Prevalence and genetic heterogeneity of Borrelia burgdorferi sensu lato in Ixodes ticks in Belgium

Borrelia burgdorferi sensu lato is a genetically diverse group of spirochetes that includes the agent of Lyme borreliosis in which genospecies tend to be associated with specific clinical features. The aim of the study was to determine the prevalence and genetic diversity of Borrelia burgdorferi sensu lato in 524 ticks collected in woods of a western province of Belgium. Presence of spirochetes in ticks was determined by phase contrast microscopy. The mean infection rate of ticks was 12.0%. Variability was observed in the prevalence of infection among the five sites examined, ranging from 2.8 to 21.6%. Identification to genospecies was determined by PCR and sequencing. The most common genomospecies were Borrelia afzelii (55%) and Borrelia garinii (21%). For the first time in Belgium, we detected Borrelia valaisiana and Borrelia spielmanii, representing 14% and 2%, respectively. Borrelia burgdorferisensu stricto counted only for 2%. Co-infections were present in 8% of ticks. We emphasize the need for clinical studies to assess the prevalence of specific genospecies-related clinical manifestations of Lyme borreliosis in Belgium.