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AEI 12:263-279 (2020)  -  DOI: https://doi.org/10.3354/aei00368

FEATURE ARTICLE
Hydrodynamic connectivity, water temperature, and salinity are major drivers of piscirickettsiosis prevalence and transmission among salmonid farms in Chile

F. Bravo1,*, J. P. S. Sidhu2, P. Bernal1, R. H. Bustamante3, S. Condie4, B. Gorton4, M. Herzfeld4, D. Jimenez5, F. O. Mardones6, F. Rizwi4, A. D. L. Steven3

1Fundación CSIRO Chile Research, Apoquindo 4700, Las Condes, Santiago, Chile
2CSIRO Oceans and Atmosphere, Ecosciences Precinct, 41 Boggo Road, Dutton Park, QLD 4102, Australia
3CSIRO Oceans and Atmosphere, Queensland BioSciences Precinct (QBP), 306 Carmody Rd, St Lucia, Brisbane, QLD 4072, Australia
4CSIRO Oceans and Atmosphere, GPO Box 1538, Hobart, TAS 7001, Australia
5Instituto Tecnológico del Salmón, Av. Juan Soler Manfredini 41, OF 1802, Puerto Montt, Chile
6Escuela Medicina Veterinaria, Pontificia Universidad Católica de Chile, Santiago, Chile
*Corresponding author:

ABSTRACT: Piscirickettsiosis is one of the most important diseases affecting farmed salmonid in Chile. Several studies have demonstrated the survival of Piscirickettsia salmonis in seawater and the 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 and the effect of seawater temperature and salinity on the dynamics of piscirickettsiosis in the Los Lagos region of Chile. Results demonstrate that environmental dynamics play a major role in disease prevalence. The strongest determinants of piscirickettsiosis prevalence were the number of infected farms in upstream waters and the extent of disease outbreaks in upstream waters (total mortality), followed by seawater salinity and temperature. In farms downstream from infected farms, observed disease prevalence 25 wk into the farming cycle was close to 100%, while in farms with little or no exposure to upstream, infected farms, prevalence reached only ~10% by the end of the farming cycle (Week 56). No previous studies have quantified the scales of connectivity associated with piscirickettsiosis or provided risk metrics of waterborne transmission of the disease among farms; these are a novel aspect of this research. The above knowledge regarding the use of the epidemiological model will allow industry and regulators to better target disease control strategies for more effective control of piscirickettsiosis in the study area.


KEY WORDS: Salmonid farming · Piscirickettsiosis · Epidemiology · Hydrodynamic connectivity · Seawater temperature · Salinity


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Cite this article as: Bravo F, Sidhu JPS, Bernal P, Bustamante RH and others (2020) Hydrodynamic connectivity, water temperature, and salinity are major drivers of piscirickettsiosis prevalence and transmission among salmonid farms in Chile. Aquacult Environ Interact 12:263-279. https://doi.org/10.3354/aei00368

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