Diagnosis of Equine Infectious Anemia Virus
The first step in diagnosing EIAV is when the horse is presented with clinical signs.
There are other diseases which show similar clinical signs
for differential diagnoses (see clinical signs). To determine what
the horse is infected with, the diagnostician will conduct many tests
to eliminate possible differentials and to assure that the horse is
infected with Equine Infectious Anemia Virus. Although
a large number of diagnostic tests have been described in the past, it
is safe to say that there is no single test available today which will
prove without doubt that a horse is suffering from equine infectious
Laboratory Tests (Serology).
should be collected for the correct identification of antibodies toward
the virus. If there are antibodies present in the serum, it means there
is virus in the horse that the body is trying to fight. The serological
tests that are most commonly used are the agar gel immunodiffusion (or
colloquially known in the horse world as Coggins) test. (2).
However, horses are usually seronegative for Coggins for 2-3 weeks
after infection and may not develop antibodies until 60 days! So a more
sensitive test would be used to detect antibodies earlier, an ELISA
test. Though the advantages are rapidity, sensitivity and objectivity,
the ELISA test may also give more false positives (8).
of the most valuable tests in virology is the polymerase chain reaction
(PCR). Not only will it identify the virus the horse, but is also very
competent at identifying the virus in the other equids (mules, donkeys,
etc). Because it is a retrovirus that uses reverse transcriptase for
viral infection, the method of reverse transcriptase polymerase chain
reaction assays (RT-PCR) can be very useful. This type of PCR can
identify the viral infection not only in horses but also in foals born
to infected mares.
interesting diagnostic is serum lipids found in cases of Equine
Infectious Anemia. The normal range of serum
lipids in the horse is 149394mg/100 ml. However, in horsesw with
this level may increase drastically up to 2550mg/100 ml. This increase
in serum lipid is so dramatic it can often
discernible to the naked eye. The cause of the increase in serum lipid
not yet known; it is possible the lipids arise after the red blood
cells are destroyed from the virus or perhaps from the damage to the
other cells in the body. (9)
a positive diagnosis is attained, the veterinarian should contact the
Canadian Food Inspection Agency, as Equine Infectious Anemia Virus is a
reportable disease. See control and prevention for more information.