What is Lyme Disease in dogs?
Transmitted through the bite of a tick, Borrelia burgdorferi is the scientific name of the bacteria that
causes Lyme Disease.  These microscopic bacteria are a type called spirochete... they have a coiled
or cork-screw appearance under the microscope.  The disease is actually named after the town in
Connecticut where an early outbreak was first described... Lyme, Connecticut.  (Remember, ticks
don't cause the disease, they merely harbor and transmit the bacteria that cause the disease.)  And
being fussy little bacteria, not just any ol' genus of tick will do as a carrier.  At least three known
species of ticks can transmit Lyme Disease.  However, the great majority of Lyme Disease
transmissions are due to the bite of a very tiny tick commonly called the Deer Tick, or Black-legged
Tick. See the image on the right.  Reference for the identification of this tick is at
(http://creatures.ifas.ufl.edu/urban/medical/deer_tick.htm). Its scientific name is Ixodes (pronounced
eye-zod-ease) scapularis.  Lyme Disease in dogs has been reported in every state but certain
geographical areas are much more likely to harbor bacteria-carrying ticks than others.

Signs of Lyme Disease in Dogs
Of the hundreds of cases of canine Lyme Disease that I have seen, over 90 percent of canine patients
were admitted with signs of limping (usually one foreleg), lymph node swelling in the affected limb, and
a temperature of 103 degrees (101 to 102.5 degrees is normal).  The limping usually progresses over
three to four days from mild and barely noticeable to complete disuse of the painful leg.  Once the dog
starts to be affected by the bacteria, Lyme Disease can progress from a mild discomfort to the stage
where a dog will be in such joint and muscle pain it will refuse to move; it is not uncommon for an
owner to have to carry a sick dog into the animal hospital.  Over the span of two or three days a dog
can progress from normal to completely unable to walk due to generalized joint pain.  In addition to
joint damage, the bacteria can affect the dog's heart muscle and nerve tissue.  If the disease is
diagnosed in time, treatment can cure the dog before permanent joint or nerve damage occurs.  
Certain antibiotics, such as the Tetracyclines, are very helpful in eliminating the disease.
Generally, the diagnosis of Lyme Disease is based upon clinical signs and history.  For example, if a
dog ran or played normally a few days ago, has had no signs of trauma or previous arthritic
discomfort, and now displays tenderness upon palpation of the affected limb and has a mild fever and
swollen lymph nodes, I'm going to seriously consider Lyme Disease as a possible diagnosis.
On the other hand, just as in human medicine, Lyme Disease is called "The Great Imitator" because it
has often been mistakenly diagnosed when another disorder is present, such as an autoimmune
disease, lymph tissue cancer, Blastomycosis, or septicemia.  Just as vexing is the fact that at times
other similar-appearing diseases are diagnosed when the culprit is actually Lyme Disease.  There are
published reports of Lyme Disease being misdiagnosed and over diagnosed in human medicine.
Keeping other disorders in mind, if I suspect Lyme Disease, I start treatment immediately, generally
prescribing an antibiotic such as tetracycline and possibly some aspirin if the dog is in a lot of pain.  
Many veterinarians do not wait for blood tests to confirm the tentative diagnosis because in dogs the
information obtained may be confusing and require too much time to hear back from the lab.  I have
seen patients that from clinical experience I know have Lyme Disease, yet their blood test curiously
indicates no exposure to the disease.   And there are numerous cases of normal-appearing, healthy
dogs with positive blood tests for Lyme Disease.
Fortunately, over ninety percent of dogs treated within the first week of obvious signs of Lyme
Disease will respond rapidly to treatment with a tetracycline antibiotic.  This medicine is administered
for at least three weeks.  In my experience, five percent of dogs will have some type of relapse of
signs such as cardiac or neurological difficulties even after treatment .  Some of these patients will
experience chronic, lifelong joint pain from the damage caused by the bacteria and its direct and
indirect stress to joint tissues.  The earlier the antibiotic is started in the course of the disease, the
better the patient's chances of a complete recovery.

Can a dog contract Lyme Disease a second time?
Yes.  But, quite honestly, we don't know for sure if the reoccurrence is a second, distinct infection or
a flare-up of the original episode (because the Borrelia organism replicates quite slowly).  And, since
dogs can harbor the bacteria in their tissues a long time before the disease is evident, Lyme Disease
cases are showing up all year long.  In the northern states, however, the summer months are the
busiest for Lyme Disease case presentations.
Learn About this tick-borne disease
by T. J. Dunn, Jr. DVM
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