Over the winter show season several cases of EHV Type 1 were diagnosed amongst horses that had been in contact with the HITS Ocala horse show facility. Biosecurity measures were quickly implemented and there was no significant spread of the disease. Quarantine of specific horse housing areas was lifted last week and many horses have begun returning home.
EHV-1 is a contagious upper respiratory disease that is transmitted through direct contact and over short distances, about 10 metres, in vapour droplets (i.e. a sneeze) much like the human cold. Occasionally this disease can create serious complications when it attacks the nervous system, causing a range of symptoms that can include weakness, hind end paralysis, inability to urinate, fever, and recumbency. This “neurologic form” of EHV occurs sporadically, and has been proven difficult to prevent even with appropriate vaccination protocols.
Horses that may have potentially been exposed to this virus include any horse that was present on the show grounds or any horse that may have come into contact with those horses from the show grounds. Most exposed horses successfully fight the infection and show no signs of illness, but occasionally clinical disease will be evident. This usually develops between 2-10 days of exposure, and the horse can shed infectious particles in their nasal secretions for up to 2 weeks.
In a perfect world, all returning horses would undergo a quarantine period of 14-21 days with their temperatures taken twice daily and monitored for clinical symptoms. While this is the ideal route, it is not always possible due to limited space and personnel. In cases where recent exposure to sick horses has occurred but quarantine is not possible, a nasal swab and blood sample from those individuals can help to determine if they are shedding the virus. Even if full quarantine is not possible, segregating the returning horses at one end of the barn, using separate grooming tools and tack, and disinfecting the stalls with bleach before mixing the groups together again can help prevent transmission from anyone shedding the virus. Minimizing barn traffic in areas where suspected exposed horses and using foot baths can help to keep potential contamination low. Ensuring that everyone in the barn is up to date on their respiratory vaccines will dramatically reduce transmission even if one of the returning horses is shedding the virus.