The Equine Disease Communication Center (EDCC) reported April 2 that a Humboldt County, Nevada, horse tested positive for equine herpesvirus-1 (EHV-) in late March.
“This newest reported case, a 14-year-old Quarter Horse mare, first exhibited clinical signs on March 21 and was swabbed on March 22, resulting in a positive PCR test for EHV-1 (wild type),” the EDCC said. “This horse was not exhibiting neurologic signs and was clinically normal on April 1.”
The affected mare’s home premises (which houses a total of five horses) has been quarantined.
“An epidemiological trace revealed this horse was most likely exposed at a rodeo in Fernley on March 8-10,” the EDCC added.
Additionally, the EDCC said the Nevada Department of Agriculture confirmed the Fallon Junior and Senior High School Rodeo scheduled for April 5-7 has been postponed.
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.