An outbreak of a potentially deadly equine virus will mean some empty stalls at the upcoming Minnesota Horse Expo. Breed and registry groups and private farms and stables won’t be bringing their horses to the expo next weekend at the Minnesota State Fairgrounds in St. Paul. Organizers are also limiting the number of show horses at the event. And, they’ll need a health certificate from a veterinarian. The horses will be limited to those brought in for clinics and demonstrations as well. Veterinarians in Minnesota have recommended a voluntary quarantine for at least two weeks from the last case of the equine virus. Nine horses have contracted the disease since the end of March.