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♦Strangles
- Fact and Fiction
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STRANGLES:
FACT AND FICTION
No word in the horse world seems to strike
more fear and stir more controversy than the
word “Strangles”. Let’s try to separate the
fact from the fiction and examine the
practical implications in dealing with this
multifactorial disease. Below are a few
commonly asked questions and comments
regarding Strangles that I’ve heard over the
years. Read on to find the answers.
1. My horse has been vaccinated, he can’t
have Strangles!
2. My horse had a case of Strangles, he’ll
never get it again!
3. It can’t be Strangles, he only has
swelling on one side of his jaw!
4. Why don’t you use antibiotics to treat
Strangles?
5. How can my horse have Strangles? He
hasn’t been anywhere around other horses.
6. The Strangles is in the soil, that’s why
you keep having outbreaks.
FACTS
1. WHAT CAUSES STRANGLES?
Strangles is caused by the bacteria
Streptococcus equi, subspecies “equi
2. WHAT ARE THE SIGNS OF STRANGLES?
Purulent nasal discharge, fever, difficult
breathing, difficulty in swallowing due to
soreness in throat, enlarged lymph node(s)
under jaw between mandibles (submandibular)
that become progressively larger until they
break open and drain a purulent (pus)
discharge. Each horse is a little different
and may not show all of the above but the
enlarged
lymph node(s) is the most classic sign. The
majority of cases I see only involve
swelling of one submandibular lymph node,
and less commonly both. There are some other
upper respiratory tract infections that
occasionally cause a temporary enlargement
of these lymph nodes, but only very rarely
do they abscess as you see with Strangles.
In my experience, if you have an enlarged
submandibular lymph node(s), the cause will
turn out to be Strangles 95% of the time.
3. WHY AREN’T ANTIBIOTICS USED TO
TREAT STRANGLES?
Generally, antibiotics only slow down the
progression of the abscesses forming within
the lymph nodes. The best way to shorten the
course of the disease is to encourage these
abscesses to open and drain once they have
formed. Anti inflammatory medications such
as phenylbutazone (Bute) may be used as
needed to control the fever and throat
soreness. However, there are
exceptions to the no antibiotic rule. In
some rare cases the lymph nodes located
within the throat area (retropharyngeal)
become so enlarged that they cause
compression and swelling in the horses
airway making breathing more difficult and
labored (thus where the term “Strangles”originated).
In these cases, high dose antibiotics and
anti-inflammatories are indicated to reduce
the swelling as quickly as possible. If this
doesn’t slow the progressive swelling, a
temporary tracheotomy may be needed to allow
the horse to breathe until the treatment has
time to take effect. In other rare cases,
the bacteria may relocate to the lungs or
internal lymph nodes. Antibiotics are
clearly indicated for this situation as
well. Others have reported successfully
using Penicillin early in the course of the
disease( before abscess formation) to
eliminate the infection and reduce
complications. Haven’t tried this, so can’t
comment on its effectiveness.
4. HOW IS IT SPREAD?
The main mode of transmission is by direct
contact with the nasal secretions or
discharge from the draining abscess of an
infected horse. Humans and inanimate objects
contaminated with the bacteria can also
carry the disease to other horses. Airborne
transmission is possible for short distances
if the horse were to cough or sneeze. The
bacteria is not a normal soil organism, is
easily killed by sunlight, and does not
persist in the soil for any length of time.
However, according to a recent report, the
bacteria can, under ideal environmental
circumstances survive on a fence board for
30-40 days, and in a water tank for up to 60
days. This helps to point out the necessity
for thoroughly cleaning and disinfecting any
thing that came in contact with an infected
horse. Strangles is one of the most common
respiratory infections in horses and has
been around and reported in the literature
for over 100 years. It has been able to
persist in the horse population through
inapparent carrier horses. These horses
harbor the bacteria in their guttural
pouches (out-pocketings of the throat)
without showing any signs and periodically
shed the bacteria through their nasal
secretions, contaminating the environment
and infecting susceptible horses. There are
some newer lab tests and techniques that are
more capable of detecting some of these
carrier animals, but they are still far from
perfect.
5. WHAT ABOUT VACCINATION? SHOULD I OR
SHOULDN’T I ?
The current and most widely used vaccine is
the intranasal version (Pinnacle)
manufactured by Fort Dodge . I’ve used quite
a bit of this vaccine without any initial
side affects, unless you want to consider
the fact that most horses don’t particularly
care for you spraying things up their noses
a side affect. It is by far the most
effective Strangles vaccine produced to
date, but still falls way short of being
ideal.
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The vaccine’s is only
around 80% effective, meaning if you
took a group of properly vaccinated
horses, and exposed them all to the
Strangles bacteria- 80% would be
protected and the remaining 20% would
still get Strangles, albeit a milder
form. Most other commonly used vaccines
approach the 95%+ effective range.
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The vaccine is composed
of live bacteria, and it can
periodically produce a case of Strangles
within a few weeks following
vaccination. The bacteria used to
produce the vaccine is a milder strain
than the naturally(”wild”) occurring
one, so the infection is also milder as
well, and reportedly is not very
contagious. The problem in the past has
been being able to distinguish one
strain from the other, but now with
recent
advances in laboratory techniques we are
able to tell the difference.
Irregardless of the strain involved, and
to be on the safe side, I handle and
treat them all the same.
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Another downside to
vaccination is the potential to produce
a nasty little condition called Purpura
Hemorrhagica. This is an autoimmune
vasculitis (inflammation of the blood
vessels) that causes pain and swelling
of the legs, and is sometimes very
difficult to treat successfully. Recent
research seems to indicate that this
condition occurs more frequently in
horses that already have a high antibody
titer from having either recovered
from a recent case of Strangles or from
being vaccinated a lot. In the ideal
world, an antibody titer to Strangles
should be determined prior to
vaccination. This is not always
practical, nor cost effective, and is
the reason it is not routinely done. A
natural case of Strangles will produce
an immunity that may last for a few
years, but it does not last a lifetime.
So, in answer to the
question “should I or should I not
vaccinate”?-It depends upon your horse’s
risk potential. If your horse is going to be
around a lot of different horses, or where
there is a lot of movement of horses, such
as horse shows, rodeos, boarding and
training facilities, then yes you probably
should vaccinate. Talk it over with your
veterinarian to determine your horses risk
potential.
6. WHAT CAN I DO TO PREVENT MY HORSE
FROM GETTING STRANGLES?
The typical scenario, when I see a case of
Strangles, is that the client bought a horse
at a sale a week or two prior, brought the
horse home, and turned him out with their
other horses. Now they have a case of
Strangles.
Ideally, any new horse brought to your place
should be quarantined and monitored for a
period of 30 days. This rule not only
applies to preventing Strangles, but to all
other communicable diseases as well and is a
good, standard farm practice.
Isolation of any infected horses until their
abscesses have completely healed, and then
another 30 days of quarantine and monitoring
for any relapses before returning them to
the herd. Anything that may have been
contaminated by a infected horse needs to be
cleaned and disinfected. before reusing. Any
good disinfectant will do the job, as the
bacteria are easily killed. Pressure washing
or steam cleaning will help to remove a lot
of organic matter that the bacteria may be
able to survive in.
Vaccination can be helpful in your
prevention program, realizing the
limitations of the vaccine as discussed in
the previous question.
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