Water bodies as interfaces and pathways for zoonotic and livestock pathogen transmission in Africa and Scotland

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Waterborne pathogens, such as Leptospira spp., Mycobacterium spp., E. coli and Campylobacter spp., are responsible for important diseases of human and livestock. Water can play an important epidemiological role by facilitating the spatial spread of disease between populations or herds through catchment-wide water flow, and/or by providing a transmission interface between animal species that act as reservoirs of infection and susceptible hosts (e.g. livestock to human transmission or wildlife to livestock transmission). Recent advances in DNA extraction protocols and quantitative molecular diagnostic assays have revolutionised the potential to address key questions, such as what types of freshwater habitats pose the greatest risk for transmission, what role do water courses play in disseminating waterborne pathogens across landscapes and how do temporal changes to water flows and physico-chemical characteristics of water sources influence the abundance of pathogens? In addition to improving our understanding of the epidemiology of waterborne pathogens within catchments, environmental sampling could form the basis of more effective surveillance strategies, as sampling of reservoir hosts can be challenging and expensive.This study will focus on two globally important waterborne pathogen genera, Leptospira spp. and Mycobacterium spp., using catchment wide sampling of water bodies from high risk settings to address key knowledge gaps in our epidemiological understanding. Leptospirosis and mycobacterial infections are key causes of livestock productivity loss and human disease. Leptospirosis is responsible for an estimated 1 million human cases and 60000 deaths annually and contact with water (occupational or recreational) is recognised as a significant risk factor, along with flooding1. Mycobacterium spp. such as M. bovis (responsible for bovine tuberculosis) and M. avium subsp. paratuberculosis (Map) (responsible for Johne's disease) are economically devastating livestock pathogens and potential public health threats2. Evidence is increasing of the role that water can play in the epidemiology of Mycobacterium spp. For example, wildlife-livestock transmission of M. bovis is more likely to occur at water sources, where animals aggregate and environmental conditions favour the survival of the pathogen3, and water course contamination with Map has been shown to be positively associated with distance down a catchment, rainfall and river flow rate4. Recent global reviews have emphasised the urgent need to improve our understanding of the role that environmental transmission plays in the epidemiology of these pathogens under different contexts1,2.