Long-term persistence of antibodies to Borrelia burgdorferi has been shown to occur in serologic surveys of dogs, but few data on the long-term outcome in these dogs exist. Other studies have suggested a possible breed predisposition to B burgdorferi infections in Bernese mountain dogs. As a result, this study sought to investigate and compare long-term clinical outcome of seropositive Bernese Mountain dogs and dogs of other breeds. Dogs from a previous study on the prevalence of B burgdorferi in Bernese mountain dogs were reevaluated 2.5 years and 3 years after the initial study. Fifty-three Bernese mountain dogs and 30 control dogs of other breeds were included. Complete blood count, serum biochemical analysis, serum serologic testing for B burgdorferi (enzyme-linked immunosorbent assay confirmed by Western blot), and urinalysis were performed. Owners were asked to fill out questionnaires on the health status of their pets. Twenty-two (42%) of Bernese mountain dogs and 11 (37%) of control dogs were considered positive for B burgdorferi antibodies at the first evaluation; 25 (47%) Bernese mountain dogs and 12 (40%) control dogs were considered positive at the second evaluation. Sixty-nine percent of the dogs demonstrated the same serologic result at both evaluations, while 31% seroconverted or seroreverted. On the basis of owner questionnaire responses, the occurrence of a poor general condition and lameness did not significantly differ between the first and second evaluations in all groups. Six Bernese mountain dogs in the first evaluation and 11 in the second were azotemic; no control dogs were diagnosed with azotemia. Serum urea concentrations did not differ, and the authors reported no indication of reduced renal function in the measures examined. The results suggest that antibodies against B burgdorferi were not associated with the development of lameness or renal disease in dogs observed for 2.5 to 3 years.

This study followed a small group of B burgdorferi–seropositive dogs to assess for signs of lameness or reduced renal function. The authors found no difference between the seropositive dogs and a control group. There is still a lot we don’t know about chronic Lyme disease in dogs as well as a lot of controversy about the nature of chronic Lyme disease in humans and whether it actually exists. While the battle between advocates and deniers of chronic Lyme disease in humans wages on, we in veterinary medicine can be comforted by the fact that vaccines to help prevent the disease and good acaricides to reduce the risk for transmission of B burgdorferi are available. Prevention is certainly the key.—Patricia Thomblison, DVM, MS

Follow-up of Bernese mountain dogs and other dogs with serologically diagnosed Borrelia burgdorferi infection: What happens to seropositive animals? Gerber B, Haug K, Eichenberger S, et al. BMC VET RES 5:18, 2009.