Animal health officials have reported cases of equine herpesvirus-1 (EHV-1) in Arizona and Iowa, the Equine Disease Communication Center (EDCC) said March 26.
The EDCC said the Arizona Department of Agriculture (ADA) reported a case of equine herpesvirus myeloencephalopathy (EHM, the neurologic form of EHV-1) in a 16-year-old Yavapai County horse that began exhibiting neurologic signs on March 22. The horse was euthanized.
Samples for “lab work (were) collected and tests are pending,” the EDCC said.
Additionally, the ADA reported a case of EHV-1 in an 8-year-old Quarter Horse mare from Maricopa County, the EDCC said. The mare developed clinical signs on March 21.
“The horse was sent to a veterinary hospital for ventricular tachycardia (an irregular and overly rapid heartbeat), limb edema (swelling), and fever and was positive for non-neuropathogenic virus,” the EDCC said.
The ADA also noted the horse had attended the Dixie Classic barrel racing event, which took place at the Washington County Legacy Horse Park, in South Hurricane, Utah.
The ADA has quarantined the affected facilities.
The Iowa State Department of Agriculture and Land Stewardship reported an EHM case in a 17-year-old Polk County Quarter Horse gelding. The horse developed lameness and neurologic signs on March 20 and was ultimately euthanized, the EDCC said. The EHV diagnosis was confirmed March 25 and officials have quarantined the facility.
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 equine herpes myeloencephalopathy (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.