What’s in the Water? Sampling for Waterborne Amoeba in Northern Orange County Ponds
On an overcast October morning, researcher and faculty member, Joe Brown, PhD, and second-year Master of Science in Environmental Engineering student, Frederik Mendoza Ulken, load their water sampling equipment in a minivan and start a 35-minute trek from the Gillings School to northern Orange County.
Along the way, Brown and Mendoza Ulken discuss the fieldwork they’ll be doing and the importance of understanding more about Naegleria fowleri (often referred to as N. fowleri), a thermophilic free-living amoeba that causes Primary Amoebic Meningoencephalitis (PAM).
Though rare, 167 PAM cases were reported in the United States between 1962 and 2024, they were almost always fatal, as only four of those individuals survived (Center for Disease Control).
Brown and Mendoza Ulken share tragic stories about families who have been personally affected by this brain-eating amoeba, including a six-year-old boy named Aven. Since his tragic passing in 2021, Aven’s family established a nonprofit, Amazing Aven’s Quest for Amoeba Awareness, that is working to better understand and prevent cases of PAM.
Details about how to predict where N. fowleri exists are difficult, but Brown is hopeful that days like this can shed more light on how, why and where this microscopic amoeba lives. “If we can identify factors that seem to drive high counts of Naegleria in water, and therefore potential for infection, that could be used in prevention efforts.”
The minivan turns off a winding rural highway and onto a gravel road. Shortly, Brown creates his own path and veers off the gravel road and into a grassy field, eventually parking between two ponds.
Up the hill from these ponds is Maple Springs Farm, an organic farm that’s grown and sold a variety of fruits and vegetables for decades.
Once parked, Brown and Mendoza Ulken jump into action. They quickly assemble their sampling equipment. Today, they are using a Smith-Root eDNA sampler. This sampler was chosen because it has some key features that could help with the researchers’ prototype development.
Once they get sufficient samples from the first pond, they move on to the larger pond.
The second pond has a wooden boardwalk, which jets out 20-feet over the water, and for decades has been a jumping off point for tired Maple Springs farmers looking to cool off after a grueling day in the Piedmont heat. And therein lies the most common scenario of N. fowleri exposure – a high-risk (think cannonball) entry into a warm, freshwater lake, pond or river.
These bodies of water can warm significantly in the summer, reaching the high temperatures where N. fowleri thrive. They also contain nutrients and bacteria that N. fowleri feed on. So, these ponds are consistent with what Brown understands from N. fowleri ecology that would be suitable habitat for the organism. These two ponds therefore represent excellent sites to both test their field sampling methods as well as better understand how N. fowleri varies in space and time.
The researchers’ near-term goal for this project is to establish a simple, field-deployable, same-day testing strategy to identify N. fowleri in recreational waters.
Ideally, this would be in the form of a kit that could be used by anyone, including government, nonprofits, other academics and the public.
Their current water sampling program is focused on refining their methods - improving detection and time-to-result and understanding how to make the process more user-friendly and cost-effective. These are difficult problems to solve: finding N. fowleri in a pond requires sampling a large amount of turbid water, that is filled with non-target organisms. It's a needle in a haystack problem, requiring sophisticated methods for sampling, processing and analysis.
The researchers are looking to transcend these challenges and develop something that is both simple and robust.
Longer term, they hope to roll out sampling to gather data on when and where N. fowleri occurs, with the goal of advancing their understanding of N. fowleri ecology.
Brown and Mendoza Ulken hop into the minivan and drive past more gently sloping farmland before arriving at the final test site.
These sampling trips are intended to help the researchers ground-truth in their sampling and analysis strategies, as they develop prototypes and refine methods.
As they pack their equipment back in the van, Mendoza Ulken reflects on the day’s work and what lies ahead, “After today’s field sampling, we’ll return to the lab to apply our new findings and improve our monitoring methods. Eventually, we will return to the field to repeat this cycle, perfecting our methods with each iteration. Once we have an optimized technique, we can start collecting large amounts of field data to inform models of how N. fowleri is distributed in the environment.”
Commenting on the work on the drive back to campus, Brown says, “It’s a slow, iterative process but one we hope can lead to a fit for purpose, deployable method. This project will have been a good investment if it results in even one life saved.”
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