D3399: Modeling microbial influences on transmission

Microbial influences on tick population dynamics and transmission of pathogens are of increasing interest, but generally we do not yet completely understand the interactions. Modeling is a valuable way to explore potential outcomes of different interactions and assess the overall effect on transmission. We are developing an individual based model of Ixodes scapularis and the interactions with Borrelia burgdorferi and Rickettsia buchneri. These two microbes, while both bacteria, differ in their transmission (horizontal vs. vertical) and their potential influence on tick biology. The model is partially based on an IBM of Rhipicephalus sanguineus tracking individual ticks through life stages and generating population dynamics in a residence. Infection with each bacteria will be added, and the microbes will affect many aspects of tick biology. Interactions between the microbes will be considered, such as R. buchneri affecting the probability of transmission of B. burgdorferi to or from white-footed mice. The model will be initiated with overwintering populations of I. scapularis, some of which are infected with the microbes, and will follow their activities through the summer transmission season. Output will be ticks of different stages in the fall and their infection levels. The number of B. burgdorferi infected questing nymphs will be tracked through the season, as this is the primary risk factor for transmission to humans. Model development and preliminary results will be discussed.