Browsing by Author "Mardones Loyola, Fernando Otoniel"
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- ItemCo-Infection by LF-89-Like and EM-90-Like Genogroups of Piscirickettsia Salmonis in Farmed Atlantic Salmon in Chile: Implications for Surveillance and Control of Piscirickettsiosis(MDPI, 2023) Rozas-Serri, Marco; Pena, Andrea; Gardner, Ian; Penaloza, Estefania; Maldonado, Lucerina; Munoz, Ariel; Mardones Loyola, Fernando Otoniel; Rodriguez, Catalina; Ildefonso, Ricardo; Senn, Carolina; Aranis, FelipePiscirickettsiosis (SRS), caused by Piscirickettsia salmonis, is the main infectious disease that affects farmed Atlantic salmon in Chile. Currently, the official surveillance and control plan for SRS in Chile is based only on the detection of P. salmonis, but neither of its genogroups (LF-89-like and EM-90-like) are included. Surveillance at the genogroup level is essential not only for defining and evaluating the vaccination strategy against SRS, but it is also of utmost importance for early diagnosis, clinical prognosis in the field, treatment, and control of the disease. The objectives of this study were to characterize the spatio-temporal distribution of P. salmonis genogroups using genogroup-specific real-time probe-based polymerase chain reaction (qPCR) to discriminate between LF-89-like and EM-90-like within and between seawater farms, individual fish, and tissues/organs during early infection in Atlantic salmon under field conditions. The spatio-temporal distribution of LF-89-like and EM-90-like was shown to be highly variable within and between seawater farms. P. salmonis infection was also proven to be caused by both genogroups at farm, fish, and tissue levels. Our study demonstrated for the first time a complex co-infection by P. salmonis LF-89-like and EM-90-like in Atlantic salmon. Liver nodules (moderate and severe) were strongly associated with EM-90-like infection, but this phenotype was not detected by infection with LF-89-like or co-infection of both genogroups. The detection rate of P. salmonis LF-89-like increased significantly between 2017 and 2021 and was the most prevalent genogroup in Chilean salmon aquaculture during this period. Lastly, a novel strategy to identify P. salmonis genogroups based on novel genogroup-specific qPCR for LF-89-like and EM-90-like genogroups is suggested.
- ItemEliciting 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, StefanGlobal 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.
- ItemIridovirus Infections among Missouri River Sturgeon: Initial Characterization, Transmission, and Evidence for Establishment of a Carrier State(2011) Kurobe, Tomofumi; MacConnell, Elizabeth; Hudson, C.; McDowell, Terry S.; Mardones Loyola, Fernando Otoniel; Hedrick, Ronald P.
- ItemMethod 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 OtonielRenibacterium 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.
- ItemSpatio-temporal distribution of hospitalizations for chronic Chagas disease and risk factors associated with in-hospital mortality and surgical intervention in Chile(2024) Atero Fredericksen, Nicolhole Alejandra; Torres Hidalgo, Marisa Lorena De Los Lour; Domínguez De Landa, María Angelica; Diethelm Varela, Benjamín Manuel; Córdova Buhrle, Francisca Alexandra; Mardones Loyola, Fernando OtonielChagas disease (CD) is a neglected parasitic zoonotic disease that affects over 6 million people worldwide. We conducted a retrospective study to analyze the spatiotemporal trends and risk factors for hospitalization rates of CD with cardiac and digestive diagnoses in Chile. We used the Mann-Kendall analysis for temporal trends, Global Moran’s Index, and Local Indicators of Spatial Association to identify spatial autocorrelation, and regression models to determine the risk factors associated with in-hospital mortality and surgical intervention. Between 2010 and 2020, a total of 654 hospitalizations were reported, corresponding to 527 individuals. The hospitalization rate steadily decreased over the years (t = -0.636; p = 0.009). The Global Moran’s I for the study period showed a positive spatial autocorrelation for hospitalization municipality and for residence municipality of CD patients (I = 0.25, p<0.001 and I = 0.45, p<0.001 respectively), indicating a clustering of hospitalizations in northern municipalities. The most frequent diagnosis was a chronic CD with digestive system involvement (55.8%) followed by a chronic CD with heart involvement (44.2%). The highest percentage of hospital discharges was observed among males (56.9%) and in the 60–79 age group (52.7%). In-hospital mortality risk was higher with increasing age (OR = 1.04), and in patients with cardiac involvement (OR = 2.3), whereas factors associated with the risk of undergoing a surgical intervention were sex (OR = 1.6) and diagnosis of CD with digestive involvement (OR = 4.4). The findings of this study indicate that CD is still a significant public health burden in Chile. Efforts should focus on improving access to timely diagnoses and treatment, reducing disease progression and hospitalization burden, and supporting clinicians in preventing complications and deaths.
- ItemThe 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.
- ItemWithin-farm spread of infectious salmon anemia virus (ISAV) in Atlantic salmon Salmo salar farms in Chile(2013) Mardones Loyola, Fernando Otoniel; Jansen, P. A.; Valdes-Donoso, P.; Jarpa, M.; Lyngstad, T. M.; Jimenez, D.; Carpenter, T. E.; Perez, A. M.