Kentucky animal health authorities have confirmed additional cases of neurologic equine herpesvirus-1 (EHV-1) in horses currently or previously residing at the quarantined facility in Oldham County. Additionally, a horse residing on a different Oldham County facility tested positive for non-neuropathogenic EHV-1.

In the initial Oldham County case, all the horse on the property were tested for EHV after four horses residing there tested positive for neurologic EHV.

“Results of testing for the EHV-1 … identified two additional horses positive for EHV-1,” the Equine Disease Communication Center reported Jan. 12. “In addition, (a) horse that had spiked a fever late last week tested positive (for) the same virus type (neuropathogenic strain).

“All three of these horses were moved from their stabling area and placed in the isolation unit, and none of remaining horses in the barn were positive for EHV-1,” the EDCC said. “Subsequently, the horse that had fever presented with neurologic abnormalities on Monday and was moved to isolation at a veterinary hospital for treatment where it continues to improve.”

At last update, the Kentucky Department of Agriculture (KDA) had traced and located all equids that left the index facility since mid-December.

“Two horses that had moved were identified as positive,” the EDCC said. “These horses are in isolation on private facilities and are being monitored with the established protocol.”

Meanwhile, in the second Oldham County case, one horse tested positive for non-neuropathogenic EHV-1 after developing a fever on Jan. 9, the EDCC said. That horse has not exhibited any neurologic signs.

“The affected horse on this new premises was moved to an isolation barn when fever was detected and plans are in place to remove him from the premises tomorrow,” the EDCC said. “The barn where this horse resided was placed under order of quarantine by the KDA. All the horses’ temperatures in all barns on the premises are being monitored and recorded daily.

“Samples (nasal swabs and whole blood) were collected from each horse residing in the affected barn and those samples were submitted to the laboratory for EHV-1 testing,” the EDCC said. “KDA has and will continue to have personnel on the grounds monitoring activity.”

The EDCC said that, although this is the second premises currently under quarantine in Oldham County, different strains of the virus are involved. There is currently no evidence that this case is related to the initial outbreak.

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 myeloencephalopathy (the neurologic form). In many horses, fever is the only sign of EHV-1 infection, 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 the neurologic form 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.