Enzootic origins for clinical manifestations of Lyme borreliosis

Both early localized and late disseminated forms of Lyme borreliosis are caused by Borrelia burgdorferi senso lato. Differentiating between the spirochetes that only cause localized skin infection fromthose that cause disseminated infection, and tracing the group of medically-important spirochetes to a specific vertebrate host species, are two critical issues in disease risk assessment and management. Borrelia burgdorferi senso lato isolates from Lyme borreliosis cases with distinct clinical manifestations (erythema migrans, neuroborreliosis, acrodermatitis chronica atrophicans, and Lyme arthritis) and isolates from Ixodes ricinus ticks feeding on rodents, birds and hedgehogs were typed to the genospecies level by sequencing part of the intergenic spacer region. In-depthmolecular typing was performed by sequencing eight additional loci with different characteristics (plasmid-bound, regulatory, and housekeeping genes). The most abundant genospecies and genotypes in the clinical isolateswere identified by using odds ratio as a measure of dominance. Borrelia afzelii was the most common genospecies in acrodermatitis patients and engorged ticks fromrodents. Borrelia burgdorferi senso stricto waswidespread in erythema migrans patients. Borrelia bavariensis was widespread in neuroborreliosis patients and in ticks from hedgehogs, but rare in erythemamigrans patients. Borrelia gariniiwas the dominant genospecies in ticks feeding on birds. Spirochetes in ticks feeding on hedgehogswere overrepresented in genotypes of the plasmid gene ospC fromspirochetes in erythemamigrans patients. Spirochetes in ticks feeding on hedgehogswere overrepresented in genotypes of ospA from spirochetes in acrodermatitis patients. Spirochetes from ticks feeding on birds were overrepresented in genotypes of the plasmid and regulatory genes dbpA, rpoN and rpoS from spirochetes in neuroborreliosis patients. Overall, the analyses of our datasets support the existence of at least three transmission pathways from an enzootic cycle to a clinical manifestation of Lyme borreliosis. Based on the observations with these nine loci, it seems to be justified to consider the population structure of B. burgdorferi senso lato as being predominantly clonal. (C) 2017 Elsevier B. V. All rights reserved.