Environmental determinants ofIxodes ricinusticks and the incidence ofBorrelia burgdorferisensu lato, the agent of Lyme borreliosis, in Scotland

Abstract

SUMMARYLyme borreliosis (LB) is the most common arthropod-borne disease of humans in the Northern hemisphere. In Europe, the causative agent,Borrelia burgdorferisensu lato complex, is principally vectored byIxodes ricinusticks. The aim of this study was to identify environmental factors influencing questingI. ricinusnymph abundance andB. burgdorferis.l. infection in questing nymphs using a large-scale survey across Scotland. Ticks, host dung and vegetation were surveyed at 25 woodland sites, and climatic variables from a Geographical Information System (GIS) were extracted for each site. A total of 2397 10 m2transect surveys were conducted and 13 250I. ricinusnymphs counted. Questing nymphs were assayed forB. burgdorferis.l. and the average infection prevalence was 5·6% (range 0·8–13·9%). More questing nymphs and higher incidence ofB. burgdorferis.l. infection were found in areas with higher deer abundance and in mixed/deciduous compared to coniferous forests, as well as weaker correlations with season, altitude, rainfall and ground vegetation. No correlation was found between nymph abundance and infection prevalence within the ranges encountered. An understanding of the environmental conditions associated with tick abundance and pathogen prevalence may be used to reduce risk of exposure and to predict future pathogen prevalence and distributions under environmental changes.