Global One Health Fellow Spotlight – Ashley Cave

What do you research?

I investigate exposures to a highly bioaccumulative and toxic class of chemicals called per- and polyfluoroalkyl substances (PFAS) in wildlife and domestic species. PFAS represent a large and complex group of thousands of man-made chemicals used worldwide in a broad range of consumer products, construction, and industrial processes for over 50 years. The broad use of these chemicals for over half a century has caused most people (and their household pets) to be exposed, typically through drinking water and food. The persistent nature of PFAS in the environment has earned them the name, ‘forever chemicals,’ and they continue to be detected in samples collected from humans, domestic animals, and wildlife across the globe. Working with an interdisciplinary team of clinical and basic science researchers from various specialties and areas of expertise, our research focuses on assessing differences in PFAS exposure in marine, aquatic, and domestic animal populations and investigating the pathologic and clinical consequences of these exposures.

In our initial investigation into PFAS contamination in marine mammals, we compared PFAS exposure in Galápagos (Zalophus wollebaeki; GSL) and California (Zalophus californianus; CSL) sea lions. We hypothesized that CSL would have higher PFAS exposure than GSL due to historic pollution in their environment. We also investigated differences in PFAS exposure between sea lion rookeries in the Galápagos archipelago. Several common PFAS and summed serum PFAS concentrations were significantly higher in CSL than in GSL. Some PFAS were also significantly higher on uninhabited than inhabited islands, suggesting that these chemicals may be being brought into the Galápagos from other regions. This work emphasized the necessity for PFAS surveillance and research into its health effects on wildlife. CSL also has one of the highest incidences of cancer among marine mammals, and we are interested to see if elevated PFAS exposure may play a role in this. You can read our work here!

In addition to quantifying PFAS levels in pinnipeds in the Pacific, we are currently bringing this work closer to home by investigating exposures in marine and aquatic mammals right here in North Carolina! We are also investigating the potential health consequences of PFAS exposure in domestic dogs. Turning to domestic dogs not only alerts us to potential threats to man’s best friend, but can also help us understand risks to wild caniforms (like the sea lion) and humans that share very similar exposures with their four-legged roommates. 

What are the implications of your research, and how does it fit into the One Health framework?

Our research is deeply rooted in Global One Health principles and incorporates each branch of the One Health triad: environmental, human, and animal health. We are most directly investigating animal health by looking at PFAS exposure levels associated with health impacts for marine, aquatic, and domestic mammals exposed to these contaminants. Environmental health is just as integral to the project. We are comparing sea lions in the mostly pristine waters of the Galápagos to sea lions in the notoriously polluted waters of California. We are also comparing PFAS contamination in marine and aquatic mammals in regions of North Carolina with documented PFAS contamination to regions where PFAS is not typically found. And finally, we are documenting potential PFAS contamination in our own homes by investigating exposures in dogs. The fundamental hypothesis of each of our projects is that the health of the environment and the pollution present in different regions will affect the health of the animals in that environment. Each of these species also serves as a sentinel for human exposure. Our work with the dogs is the clearest example of this, as dogs tend to drink water from the same sources as their owners and are thus exposed to similar levels of contaminants. Marine mammals also serve as excellent sentinel species and can demonstrate PFAS accumulation in a fish-eating mammal. This is particularly relevant for communities that rely on subsistence fishing. 

Our work has and will continue to highlight populations with elevated PFAS exposure and demonstrate the negative health consequences associated with this. We provide data to aid in the conversation about what we can do to limit the amount of man-made chemicals in the environment, and thus protect wildlife (including endangered species), pets, and humans alike.

What/who inspired you to pursue this field of study?

A variety of experiences and people have inspired me to investigate the impacts of anthropogenic exposures in animals. Starting way back at the beginning, growing up on a farm alongside a variety of pets, livestock, and wildlife initially sparked my curiosity and appreciation for animals and their health. Living in the middle of a cornfield, the use of herbicides, pesticides, and fertilizers was a common occurrence. My mom always had my brother and me stay inside while the crops were being sprayed because it could “make us sick,” and I always wondered what those sprays were doing to the animals that couldn’t come inside. 

When I got to college, I started researching impacts of the herbicide dicamba on rusty crayfish, as they can be exposed by runoff entering streams and creeks. I also had an internship at the Columbus Zoo and Aquarium investigating animal behavior. These experiences along with my time as a veterinary assistant solidified my desire to pursue a DVM/PhD where I would study wildlife, domestic animals, and the impacts of pollutant exposure.

It was not until I got to vet school that I realized exactly what that would look like. Meeting my mentors, Dr. Greg Lewbart and Dr. Matthew Breen, and learning about their research really focused my picture of what I wanted my career to be. I was fascinated by Dr. Lewbart’s work assessing the health of endangered and endemic wildlife in the Galápagos and by Dr. Breen’s work investigating cancer in California sea lions and emphasis on utilizing the domestic dog as a sentinel for natural exposures. Ever since, I have been working with both of these incredible mentors to develop projects where we investigate exposures and their health consequence in domestic and wild mammals.

What do you view as a critical global challenge in One Health, and how could your discipline contribute to addressing it?

I view the increased prevalence of non-communicable diseases (cancer, obesity, endocrine disorders, etc.) and its links to pollutant exposure as a critical challenge in One Health. The American Cancer Society has reported that cancer rates in young adults in the United States have increased in each generation since 1920. Elevated exposures to man-made chemicals are one of the many factors that may be contributing to this devastating increase. Many of these chemicals have been associated with cancer in wildlife and domestic animals as well. My ultimate career goal is to understand the scope of anthropogenic pollution in our environment and the negative effects that these chemicals are having on all species. 

Non-communicable diseases can show up decades after exposure to harmful chemicals in people, and thus literature investigating these impacts is limited. This is where the utilization of sentinel species can help. Dogs have been used as sentinel species for more than 50 years in a variety of studies. Shorter lifespans, similar exposures, and propensity to develop diseases observed in people make dogs particularly useful models in assessing environmental exposure to contaminants and the effects of such exposures. Our work documents exposures that naturally occur in domestic dogs and investigates associations with diseases these dogs may later develop. Results from this type of work serve as an early warning bell for the types of diseases we may see in humans with similar exposures decades down the line.

How has the Global One Health Fellowship helped shape your career trajectory?

This fellowship has opened my eyes to various disciplines that I had not previously realized incorporated One Health perspectives, let alone overlapped with my own field of study. In particular, natural disaster research, social sciences, medical geography, and synthetic biology are fields I did not know much about prior to interacting with the other fellows. I am now interested in incorporating these fields into my own work. A few ideas I am excited to pursue in the future include investigating exposures related to weather disasters and flooding events, thinking about social and economic consequences in addition to the health consequences of exposures, and thinking about ways that exposure testing could be made more accessible and affordable. 

What was your favorite part of the Global One Health Fellowship?

My favorite part of the Global One Health Fellowship has been connecting with the other fellows! It has been inspiring to see so many talented people researching fascinating topics in similar stages of their programs. It has also been surprising and enlightening to discover the ways that our fields – though very different from each other – overlap in so many ways. This has given me new perspectives on directions that I could pursue in my own research, hopefully collaborating with the fellows!

What are your next steps?

My immediate next step is continuing my research into the health effects of PFAS exposure! After I finish up my PhD, I will jump back into vet school for my final two years. I don’t know what life looks like after vet school just yet, but my goal is certainly to continue researching the impacts of exposure to anthropogenic chemicals in all species, likely in academia!