Modelling the effects of tick-host interaction on pathogen dynamics: TBE as a case study

Tick-borne encephalitis (TBE) is an emerging vector-borne zoonosis reported in Europe with complex transmission routes that involve key vertebrate host species and a major tick vector. Understanding interactions between ticks and main hosts involved in TBE virus (TBEv) cycle is crucial to quantify TBEv emergence and spread. We used eco-epidemiological models to explore the dynamics of ticks and TBEv infection in relation to the density of two key hosts, deer and rodents. Both hosts may act as tick amplifiers, but at high densities may also dilute pathogen transmission. Results were validated with empirical data from selected foci in Italy and Slovakia. In addition, we explored the effect on TBEv dynamics when using various distributions to describe tick aggregation on rodents. We modelled the number of ticks per rodent observed in Trentino (Northern Italy) with different theoretical distributions. Power Law (PL) distribution better described the heterogeneity observed in our data. Using a stochastic model, we observed that TBEv infection is highly dependent on the capability of the implemented model to describe tick burden on rodents. We found that the epidemic threshold and equilibria obtained with PL distribution are a good approximation of those observed in simulations feed with empirical distribution.