Detection of Borrelia burgdorferi DNA in tissues from dogs with presumptive Lyme borreliosis

Objective - To develop a quantitative PCR assay for detection of Borrelia burgdorferi DNA in formalin-fixed, paraffin-embedded tissues; compare results of this assay with results of immunohistochemical staining of tissues from seropositive dogs; and determine whether B burgdorferi DNA could be detected in renal tissues from dogs with presumptive Lyme nephritis. Design - Cohort study. Sample Population - Archived tissue samples from 58 dogs. Procedures - A quantitative PCR assay was performed on formalin-fixed, paraffin-embedded tissue sections from the dogs. Results were compared with results of immunohistochemical staining, B burgdorferi serostatus, clinical signs, and necropsy findings. Results - 38 dogs were classified as having positive or equivocal results for Lyme borreliosis, and 20 were classified as having negative results on the basis of clinical signs, serologic findings, and pathologic abnormalities. Borrelia burgdorferi DNA was amplified from tissue samples from only 4 (7%) dogs, all of which had been classified as having positive or equivocal results for Lyme borreliosis and had signs of presumptive Lyme nephritis. Results of PCR assays of renal tissue were positive for only 1 dog, and there was no agreement between results of immunohistochemical staining (ie, detection of B burgdorferi antigen) and results of the PCR assay (ie, detection of B burgdorferi DNA) for renal tissues. Conclusions and Clinical Relevance - Results indicated that detection of B burgdorferi DNA in formalin-fixed, paraffin-embedded tissues is feasible, but that intact B burgdorferi DNA, is rarely found in tissues from naturally infected dogs, even tissues from dogs with presumptive Lyme borreliosis. Further, findings support the contention that Lyme nephritis may be a sterile, immune complex disease.