A 14-year-old Thoroughbred gelding at the Turf Paradise racetrack in Maricopa County, Arizona, has tested positive for EHV-1 variant D752. The horse developed clinical signs on February 14, including hindlimb ataxia, weakness, difficulty rising and difficulty maintaining a standing posture. His positive test results were reported on February 18. The horse is now recovering.
Thirty-six horses from Barns C9 and C8W were immediately placed quarantined. Turf Paradise has restricted movement from the backside until further notice. Biosecurity measures have been implemented for all horses in the quarantined barns, including twice-daily temperature monitoring, movement restriction and area disinfection.
A 4-year-old racehorse filly from Barn K6 also developed clinical signs, including depressed attitude, fever and leaning on the stall wall. The filly had raced on February 18 and was claimed from barn D9. She was referred to an equine hospital in the Phoenix area. Barns K6 and K5E were also placed under quarantine, but the filly’s test results came back negative for EHV-1.
EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.
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 EHM.
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.