Horse owners recently attended a symposium on equine healthcare, which was hosted by Oklahoma State University Center for Veterinary Health Sciences and Department of Animal Science, Division of Agricultural Sciences and Natural Resources, and the Oklahoma Cooperative Extension Service.

While many important topics were presented, one particular segment covered the control and prevention of Equine Viral Arteritis (EVA). EVA is a disease that affects horses. In the acute phase of disease it causes generalized illness primarily of the respiratory tract. It can also cause abortion in pregnant mares and pneumonia in new born foals. In stallions after the acute respiratory illness resolves, 30–60 percent may become persistently infected shedding virus only in the semen from months to many years, serving as the natural reservoir in the horse population.

According to Reed Holyoak, DVM, PhD, DACT, associate professor of Theriogenology and Bullock Professorship in Equine Theriogenology, the key is to restrict dissemination of EVA in breeding populations. Dr. Holyoak offers these tips to help horse owners prevent EVA.

• Isolate all new arrivals for 3 to 4 weeks
• Segregate pregnant mares from other horses
• Maintain pregnant mares in small groups according to expected foaling dates
• Establish Equine Artificial Insemination Industry semen quality and handling standards
• Determine the infectivity status of all semen for artificial insemination
• Each breeding season test new breeding stallions for EVA titers
• Culture semen from all non-vaccinated stallions with positive titers for infectious virus
• Annually vaccinate non-carrier breeding stallions 4 weeks before each breeding season
• Isolate any EVA-carrier stallions
• Observe strict precautions when breeding or collecting semen
• Limit breeding carrier stallions to vaccinated mares or mares with natural titers
• Vaccinate sero-negative mares 3 weeks before breeding to a known carrier stallion or artificially inseminating with infectious semen
• Isolate initial vaccinated mares for 3 weeks post breeding from all but known EVA sero-positive horses
• Vaccinated mares should not have contact with pregnant mares by any route—aerosol, respiratory and/or indirect contact
• Vaccine all immature colts before 270 days of age (6 to 7 months)

“If these practices were implemented, over a number of years we would see a great reduction in the number of carrier stallions,” says Dr. Holyoak. “Following these recommendations would effectively eliminate the primary reservoir of EVA.”

For more information on EVA, visit http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-3254/VTMD-9132.pdf. For information on equine healthcare and other services available at the Oklahoma State University Center for Veterinary Health Sciences, visit http://www.cvhs.okstate.edu.