Whirling Disease: Reviews and Current Topics

Laboratory Studies Indicating that Living Brown Trout Salmo trutta Expel Viable Myxobolus cerebralis Myxospores

R. Barry Nehring, Kevin G. Thompson, Karen A. Taurman and David L. Shuler

doi: https://doi.org/10.47886/9781888569377.ch12

ABSTRACT. In Colorado, Windy Gap Reservoir is a focus of Myxobolus cerebralis infectivity of greater intensity than may be explained by the potential contribution of M. cerebralis myxospores by dead fish. One mechanism that would help explain this situation is the expulsion of viable M. cerebralis myxospores by living infected fish. We conducted laboratory experiments to see if Tubifex tubifex, purged of infection by incubation at 26°C for a minimum of 30 d, could become reinfected by exposure to feces and wastes from aquaria containing M. cerebralis-infected brown trout Salmo trutta. In two separate experiments, replicate experimental units of T. tubifex were thoroughly infected in this manner. By comparison, evidence of infection in negative control replicates was much weaker in both experiments. It is possible that the purging process used to remove initial infection was not 100% effective, yet the differences between experimental and negative control replicates were dramatic. Positive control replicates, intentionally exposed to harvested myxospores of M. cerebralis, became heavily infected in both experiments. These results strongly support the hypothesis that brown trout are capable of expelling viable M. cerebralis myxospores.