Browsing by Author "Mardones Loyola, Fernando Otoniel"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Eliciting expert judgements to estimate risk and protective factors for Piscirickettsiosis in Chilean salmon farming
    (2019) Estévez Weinstein, Rodrigo Antonio; Mardones Loyola, Fernando Otoniel; Alamos, Felipe; Arriagada, Gabriel; Carey, Jan; Correa, Christian; Escobar-Dodero, Joaquín; Gaete, Alvaro; Gallardo, Alicia; Ibarra, Rolando; Ortiz, Cristhian; Rozas-Serri, Marco; Sandoval, Osvaldo; Santana, Jaime; Gelcich, Stefan
    Global production of farmed salmon is increasingly threatened by emerging infectious diseases. Piscirickettsiosis or Salmonid Rickettsial Septicemia (SRS), a disease caused by the bacterium Piscirickettsia salmonis, is the major responsible for the overall disease-specific mortalities in the Chilean salmon industry. In this study, we applied a structured expert elicitation process to identify risk and protective factors associated with severe outbreaks of SRS during a production cycle. We used a qualitative based-expert approach to calculate risk estimators for ten risk factors and seven protective factors. In the expert elicitation process, each participant independently estimated factors in two rounds. Between the first and second round, we facilitated a workshop among experts to discuss preliminary results. As a result, the inter-expert variation of the experts' estimates was systematically reduced. Our results are concordant with preliminary studies about risk factors for SRS. Importantly, we identified novel factors that may be associated to an increased risk for severe SRS outbreaks, such as fouling of cages, density of farms in neighborhoods, presence of sea lions and early mature salmonids. Novel factors that appear to reduce the risk of severe outbreaks of SRS were synchronized farm rest periods, opportune diagnosis and necropsy training. Using these results, we propose an intervention model to provide better information for strategic decision making.
  • No Thumbnail Available
    Item
    Method for lineage typing of epidemic Renibacterium salmoninarum in Chilean salmon farms
    (2023) Mora Salas, Patricia Del Rosario; Zapararte, Sebastián; Villouta Wheeler, Pamela Alejandra; Araya León, Henry; Avendaño Herrera, Rubén; Melo Ledermann, Francisco Javier; Mardones Loyola, Fernando Otoniel
    Renibacterium salmoninarum (Rs) is the etiological agent of bacterial kidney disease (BKD), which significantly affects farmed and wild salmonids worldwide. Although the whole genome of Rs (~3.1 million nucleotides) is highly conserved, genomic epidemiology analyses have identified four sub-lineages from Chilean isolates. A total of 94 Rs genomes from the BIGSdb aquaculture database were aligned and compared using bioinformatics tools, identifying 2199 independent single-nucleotide polymorphisms (SNPs) spread along the genome. A detailed analysis of the distribution of the SNPs showed five local zones of a length in the range of 10–15 kbp that should be used to unambiguously identify a specific sub-lineage. Based on the Rs type strain DSM 20767T, we designed multiplex PCR primers that produce specific amplification products which were further sequenced by the Sanger method to obtain the genotype of the sub-lineage. For the genetic typing, we evaluated 27 Rs isolates recovered from BKD outbreaks from different fish species and regions of Chile. Based on the findings reported here, we propose the PCR approach as a valuable tool for the rapid and reliable studying of the relationships between Rs isolates and the different sub-lineages without requiring the sequencing of the entire genome.
  • No Thumbnail Available
    Item
    The role of fish movements and the spread of infectious salmon anemia virus (ISAV) in Chile, 2007-2009
    (2014) Mardones Loyola, Fernando Otoniel; Martinez-Lopez, B.; Valdes-Donoso, P.; Carpenter, T. E.; Perez, A. M.