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Forest management is increasingly focused on enhancing structural complexity. An increase in structural complexity is assumed to increase the abundance and diversity of fauna, including vertebrates. This faunal assemblage serves, in turn, as host community for a suite of vectors and their pathogens, so that structural complexity may cascade through a network of interactions in forest ecosystems. Here we use a network of 19 forest plots representing a gradient of structural complexity and dominant tree species (oak, beech, poplar) to test two hypotheses on the effect of structural complexity on the prevalence of tick-borne pathogens. Our first hypothesis is that tick densities will increase with increasing structural complexity, assuming that each life stage has higher chances of finding a suitable host. The second hypothesis is that the pathogen prevalence in ticks and small mammals decreases (cf. dilution hypothesis) or increases (cf. amplification hypothesis) with increasing structural complexity. These expectations are tested through a community-level analysis, looking at twelve pathogens: seven genospecies of Borrelia (B. afzelii, B. bavariensis, B. garinii, B. burgdorferi sensu stricto, B. spielmanii, B. valaisiana and B. miyamotoi) , Babesia s.s., Babesia microti, Anaplasma phagocytophilum, Rickettsia helvetica and Spiroplasma ixodetes. We found that more structurally complex forests have a higher density of questing nymphs (in June and July, during the peak of nymph activity). We did not find a clear change in pathogen prevalence with increasing structural complexity in ticks, wood mice and bank vole; the effect was different for the different pathogens and between the different dominant tree species. No clear co-occurrence patterns of pathogens were found. The density of infected nymphs and thus the disease risk is higher in more complex forests. A potential solution is to focus on decreasing the human-tick interactions in forests instead of trying to decrease the number of questing ticks. [Display omitted] • Forest management is progressively centering on increasing structural complexity. • Density of questing ticks is higher in more structural complex forests. • Pathogen prevalence does not change with increasing structural complexity. • Risk of tick-borne diseases is higher in more structural complex forests. [ABSTRACT FROM AUTHOR]

Ticks are becoming increasingly recognised as important vectors of pathogens in urban and peri-urban areas, including green space used for recreational activities. In the UK, the risk posed by ticks in such areas is largely unknown. In order to begin to assess the risk of ticks in urban/peri-urban areas in southern England, questing ticks were collected from five different habitat types (grassland, hedge, park, woodland and woodland edge) in a city during the spring, summer and autumn of 2013/2014 and screened for Borrelia burgdorferi sensu lato. In addition, seasonal differences in B. burgdorferi s.l. prevalence were also investigated at a single site during 2015. Ixodes ricinus presence and activity were significantly higher in woodland edge habitat and during spring surveys. DNA of Borrelia burgdorferi s.l. was detected in 18.1% of nymphs collected across the 25 sites during 2013 and 2014 and two nymphs also tested positive for the newly emerging tick-borne pathogen B. miyamotoi . Borrelia burgdorferi s.l. prevalence at a single site surveyed in 2015 were found to be significantly higher during spring and summer than in autumn, with B. garinii and B. valaisiana most commonly detected. These data indicate that a range of habitats within an urban area in southern England support ticks and that urban Borrelia transmission cycles may exist in some of the urban green spaces included in this study. Sites surveyed were frequently used by humans for recreational activities, providing opportunity for exposure to Borrelia infected ticks in an urban/peri-urban space that might not be typically associated with tick-borne disease transmission. [ABSTRACT FROM AUTHOR]

Human granulocytic anaplasmosis and tick-borne fever, affecting livestock, are diseases caused by an infection with the bacterium Anaplasma phagocytophilum. Its transmission dynamics between vertebrate hosts and ticks remain largely unknown and the potential impact on public health in the United Kingdom is unclear. This study aimed to assess the distribution and estimate the prevalence of A. phagocytophilum in questing Ixodes ricinus at recreational locations across England and Wales over six years. An additional objective was to investigate possible associations between prevalence, habitat and presence of ruminant hosts. Ixodes ricinus ticks were collected each spring at 20 recreational locations across England and Wales between 2014 and 2019. Nymphs were tested for infection with A. phagocytophilum by detection of bacterial genome in DNA extracts, targeting the msp2 gene locus. Positive samples were further investigated for the presence of different ecotypes based on the G roEL region. Of 3,919 nymphs tested, the mean infection prevalence was 3.6% [95%CI: 3.1-4.3] and ranged from 0 to 20.4%. Northern England had a higher overall prevalence (4.7% [95%CI: 3.4-6.4]) compared to Southern England (1.8% [95%CI: 1.3-2.5]) and the presence of sheep was associated with higher A. phagocytophilum prevalence (8.4% [95%CI: 6.9-10.1] vs 1.2% [95%CI: 0.8-1.7] when absent). There was also a negative correlation with the prevalence of Borrelia burgdorferi s.l. (causing Lyme borreliosis). When investigating the diversity of A. phagocytophilum , ecotype I accounted for 86.8% of samples and ecotype II for 13.2%. Our study presents an overview of A. phagocytophilum prevalence in questing I. ricinus in recreational areas across England and Wales and discusses the potential public and veterinary health relevance. [ABSTRACT FROM AUTHOR]