Background:
Lyme disease is a recently identified infectious disease in the
United States affecting dogs and humans, as well as cats, cattle and
horses. Lyme disease is caused by Borrelia burgdorferi, an
extracellular organism that is transferred from host to host by a
bloodsucking organism such as a tick. The Ixodes tick is the primary
culprit, spreading the disease through a process which may take over
12 hours. The adult tick is active in the fall, spring and early
summer. The adult tick is carried through the environment by deer
and other large mammals. Birds may assist in moving the tick over
long distances. The male and female adult tick feed on the dog and
other large animals. Once sated, the female tick falls off the host
and lays hundreds of eggs in the environment. Most Lyme disease is
confined to discrete areas of the country: the north-central states
and the central to north Atlantic region. In high incidence areas,
two-thirds to three-quarters of the dog population has been exposed
to the disease. However, only a small percentage of them show
clinical signs. In areas where the disease is prevalent, thus, a
positive test for Lyme antibodies only indicates that the dog has
had some exposure to the disease and does not indicate recent
infection. The high incidence of infection combined with a
relatively low rate of signs of the disease suggests that dogs seem
to tolerate the organism or may be able to defend themselves
successfully.
Clinical Signs:
The most common sign of Lyme disease in the dog is arthritis in more
than one joint. These joints may be painful, warm and swollen, and
the dog may be reluctant to move. Other symptoms include fever, lack
of appetite or swollen lymph nodes. Dogs do not appear to develop
any of the long-term complications that afflict humans such as
degenerative long term arthritis, serious neurological complications
and cardiac problems. The dog's immune response to the organism is
not clearly understood. The length of infection may persist for
quite some time, one to two years before elimination.
Diagnosis:
If your veterinarian suspects that your pet is afflicted with Lyme
disease, he or she will collect a blood sample to measure antibodies
against the parasite. Current theories suggest that dogs build
antibodies for as long as 1-2 years. Most dogs with signs of the
disease will improve greatly within 1-2 days when treated with
antibiotics, like Doxycycline.
Treatment:
Treatment of the disease most often includes a ten to fourteen day
course of Doxycycline. However, prevention is critical to
controlling further infection. Effective tick control should be
implemented, using topical oils (Frontline), sprays (Preventick) and
powders. Other products containing permethrins, amitraz and
organophosphates provide good tick control. Several commercial
vaccinations also are available against Lyme in the dog. The
efficacy of the vaccine is primarily anecdotal. Reports in the field
suggest that effective protection can decrease the incidence of
infection by as much as 80%, thus lowering the overall rate from 5%
to 1%. Occasional claims of Lyme disease developing in vaccinated
dogs suggest the possibility of vaccine side-effects. Good
controlled field trials have not been performed. Recommended for
pets which are routinely kenneled, or which are to be showed or
boarded. The duration of the protective effect is debated.
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