title: Genetic analysis and comparative virulence of infectious salmon anemia virus (ISAV) types HPR7a and HPR7b from recent field outbreaks in Chile.
abstract: BACKGROUND
  Infectious salmon anemia (ISA) is a serious disease of marine farmed Atlantic salmon, Salmo salar L. caused by ISA virus (ISAV). ISAV genomic segments 5 and 6 encode surface glycoproteins hemagglutinin-esterase (HE) and F protein important for the pathogenicity of ISAV. In this study, we describe the genetic characteristics and relationship between ISAV-HPR7a and ISAV-HPR7b strains that caused the ISA outbreaks in Chile in 2013 and 2014, respectively, and the evolution of the ISAV clades since 2009 based on segment 5 and 6 sequences.
  
  
  METHODS
  The study material included samples from six ISA cases in Chile. RNA was extracted from salmon tissues and ISAV isolated from cell culture; segments 5 and 6 were amplified by RT-PCR and compared by alignment with ISAV sequences from the GenBank database.
  
  
  RESULTS
  ISAV-HPR7a and ISAV-HPR7b belong to the European Genotype I strains only found in Europe and Chile, and in both cases, show high similarity in segments 5 and 6 with identity between 95-96%. Our data confirm the hypothesis that the original virus was introduced to Chile in 1996. Compared to the 2007 ISAV-HPR7b isolate, the 2014 ISAV-HPR7b does not have an insertion in segment 5 and was associated with low mortality, which suggests that ISAV virulence was attenuated by the absence of the insertion in segment 5. In contrast, the highly virulent ISAV-HPR14 from April 2013 outbreak did not have the insertion in segment 5 either.
  
  
  CONCLUSIONS
  Variability in the ISAV virulence markers supports the quasispecies theory that multiple evolution forces are likely to shape ISAV genetic diversity. Our findings provide evidence of continuing evolution of ISAV in the Chilean aquaculture industry.
authors.affiliation: Centro de Investigaciones Biológicas Aplicadas (CIBA), Diego de Almagro Norte 1013, No. 10, Puerto Montt, Chile. marcos.godoy@uss.cl.|Facultad de Medicina Veterinaria, Universidad San Sebastian, Lago Panguipulli 1390, Puerto Montt, Chile. marcos.godoy@uss.cl.|ETECMA, Diego de Almagro Norte 1013, No. 10, Puerto Montt, Chile. marcos.godoy@uss.cl.
authors.forename: Marcos G
authors.initials: MG
authors.lastname: Godoy
authors.affiliation: Centro de Investigaciones Biológicas Aplicadas (CIBA), Diego de Almagro Norte 1013, No. 10, Puerto Montt, Chile. rudy.suarez@ciba.cl.
authors.forename: Rudy
authors.initials: R
authors.lastname: Suarez
authors.affiliation: ETECMA, Diego de Almagro Norte 1013, No. 10, Puerto Montt, Chile. eduardo.lazo@etecma.cl.
authors.forename: Eduardo S
authors.initials: ES
authors.lastname: Lazo
authors.affiliation: Centro de Investigaciones Biológicas Aplicadas (CIBA), Diego de Almagro Norte 1013, No. 10, Puerto Montt, Chile. katerina.llegues@ciba.cl.
authors.forename: Katerina O
authors.initials: KO
authors.lastname: Llegues
authors.affiliation: Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, P.E.I., C1A 4P3, Canada. mkibenge@upei.ca.
authors.forename: Molly J T
authors.initials: MJ
authors.lastname: Kibenge
authors.affiliation: Department of Computer Science and Information Technology, University of Prince Edward Island, 550 University Avenue, Charlottetown, P.E.I., C1A 4P3, Canada. ywang@upei.ca.
authors.forename: Yingwei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, P.E.I., C1A 4P3, Canada. kibenge@upei.ca.
authors.forename: Frederick S B
authors.initials: FS
authors.lastname: Kibenge
mesh_terms: D000818:Animals; D002677:Chile / Q000453:epidemiology; D016000:Cluster Analysis; D004196:Disease Outbreaks; D019143:Evolution, Molecular; D005393:Fish Diseases / Q000821:virology*; D014644:Genetic Variation; D046829:Isavirus / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D020317:Salmo salar; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D014774:Virulence
chemical_list: D012367:RNA, Viral