The objective of this thesis was to assess the risk of exposure to Mycobacterium avium subsp. paratuberculosis (MAP) via milk and milk products for the Slovenian consumer. MAP is suspected to be linked to Crohn’s disease and some other chronic human diseases. Although causality has not yet been confirmed, it is important to improve the understanding of the risk of human exposure. Cattle are believed to be the main source of MAP for humans. In cattle, MAP causes paratuberculosis or Johne’s disease, a worldwide endemic disease with large economic consequences. Due to the lack of empirical data, we applied two models as tools for obtaining data on the epidemiological situation of MAP, specific for the Slovenian dairy sector. A stochastic compartmental model was developed to study the within-herd spread of MAP in a typical Slovenian dairy herd and a susceptible-infectious model on the temporal network of cattle movements to estimate the prevalence of MAP using four different scenarios for probabilities of transmission. The obtained results were used in the quantitative risk assessment model with Monte Carlo simulations to assess possible human exposure to MAP via milk and milk products. Additionally, network analysis of Slovenian cattle movements was performed to estimate the prospect of targeted MAP intervention measures. The results suggest that network analysis may provide support in the optimization of paratuberculosis control in Slovenia. The compartmental model showed a similar within-herd prevalence of MAP in Slovenia as was previously estimated, which was opposite to what we hypothesized. Concerning the underlying assumptions and uncertainties, we estimated that the overall risk of exposure to MAP via milk and milk products for the Slovenian consumer is low. The quantitative exposure assessment was performed for raw milk, pasteurised whole milk and ultra-high temperature treated milk; nevertheless, we believe that the results can be extended, at least in part, to other milk products at the respective level of production. For people consuming raw milk and raw milk products from farms with paratuberculosis, the risk of exposure to MAP is high. However, the simulated amount of MAP per litre of raw bulk tank milk was low. It is important to emphasise that the risk of exposure to MAP via pasteurised retail milk and via other processed milk is most likely insignificant. Our results could provide support for informed decision-making in MAP intervention measures in Slovenia and in case the link between MAP and human diseases is confirmed also as a start for possible risk mitigation efforts. These results could be applicable to other countries with a similar dairy farm structure.
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