Most dogs and cats seropositive for Borrelia burdorferi (Bb) seroconvert (i.e. develop antibodies) but show no clinical signs. Cats exposed experimentally show no clinical signs (CS) even after second exposure and overall it is unknown if cats develop CS of Lyme Borreliosis (LB).
The two most common forms of LB include Lyme arthritis and Lyme nephritis. Signs of Lyme arthritis, seen in a small subset of infected dogs, are transient or respond quickly to oral antibiotics. Lyme nephritis, thankfully, is much less common than Lyme arthritis. Neurological and cardiac manifestations of LB in dogs are not well documented.
Spirochetes migrate from the midgut of the tick (Ixodes scapularis) into the host usually after 36 to 48 hours of tick attachment. Other organisms (co-infectors) can be transmitted by the same tick and cause similar clinical signs to Lyme borreliosis and increase morbidity. When discussing with owners about tick exposure, always ask about travel history and the local deer population. Where there are deer, there are ticks.
We recommend screening healthy dogs annually for LB if the organism has been documented in your region. Serology is the only recommended modality to evaluate for exposure to Bb. The IDEXX SNAP4DxPlus is a qualitative test developed for annual screening. Testing returns a "yes or no" answer and is what I recommend as an initial screening test. Remember, IDEXX developed this test as an annual screening test rather than a "diagnosis" test. It is important to remember this test is not a diagnosis test, nor is the test affected by vaccination.
Healthy dogs testing negative require no further diagnostics. Healthy dogs testing positive should have a minimum database (MDB) evaluated. This includes a CBC, chemistry, and urinalysis to screen for cytopenias, azotemia, hyperglobulinemia, hypoalbuminemia and proteinuria. Proteinuric patients should also have a urine protein-creatinine ratio evaluated along with a blood pressure.
When submitting a urine protein creatinine ratio, an in hospital sample obtained at the day of the appointment is appropriate. It is important to remember that when there is protein in the urine, to consider the presence of bacteria in the urine even if no signs of urinary infection are present. I see patients weekly who have no signs of urinary tract infection, a completely inactive urine sediment on urinalysis, but culture positive for bacteria on urine culture. These patients are diagnosed with the syndrome of “subclinical bacteriuria” (i.e. bacteria in the urine with no infection). This topic is beyond the scope of this article. Briefly, these infections, or better described as “colonizations”, generally do not require treatment but can affect your urine protein creatinine ratio. Clearing these bacteria from the urine and retesting of the urine protein creatinine ratio is recommended.
Although still debatable, most clinicians including myself feel that if the MDB is normal in an otherwise healthy patient, then neither further diagnostics nor treatment is recommended.
If the MDB reveals abnormalities in the healthy patient, or your patient exhibits CS associated with LB (e.g. arthritis, fever, lethargy, lymphadenopathy, "slowing down"), then follow-up testing with the Lyme Quant C6 (IDEXX) is required. This test should be performed before starting treatment ("baseline titer"). It should also be rechecked three to six months after treatment for two reasons: (1) to confirm that the titer has dropped significantly from the baseline titer (i.e. confirm a response to treatment) and (2) to obtain a new baseline titer to refer to in case you suspect reinfection in the future. I also recommend obtaining samples pre-treatment to screen for other infectious organisms such as Anaplasmosis, Ehrlichiosis, Bartonellosis, Babesiosis, RMSF, Heartworm, Leptospirosis, especially in patients with findings such as thrombocytopenia, immune mediated anemia, and proteinuria.
Four weeks of doxycycline is recommended at either 10 mg/kg once daily or divided twice daily. CS of Lyme Arthritis should rapidly improve within one to three days. Treatment of pain is best with gabapentin rather than NSAIDs to avoid the need for a washout period in case corticosteroids are needed for a persistent immune mediated polyarthritis. Although considered beyond the scope of this article, treatment of Lyme Nephritis includes doxycycline along with the standard treatments for glomerulonephritis, (including a low protein diet, ace-inhibitors, aldosterone receptor blockers, antithrombotics, antihypertensive agents, omega-3 fatty acids, and immunosuppressive agents.