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