No abstract

BackgroundThe 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 questing 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 different vegetation types or indices, all compiled on local scales. Here, a quantitative approach on the landscape scale is introduced.MethodsDuring 2 years, 2013 and 2014, host-seeking ticks were collected each month at 25 sampling sites by flagging 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.ResultsThe 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 374 nymphs/100 m2), explained variance (46 %) and prediction error (61 nymphs/100 m2) were lower in 2014. The models were used to compile high-resolution maps with 0.5 km2 grid size for the study region of the German federal state Baden-Württemberg. The accuracy of the mapped tick densities was investigated by leave-one-out cross-validation resulting in root-mean-square-errors of 227 nymphs/100 m2 for 2013 and 104 nymphs/100 m2 for 2014.ConclusionsThe methodology introduced here may be applied to further tick species or extended to other study regions. Finally, the study is a first step towards the spatial estimation of tick-borne diseases in Central Europe.Electronic supplementary materialThe online version of this article (doi:10.1186/s12942-015-0015-7) contains supplementary material, which is available to authorized users.

No abstract

Since the publication of "An annotated checklist of the ticks of Germany" in 2012, the list now includes two additional ixodid species. Ixodes acuminatus is endemic in several countries bordering Germany. Sufficient specimens have now been found in southwestern Germany to show that this species is also native there. The other species, Ixodes inopinatus, has its main area of distribution in the western Mediterranean, and it is not yet clear whether the two females and one male found in Rhineland-Palatinate were accidental introductions or are part of a viable population. Although it is only two years since our checklist of the ticks of Germany was published (Petney et al. 2012), two species have now been recorded that were not identified previously in this country; one is already known for other Central European countries, while the other is newly described (Estrada-Peña et al. 2014). Ixodes acuminatus Neumann, 1901 There is some debate about whether the eastern Palearctic species Ixodes redikorzevi Olenev, 1927, is a synonym of I. acuminatus. Along with Guglielmone et al. (2014) we consider that this is not the case until a comparison of types has been carried out. However, should the synonymy be confirmed, then the range of this species would be extended to include parts of Eastern Europe, China, the eastern Mediterranean and the Middle East. Small mammals hosted numerous larvae and nymphs of this species over three years of collection so that I. acuminatus is now confirmed as endemic to Germany.

A healthy ecosystem is sustainable, meaning that it has the ability to maintain its structure and functions over time. Past definitions concerning the health of an ecosystem included, among others, both the diversity and complexity of the system, meaning that a healthy ecosystem is a diverse one. In the last decade, researchers have started to focus more on the importance of biodiversity for the distribution and maintenance of diseases in ecosystems, and therefore the ecosystems' role for human health. Based on a vector-borne model of Lyme disease, it was claimed that with a higher biodiversity of non-reservoir hosts for a pathogen, transmission events and infection risk would become reduced, called the dilution effect. This was further adapted for other vector-borne and nonvector-borne diseases, providing evidence for both the absence and the presence of the dilution effect in the wild. Until now, there is still a large lack of knowledge about the mechanisms driving disease transmission in the wild. The aim of this review is to provide insight into disease systems that were studied in relation to biodiversity and disease transmission risk. Furthermore, we discuss methods and strategies which are necessary to improve our understanding of the impact of biodiversity on disease systems and to help fill the existing gaps in our current knowledge.

Ticks and tick-borne diseases are of great significance for the health of humans and animals. However, the factors influencing their distribution and dynamics are inadequately known. In a project financed by the Baden-Württemberg Ministry of the Environment, Climate and Energy Industry, as part of the program BWPLUS, interdisciplinary specialists work together to determine the influence of weather, (micro)climate, habitat, land use, human activities, and the population dynamics of host animals on the distribution and abundance of ticks and the diseases that they transmit in Baden-Württemberg. The project comprises four modules: the large-scale distribution of ticks in Baden-Württemberg (module 1), detailed studies of host-tick-pathogen interaction in relation to the microclimate (module 2), and the spatial occurrence of important tick-borne pathogens (module 3). The fourth module involves the comprehensive analysis and synthesis of all data in order to determine the relative importance of the factors studied and to develop a risk model. Recently, intensive investigations into tick control have been undertaken using various entomopathogenic fungi and nematodes as well as a parasitoid wasp. Our aim was to determine whether these natural enemies could be used to effectively reduce the number of free-living ticks.