Jason T. Hoverman

Per‐ and polyfluoroalkyl substances (PFAS) are environmental contaminants of growing concern due to their potential negative effects on wildlife and human health. Per‐ and polyfluoroalkyl substances have been shown to alter immune function in various taxa, which could influence the outcomes of host–parasite interactions. To date, studies have focused on the effects of PFAS on host susceptibility to parasites, but no studies have addressed the effects of PFAS on parasites. To address this knowledge gap, we independently manipulated exposure of larval northern leopard frogs ( Rana pipiens ) and parasites (flatworms) via their snail intermediate host to environmentally relevant PFAS concentrations and then conducted trials to assess host susceptibility to infection, parasite infectivity, and parasite longevity after emergence from the host. We found that PFAS exposure to only the host led to no significant change in parasite load, whereas exposure of parasites to a 10‐µg/L mixture of PFAS led to a significant reduction in parasite load in hosts that were not exposed to PFAS. We found that when both host and parasite were exposed to PFAS there was no difference in parasite load. In addition, we found significant differences in parasite longevity post emergence following exposure to PFAS. Although some PFAS‐exposed parasites had greater longevity, this did not necessarily translate into increased infection success, possibly because of impaired movement of the parasite. Our results indicate that exposure to PFAS can potentially impact host–parasite interactions. Environ Toxicol Chem 2024;00:1–10. © 2024 SETAC