Testing of horses conducted on Tuesday at Churchill Downs enabled the Kentucky Department of Agriculture (KDA) to confidently release two groups of horses that had been previously exposed to EHV-1, according to an alert released by the Equine Disease Communication Center.
Exposed horses under the care of three trainers had been placed in separate barns. Horses under care of two of the trainers were sampled Tuesday (blood and nasal swabs) with negative results reported. With these results and having had no known exposure to a clinical horse in 14 days, the KDA released these four horses.
Additionally, the KDA has successfully demonstrated by testing that four of the previous asymptomatic positive horses no longer have detectable EHV-1 DNA in blood or nasal swab, so those four have also been released.
The index case first showed clinical signs on Nov. 28, 2022, resulting in a quarantine of 13 horses in Barn 37. Testing of those 13 horses did identify five additional positive horses, which were immediately placed in secured isolation at Barn 42.
As of Dec. 14, the KDA continues to have three exposed horses under the care of one trainer that have not been resampled, are being monitored daily, and remain under quarantine.
As indicated above, four of the six asymptomatic horses that had been isolated at Churchill have completed required testing and have been released from quarantine. The two remaining positive horses continue to be asymptomatic and remain in isolation under quarantine. The index horse continues to improve and remains isolated at the veterinary referral hospital.
Additionally, horses in Barns 36 and 38 are considered indirectly exposed and have not been sampled. They are being monitored daily and remain under quarantine. The KDA will continue monitoring these horses and will immediately test if symptoms appear or illness is suspected and has provided two approved protocols to qualify horses in these two barns for release. These horses can qualify for release by testing negative 14 days since last opportunity of indirect exposure. Alternatively, assuming no clinical cases develop or are suspected in Barns 36 and 38, these horses could qualify for release 28 days after last opportunity of indirect exposure. The KDA currently identifies Nov. 30, 2022, as last known indirect exposure with Dec. 1, 2022 being day one post indirect exposure.
Churchill Downs implemented heightened biosecurity measures and lifted exit restrictions on horses from the unaffected barns provided they have a valid Health Certificate issued within 24 hours of departure beginning Dec. 3, 2022.
There are nine strains of equine herpesvirus on record, and many horses are exposed to some form of EHV with no serious side effects or symptoms. Three strains are considered serious health risks, including EHV-1, which may present with fever and respiratory symptoms and can also carry neurological symptoms and a risk of death. Symptoms of the neurologic form of EHV-1 include fever and nasal discharge, followed by lack of coordination, lethargy, head tilt, and inability to balance or stand. EHV-1 is highly contagious and may be transmitted through contaminated equipment, contact between horses, and on clothing or hands of humans working with sick horses. Veterinarians aren't sure how long the virus can survive in the environment, or how well it travels through the air. The Paulick Report compiled a list of frequently-asked questions about EHV-1 during an outbreak at Sunland Park five years ago.
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