As plastic waste is entering aquatic ecosystems and breaking down via chemical and physical processes, microplastic ingestion is an increasing threat to water-dwelling species. In this experiment, 180 rainbow trout consumed diets containing nylon fibers, nylon particles, or no plastic. Half of each treatment group was dosed with infectious hematopoietic necrosis virus. Effects of virus exposure were analyzed via histopathological observation, mortality data, and shedding samples. Shedding data demonstrated that fish consuming no plastic had significantly higher shedding than plastic-dosed fish, especially nylon fibers (p = 0.017). However, histopathology and mortality data indicated no significant trends. We concluded that fish were exposed to an insufficient dosage of IHNV, preventing measurable effects on the shedding kinetics, mortality rates, and histopathology effects. This was supported by a lack of significant mortality (1.14%), few fish (15.91%) positive for viral shedding, and no significant difference in shedding on days 3 vs 5 (p > 0.05). Additionally, we concluded that plastic-consuming fish may have had an active immune response to the nylon in their diets, causing innate immune priming and enabling them to better fight against viral infection, supported by existing research demonstrating piscine immune gene activation when exposed to microplastics. Our conclusions demonstrate that microplastic ingestion prior to exposure to the IHNV pathogen could potentially decrease the spread and severity of infection due to immune system priming. Further research evaluating different virus dosages and exploration of active immune response genes at different time points before and after plastic dosage and viral exposure.
Author(s): Katie R. Gabe, Andrew R. Wargo, Hannah N. Brown
Advisor(s): Michael J. Vanni, Department of Biology
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