Sand lizards (Lacerta agilis) decrease nymphal infection prevalence for tick-borne pathogens Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in a coastal dune ecosystem

<p>1. Understanding which factors determine tick-borne disease hazard can contribute to effective disease control. In Europe, the hazard of the pathogens <em>Borrelia burgdorferi</em> s.l. and <em>Anaplasma phagocytophilum</em> is determined by local tick densities (mainly <em>Ixodes ricinus</em>) and the reservoir competence of the host species community. Sand lizards (<em>Lacerta agilis</em>) are common hosts for larvae and nymphs of <em>I. ricinus</em> and non-competent reservoirs for both pathogens. Consequently, high relative abundance of <em>L. agilis</em> is hypothesized to be associated with lower infection prevalence in nymphs. Here, we aimed to test whether this effectively occurs in natural settings.</p> <p>2. We sampled different habitat types within a heterogenous dune landscape at the Dutch coast and estimated 1) <em>L. agilis</em> densities, 2) host community competence, 3) the density and infection prevalence of questing<em> I. ricinus</em> ticks, and 4) the number and infection prevalence of ticks feeding on <em>L. agilis</em>.</p> <p>3. Captured <em>L. agilis</em> had high tick burdens and contributed substantially to feeding <em>I. ricinus</em> larvae in their natural habitat. <em>B. burgdorferi</em> s.l. and <em>A. phagocytophilum</em> were virtually absent from feeding larvae and nymphs.</p> <p>4. The nymphal infection prevalence of both pathogens in questing ticks was lower in habitat types where <em>L. agilis</em> was more abundant. Hence, <em>L. agilis</em> strongly reduced community competence.</p> <p>5. The density of questing nymphs was higher in habitat types with denser vegetation and also varied more between habitat types than infection prevalence. As a result, nymphal density had a stronger effect on the density of infected ticks than did nymphal infection prevalence.</p> <p>6. Synthesis and applications. Coastal dune habitats favourable for <em>L. agilis</em> have lower densities of questing nymphs, and a lower human infection hazard. These results might be applicable to similar ecosystems where <em>L. agilis</em> is present. From a public health perspective, this underlines the importance of preserving early successional habitat, as encroaching shrubs are associated with higher tick-borne disease hazard, and vegetation removal might be a solution to reduce hazard in coastal dunes. The high degree of spatial heterogeneity in the abundance of tick-borne pathogens also poses opportunities to manage recreational activities to limit human exposure to tick-borne diseases.</p>