The British Horse Society and Royal (Dick) School of Veterinary Science said horse owners needed reminding of the importance of equine flu vaccination, which prevents horses and ponies succumbing to this virus.
"We've had a timely 'heads up' from the Animal Health Trust that equine flu is being diagnosed in Scotland at the moment, with the latest outbreak being near Edinburgh," said Helene Mauchlen from The British Horse Society.
"Influenza vaccination does offer effective protection and, with horses mixing regularly at the peak of our competition circuit, it is vital that owners take precautions to prevent equine flu from spreading."
Professor Bruce McGorum from the Royal (Dick) School of Veterinary Science advised owners to keep their horse's vaccinations up to date, and to arrange vaccination of any unvaccinated horses.
"Influenza can spread rapidly through a horse population, causing lethargy, fever, nasal discharge and coughing.
"The Animal Health Trust has notified us of a recent increase in the number of cases of equine influenza in Scotland predominantly, but not exclusively, involving unvaccinated animals.
"Influenza vaccination is recommended not only because it prevents development of the clinical disease, or reduces the severity and duration of flu symptoms, but also because it reduces the spread of infection through the horse population."