Decoding the Geography of Natural TBEV Microfoci in Germany: A Geostatistical Approach Based on Land-Use Patterns and Climatological Conditions

Abstract

Tickborne-encephalitis (TBE) is a potentially life-threating neurological disease that is mainly transmitted by ticks. The goal of the present study is to analyze the potential uniform environmental patterns of the identified TBEV microfoci in Germany. The results are used to calculate probabilities for the present distribution of TBEV microfoci in Germany based on a geostatistical model. Methods: We aim to consider the specification of environmental characteristics of locations of TBEV microfoci detected in Germany using open access epidemiological, geographical and climatological data sources. We use a two-step geostatistical approach, where in a first step, the characteristics of a broad set of environmental variables between the 56 TBEV microfoci and a control or comparator set of 3575 sampling points covering Germany are compared using Fisher’s Exact Test. In the second step, we select the most important variables, which are then used in a MaxEnt distribution model to calculate a high resolution (400 × 400 m) probability map for the presence of TBEV covering the entire area of Germany. Results: The findings from the MaxEnt prediction model indicate that multi annual actual evapotranspiration (27.0%) and multi annual hot days (22.5%) have the highest contribution to our model. These two variables are followed by four additional variables with a lower, but still important, explanatory influence: Land cover classes (19.6%), multi annual minimum air temperature (14.9%), multi annual sunshine duration (9.0%), and distance to coniferous and mixed forest border (7.0%). Conclusions: Our findings are based on defined TBEV microfoci with known histories of infection and the repeated confirmation of the virus in the last years, resulting in an in-depth high-resolution model/map of TBEV microfoci in Germany. Multi annual actual evapotranspiration (27%) and multi annual hot days (22.5%) have the most explanatory power in our model. The results may be used to tailor specific regional preventive measures and investigations.

Revealing the Tick Microbiome: Insights into Midgut and Salivary Gland Microbiota of Female Ixodes ricinus Ticks

“…In this study, these methods were omitted as our focus rested on the complete BC of ticks as encountered in the field. Moreover, environment-associated bacteria might allow conclusions on the tick’s location, especially concerning the geographical distribution of tick-borne pathogens [ 44 ]. In contrast, the environmental BC was problematic when analyzing low biomass samples (i.e., MG or SG samples) as the proportion of total bacterial DNA in these samples was already low and high amounts of environmental BC might be overamplified in the PCR steps.…”

Seroprevalence of Tick-Borne Encephalitis (TBE) Virus Antibodies in Wild Rodents from Two Natural TBE Foci in Bavaria, Germany

“…From this, we can infer that the virus cycle between juvenile ticks and rodents occurs in several small microfoci with an average size of about 0.5 to 1 ha forming a natural focus. From these microfoci, infected adult ticks passively migrate with the help of larger wild animals to other locations to form a new microfocus under adequate conditions, which would be, i.e., formed by the presence of vector and reservoir hosts, suitable climatic conditions for the vitality of I. ricinius and the presence of coniferous or mixed forests [ 11 ].…”

“…All subtypes of TBEV are maintained in complex natural endemic transmission cycles, so-called microfoci with an average size of about 0.5–1 ha [ 11 ], involving ticks as natural vectors. In Central Europe, Ixodes ricinus ticks are the main vectors transmitting the European subtype to naïve hosts through blood meals after becoming infected with TBEV when feeding on a viremic host or co-feeding with an infected tick in close proximity to a non-viremic host [ 2 , 12 , 13 ].…”

First Expert Elicitation of Knowledge on Possible Drivers of Observed Increasing Human Cases of Tick-Borne Encephalitis in Europe

“…The microclimatic temperature is another key driver of vector-borne disease transmission, as replication of arboviruses within the poikilothermic vectors is highly dependent on environmental temperature [ 59 , 60 ]. Indeed, the extrinsic incubation period and the blood meal digestion period are influenced by the temperature surrounding the vectors [ 60 , 61 , 62 ]. Additional microclimatic data are needed for a more accurate prediction of vector-borne diseases like TBE [ 61 ].…”

“…Indeed, the extrinsic incubation period and the blood meal digestion period are influenced by the temperature surrounding the vectors [ 60 , 61 , 62 ]. Additional microclimatic data are needed for a more accurate prediction of vector-borne diseases like TBE [ 61 ]. The impact of climate change on the risk of TBEV transmission is a question of interest.…”