multi-week equestrian event.

Outbreak Details and Initial Reaction

• During the event, eight horses—out of a group of 38 horses undersame trainer—recorded elevated rectal temperatures within a 48 hour window. The temperatures ranged from 38.4 to 39.0°C, indicative of potential infection.
• Initial testing using a point-of-care PCR assay identified EHV-1 in two of the eight symptomatic horses. These results were later confirmed via quantitative PCR testing (qPCR).
• Due to the impossibility of isolating the entire group at risk, as a precaution, all 38 horses were moved to an external equine facility, separate from the equestrian event. This move was for daily monitoring and weekly EHV-1 qPCR testing via nasal secretions.

Monitoring and Test Results

• Over a 28-day monitoring duration, EHV-1 was detected—via qPCR testing of nasal secretions—in 22 of the 38 horses (approximately 58%). Only one additional horse developed a fever.
• The period of monitoring ended once all 38 horses tested negative for EHV-1 twice, with the tests conducted 7 days apart.
• After these negative results, 17 horses returned to the equestrian event to compete for the remaining 2 weeks of the regulation.

Research Findings and Recommendations

• The research enumerates the significance of isolating and testing horses not only with visible symptoms (fever) but also those with subfebrile conditions, as EHV-1 can cause a silent infection, i.e., an infection without noticeable symptoms.
• The action of moving the potentially exposed horses to an off-site facility enabled detailed monitoring and reduced the risk of exposing other show horses, both direct and indirect, to the virus.
• The adopted biosecurity protocols, with regular testing for EHV-1 through nasal secretions, facilitated the safe return of the horses to the event.
• The research concluded the essential steps in limiting the spread of EHV-1 are: regular assessment of rectal temperature, promptly isolating horses with elevated rectal temperature, and conducting on-site EHV-1 PCR testing.