Waterborne, multi-host pathogens are responsible for important diseases of humans and livestock. Water sources play an important epidemiological role in the transmission of these pathogens 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).
Leptospira spp. and Mycobacteria spp. are two globally important genera of waterborne pathogens. Leptospirosis is responsible for an estimated 1 million human cases and 60000 deaths annually and occupational or recreational contact with water or flooding are recognised as significant risk factors for human and reservoir host infection infection1. Mycobacteria spp., particularly the nontuberculous mycobacteria (NTM), also survive for prolonged periods in aquatic environments, where they can survive disinfection2. Various NTM are increasingly recognised as important causes of opportunistic infections in humans2,3 and some, such as M. avium subsp. paratuberculosis (Map), are responsible for economically devastating livestock diseases, such as paratuberculosis (Johne’s disease)4. Despite their ability to survive for prolonged periods in the environment, both Leptospira spp. and Mycobacteria spp. are challenging to culture, resulting in a poor understanding of their epidemiology.
Recent advances in environmental DNA extraction protocols and quantitative molecular diagnostic assays have revolutionised our ability to detect and type these infections from environmental samples. These approaches allow us to address key questions related to the epidemiology of these pathogens, such as what types of freshwater habitats pose the greatest risk for transmission, what role do water courses play in disseminating these pathogens across landscapes and how do temporal changes to water flows and physico-chemical characteristics of water sources influence their abundance?
This project will draw on existing collaborations with projects in South Africa and Madagascar that cover a variety of contexts from urban to rural environments and can provide important background information on infection prevalence amongst potential animal reservoirs and exposure risk in humans/livestock. Using hierarchical models that account for uncertainty in detection at all stages of the sampling process (from the field to the lab), critical knowledge gaps related to the epidemiology and control of Leptospira spp. and Mycobacteria spp. will be addressed. These include: (i) the relative importance of wildlife or livestock hosts in driving the environmental contamination of water resources associated with human-wildlife-livestock aggregation and transmission; (ii) how known differences in the ability of different Leptospira and Mycobacteria spp. to survive in the environment impact on levels of environmental contamination; (iii) the extent to which freshwater habitats facilitate transmission of Leptospira spp. and Mycobacterium spp. across the human-wildlife-livestock interface and (iv) how environmental contamination is influenced by upstream land-use and the abundance of animal reservoirs.
Leptospirosis and paratuberculosis are also economically important causes of livestock productivity loss in Scotland, where routine herd surveillance is undertaken as part of cattle health schemes. Therefore, the student will also engage with local stakeholders and utilise the approaches developed on existing samples from Africa to address key questions related to the role of water in the transmission of these pathogens in Scotland. By contrasting results for the same pathogens from both developed and developing country settings, unique insights will be generated into how setting-specific differences in climate, reservoir host diversity and water utilisation drive transmission of these important pathogens.
Ultimately, this project will deliver new insight into the epidemiology of these diseases that will inform future strategies for surveillance and mitigating risk in Africa and elsewhere. The project will show-case the value of a multi-disciplinary “One Health” approach which recognises that the health of humans, animals and their environments are inter-connected. The project would suit a student with a background in molecular ecology or epidemiology and numerical skills, who has interests in spatial epidemiology, disease ecology and landscape genetics. The supervisory team is diverse and includes ecologists, a veterinary surgeon and a medical clinician allowing the student to draw on a wide range of expertise. The student will be given a thorough training in laboratory skills, the analysis of genomic and genetic data and advanced statistical modelling and there will be opportunity for the student’s interests to drive the evolution of the project.
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