In many horses, fever is the only sign of EHV-1 infection, which can go undetected.
Photo: Kevin Thompson/The Horse
The Louisiana Department of Agriculture and Forestry (LDAF) announced Jan. 18 that the quarantine at the New Orleans Fair Grounds Racetrack facility could be lifted Jan. 21. Testing indicates there are no new cases of neurologic equine herpesvirus-1 (EHV-1, also known as equine herpes myeloencephalopathy or EHM).
The last case of EHM was detected on Dec. 31, 2016. Horses, however, are still being monitored for signs of both EHM and EHV-1.
The quarantine will phase out starting with the 42 barns where horses never showed signs of being clinically ill.
“We are encouraged that the disease seems to be contained,” said Louisiana Agriculture and Forestry Commissioner Mike Strain, DVM. “These measures were taken for the health and safety of all horses in the state. We continue to work with the Fair Grounds and (Louisiana State) Racing Commission to ensure that biosecurity measures will be maintained.”
As of Jan. 18, 39 horses remained in isolation. There are six quarantined barns and one isolation barn. All horses that tested positive for EHV-1 will remain in isolation until they test negative for the virus. Horses that were exposed to the disease but do not test positive will remain quarantined and will be released on a case by case basis.
“After consulting with the state veterinarian, USDA Veterinary Services, LSU (Louisiana State University), and outside experts on infectious diseases, we feel this is a logical plan to allow the release of unaffected horses,” Strain said. “The horses that remain in isolation are most at-risk. We will continue to monitor these horses until they are in the clear. However, should there be another case of EHV-1 or EHM, we will respond accordingly.”
Sixty-five ship-in (day race) horses that were possibly exposed to an EHV-1-positive horse in the receiving barn and placed in isolation at undisclosed locations will follow the same procedures before release.
A full breakdown of affected barns at the track and possible quarantine release plans is available online. http://www.ldaf.state.la.us/wp-content/uploads/2017/01/New-Orleans-Fairgrounds-Racetrack-Incident-Plan-Addendum.pdf
Late last month, a 2-year-old thoroughbred gelding reportedly developed a fever and neurologic signs and was euthanized. Nasal swab and blood tests were confirmed positive for the neurologic strain of EHV-1 at the Louisiana Animal Disease Diagnostic Laboratory. The virus is spread most commonly by direct horse-to-horse contact. It can also be spread through the air, contaminated equipment, clothing, and hands.
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.