Presence and distribution of Borrelia burgdorferi sensu lato species in internal organs and skin of naturally infected symptomatic and asymptomatic dogs, as detected by polymerase chain reaction.

Tissues from Dutch family dogs symptomatic for borreliosis according to established criteria and from infected but asymptomatic dogs were tested for Borrelia burgdorferi sensu lato DNA using a polymerase chain reaction. Subsequently, B. burgdorferi sensu stricto, B. garinii, B. afzelii, and B. valaisiana were identified by hybridization. Symptomatic dogs showed a higher prevalence of Borrelia in liver samples (9 of 15) than asymptomatic dogs (9 of 43) p = 0.0049. Overall, B. garinii was the most prevalent species and occurred together with up to three other species in on liver sample. B. burgdorferi sensu stricto however, was predominantly detected in samples of synovial membranes, skin, cerebrospinal fluid, bladder, heart, and bone marrow. Nine out of 10 symptomatic dogs with a very high antibody titre were positive for Borrelia DNA by PCR in one or more of these tissues. We conclude that dissemination in naturally infected European dogs occurs and that the two most prevalent species, B. burgdorferi sensu stricto and B. garinii, differ in their tropism.