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Infectious salmon anaemia virus (ISAV) in Chilean Atlantic salmon (Salmo salar) aquaculture: emergence of low pathogenic ISAV-HPR0 and re-emergence of virulent ISAV-HPR∆: HPR3 and HPR14.

Godoy MG, Kibenge MJ, Suarez R, Lazo E, Heisinger A, Aguinaga J, Bravo D, Mendoza J, Llegues KO, Avendaño-Herrera R, Vera C, Mardones F, Kibenge FS - Virol. J. (2013)

Bottom Line: We analyzed this variant in 66 laboratory-confirmed ISAV-HPR0 cases in Chile in comparison to virulent ISAV-HPR∆ that caused two new ISA outbreaks in April 2013.The ISAV-HPR14 had the ISAV-HPR0 residue pattern 360PAT362, which is the only type of ISAV-HPR0 variant found in Chile.This suggested to us that the 2013 ISAV-HPR∆ re-emerged from ISAV-HPR0 that is enzootic in Chilean salmon aquaculture and were not new introductions of virulent ISAV-HPR∆ to Chile.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, P,E,I,, C1A 4P3, Canada. kibenge@upei.ca.

ABSTRACT

Abstact: Infectious salmon anaemia (ISA) is a serious disease of marine-farmed Atlantic salmon (Salmo salar) caused by ISA virus (ISAV), which belongs to the genus Isavirus, family Orthomyxoviridae. ISA is caused by virulent ISAV strains with deletions in a highly polymorphic region (HPR) of the hemagglutinin-esterase (HE) protein (designated virulent ISAV-HPR∆). This study shows the historic dynamics of ISAV-HPR∆ and ISAV-HPR0 in Chile, the genetic relationship among ISAV-HPR0 reported worldwide and between ISAV-HPR0 and ISAV-HPR∆ in Chile, and reports the 2013 ISA outbreak in Chile. The first ISA outbreak in Chile occurred from mid-June 2007 to 2010 and involved the virulent ISAV-HPR7b, which was then replaced by a low pathogenic ISAV-HPR0 variant. We analyzed this variant in 66 laboratory-confirmed ISAV-HPR0 cases in Chile in comparison to virulent ISAV-HPR∆ that caused two new ISA outbreaks in April 2013. Multiple alignment and phylogenetic analysis of HE sequences from all ISAV-HPR0 viruses allowed us to identify three genomic clusters, which correlated with three residue patterns of ISAV-HPR0 (360PST362, 360PAN362 and 360PAT362) in HPR. The virus responsible for the 2013 ISAV-HPR∆ cases in Chile belonged to ISAV-HPR3 and ISAV-HPR14, and in phylogenetic analyses, both clustered with the ISAV-HPR0 found in Chile. The ISAV-HPR14 had the ISAV-HPR0 residue pattern 360PAT362, which is the only type of ISAV-HPR0 variant found in Chile. This suggested to us that the 2013 ISAV-HPR∆ re-emerged from ISAV-HPR0 that is enzootic in Chilean salmon aquaculture and were not new introductions of virulent ISAV-HPR∆ to Chile. The clinical presentations and diagnostic evidence of the 2013 ISA cases indicated a mixed infection of ISAV with the ectoparasite Caligus rogercresseyi and the bacterium Piscirickettsia salmonis, which underscores the need for active ISAV surveillance in areas where ISAV-HPR0 is enzootic, to ensure early detection and control of new ISA outbreaks, as it is considered a risk factor. This is the first report of ISA linked directly to the presence of ISAV-HPR0, and provides strong evidence supporting the contention that ISAV-HPR0 shows a strong relationship to virulent ISAV-HPR∆ viruses and the possibility that it could mutate to virulent ISAV-HPR∆.

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Number of confirmed infectious salmon anaemia virus (ISAV) cases in Chile from 2007 to 2013. The red bar corresponds to ISA outbreak (virulent ISAV-HPR∆) and the yellow bar to low pathogenic ISAV (ISAV-HPR0) positive cases.
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Figure 1: Number of confirmed infectious salmon anaemia virus (ISAV) cases in Chile from 2007 to 2013. The red bar corresponds to ISA outbreak (virulent ISAV-HPR∆) and the yellow bar to low pathogenic ISAV (ISAV-HPR0) positive cases.

Mentions: In Chile, the first clinical case of ISA in marine-farmed Atlantic salmon (S. salar) occurred in Chiloe Island (Southern Chile, X Region) in mid-June 2007, and the virus was identified as ISAV HPR7b belonging to the European genotype (or Genotype I) [8,22]. Figure 1 shows the prevalence of laboratory-confirmed ISA and ISAV-HPR0 cases in Atlantic salmon (S. salar) farm sites in Chile from July 2007 to April 2013. Following the index case, there was a rapid increase of ISA cases, reaching a peak of 24 cases in November 2008 and then a dramatic drop to December 2010. This decrease was due to a significant decrease in Atlantic salmon biomass being farmed and the implementation of new regulations of biosecurity measures [27].


Infectious salmon anaemia virus (ISAV) in Chilean Atlantic salmon (Salmo salar) aquaculture: emergence of low pathogenic ISAV-HPR0 and re-emergence of virulent ISAV-HPR∆: HPR3 and HPR14.

Godoy MG, Kibenge MJ, Suarez R, Lazo E, Heisinger A, Aguinaga J, Bravo D, Mendoza J, Llegues KO, Avendaño-Herrera R, Vera C, Mardones F, Kibenge FS - Virol. J. (2013)

Number of confirmed infectious salmon anaemia virus (ISAV) cases in Chile from 2007 to 2013. The red bar corresponds to ISA outbreak (virulent ISAV-HPR∆) and the yellow bar to low pathogenic ISAV (ISAV-HPR0) positive cases.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222741&req=5

Figure 1: Number of confirmed infectious salmon anaemia virus (ISAV) cases in Chile from 2007 to 2013. The red bar corresponds to ISA outbreak (virulent ISAV-HPR∆) and the yellow bar to low pathogenic ISAV (ISAV-HPR0) positive cases.
Mentions: In Chile, the first clinical case of ISA in marine-farmed Atlantic salmon (S. salar) occurred in Chiloe Island (Southern Chile, X Region) in mid-June 2007, and the virus was identified as ISAV HPR7b belonging to the European genotype (or Genotype I) [8,22]. Figure 1 shows the prevalence of laboratory-confirmed ISA and ISAV-HPR0 cases in Atlantic salmon (S. salar) farm sites in Chile from July 2007 to April 2013. Following the index case, there was a rapid increase of ISA cases, reaching a peak of 24 cases in November 2008 and then a dramatic drop to December 2010. This decrease was due to a significant decrease in Atlantic salmon biomass being farmed and the implementation of new regulations of biosecurity measures [27].

Bottom Line: We analyzed this variant in 66 laboratory-confirmed ISAV-HPR0 cases in Chile in comparison to virulent ISAV-HPR∆ that caused two new ISA outbreaks in April 2013.The ISAV-HPR14 had the ISAV-HPR0 residue pattern 360PAT362, which is the only type of ISAV-HPR0 variant found in Chile.This suggested to us that the 2013 ISAV-HPR∆ re-emerged from ISAV-HPR0 that is enzootic in Chilean salmon aquaculture and were not new introductions of virulent ISAV-HPR∆ to Chile.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, P,E,I,, C1A 4P3, Canada. kibenge@upei.ca.

ABSTRACT

Abstact: Infectious salmon anaemia (ISA) is a serious disease of marine-farmed Atlantic salmon (Salmo salar) caused by ISA virus (ISAV), which belongs to the genus Isavirus, family Orthomyxoviridae. ISA is caused by virulent ISAV strains with deletions in a highly polymorphic region (HPR) of the hemagglutinin-esterase (HE) protein (designated virulent ISAV-HPR∆). This study shows the historic dynamics of ISAV-HPR∆ and ISAV-HPR0 in Chile, the genetic relationship among ISAV-HPR0 reported worldwide and between ISAV-HPR0 and ISAV-HPR∆ in Chile, and reports the 2013 ISA outbreak in Chile. The first ISA outbreak in Chile occurred from mid-June 2007 to 2010 and involved the virulent ISAV-HPR7b, which was then replaced by a low pathogenic ISAV-HPR0 variant. We analyzed this variant in 66 laboratory-confirmed ISAV-HPR0 cases in Chile in comparison to virulent ISAV-HPR∆ that caused two new ISA outbreaks in April 2013. Multiple alignment and phylogenetic analysis of HE sequences from all ISAV-HPR0 viruses allowed us to identify three genomic clusters, which correlated with three residue patterns of ISAV-HPR0 (360PST362, 360PAN362 and 360PAT362) in HPR. The virus responsible for the 2013 ISAV-HPR∆ cases in Chile belonged to ISAV-HPR3 and ISAV-HPR14, and in phylogenetic analyses, both clustered with the ISAV-HPR0 found in Chile. The ISAV-HPR14 had the ISAV-HPR0 residue pattern 360PAT362, which is the only type of ISAV-HPR0 variant found in Chile. This suggested to us that the 2013 ISAV-HPR∆ re-emerged from ISAV-HPR0 that is enzootic in Chilean salmon aquaculture and were not new introductions of virulent ISAV-HPR∆ to Chile. The clinical presentations and diagnostic evidence of the 2013 ISA cases indicated a mixed infection of ISAV with the ectoparasite Caligus rogercresseyi and the bacterium Piscirickettsia salmonis, which underscores the need for active ISAV surveillance in areas where ISAV-HPR0 is enzootic, to ensure early detection and control of new ISA outbreaks, as it is considered a risk factor. This is the first report of ISA linked directly to the presence of ISAV-HPR0, and provides strong evidence supporting the contention that ISAV-HPR0 shows a strong relationship to virulent ISAV-HPR∆ viruses and the possibility that it could mutate to virulent ISAV-HPR∆.

Show MeSH
Related in: MedlinePlus