b'EHV-1: THEN AND NOWFLICKR CC VIA TRAILERS OF THE EAST COASTHorses unknowingly exposed to EHV-1 while at events can spread the virus to horses at their home farms upon returning.Here well recap those notable diseaseoutbreaks occurred. The social stress ofveterinarians confirmed the first case of events, their import, and what wevebringing horses together, along with theEHM after all horses had departed from learned. potential nutritional challenges of feed- the event.ing a large number of horses that wereThe Colorado veterinarian examining Learning From the Past newly commingled in a group, as well asthe first EHM cases immediately notified Our sources believe the following to bethe fact that many of these horses werestate veterinary officials, who then con-some of the most memorable and signifi- older animals may have prompted thattacted the Utah state veterinarian, says cant outbreaks: outbreak. We learned that host factorsTraub-Dargatz. Together the State Animal Colorado, 1980sTraub-Dargatz recallsbeyond the virus lead to some animalsHealth Officials (SAHO), the American CSU having an influx of EHV cases fromdeveloping the severe disease and someAssociation of Equine Practitioners an outbreak associated with horses fromnot. (AAEP), and the American Horse Council different dude ranches overwinteringUniversity of Findlay, 2003The EHV-1recognized the potential scope of the out-together. Caretakers noticed the firstoutbreak within this Ohio universitysbreak and asked the USDA to assist. case in this outbreak when they foundequine program resulted in 12 equineState animal health officials and the an older horse down in the pasture. Theydeaths. Of the 135 horses at the facility,equine industry came together, she says. subsequently noticed multiple horses117 showed clinical signs of EHV-1 infec- The USDA had not played a role in EHV with abnormal gaits, three of which weretion, 46 of which displayed neurologicoutbreak mitigation prior to this request sent to CSU and diagnosed with the neu- signs. Horses in the program had beenand subsequently has developed recom-rologic form of EHV: equine herpesvirusvaccinated against EHV every couple ofmendations. The industry worked with myeloencephalopathy (EHM).months, and new arrivals were vaccinat- state health officials in a cohesive effort ed within 10 to 45 days of arrival. Datato contact owners of potentially exposed analysis after the outbreak (Henninger ethorses. This outbreak was remarkable not 2,000horses al. 2007) revealed risk factors for develop- only in scale, but in the coming together ing EHM included: of key groups that played a role in mitiga- Being older than 5;tion of the outbreak, as well.were exposed andHaving a temperature higher thanTraub-Dargatz says an outbreak of 13died as a result of 103.5 degrees F; and this scale has an economic spinoff effect, Having the highest rectal temperaturecausing many equine events to be can-on or after the third day of fever onset. celed and equestrian professionals, event the Ogden outbreak Ogden, 2011This pivotal outbreakservices, and their supporting communi-following a large cutting horse competi- ties to incur financial losses.tion in Ogden, Utah, was in many ways aBy the time the USDA deemed the A large number of horses were af- game changer in recognizing the impor- outbreak contained a month later, more fected in this outbreak, she says. Fortance of biosecurity and communicationthan 2,000 horses had been exposed, and me, this is memorable in that EHM iswithin the equine industry. In this case13 had died. Many sick horses had not not a new disease; weve seen it for a longhorses attending the show were exposedattended the event but were infected by timebefore some of the higher-profileto EHV-1 without anyone realizing it, andexposed horses returning home. 28August 2019The Horse | TheHorse.com'