Warming lakes and rivers may spread fish pathogens.

This article focuses on research investigating the spread of the fish parasite Tetracapsuloides bryosalmonae in the Great Lakes region as warming waters potentially facilitate its reproduction. Led by an assistant professor at Michigan State University, the Fish Pathobiology and Immunology Laboratory (FPIL) has detected this myxozoan parasite—an “Emergency Pathogen” known to cause proliferative kidney disease (PKD) in salmonid fish—in multiple Great Lakes and rivers. The parasite’s life cycle involves infection of bryozoans, microscopic aquatic invertebrates, which then release spores infecting fish; it cannot spread directly between fish. While no PKD-related fish mortality has yet been documented locally, the research aims to identify infected fish stocks and water bodies to guide fish stocking and to develop detection methods, including environmental DNA (eDNA) techniques, to monitor parasite presence and seasonal dynamics.