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AEI
Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00368

    Hydrodynamic connectivity, water temperature, and salinity are major drivers of Piscirickettsia salmonis dispersion and transmission among salmon farms in Chile

    F. Bravo, J. P. S. Sidhu, P. Bernal, R. H. Bustamante, S. Condie, B. Gorton, M. Herzfeld, D. Jimenez, F. O. Mardones, F. Rizwi, A. D. L. Steven

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    ABSTRACT: Piscirickettsiosis is one of the most important diseases affecting farmed salmon in Chile. Several studies have demonstrated the survival of Piscirickettsia salmonis in seawater and horizontal transmission from infected to non-infected fish, however, the extent of waterborne transmission between farms has not been quantified. In this study, we used a stochastic hydrodynamic connectivity-based disease spread model to determine the role of hydrodynamic connectivity among farms, seawater temperature, and salinity on the piscirickettsiosis dynamics in the Los Lagos Region of Chile. The results demonstrate that environmental dynamics play a major role in disease prevalence. The strongest determinants of piscirickettsiosis prevalence were the number of infected farms upstream, the extent of disease outbreaks in upstream waters (total mortality), followed by the seawater salinity and temperature. The observed prevalence of piscirickettsiosis after 25 wk of the farming cycle was close to 100% in the farms exposed to upstream infected farms. However, in the farms with little or no exposure to upstream infected farms disease prevalence was only ~10% by the end of the farming cycle. No previous studies have quantified the scales of connectivity associated with piscirickettsiosis nor provided risk metrics of waterborne transmission of the disease among farms, these being a novel aspect of this research. The adoption of this knowledge and the epidemiological model will allow industry and regulators to better target disease control strategies of piscirickettsiosis in the study area and thereby improve their overall effectiveness.