Mycobacterium avium ssp. paratuberculosis detection in animals, food, water and other sources or vehicles of human exposure: A scoping review of the existing evidence

Mycobacterium avium ssp. paratuberculosis is the etiologic agent of Johne’s disease in ruminants and is hypothesized to be an infectious cause of Crohn’s disease, as well as some other human diseases. Due to key knowledge gaps, the potential public health impact of M. paratuberculosis is unknown. This scoping review aims to identify and characterised the evidence on potential sources and vehicles of M. paratuberculosis exposure for humans to better understand how exposure is likely to occur. Evidence from 255 primary research papers is summarized; most examined the prevalence or concentration of M. paratuberculosis in animals (farmed domestic, pets and wildlife) (n=148), food for human consumption (62) (milk, dairy, meat, infant formula) or water (drinking and recreational) and the environment (farm, pasture and areas affected by runoff water) (20). The majority of this research has been published since 2000 (Figure- abstract). Nine case-control studies examining risk factors for Crohn’s disease highlighted significant associations with the consumption of processed meats and cheese, while direct contact with ruminants, high risk occupations (farmer, veterinarian), milk consumption and water source were factors not associated with the disease and/or M. paratuberculosis exposure status. Molecular epidemiology studies demonstrated strain-sharing between species. Produce and seafood were the only previously suggested sources of human exposure for which there was no supporting evidence identified in this scoping review. The results of this review indicate that ruminant populations from around the globe are infected with M. paratuberculosis and many non-ruminant species have also been found to carry or be infected with M. paratuberculosis. Several potential sources for human exposure to M. paratuberculosis were identified; however there remain important gaps in quantitative information on the prevalence and concentration of M. paratuberculosis in contaminated sources of exposure. This information is critical to understanding the risk of exposure, opportunities for risk mitigation interventions and modelling exposures to distill the importance of various sources of human exposure to M. paratuberculosis including direct contact with animals and the environment as well as consumption of contaminated foods and water. Results of this study may be used to prioritize future research and to support evidence-informed decision-making on the M. paratuberculosis issue.