Nasal discharge is a sure sign of respiratory equine herpesvirus. Anytime your horse comes in contact with new equids, he’s at risk of contracting equine herpesvirus-1 (EHV-1). More than just a cause of snotty noses in young horses, EHV-1 is highly contagious and can cause a variety of ailments, including rhinopneumonitis (a respiratory disease usually found in young horses, resulting in the aforementioned “snotty nose”), abortion in broodmares (often coming in “storms” on breeding farms, where several mares contract the disease and lose their pregnancies), and equine herpesvirus myeloencephalopathy (EHM, the often deadly neurologic form).
Below are 12 facts to remember about EHV-1 in horses:
- Clinical signs depend on the form of the disease. Respiratory signs can include fever and nasal discharge; neurologic horses will typically have ascending paralysis (muscle weakness or loss of muscle function), and pregnant mares will abort their foals.
- Experts say EHV-1 is the most important cause of abortion in U.S. mares. Because of this, veterinarians recommend vaccinating mares at five, seven, and nine months of gestation.
- In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected.
- A highly infectious and contagious pathogen, EHV-1 can spread quickly through equine populations. This is especially true at horse shows and events where unfamiliar horses commingle in close quarters while under stress from travel and competition, which makes them more vulnerable to disease.
- Veterinarians have long identified neurologic signs as an uncommon consequence of EHV-1 infection; however, in the past 20 years, EHM has been reported with increasing frequency, especially in the United States.
- Disease caused by EHV-1 can range in severity from mild to severe.
- If you suspect a horse has EHV-1, isolate him from other herd members immediately. The sooner you respond to a suspected contagious disease incident, the better you can contain the disease and prevent the pathogen from spreading on or between farms.
- Current vaccines are not labeled for use in preventing the neurologic form of EHV-1—only rhinopneumonitis and abortion—and EHM clinical signs have been observed in well-vaccinated horses.
- Since December 1, 2015, all horses entering the grounds of a U.S. Equestrian Federation licensed competition must be accompanied by documentation that they received equine influenza and EHV vaccinations within the six months prior.
- Proper biosecurity protocols can help reduce horses’ risk of contracting an infectious disease such as EHV. In response to the multistate outbreak originating at the 2011 National Cutting Horse Association Western National Championship, in Ogden, Utah, many equine event facilities and organizations developed more comprehensive biosecurity measures to protect competitors.
- The EHV-1 vaccine is considered “risk-based.” Risk-based vaccines protect against a variety of diseases that can affect certain horses but are not necessarily a risk for all horses.
- Researchers in the United States and Europe are studying the use of antiviral medications for EHV-1 cases. These drugs might help reduce disease severity and virus shedding but haven’t yet proven effective once a horse is neurologic.
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