Walking On Volume 6, Issue 1, January 2019 | Page 12

For the Health of It
What Is the Coggins’ Test?
By Ron Petracek
The Coggins’ test is for a se-
rious equine virus called equine
infectious anemia (EIA). There is
no vaccine or cure for EIA, which
is also known as “swamp fever”
because of the warm, wet regions
of the United States in which it is
more common.
There are three stages to EIA.
The acute stage is when the horse
shows the symptoms of the disease,
which include fever; listlessness;
swelling in the chest, belly or legs;
and no appetite. Although, while
the infection progresses, he may
not show any symptoms at all, and
it may take over a month for the
horse to test positive on the Cog-
gins’ test.
According to the Indiana State
Board of Animal Health, between
30 and 50 percent of horses infect-
ed with EIA die within two to four
weeks of showing initial symptoms.
Horses that survive the acute
phase enter the chronic phase
where they will have recurring
symptoms of the disease including
weight loss, fever and anemia. Such
horses can survive up to a year or
more in this stage before finally
succumbing to the disease. While
appearing healthy at some times,
horses can experience acute epi-
sodes again when under stress such
as when faced with hot weather,
hard work or other disease, accord-
ing to the Indiana State Board of
Animal Health.
EIA is transmitted to horses by
insects such as deerflies and horse-
flies. It can also be transmitted to
12 • Walking On
horses through instruments con-
taminated with infected blood such
as needles or tattoo equipment.
Some horses can also be in the
asymptomatic carrier stage where
they do not show any signs of
disease but will test positive on
the Coggins’ test. But these horses
can also experience acute episodes
when stressed. The Indiana State
Board of Animal Health notes that
these horses in the asymptomatic
carrier stage present the greatest
danger to healthy horses in public
gatherings like horse shows or clin-
ics because they appear healthy.
Surviving horses are unable to
completely clear themselves of the
virus and will remain infected for
the rest of their lives, according
to the Animal Disease Diagnostic
Laboratory at Purdue University.
Affective control of the disease de-
pends on isolation of new, sick, un-
tested or positively testing horses;
hygiene with regard to needles and
like equipment such as dental tools,
fly control and identification of
positive animals.
Horse owners are often
required to submit a negative
Coggins’ test in order to show,
move to a new stable, sell their
horse or transport their horse
across state lines. A negative
Coggins’ test proves that your
horse is safe to have around
other healthy horses.
According to the US De-
partment of Agriculture
(USDA) Animal and Plant
Health Inspection Service
(APHIS) fact sheet on the EIA
virus, it is the “first persistent virus
for which antigenic drift was de-
fined. (Antigenic drift is the virus’s
ability to change its form sufficient-
ly so that it is no longer vulnerable
to existing antibodies.)”
To determine if a horse is neg-
ative on a Coggins’ test, a blood
sample from the horse is tested for
the presence of EIA antibodies. An-
tibodies are proteins produced by
the immune system that recognizes
and helps fight infections and other
foreign substances in the body. The
antibody is specific to the EIA anti-
gen (a foreign substance causing an
immune response).
The Coggins’ test was developed
by Dr. Leroy Coggins, a veterinary
virologist, in the 1970s. According
to the Animal Disease Diagnostic
Laboratory at Purdue University,
the test has a 95% accuracy rate and
is the most used test for EIA though
other tests can be used when the re-
sults are questionable or to confirm