Of ticks, mice and men - shaping the ecology of tick-borne pathogens in Baden-Württemberg

Ticks cause more vector-borne diseases than any other blood-feeding arthropod in Europe; and their abundance is increasing. Influential US studies show that small mammals are key hosts regulating ticks and tick-borne pathogens (TBP), serving as blood meal hosts and TBP reservoirs. The relevance of these studies to Europe is, however, unknown. Therefore, my aim was the determination of the relative influence of small mammal hosts and environmental factors on the dynamics of ticks and TBPs in BW

Estimating Ixodes ricinus densities on the landscape scale

Background: The study describes the estimation of the spatial distribution of questing nymphal tick densities by investigating Ixodes ricinus in Southwest Germany as an example. The production of high-resolution maps of quest-ing tick densities is an important key to quantify the risk of tick-borne diseases. Previous I. ricinus maps were based on quantitative as well as semi-quantitative categorisations of the tick density observed at study sites with differ-ent vegetation types or indices, all compiled on local scales. Here, a quantitative approach on the landscape scale is introduced. Methods: During 2 years, 2013 and 2014, host-seeking ticks were collected each month at 25 sampling sites by flag-ging an area of 100 square meters. All tick stages were identified to species level to select nymphal ticks of I. ricinus, which were used to develop and calibrate Poisson regression models. The environmental variables height above sea level, temperature, relative humidity, saturation deficit and land cover classification were used as explanatory variables. Results: The number of flagged nymphal tick densities range from zero (mountain site) to more than 1,000 nymphs/100 m2. Calibrating the Poisson regression models with these nymphal densities results in an explained variance of 72 % and a prediction error of 110 nymphs/100 m2 in 2013. Generally, nymphal densities (maximum 37

Additional file 2. of Estimating Ixodes ricinus densities on the landscape scale

Poisson regression model with in-situ measurements. Table S1. Environmental variables observed at the 25 sampling sites. Sites specific environmental variables from in-situ measurements comprising temperature T in °C, relative humidity RH in %, saturation deficit SD in hPa as well as land cover classes A (agricultural land), B (broad-leaved forest), C (coniferous forest) and M (mixed forest) for 2013 and 2014. Table S2. Summary of regression models for 2013 and 2014 using in-situ variables. For each explanatory variable the regression coefficient b, the standard error SE, the z-value (test statistics) and the p-value (significance) are given. Note that land cover classifications A, B, C and M are categorical variables set to 0 (false) or 1 (true), from which class A was selected as default (b = 0). Figure S2. Observed vs. modelled Ixodes ricinus nymphs per 100 m2. Comparison of observed vs. modelled nymphal densities using in-situ measured explanatory variables for 2013 (left) and 2014 (right). The model performance is expressed by explained pseudo variances R p 2 and root mean square errors (RMSE)

Additional file 1: of Estimating Ixodes ricinus densities on the landscape scale

Figure S1. Ixodes ricinus nymphal ticks per 100 m2 for 2014. Map of the total number of nymphal ticks monthly flagged during 2014 and interpolated to the entire region of Baden-WĂźrttemberg, Germany. Sampling locations are marked by a circle showing both the observed (left half) and the modelled (right half) tick density

Additional file 3: of Estimating Ixodes ricinus densities on the landscape scale

Figure S3. Time series of monthly Ixodes ricinus nymphal ticks per 100 m2. Selected sites for land classes C, A, M and B