Using Force-of-Infection Models to Develop a Fish Health Indicator for Chesapeake Bay Striped Bass

Mycobacteriosis is a chronic bacterial disease characterized by visceral granulomatous inflammation that can progress to severe dermal ulceration and emaciation. In Chesapeake Bay, a mycobacterial epizootic has persisted in the Striped Bass (Morone saxatilis) population for over a decade, raising concerns over the economic and ecological impacts of disease on a valuable species. The purpose of this study is to develop an indicator of striped bass health that may be useful for fisheries and water quality managers by using epidemiological models to estimate mortality associated with mycobacterial disease. The epidemiological model used is a force-of infection model; it uses age-structured data on apparent prevalence to estimate the disease-associated mortality and force of infection (the rate at which susceptible individuals acquire an infectious disease).The model will also help to provide an explanation as to the cause of the increased prevalence of mycobacteriosis in striped bass by incorporating environmental covariates (e.g, water quality, nutrition/body condition, population density). Including these covariates in the model will enable us to test for environmental factors contributing to the force-of-infection and mycobacteriosis-associated mortality. Correlations between mycobacteriosis-associated mortality and water quality may provide a direct quantitative link between Chesapeake Bay water quality and striped bass health and production.