Modelling the ecological dynamics of tick borne pathogens in a risk assessment perspective

Abstract

Modelling the ecological dynamics of tick borne pathogens (TBP) must be based upon the integration of information from multiple disciplines. As an example, including genetic variability of Borrelia burgdorferi s.l., into next generation matrix models suggested that conclusions from previous approaches, based upon quantitative relationships among interacting ticks and hosts, should be reconsidered. Individual-based models, such as those based on networks, by taking into account the aggregation of ticks among hosts, show that the epidemic threshold (a critical value of transmission probability, under which the TBP eventually dies out) is lower than expected based upon other methods. In a similar approach, food web models can be used to evaluate the relative importance of vertebrates in supporting the persistence of the ticks and TBP. Models can be used in the main phases of risk assessment of expanding home range of TBP: release assessment from endemic areas (potential sources of hazards for other areas), dispersal of TBP to previously free areas (exposure assessment); consequence assessment in newly invaded areas. Surveillance of introduction, and of trends of TBP following the invasion of a new area, can benefit from modelling, by investigating the relationships between indicators, such as, for example, acarological risk, and prevalence of antibodies in sentinel animals.