Land use intensity has an impact on Borrelia burgdorferi sensu lato prevalence and genodiversity in ticks from Central Germany.

Abstract

Background: Ticks are important vectors of zoonotic pathogens, with Ixodes ricinus being the most abundant and main vector in Europe of Borrelia burgdorferi sensu lato (s.l.), the causative agent of Lyme borreliosis. Both vector and reservoir hosts are dependent on habitat structure, which is anthropogenically influenced by land use intensity. This study aimed to analyse the prevalence of B. burgdorferi s.l. and their genodiversity in ticks along a land use gradient in grassland and forest in Central Germany.

Methods: Ticks were collected from 25 grassland and 25 forest sites by using the flagging method and tested for Borrelia  spp. using real-time polymerase chain reaction. Positive samples were further analysed by using multi-locus sequence typing to identify the exact B. burgdorferi s.l. genospecies and sequence types. To analyse the prevalence of Borrelia and the density of I. ricinus, confidence intervals, generalized linear mixed models, linear models, generalized linear models (Tweedie distribution), model selection (delta Akaike information criterion corrected for small sample size < 2), relative abundance index and the Shannon index were used.

Results: In total, 210 of the 1896 ticks collected tested positive for Borrelia (11.08%). The prevalence in I. ricinus ticks was identical in females (48/156; 30.77%) and males (44/143; 30.77%) and lower in nymphs (118/1152; 10.24%). Ixodes ricinus collected from grassland were significantly more frequently infected (29.36%) than those from woodland (6.43%). A positive correlation between land use intensity and the infection rate of ticks with B. burgdorferi s.l. was found in both grassland and woodland. Furthermore, the relative abundance index of predatory and small mammals had a positive effect on Borrelia spp. prevalence in I. ricinus nymphs. Multilocus sequence typing was performed for 184 samples. The most frequently found genospecies was Borrelia afzelii (65.76%), followed by Borrelia garinii (17.93%), Borrelia valaisiana (13.59%), and Borrelia burgdorferi sensu stricto (2.72%). Furthermore, 59 known and 41 new sequence types were detected.

Conclusions: Borrelia burgdorferi s.l. genotypes with zoonotic potential show variable host adaptation, which seems to promote high intraspecific pathogen diversity. The results of our study support the dilution hypothesis as they show that conserving native forests and species diversity may support the biodiversity of Borrelia spp. while reducing their overall prevalence.