GRAND ISLAND, Neb. (AP) — Racehorses have been quarantined at Fonner Park in Grand Island because three horses there tested positive for equine herpes.

The Nebraska Agriculture Department says one of them has been euthanized, but the remaining two are getting better with treatment.

The 750 to 850 horses at Fonner Park can’t leave until the minimum 21-day quarantine is lifted. Fonner will continue racing through May 7, but the 150 or so horses in the same barn as the three that tested positive won’t be allowed to race.

Prairie Meadows Race Track in Altoona, Iowa, has quarantined and is monitoring horses that arrived from Fonner Park within the past week.

Symptoms of the disease include fever, decreased coordination, hind limb weakness, leaning against a wall to maintain balance, lethargy and the inability to rise.