Equine Health Update Issue 2 Volume 19 - Page 19

EQUINE | Equine Disease Update However, the success of these tactics depends on fac- tors beyond any veterinarian’s control. For example, there’s the disease transmission that happens prior to the onset of the first clinical case. “The speed at which an outbreak occurs depends on the interval between (horses’) contact with the first clinical cases and signs of disease in the subsequent contacts,” noted Morresey. Respiratory disease can spread slowly within a popula- tion. An infection might spread considerably before any- one even recognizes the first case. This limits the veteri- narian’s ability to stop disease, and it can make isolation protocols ineffective. A tendency to “shoot the messenger” in such situations makes a veterinarian’s job difficult, he said, especially if it involves suspending horse movement and curtailing day-to-day operations. Nonetheless, appropriate bios- ecurity protocols must be instituted, including barrier precautions (glove wearing, etc.), containment proce- dures, and disinfection. Lessons Learned From Outbreaks Angela Pelzel-McCluskey, DVM, equine epidemiologist for APHIS Veterinary Services, knows well how diseases spread and which ones require an all-hands-ondeck re- sponse. She shared some lessons learned from respond- ing to recent outbreaks of high-impact diseases. High-impact means the disease could: • Be especially virulent; • Affect a large number of equids, owners, or prem- ises; • Be associated with high morbidity (illness) or mor- tality (death) rates; • Be considered a foreign disease; • Have limited intervention options; • • Have significant trade ramifications; or Elicit significant concern or panic. Recent outbreaks of note include the 2008 contagious equine metritis outbreak that affected 23 stallions; the 2015-2016 vesicular stomatitis outbreak, with cases confirmed on 823 properties in eight states; the large- scale piroplasmosis outbreak in 2009, in which more than 400 horses in a herd tested positive; 39 equine in- fectious anemia-positive racehorses found in California from 2012 to 2015; and the 2011 equine herpesvirus myeloencephalopathy (EHM) outbreak in Ogden, Utah, with 57 EHV-1 cases and 33 EHM cases confirmed on 62 premises. Five different d