The Equine Disease Communication Center (EDCC) reported Sept. 22 that animal health officials have confirmed a case of equine herpesvirus myeloencephalopathy (EHM), the neurologic form of equine herpesvirus-1 (EHV-1), in a Montgomery County, Maryland, horse.
“On Sept. 21, the Maryland Department of Agriculture Animal Health Program confirmed a positive EHM case in a 12-year-old Warmblood gelding,” the EDCC said. “The neurological horse was seen earlier and treated as an outpatient on Sept. 21 at a private veterinary clinic Loudoun County, Virginia, before returning home to a private farm in Montgomery County, Maryland. A hold order placed on the farm the evening of Sept. 21.
“There are 18 horses on the farm in three barns,” the EDCC continued. “The positive gelding is isolated from all horses on the farm. The positive gelding was previously housed with four horses in one barn. The other two barns are more than 30 feet away from the exposed barn. Strict isolation and biosecurity protocols are in place at the exposed barn with body temperatures taken twice daily.”
No equine movement is permitted on or off the farm, regardless of which barn the horses are stabled in, the EDCC said.
“The attending veterinarians that administers to this farm will be notified of the hold order and apprised of the procedures taken to control the spread of EHV-1/EHM,” the EDCC said. “Possible links to the positive gelding are actively being investigated.”
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 (the neurologic form). 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 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.
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 present 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.