Researchers in the University of Kentucky Martin-Gatton College of Agriculture, Food and Environment have found that air sampling at major equestrian events could offer a new way to monitor for equine herpesviruses.
Published in Equine Veterinary Journal, the study examined temporary stabling facilities at eight international equestrian events in Spain and the United States. Researchers collected 37 air samples and 205 surface samples over 10 months to test for equine herpesvirus (EHV)-1 and EHV-4, two viruses that can spread among horses at competitions and when returning home.
"EHV-1 remains a major concern across the horse industry," said study author Lutz Goehring, professor at the UK Gluck Equine Research Center and holder of the Warren Wright, Sr. - Lucille Wright Markey Professorship. "The virus can cause respiratory disease, abortion and equine herpesvirus-associated myeloencephalopathy, a neurologic condition that can leave horses unable to stand."
Recent outbreaks at major events, including the 2021 outbreak in Valencia, Spain, prompted the International Equestrian Federation to fund the study which would seek to find earlier ways to detect viral activity during competitions.
"Our goal was to find out whether there are other options besides daily nasal swab sampling," Goehring said. "Air sampling gives you a way to look at a group environment without going horse to horse."
Air samples were collected over a period of six hours. The team found EHV-1 in 20 of 28 air samples collected in Spain, three of three air samples in Florida and three of six air samples collected in Kentucky.
EHV-4 also appeared in air samples, but its pattern varied by location and potentially by season. Researchers found no EHV-4 in Florida's three air samples, while in Spain detected it in 12 of 28 and recorded it in five of six Kentucky samples.
Researchers found no significant difference between air samples collected during higher-activity afternoon hours and those collected overnight, suggesting that the timing of sampling may not have had much effect under the conditions studied.
The work does not show how far the virus can travel through a barn or which horse may have contributed to a positive air sample. The study relied on molecular detection of viral DNA rather than virus isolation, so they were not able to determine infectivity or measure direct transmission risk.
Still, Goehring said the findings matter because they show viral material may be present in shared event spaces even when no horses are showing obvious warning signs.
"We were surprised by the outcome," Goehring said. "Herpesviruses can reactivate from a sleeper state, similar to the reappearance of a 'cold sore' in people. We thought reactivation in horses would be rare. We were surprised by the frequency of detection. We did not detect the numbers we typically see with induced, experimental infections. Our results suggest a fairly small plume present at event centers or barn areas, even without reported clinical problems at the time."
Traditional surveillance often depends on repeated nasal sampling, which takes time, adds labor and can test the patience of both horses and handlers. Air sampling draws on public-health work used in shared indoor spaces during COVID-19.
"It could offer a practical, noninvasive way to monitor group settings such as a barn aisle, rather than relying only on repeated individual horse testing; however, sampling equipment is currently too pricey to be implemented on a large scale," Goehring said.
The findings do not mean horse owners should raise their anxiety level attending horse events, Goehring said. Instead, he sees the results as a reminder that good biosecurity still matters during and after shows.
"There's no reason to panic, but we need to take this information and find better ways to make sure horses are safe at these events," Goehring said. "That can mean clearer do's and don'ts for horse people, better biosecurity and more thought about how to reduce spread in shared spaces."
Goehring suggested owners can lower risk by keeping vaccinations current, limiting direct contact between unfamiliar horses and avoiding shared equipment, especially at large gatherings where horses travel in from many different places.
Research reported in this publication was supported by the International Equestrian Federation. The opinions, findings, and conclusions or recommendations expressed are those of the author(s) and do not necessarily reflect the views of the International Equestrian Federation.
