Lyme disease can mimic many other diseases, and it is very difficult to provide a reliable diagnosis. There is no specific routine laboratory test to confirm or rule out the presence of Lyme borreliosis with 100% accuracy. Bacterial cultures can be used for Borrelia cultivation from skin biopsies, but this test is very time consuming.
Diagnosis of Lyme borreliosis is based primarily on clinical signs. Since dogs generally do not develop the characteristic skin lesions (e.g. erythema migrans) commonly found in humans, diagnosis is more difficult. Moreover, many dogs seroconvert in response to infection but never develop clinical signs.
- Serologic testing may provide valuable supportive diagnostic information in addition to clinical signs. When serologic testing is indicated, it is recommended testing initially with a sensitive first test, either an enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescence assay (IFA), followed by testing with the more specific Western immunoblot (WB) test to corroborate equivocal or positive results obtained with the first test. Although antibiotic treatment in early localized disease may blunt or abrogate the antibody response, a strong serological reactivity can be observed during early disseminated or late-stage disease, demonstrated by the expanded WB immunoglobulin G (IgG) banding patterns to diagnostic B. burgdorferi antigens. Following, the standard test systems are shortly outlined:
- 1st generation tests: IFA is a simple test system, but due to the fact that the amount of fluorescence is estimated by the person performing the test, it should only be used by experienced laboratory personnel. Meanwhile the test is regarded to be slightly obsolete and should not be used exclusively.
- 2nd generation tests: ELISA is a very sensitive, but not sufficiently specific test. In case of Borrelia lysate used as antigen, a differentiation of the detected antibodies is not possible. Furthermore often antibodies of an infection cannot be distinguished from those of a vaccination. Weak positive ELISA results and sera of vaccinated dogs should be screened with ELISA in combination with Western blot.
- 3rd generation tests: The C6-peptide ELISA is detecting an early and very specific antibody reaction onto the surface peptide C6. The test has three major advantages: Vaccinated dogs do not develop C6-antibodies, after successful antibiotic therapy the amount of C6 antibodies declines and finally infection with all three major species can be detected by the same test.
Antibodies often persist for months or years following successfully treated or untreated infection. Thus, seroreactivity alone cannot be used as a marker of a prevalent disease. In general, neither positive serologic test results nor a history of previous Lyme borreliosis assures that an individual has protective immunity. Repeated infection with B. burgdorferi has been documented.
- Cultivation: The diagnostic usefulness of this procedure is limited because of the need for a special bacteriologic medium (modified Barbour-Stoenner-Kelley (BSK II)-medium) and protracted observation of cultures. It may take 6-8 weeks until sufficient growth. Furthermore a high risk of contamination of the cultures exists, making sterile sampling essential. Only specialized laboratories should be consulted to obtain reliable test results.
- Darkfield microscopy: It has especially been used for the diagnosis of Borrelia infection of ticks, but the technique is neither specific nor very sensitive. Different spirochetes cannot be differentiated.
- Polymerase chain reaction (PCR): This technique is a very specific and sensitive tool. Besides different protocols and specific primers, the technique is limited by the type of tissue used and the number of bacteria available in the sample. It has been used to amplify genomic DNA of B. burgdorferi s.l. in skin, blood, cerebro-spinal fluid, and synovial fluid. Meanwhile multiplex PCRs have been developed to detect several species and quantitative real time PCRs have been developed for a quantification of the pathogen. Nevertheless due to the mentioned limitations a negative result does not exclude an infection. For the detection of Borrelia in ticks this technique is used in laboratory diagnosis.
- Appel MJG: Lyme disease in dogs. Comp Cont Educ Pract Vet. 2002, 24 (Suppl.), 19-23
- Straubinger RK, Dharma Rao T, Davidson E, et al.: Protection against tick-transmitted Lyme disease in dogs vaccinated with a multiantigenic vaccine. Vaccine 2002, 20, 181-93