Equine herpesvirus-1 (EHV-1) is a highly contagious virus in horses that can lead to respiratory illness, reproductive issues, and neurological problems. Since infected horses can transmit the virus over extended periods, it’s crucial for horse owners to take strict precautions during outbreaks.
Dr. Jared Janke, a clinical associate professor of equine internal medicine at Texas A&M, highlights five vital facts about EHV-1 for horse owners.
EHV-1 spreads through direct horse-to-horse contact, airborne transmission within 30 feet, and indirectly via people or equipment. The virus can be contagious before symptoms appear, making isolation and halting the movement of exposed horses essential to controlling its spread. Owners should avoid sharing grooming tools, feed, water, and equipment between healthy and infected horses, as the virus can survive in the environment for weeks. Additionally, handlers should change clothes and wash thoroughly after contact with infected animals.
The virus causes three primary symptom groups: respiratory, reproductive, and neurological, with the neurological form termed equine herpes myeloencephalopathy (EHM) being the most severe and contagious. Symptoms usually emerge 5-10 days post-infection but take longer for EHM. Signs of EHM include high fever, lack of coordination, weakness, urine dribbling, and reduced tail sensation. Less common neurological symptoms involve facial nerve issues and head tilting. Non-neurological symptoms may include nasal discharge, coughing, and abortion in mares. Fever is the most common but fluctuates, so owners should monitor temperatures twice daily and watch closely for early neurological signs.
If symptoms arise, owners should immediately contact their veterinarian for diagnosis, treatment, and isolation guidance. Fever with hind leg coordination loss, urine dribbling, or weak tail tone should prompt isolation and veterinary consultation. Diagnosis involves nasal swabs and blood tests, usually with results in 1-2 days. Because EHV-1 is highly contagious, sick horses must be isolated until confirmatory diagnostics are complete. Reporting to state animal health authorities is required due to the serious threat EHM poses to the horse industry.
Treatment centers on symptom management with quarantine protocols guided by animal health officials. Supportive care like intravenous fluids and anti-inflammatory drugs is the mainstay. Although antiviral drugs are used, their effectiveness is uncertain and seems greater when given before or shortly after symptoms start. Once a horse can no longer stand, treatment becomes much more challenging. Prognosis varies, but survival rates in EHM outbreaks hover around 70-80%, especially if horses maintain mild to moderate signs and can stand. Infected horses may still shed the virus after recovery and require repeated testing before release from isolation.
Vaccination against EHV-1 is common but does not fully prevent infection or EHM symptoms. However, vaccinated horses tend to shed less virus, reducing environmental contamination. Veterinarians can guide vaccine choices. The best prevention is to keep healthy horses separate from infected ones, their equipment, and people who have been exposed. During outbreaks, avoid traveling with horses until it’s deemed safe by health officials. Regularly taking horses’ rectal temperature twice daily and isolating suspected cases early helps detect infections quickly. Early veterinary contact increases chances for preventive treatment and containment.
During an EHV-1 outbreak, closely monitoring horses and acting swiftly at signs of infection are critical. Simple steps can significantly curb the spread of this serious equine disease.
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Fan Take: EHV-1 poses a serious threat to the health and safety of racehorses, potentially sidelines key competitors, and impacts racing schedules and industry economics. Vigilance, early detection, and strict biosecurity are essential to protect the racing community and maintain the sport’s integrity.
