Horses stabled in the third Churchill Downs barn placed under quarantine by the Kentucky Department of Agriculture because of confirmed cases of equine herpes virus have been cleared to return to the track for limited training. Those horses will take part in special training hours beginning Tuesday. Horses in Barn 6, all of which are trained by Ronny Werner, have met the requirements of a protocol developed by the Kentucky Department of Agriculture that allows for a return to training apart from the track's general horse population. The clearance means that horses in all three barns placed under quarantine are now back on the track.Horses trained by Paul McGee, Bill Cesare, and Ron Ellis met the protocol May 21 and returned to training that evening and horses in Steve Asmussen's barn were allowed to take part in the separate training sessions May 23 Although the horses housed in the three barns have been permitted to return to the track during special training hours, they remain in quarantine and are not allowed to mix with the rest of the horse population at Churchill Downs. The training schedule for the horses affected by the equine herpes virus quarantine includes late morning sessions at 11 a.m. (all times EDT) on Monday and Tuesday, days on which the track is not racing. Evening training at 6:15 p.m. is planned on racing days, which include Wednesday, Thursday, Saturday and Sunday. No separate training is planned on Fridays because of Churchill Downs' late 2:45 p.m. post time.Regular training at Churchill Downs is conducted daily from 6-10 a.m.The Kentucky Department of Agriculture's protocol for participation in the separate training hours required that no horses in a quarantined barn display any clinical symptoms of equine herpes over a seven-day period.Once that requirement was met, a blood screening was performed on every horse in the barn. Results of the blood screens on all horses in the barn had to be "negative" for any of the barn's horses to be allowed to participate in the special quarantine training hours.The clinical symptoms of equine herpes virus include fever or the development of an upper respiratory infection. The symptoms can also include lethargy, loss of appetite, a nasal discharge or a cough. The most severe neurological symptoms of the disease include a loss of coordination by an individual horse and the inability to stand. Equine herpes virus is spread through the air, although equine medical experts say the virus is short lived and does not travel far. Laboratory experiments have shown that the virus travels as far as 35 feet.Quarantine or isolation procedures are regarded as the most effective measures to contain the virus. Officials with the Kentucky Department of Agriculture say the recommended length of the quarantine is 21 days after the last horse in a barn displays clinical symptoms of the virus. The disease has an incubation period of 2-to-10 days.Horses scheduled to ship in or out of the Churchill Downs stable area are required to present a 24-hour health certificate signed by a veterinarian before they will be allowed to do so. Bio-security measures are in place at each of the track's quarantined barns.The Kentucky Agriculture Department continues to search for the source of the equine herpes virus outbreak at Churchill Downs.