EQUINE | Equine Disease Quarterly
states, two involving strains of the G3 genotype and four
the G14 genotype; nine cases of Lawsonia enteropathy;
and 10 cases of infection with Clostridium perfringens
Toxin A genotype.
Eastern equine encephalomyelitis (EEE) was reported by
the USA, with 30 cases diagnosed in the fourth quarter,
10 in Michigan and nine in Indiana. The majority were in
unvaccinated horses that died or were euthanized.
France, Germany, Portugal, and the USA confirmed cases
of West Nile (WN) encephalitis. Outbreaks in France
(seven), Germany (three), and Portugal (one) involved
one or two cases. A total of 25 cases were recorded in
the USA, of which 10 were in Colorado and six in Florida.
One case was positive for both EEE virus and WN virus.
The RSA confirmed one case of equine encephalosis,
and the USA diagnosed three cases of equine protozoal
myelitis during the period under review.
The fourth quarter saw an additional 35 outbreaks of
vesicular stomatitis reported by the USA on premises
in eight states. No new affected premises have been
identified since late November.
The USA confirmed two outbreaks of Rhodococcus equi
infection, but this significantly underrepresents the
incidence of this endemic disease in the country.
Epiglottic Entrapment
The epiglottis is a triangular shaped cartilage located
in the throat at the base of the entrance to the airways.
During normal breathing, it is situated above the soft
palate and facilitates air movement. When eating, the
epiglottis moves upwards and backwards to allow
swallowing and to prevent food from entering the
airways. To allow for such movement, the lower surface
of the epiglottis has a loosely attached, elastic mucosa
(subepiglottic mucosa). Epiglottic entrapment occurs
when the subepiglottic mucosa becomes positioned
above the epiglottis, restricting movement.
The most common presenting sign in cases of
epiglottic entrapment is abnormal respiratory noise.
The abnormally positioned subepiglottic mucosa
creates a slightly narrowed airway, as well as increased
air turbulence, which creates a harsh respiratory noise.
Horses in a higher plane of work, racehorses for example,
can also present with exercise intolerance. In horses
performing at high speeds, even mild narrowing of the
airway can result in decreased athletic performance,
and, as a result, decreased earnings. Coughing and
nasal discharge occur in some cases, as an abnormally
functional epiglottis can contribute to disruption
of airflow and slightly interfere with the swallowing
process. As none of these changes indicate a specific
cause of disease, transnasal endoscopy is often used
to further investigate horses exhibiting these clinical
signs. This procedure is commonly done in many cases
with suspected upper airway disease and involves
the passage of a small, flexible camera up the horse’s
nose to visualize the airway. Most horses tolerate this
intervention well with minimal restraint or sedation.
The majority of cases have persistent epiglottic
entrapment; however, a small number of horses
experience intermittent epiglottic entrapment, which
is relieved when the horse swallows. The membrane
entrapping the epiglottis can vary in thickness, width,
and can become ulcerated. In addition to endoscopic
evaluation, a radiograph of the laryngeal region can
also be obtained to assess the patient for epiglottic
hypoplasia (a smaller than normal epiglottis) as this can
be an uncommon cause of epiglottic entrapment.
Surgery is the most common treatment option for this
condition. An incision is made through the abnormally
positioned subepiglottic mucosa to release the
18 • Equine Health Update •