Animal health officials reported several updates on equine herpesvirus-1 (EHV-1) in California over the weekend, in addition to one quarantine release in Pennsylvania.
Five more horses at a boarding facility in San Mateo County, California, tested positive for EHV-1 on June 17, bringing the farm’s total positives to six. One of the new cases, a mare, developed a transient fever, while the other four were asymptomatic (the mare previously reported as infected had experienced a fever and mild neurologic signs). The California Department of Food and Agriculture (CDFA) reported that the horses, which were all vaccinated for EHV-1, are recovering, and four other horses at the facility were exposed.
Additionally, the San Mateo boarding facility where 300 horses were exposed and 2 tested positive—an incident officials reported has no known epidemiological link to the other affected farm in the county—has been released from quarantine.
The CDFA reported a new case of equine herpesvirus in Los Angeles County, California, where a horse with neurologic signs previously tested positive last week. The 30-year-old gelding presented with a transient fever and is reported to be vaccinated, affected, and alive.
Finally, the Pennsylvania Department of Agriculture reported that a quarantine related to the previously recorded Bucks County neurologic equine herpesvirus case has been lifted, since 21 days have passed since the previous case without any additional cases identified.
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.