Brought to you by Merck Animal Health, the Official Animal Health Care Provider of the USEA.
Runny nose, fever, cough, fatigue. Infectious upper respiratory disease can have significant consequences for our horses’ health and come in several forms. The most common causes in the horse include equine influenza virus (EIV), equine herpesvirus (EHV) – also known as rhino – and Streptococcus equi subspecies equi (S. equi) – better known as strangles. In a nationwide surveillance study by Merck Animal Health, equine influenza and equine herpesvirus type 4 (EHV-4) are diagnosed more frequently than strangles and equine herpesvirus type 1 (EHV-1).
Some of the biggest risk factors are travel, exposure to new horses and environments, and stress from training or work pressure. Vaccination coupled with good husbandry is the most economical and effective way to protect these individuals.
Equine Influenza Virus
Equine influenza virus is one of the most common infectious upper respiratory diseases of the horse. It is widespread in the equine population of the United States and throughout the world. It spreads quickly because the incubation period is only 24 to 48 hours, and the virus can be transmitted through the air. In fact, coughing can spread nasal droplets more than 200 yards. Horses that are sick for the first time can shed the virus in nasal secretions for as long as seven to 10 days. Indirect transmission of the virus can also occur via hands, clothing, and common use articles such as bits, brushes, and buckets.
Recovering horses require a minimum of three weeks of rest or at least one week of rest for every day of fever. Premature return to exercise may be associated with complications including secondary bacterial infections, reactive airway disease, and exercise intolerance.
Once thought to be a disease primarily of the young, Merck Animal Health has discovered through its ongoing respiratory disease surveillance program (conducted in partnership with University of California, Davis) that EIV is common in broader age groups as well. The equine influenza virus is constantly undergoing change (known as antigenic drift) and the latest changes seem to have made older horses more susceptible to the disease.
A strict vaccination protocol incorporating the modified live EIV vaccine (Flu Avert® I.N.) coupled with good biosecurity measures is the best method of prevention of equine influenza.
Equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) can each infect the respiratory tract, causing disease that varies in severity. EHV-4 is typically associated with upper respiratory disease in younger horses; while EHV-1 can cause respiratory disease, late-term abortions, early foal deaths, and neurologic disease. After initial infection, equine herpesvirus remains dormant (latent) in the horse. Stressful events, such as hauling, handling, and training can reactivate the virus and viral shedding can occur “silently” – without symptoms.
A horse affected by the neurologic form of EHV-1 does not typically show outward signs of respiratory disease associated with EHV-1 but does exhibit fever and depression in addition to neurologic deficits. Currently, there is not a vaccine labeled to prevent the neurologic form of EHV-1. Vaccination protocols decrease the severity of respiratory disease and reduce nasal shedding in infected horses, thereby increasing herd immunity.
Both EHV-1 and EHV-4 spread via coughing horses, by direct and indirect contact, nasal secretions, and in the case of EHV-1 abortion, contact with aborted fetuses, fetal/placental fluids, and the placenta.
Strangles (Streptococcus equi)
Strangles is a highly contagious disease caused by the abscess-forming bacteria Streptococcus equi. Also referred to as “distemper,” strangles commonly affects young horses, but horses of any age can be infected. A hallmark of the disease is enlarged, swollen, and tender lymph nodes around the head, under the jaw, and around the throat latch that frequently abscess, rupture, and drain. Abscesses can develop in other places of the body, both externally and internally. The bacteria itself is hardy and survives in a moist environment and organic debris such as manure for up to six to seven weeks. While vaccination is available, a good biosecurity plan is paramount in controlling this disease.
Take Home Message
Equine infectious respiratory diseases can attack suddenly and be devastating to your horse, as well as other horses in the herd, farm, or stable. Preventing disease through proper vaccination is far safer, easier, and more economical than treating the disease after the horse is already sick. Consult with your veterinarian to design the most appropriate vaccination protocol for your horses and remember a critical part of any preventive care plan is proper biosecurity measures. For more information, visit www.Merck-Animal-Health-Equine.com.
Copyright © 2018 Intervet Inc., d/b/a Merck Animal Health, a subsidiary of Merck & Co., Inc.
Five-star eventer Kim Severson taught a show jumping clinic in January at Milestone Sport Horses in Lovettsville, Virginia where she instructed riders on the importance of forward riding for successful jumping. In this exercise, which Severson progressively adds additional pieces to, riders are instructed to focus on the quality of their canter.
On Wednesday, March 10, 2021 at 7:00 p.m. Central time, join Eric Dierks for a live stream interview with David O'Connor. David was an alternate for the 1988 Summer Olympics, and riding Wilton Fair, was part of the U.S. team at the 1990 World Equestrian Games, where he placed 35th individually and the team finished fourth.
Billy Jackson was introduced to horses at a young age through his local 4-H program. “One of my mom's close friends was a large animal vet and she really encouraged me to stay with it,” Jackson said. As an adult, he is a Marketing Project Manager, and when he’s not at work, he’s a lower level eventer based at Poplar Place Farm.
Are you following along with the action from home this weekend? Or maybe you're competing at an event and need information fast. Either way, we’ve got you covered! Check out the USEA’s Weekend Quick Links for links to information including the prize list, ride times, live scores, and more for all the events running this weekend.