In a recent study, horses trailered over a long distance developed subclinical signs of airway disease and showed signs of virus activation, such as increased shedding of EHV-2 and -5. | Photo: iStock

Researchers know that transport—especially long-distance—can affect horses’ immune systems, making them more susceptible to developing disease. But recent study results suggest it could also make horses more likely to spread disease.

In a recent study, horses trailered over a long distance developed subclinical (inapparent) signs of airway disease and showed signs of virus activation, such as increased shedding of equine herpesviruses (EHV)-2 and -5, said Katharine Muscat, PhD, of the University of Sydney Faculty of Science, in Australia.

In their study, Muscat and colleagues collected blood samples and nasal swabs and carried out endoscopies and tracheal washes on 12 apparently healthy horses aged 3 to 8. Then, they had these horses transported in groups of six for an eight-hour journey with a 15-minute break halfway. Once the horses returned, they collected nasal swabs on arrival and again one and five days later and collected blood samples 12 to 24 hours after arrival and two weeks later. They performed follow-up tracheal washes and endoscopies five days after the horses returned