Because Remington Park’s race meet has concluded, officials will now utilize empty barns to further separate and isolate trainers’ horses that have resided in the quarantine barn. The 13 exposed horses in the isolation barn continue under biosecurity measures and twice-daily temperature monitoring. ODAFF officials continue to monitor the situation on-site.
The first horse that tested positive, a 3-year-old Thoroughbred mare, was euthanized Nov. 12 due to the severity of her clinical signs of the neurologic form of EHV-1. At that time, 66 horses in her barn were placed under quarantine.
On Nov. 21, ODAFF confirmed two additional horses with positive EHV-1 tests: one in the index case’s barn and one in a second barn, where 100 horses were exposed and placed under quarantine.
Following the quarantines, New Mexico and Kentucky state officials restricted admission to racetracks in their states of horses from Remington Park.
On Nov. 27, ODAFF confirmed that eight additional horses at Remington Park’s second quarantined barn tested positive for EHV-1. Although they showed no clinical signs, they were moved to an isolation barn pending completion of their quarantine period.
On Dec. 5, ODAFF officials released the quarantine placed on the first affected barn at Remington Park. Horses in this barn completed the 14-day restriction without exposure to any EHV-1 positive horses and without showing clinical signs of EHV-1 or fevers. They also tested negative for the virus, with tests one week apart. In the second of two quarantined barns, one additional horse tested positive by polymerase chain reaction (PCR) and was moved to an isolation facility.
On Dec. 17, TheHorse.com reported on ODAFF’s confirmation of two additional horses that tested positive by polymerase chain reaction (PCR) for equine herpesvirus-1 (EHV-1) at Remington Park. The two horses were subsequently moved to the isolation barn, which was the second barn that officials quarantined at the racetrack since the outbreak’s onset on Nov. 12. The isolation barn was quarantined on Nov. 20.
Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and equine herpesvirus myeloencephalopathy (EHM, the neurologic form).
In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.
Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.
Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.
Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.