2015 Reported Occurrences of Equine Herpesvirus Myeloencephalopathy at Exhibitions; Kentucky’s Perspective and Position Updated

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Equine herpesvirus type 1 (EHV-1) is described to be a highly contagious pathogen that is ubiquitous in horse populations throughout the world. Infection in horses can result in a variety of ailments that include respiratory disease, abortions, neonatal deaths and the neurologic disease termed equine herpevirus myeloencephalopathy (EHM).

Recently, we have received alerts of equine herpesvirus myeloencephalopathy being diagnosed in multiple states. States having cases of EHM diagnosed in recent months include Illinois, Iowa, Michigan, Oregon and Pennsylvania. As part of our investigative effort, we have been monitoring each reported incident speaking with individuals familiar with the epidemiologic specifics of the different disease occurrences. Many of the cases are described as being associated with exposure and transmission potentially having occurred at equine events, affecting horses of different breeds and disciplines.

Subsequently, these outbreaks are reported to have resulted in a number of events in Midwestern states having been canceled or rescheduled. As a result, the Kentucky State Veterinarian's Office has received numerous inquiries from event managers and exhibitors planning for shows scheduled to be held here in Kentucky throughout the summer.

The apparent increased frequency of disease and severity of symptoms being seen has lead Kentucky State Veterinarian Robert Stout to conclude extra precaution needs to be initiated and implemented to aide in mitigating the associated risk at equine events.

We first want to remind all associated parties that mitigating risk of disease is a shared responsibility that requires commitment from each individual exhibitor, event managers, facility operators, veterinarians and animal health officials.

We are directing Kentucky facility managers and the managers of shows/exhibitions planned to be held in Kentucky to immediately review their biosecurity practices and if needed elevate their biosecurity plan to minimize opportunity of horses having direct or indirect contact with one another. Indirect contact would include common water and feed sources as well as shared equipment and common areas.

The goal of a biosecurity plan is to prevent the transmission of infectious agents among individuals and the components of a successful program will include cooperation of management, facility layout, decontamination, and when applicable immunization. Each of these factors directly affects the success or failure of the program.

A copy of the USDA’s biosecurity guidelines is available on the Internet at www.aphis.usda.gov/publications/animal_health/2011/bro_keep_horses_healthy.pdf and does provide good general guidance of practices that should be routinely implemented and we encourage show managers to share these directions with all exhibitors. Our office is happy to assist facilities, show management and event veterinarians in evaluating their individual plans and when a need is identified, assist in adapting the plans.

As an additional preventive measure, we encourage horse owners to consult with their veterinarians and after evaluating an individual animal’s vaccination status and consider if there is need or benefit to stimulating an immune response by vaccinating against EHV-1. We acknowledge the available vaccines’ labels make no claim to prevent neurologic disease; but based on our experience managing outbreaks of this disease, and in consultation with infectious disease experts and research scientist, we continue to be of the opinion the vaccine does have a meaningful level of efficacy and may aide in reducing the impact of a disease incident.

We have had mandatory EHV-1 vaccination of all horses entering Kentucky racetracks since 2007. Additionally, the United States Equestrian Federation (USEF) amended their vaccination rule earlier this year and will begin requiring EHV-1 vaccination of horses participating at USEF sanctioned events. The rule, requiring vaccination at 6-month intervals, has been formally adopted and though it doesn’t go into effect until 12/1/15, my understanding is many USEF event managers have proactively included the vaccination as a requirement for participation in USEF events being held this summer.

In response to the identified increased risk, the Kentucky Department of Agriculture has and will continue to operate with elevated regulatory surveillance and equine health inspection activity at many events in Kentucky. Exhibitors can expedite their passage through our inspection points by having their health documents organized and horses loaded in a manner that will allow visual inspection. In addition to the surveillance and inspection activity, we will be working closely with show managers and veterinarians to insure immediate notification and quick response to any suspected communicable disease.

We continue to monitor these different disease events, and will adjust our strategies as warranted and provide updates as changes occur.

E.S. Rusty Ford, Equine Programs Manager, Office of the Kentucky State Veterinarian.