Why all the concern
in adopted greyhounds?
Studies have shown that it can take as
long as 5-7 years following a bite from an Ehrlichia-carrying tick
for a dog to show symptoms. By then, a greyhound is long gone from
the tick-infested racing kennel or farm and possibly living in an
area where Ehrlichia is unheard of. The greyhound may present with a
variety of mysterious ailments, some of which can be serious and
fatal if not treated. Veterinarians working with adopted greyhounds
should maintain a high index of suspicion for Ehrlichia.
Ehrlichia canis is the most common
Ehrlichia species infecting dogs, but there are others (E. platys,
E. risticii, E. equi) and researchers suspect that there are many
more. E. canis is a rickettsia (an organism somewhere between a
bacteria and parasite) carried by the brown dog tick - a common if
not universal problem in racing kennels. Greyhounds from all over
the country mingle together sharing their ticks, making racing
kennels a smorgasbord of tick-borne diseases.
Acute (first few weeks) signs of
Ehrlichia, such as runny eyes/nose and cough (resembling distemper)
would not be expected in adopted racers. Virtually all adopted
greyhounds will be in the chronic stage. There may be vague signs
such as lethargy, fever, anorexia, and weight loss. Greyhounds may
have bleeding, bone marrow suppression, eye disease, neurologic
signs, neck/spinal pain, polyarthritis, enlarged spleen, enlarged
lymph nodes, or kidney disease. Bloodwork may show anemia, low white
blood cell counts, low platelets, increased protein
(hyperglobulinemia), and increased ALT/ALKP.
Ehrlichia testing is done with antibody
titers. Titers measure the body's immune response to the bug, not
the amount of bug in the dog's body. Most labs titer from 1:20 to
1:1,000,000 or more. In general, the more chronic the infection, the
higher the titer. The IDEXX in-office "combo" test
(heartworm/Lyme/Ehrlichia) catches titers over 1:100. While sick
dogs usually test positive, they might not if:
They have a poor immune response (the reason why a very sick
dog sometimes tests negative).
They carry an Ehrlichia strain other than the standard E.
canis the lab tests for.
They have a titer <1:100 on the IDEXX test, or
There is variation between labs.
There is not necessarily a correlation
between the severity of the disease and the titer number. All
positive titers should be treated.
Ehrlichia dogs respond dramatically and
quickly (within days) to doxycycline dosed at 5 mg per pound twice
daily. For this reason, greyhounds should be started on doxycycline
as soon as Ehrlichia is suspected. If not immediately available at
the veterinary office, all human pharmacies carry doxycycline (a
tetracycline family antibiotic). Often patients are vastly improved
by the time their titer results are back from the lab. This
doxycycline trial can be as useful as the titer results in
determining whether to continue with treatment. The standard regimen
we use in Arizona where Ehrlichia is endemic is 5 mg per pound twice
daily for 2 months. Doxycycline must always be given with food -
otherwise it may upset the stomach. Alternatively, Ehrlichia can be
treated (offlabel) with Imizol, an injectable drug approved for the
treatment of Babesia, another tick-borne disease. The Imizol
protocol is two injections two weeks apart.
There is a poor correlation between
resolution of infection and serum antibody titers. In patients with
high antibody titers, the antibody concentrations decline very
slowly (over years) following effective therapy. In many patients,
the antibody titers persist at high concentrations indefinitely. The
PCR (polymerase chain reaction) test, which tests either positive or
negative (no numeric value) for Ehrlichia DNA in the bloodstream,
may be used for follow-up testing, but is not perfect either.
The most reliable indices of response to
therapy are clinical signs, CBC changes (i.e. anemia, platelet
counts), and serum globulin concentrations. A reasonable approach is
to monitor recovered dogs with a CBC and titer at six-month
intervals as long as the dog remains clinically normal. If clinical
signs develop or the CBC becomes abnormal, re-treat, using Imizol if
doxycycline was used the first time around. The majority of
Ehrlichia dogs will require only one treatment course, but owner and
veterinarian should remain watchful in order to recognize a relapse.
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