| Infectious salmon anemia (ISA) is caused by an Orthomyxovirus, phylogenetically related to influenza viruses and referred to as ISA virus (ISAV) that predominantly affects Atlantic salmon (Salmo salar L.) during the salt-water stage of production, and wild stages. ISAV infection is a major threat to farmed and wild Atlantic salmon worldwide. Many epidemics have recently been reported in the most important salmon farming regions of the world, and in June 2007, ISAV was confirmed in southern Chile, and resulted in the single largest ISA epidemic the world has ever experienced. Since then, ISA has had a profound negative economic impact on the Chilean salmon industry through job losses and decreased revenue. This dissertation research addressed important aspects of the epidemiology of ISAV, including 1) the epidemiological investigation and assessment of spatio-temporal clusters of outbreaks, 2) estimation of the farm-level basic reproduction number ( Rf), 3) characterization of the within-farm spread of the virus, and 4) evaluation of the role of live fish movements in the spread of ISAV, and the identification of husbandry, spatial and contact-network risk factors for time-to-ISAV infection in salmon farms in southern Chile. This research provides insight on the field value of key epidemiological parameters that may be used to support the design and implementation of risk-based surveillance and control programs, to parameterize or validate epidemiological models to predict disease spread, and to evaluate alternative control and intervention strategies that may be used to control future epidemics. |
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