Biosecurity and good communication are critical in the face of an infectious disease outbreak. | Photo: Alexandra Beckstett/The Horse

The equine herpesvirus (EHV) cases diagnosed in Ocala, Fla., in February and March of this year remind us of the importance of biosecurity precautions and timely, accurate communication during infectious disease outbreaks. The state veterinarian’s office worked closely with horse show veterinarians and management to address the issue in a thorough and rapid manner. Although we all appreciate the prompt release of pertinent information, this can be challenging in the face of a disease outbreak investigation.

In this case, the index horse presented to the University of Florida Large Animal Hospital (UF LAH) isolation unit on Wednesday, Feb. 20. Veterinarians confirmed the suspected diagnosis of equine herpesvirus myeloencephalopathy (EHM, the neurologic form of EHV-1) late Thursday, Feb. 21. The UF LAH contacted the state veterinarian’s office and released an official statement on Feb. 22. The state initiated their investigation shortly thereafter. The tent on Horse Shows in the Sun (HITS) showgrounds that previously housed the index horse was quarantined while veterinarians and officials performed further testing and trace-back of other potential cases. Initial evaluation was complicated by the fact that numerous horses presented with fever, but subsequently tested positive for influenza and not equine herpesvirus.

As the initial investigation progressed, additional horses from adjacent tents tested positive for EHV-1. This prompted quarantine of the entire showgrounds, and movement on and off the premises was prohibited beginning Feb. 27. The state managed a comprehensive quarantine of the show, as well as 17 additional off-site premises that horses had been moved to. Fortunately, only one additional horse developed EHM and was referred to the UF LAH for further evaluation and -treatment