Per/polyfluoroalkyl substances (PFAS) are contaminants of emerging concern. These globally spread chemicals are especially common in aquatic systems, presenting an ecological risk to the wildlife relying on those habitats. PFAS rapidly bioaccumulate in larval amphibians and studies increasingly demonstrate detrimental effects on larval growth and development. Additionally, it has been hypothesized that PFAS could impair the immune function of amphibians. Given that disease is one of the major contributors to global amphibian declines, PFAS have the potential to significantly alter host-pathogen interactions in this system. However, the effects of PFAS in conjunction with other natural stressors are unknown. We examined the effects of PFAS exposure on the interaction between larval Northern Leopard Frogs (Lithobates pipiens) and trematodes (Echinoparyphium spp.). Our focal PFAS were perfluoroocatane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS), which commonly occur at contaminated sites. Larvae were exposed to 10 ppb or 100 ppb concentrations of each PFAS for 10 days. Following the chemical exposure, the larvae were moved to fresh water and exposed individually to 50 trematodes to test their ability to resist infections.
Results/Conclusions
We found that exposure to PFAS significantly influenced trematode loads in Northern Leopard Frog larvae. However, the effects were dependent on the chemical and concentration. More specifically, larvae exposed to 10 ppb of PFHxS had 17.5% greater parasite loads relative to the control. However, exposure to 100 ppb of PFHxS did not alter parasite load compared to the control. We also found no effect on either concentration of PFOS on parasite loads in the larvae compared to the control. Although more work is needed to determine the mechanism, these findings suggest that PFHxS may have greater immunosuppressive effects on amphibian larvae than PFOS. The lack of a dose-response relationship for PFHxS is consistent with previous literature on endocrine disrupting chemicals including PFAS. Figure work examining a broader range of concentrations and parasite exposure levels is warranted. Collectively, our study calls attention to the potential effects of PFAS exposure on disease risk in natural systems.