Coprophagous Flies: A Novel Approach for Fecal Source Tracking in Terrestrial Environments

Sanitation services bring health and economic benefits to communities. Yet, regions remain where sanitation infrastructure is inadequate. This may cause feces to spread into the environment. When people are exposed to feces that contains pathogens, they may become sick with diarrheal disease. Globally, diarrhea causes 450,000 deaths among children under five each year. The goal of this project is to develop new methods to identify hotspots of contamination using coprophagous flies (i.e., flies that eat feces). This goal will be achieved by tracking microbes and genes carried by coprophagous flies during experiments conducted in the lab and in the field. Successful completion of this research will potentially transform our ability to use flies as remote samplers of feces in the environment. The data generated may enable public health departments and other stakeholders to better allocate resources to communities with inadequate sanitation. Further benefits to society include the training of undergraduate and graduate students at the interface of engineering, public health, and biology to better address complex health issues. Quantifying environmental fecal contamination typically employs culture-dependent or culture-independent assays for fecal indicator bacteria. Government agencies and public health departments almost exclusively apply these methods to surface waters as required by regulations. However, analogous methods are needed to characterize fecal contamination in terrestrial environments. One potential solution is the use of coprophagous flies that feed on fecal waste in the environment acting as composite samplers. This research project is based on the hypothesis that coprophagous flies may act as composite samplers of localized environmental fecal contamination by repeatedly feeding on uncontained wastes. Specific objectives to test this hypothesis are to: (i) Determine ingestion and persistence of fecal indicators in coprophagous flies under a range of environmental conditions; (ii) Quantify fecal indicators in wild caught coprophagous flies from communities with and without adequate sanitation; and (iii) Identify drivers of localized terrestrial fecal contamination in flies. Laboratory feeding studies include the testing of fecal waste transport by flies under controlled conditions (i.e., time, temperature, humidity). Field-based studies will focus on fly collection and analysis of genetic and microbe targets, with modelling to elucidate underlying mechanisms of localized fecal loading to the environment. The new data generated will advance our understanding of coprophagous flies as composite samplers and develop a novel approach to identify terrestrial fecal contamination hotspots that could be prioritized for improved engineering controls. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.