Modelling spread of bacteria between farm animals to assess the effect of new control measures

Despite ongoing control efforts, Salmonella spp. and Campylobacter spp. are still common causes of bacterial zoonosis. As poultry is most likely an important reservoir for both pathogens, new approaches for eradicating these bacteria from flocks and farms could make an important contribution to limiting the disease burden in humans. To develop new control strategies, a better quantitative understanding is needed of how infections are introduced into farms and spread within and between flocks. As a tool to quantify this transmission and to assess biosecurity strategies, we here aim to develop mechanistic epidemiological models that describe transmission based on mechanisms for how bacteria are displaced in the environment during the period they survive. A model that can portray spatial spread of bacteria through the environment incorporating diffusion of contaminated material has been used previously to describe experimental observations on transmission of bacteria between spatially separated animals. In order to further validate this model, possible effects of dynamic host properties on the outcome of the experiments need to be considered. To elucidate the relevance of factors such as acute stress or the aging process, a model extended with these properties will be constructed and applied to tailored new transmission experiments. The main goal of the PhD is to develop tools that can describe mechanisms underlying indirect transmission in the simplest possible way and that at the same time are sufficiently complex to assess the effectivity of new biosecurity strategies to reduce infection prevalence in flocks.