Strain-specific virulence of Perkinsus marinus and related species in Eastern oysters: A comprehensive analysis of immune responses and mortality.

In this study, we investigated the variability in virulence among different strains of Perkinsus marinus and other Perkinsus species in Eastern oysters (Crassostrea virginica), examining the immune responses and mortality rates of oysters exposed to different Perkinsus isolates. Compared with the other assessed strains, P. marinus strain ATCC 50787 was found to induce significantly (P < 0.05) higher levels of reactive oxygen species, nitric oxide, and necrosis in oyster hemocytes. Perkinsus chesapeaki (ATCC PRA-65) elicited strong immune responses and high mortality in Eastern oysters at rates similar to those induced by the most virulent P. marinus strain. In contrast, P. olseni and P. honshuensis induced low levels of immune response and mortality. In vivo survival assays confirmed that strains inducing high immune responses in vitro also caused high mortalities in oysters. Our findings in this study highlight the importance of considering strain-specific virulence when studying Perkinsus infections in oysters. These findings have implications for understanding host-parasite interactions and managing Perkinsus-related diseases in oyster populations, particularly from the perspectives of aquaculture and conservation.