Pet Health Library – Marin Pet Hospital, San Rafael, CA

submitted 4/2003

Definition: A polysystemic tick transmitted spirochete disease found in the northeastern coastal states, southeast, Midwest, and western states.

Etiologic Agent involved with Lyme Borreliosis is the spirochete, Borrelia burgdorferi

Vector: The vector is the deer tick (Ixodes sammini in the Northeast, Ixodes scapularis in the southeast and Ixodes pacificus in the western states and California). Other species of ticks (including the dog tick) and insects such as horseflies, deerflies, and mosquitoes can carry B. burgdorferi; however, only ticks have been linked with disease transmission. The route of infection is through the bite of an infected tick and requires 48 hours of attachment to the host. Mice are the main reservoirs due to the fact that they maintain the larval and nymph stages. Deer support the adult population but it is thought that they do not become infected by the spirochete. Birds however, may also be important reservoirs because they can transmit ticks and spirochetes over long distances.

Clinical Signs associated with Lyme Borreliosis infection are typically subclinical, but may be septic or immune mediated. These include:

· Sudden joint lameness (usually bilateral and involves the carpus) and evidence of severe pain, depression, fever, inappetence, lethargy, lymphadenopathy, limb shifting due to polyarthritis, acute progressive renal failure and protein losing glomerulonephropathy (especially in Labradors, and Golden Retrievers.), rheumatoid arthritis, meningitis, and myocarditis

Hematological and Biochemical Abnormalities are not usually seen with Lyme Borreliosis.

· Azotemia, protenuria, hematuria, pyuria, and tubular casts have been associated with dogs that have renal involvement of the infection.
· Synovial fluid analyses are consistent for supportive polyarthritis with increased leukocyte numbers seen. Borrelia organisms are rarely isolated from joint fluid

Diagnosis of Lyme Borreliosis, like other tick borne diseases, can be difficult. There can be many other causes for the clinical signs seen with the disease and more than 50% of seropositive dogs remain asymptomatic while dogs with acute disease may be seronegative. To document seroconversion, retesting should be done in 3 to 4 weeks. Diagnosis should then be made on a combination of criteria:

· Recent exposure to an endemic area
· Detection of ticks on dog
· Serologic test results, Enzyme-linked immunosorbent assay (ELISA) is considered more sensitive and specific than the indirect fluorescent antibody (IFA) test

serum titers
< 1:28 = NEG
1:128-1:256 = low +
1:512 or > = high +

· Prompt response to antibiotic therapy
· Immune-mediated diseases should be ruled
· Radiographs and joint taps to rule out other causes of lameness

Treatment for Lyme Borreliosis consists of antibiotics and supportive care.

· Doxycycline 10 mg/kg PO q 12 hours for 14-30 days
· Cephalexin and Amoxicillin 22 mg/kg PO q 12 hours for 14-30 days
· Azithromycin or Ceftriaxone should be used for refractory infection 5mg/kg PO q 12 hours
· Anti-inflammatory drugs to reduce joint pain and swelling is debatable

Prognosis is good with proper treatment therapy. If the patient does not respond to antibiotic therapy in 7-10 days, the antibiotic should be changed.

Prevention is through avoidance of tick-infested areas, control with the use of sprays, spot-ons, collars and vaccination (reserve vaccines for high risk dogs-outdoor, hunting, field trial)