Infected birds develop a high
viremia and serve as the source
of virus to infect mosquitoes.
The incubation period in horses
is 7-10 days and clinical signs in
horses consist of low-grade fever,
anorexia, and lethargy progressing
to neurologic signs that may
appear suddenly and worsen over
the ensuing days. Fortunately, once
infected, horses due to low virus
levels.
may be useful as an early marker of placental insult.
In addition to endocrine monitoring, measurement
of acute phase proteins in blood may also be a
useful biomarker for placentitis in mares. Serum
concentrations of acute phase proteins are elevated
when inflammation is present. This group of proteins
is mainly produced by the liver in response to
an inflammatory stimulus. The major acute phase
protein in the horse is serum amyloid A (SAA),
whereas the minor acute phase proteins include
haptoglobin and fibrinogen. In ongoing research at
the Maxwell H. Gluck Equine Research Center, mares
with experimentally induced placentitis have a rapid
and dramatic elevation in SAA within two days
after intracervical inoculation with Streptococcus equi
subspecies zooepidemicus. Although SAA appears
to be a very sensitive indicator for acute bacterial
placentitis, it is also a very nonspecific indicator,
as many other acute inflammatory conditions may
result in an elevation of SAA.
Ultimately, it appears likely that more than one
biomarker may be required for accurate and early
detection of placentitis in the mare. Ongoing research
will address these needs and evaluate the utility of
these markers in mares under field conditions.
Since the appearance of WNV,
cases have continued to be diagnosed in horses in
the United States and Kentucky. As of November,
Kentucky officials reported 12 cases of WNV for 2013.
These cases occurred in 10 Kentucky counties. None
of the 12 horses were vaccinated against WNV. Seven
were Quarter Horses, two were Standardbreds, and
the remaining were a Paint Horse, a Percheron cross,
and a Rocky Mountain Horse. Ten of the horses
survived, and two were euthanized. In 2012, 13 cases
of WNV were reported versus one case in 2011. The
2012 cases were centered in Central Kentucky while
in 2013 the cases were in Western Kentucky.
Eastern equine encephalomyelitis (EEE) is uncommon
in Kentucky. This viral disease is also mosquito
transmitted and is characterized by clinical signs
similar to those seen with WNV. Eastern equine
encephalomyelitis is considered to have a mortality
rate approaching 90 percent. In 2013 in Kentucky,
two cases of EEE were reported. One case was in a
10-year-old Tennessee Walking Horse and the other
in a 17-year-old Quarter Horse.
Neither had been vaccinated against EEE, and both
horses died as a result of disease.
The American Association of Equine Practitioners
includes WNV and EEE in their list of core vaccinations
for horses. The other core vaccinations are Western
equine encephalomyelitis, tetanus, and rabies.
CONTACT:
Drs. Barry Ball
(859) 218-1141
[email protected]
Igor Canisso, and Mats Troedsson
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky
Additional information can be found at http:// www.
k yagr.com/statevet/equine -infectious- diseases.
html#west.
Equine Encephalitis Cases
West Nile virus (WNV) causes disease in humans,
horses, and birds. It is a mosquitoborne virus that
first appeared in the United States on the East Coast
in 1999. Many horses were infected and died during
the following years, and WNV is now considered
endemic in the US.
CONTACT:
Dr. Neil M. Williams
(859) 257-8283
[email protected]
Veterinary Diagnostic
Laboratory
University