The disease ecology of urban litter – solid waste management and vector-borne diseases in Malawi

Overview

Discarded plastic waste in the peri-urban environment is a serious challenge for sustainable waste management and for the delivery of environmental and public health. In many cities in sub-Saharan Africa, plastic wastes block urban drainage systems, and during rain events this often leads to localised flooding, with an increased risk of exposure to raw sewage in standing water. Importantly, urban plastic litter can act as a transient receptacle for rainwater and thus provide a larval habitat for mosquitoes. Although the role of plastic pollution on mosquito ecology is poorly understood, this increased abundance of mosquito habitat in the peri-urban environment can lead to increased vector density and the incidence of vector-borne diseases such as malaria, Zika, dengue and lymphatic filariasis. Urban wastes can also be an attractant for flies, e.g. filth flies such as the house fly (Musca domestica), which can transfer enteric diseases such as dysentery, diarrhoea, typhoid and cholera, particularly if the waste has been in contact with a source of faecal contamination (e.g. following flooding or via scavenging by domestic or wild animals). Consequently, urban litter may also play an important role in the emergence of novel zoonotic diseases or genes for anti-microbial resistance. Therefore, quantifying whether plastic waste in the peri-urban environment is providing breeding sites for disease vectors, is important for addressing the Sustainability Development Goals (e.g. SDG3), and critical for incentivising policy-makers to provide resources to local communities for the removal of urban litter as part of a sustainable strategy to reduce disease burden and the risk of emerging infectious diseases.

The aim of this project is to uniquely link pathogen ecology with disease & waste management within a multidisciplinary framework and provide tangible evidence for an increased disease burden due to peri-urban plastic waste.

Key research questions:
Understanding the multidisciplinary interactions between sustainable disease management & sustainable waste management will be directly addressed through this studentship by focussing on the following questions:
1. Do different types of plastic litter preferentially attract mosquito oviposition, and can plastic litter facilitate disease transfer via flies?
2. Can a reduction in urban litter reduce pathogen and vector abundance (and disease burden)?
3. How do people interact with plastic litter and do they view it as a source of disease either through mosquitos or enteric diseases?
4. What are the socio-political obstacles for incentivising governments to remove peri-urban litter and increase sustainable waste disposal?

Methodology

Add details about the research methods that will be employed during the project, including fieldwork and placements. Add in details of any collaborations/advisors outside of IAPETUS2 in this section.

This interdisciplinary project will link environmental microbiology, waste management and disease ecology with sustainable development, public health and medical anthropology. The project will adopt methods and theories from both the natural & social sciences and will employ both qualitative & participatory approaches with a significant level of engagement with local communities. Field work will be carried out in Malawi and will focus on the peri-urban landscape of Blantyre. During two field seasons in Africa (each trip lasting between 4-5 months) the student will use a combined field and lab approach to (i) quantify the extent to which standing water associated with plastic waste supports populations of mosquitoes (identified by both molecular approaches and identification of larval stage); (ii) conduct a series of controlled laboratory ‘choice experiments’ to determine if mosquitoes preferentially oviposit in different types (e.g. polyethylene, polyethylene terephthalate, polystyrene), colours or sizes of typical plastic wastes in the urban environment, together with an assessment of the associated larval survival; and (iii) determine the potential for flies to spread disease from different categories of plastic litter. Spatial and statistical analysis will correlate mosquito/fly abundance with particular litter types, and this information will be used to develop a GIS-assisted landscape epidemiology model (created in the integrated ArcGIS platform), that will also incorporate data on community health, e.g. from clinical reports of malaria and diarrhoeal diseases. Peri-urban drainage systems & sanitation facilities will also be mapped, and the ‘blockage potential’ from rubbish and wastes quantified in terms of increased standing water. In addition, following rain events mosquito larvae will be identified in litter-associated standing water over the subsequent days. A participatory ethnographic approach, drawing on a combination of semi-structured interviews, focus group discussions and participant observation, will be used during fieldwork to understand how local rural communities interactive with waste, and perceive issues of plastic waste and the impact on human health, and how they might be incentivised to adopt strategies that decreases plastic waste in the community by a greater knowledge of how disease interacts with plastic waste disease burden.

Project Timeline

Year 1

Following a critical review of the literature (months: 0-4), the student will undertake a short ‘Problem-framing’ field mission to Blantyre to identify key stakeholders and begin the design of pilot experiments. Back in the UK, the student will attend a range of training courses plan and design (incl. ethics and risk assessments), the experiments for the next field mission

Year 2

During an extended fieldwork mission, the student will undertake an intensive series of field experiments complemented by laboratory mesocosm experiments to quantify the effects of plastic waste on vector dynamics.

Year 3

During the final field visit, in addition to completing ecological fieldwork, the student will also conduct surveys to understand the perception of plastic waste in the community, and organise and lead a workshop with local stakeholders to disseminate the finding from the whole project

Year 3.5

The student will co-develop a policy brief for governmental regulators and the remaining time will be spent writing up the thesis and papers for publication

Training
& Skills

The student will benefit from becoming part of the SPACES team. The SPACES project is a ca. £3.5 million GCRF project focused on understanding the impacts of plastic waste on human health in East and Southern Africa. This studentship will provide a platform to build an interdisciplinary research career in sustainable development and public health. Extensive skill development in field work will include comprehensive training in sampling & monitoring techniques, while the student will also benefit from working closely with experienced field researchers in Africa. The studentship will broaden the scope of the applicant’s skills base by providing specialist training in the identification of vectors and the safe handling of pathogenic microorganisms. The student will develop broad expertise in the environmental sciences, including microbiological techniques and GIS modelling methodologies, together with skills in the social and anthropological sciences & applied geography

References & further reading

University of Stirling ‘Environmental Sustainability and Human Health’ Research Group: https://eshh-stirling.com/

Further Information

For informal enquires: Prof Richard Quilliam (Richard.Quilliam@stir.ac.uk – tel: 01786 467769)

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