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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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Phylogenetic tree of segment 5 sequences from selected ISAV isolates of European genotype. The analysis was performed using 625 nucleotides of the 5′ portion of the F gene (excluding the nucleotides responsible for the Q266L mutation). The phylogenetic tree was constructed by maximum likelihood (ML) using Tamura-Nei and Neighbor-joining [51]. All ISAV-HPR0 viruses are shown in blue and the ISAV-HPR∆ viruses (ISAV-HPR3 and ISAV-HPR14) associated with the 2013 ISA outbreaks in Chile are shown in red.
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Figure 6: Phylogenetic tree of segment 5 sequences from selected ISAV isolates of European genotype. The analysis was performed using 625 nucleotides of the 5′ portion of the F gene (excluding the nucleotides responsible for the Q266L mutation). The phylogenetic tree was constructed by maximum likelihood (ML) using Tamura-Nei and Neighbor-joining [51]. All ISAV-HPR0 viruses are shown in blue and the ISAV-HPR∆ viruses (ISAV-HPR3 and ISAV-HPR14) associated with the 2013 ISA outbreaks in Chile are shown in red.

Mentions: The phylogenetic analysis of segment 5 sequences from selected ISAV isolates of European genotype, including sequences from ISAV-HPR0 and ISAV-HPR∆ viruses in Chile is presented in Figure 6. Similarly to segment 6 sequences (Figure 5), the Chilean 2013 ISAV-HPR∆ viruses form two main subgroups; a major subgroup (ISAV-HPR3_CGA/2826, CGA/CH1277, CGA/CH1287, CGA/3016, CGA/3663, and ISAV-HPR14_CGA/3015, is very closely related to Chilean ISAV-HPR0_CGA/CH3674 and a minor subgroup (ISAV-HPR3_CGA/CH1271, CGA/CH3201 and CGA/CH3688) is very closely related to Chilean ISAV-HPR0_CGA/CH1390, CGA/CH1420, CGA/CH1656, and CGA/CH1673 (Figure 6). It is noteworthy that the ISAV-HPR0_Scot157/08 from Scotland which grouped with the 2013 ISAV-HPR∆ viruses in Chile on segment 6 is not related to these viruses on segment 5 (Figure 6).


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)

Phylogenetic tree of segment 5 sequences from selected ISAV isolates of European genotype. The analysis was performed using 625 nucleotides of the 5′ portion of the F gene (excluding the nucleotides responsible for the Q266L mutation). The phylogenetic tree was constructed by maximum likelihood (ML) using Tamura-Nei and Neighbor-joining [51]. All ISAV-HPR0 viruses are shown in blue and the ISAV-HPR∆ viruses (ISAV-HPR3 and ISAV-HPR14) associated with the 2013 ISA outbreaks in Chile are shown in red.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Phylogenetic tree of segment 5 sequences from selected ISAV isolates of European genotype. The analysis was performed using 625 nucleotides of the 5′ portion of the F gene (excluding the nucleotides responsible for the Q266L mutation). The phylogenetic tree was constructed by maximum likelihood (ML) using Tamura-Nei and Neighbor-joining [51]. All ISAV-HPR0 viruses are shown in blue and the ISAV-HPR∆ viruses (ISAV-HPR3 and ISAV-HPR14) associated with the 2013 ISA outbreaks in Chile are shown in red.
Mentions: The phylogenetic analysis of segment 5 sequences from selected ISAV isolates of European genotype, including sequences from ISAV-HPR0 and ISAV-HPR∆ viruses in Chile is presented in Figure 6. Similarly to segment 6 sequences (Figure 5), the Chilean 2013 ISAV-HPR∆ viruses form two main subgroups; a major subgroup (ISAV-HPR3_CGA/2826, CGA/CH1277, CGA/CH1287, CGA/3016, CGA/3663, and ISAV-HPR14_CGA/3015, is very closely related to Chilean ISAV-HPR0_CGA/CH3674 and a minor subgroup (ISAV-HPR3_CGA/CH1271, CGA/CH3201 and CGA/CH3688) is very closely related to Chilean ISAV-HPR0_CGA/CH1390, CGA/CH1420, CGA/CH1656, and CGA/CH1673 (Figure 6). It is noteworthy that the ISAV-HPR0_Scot157/08 from Scotland which grouped with the 2013 ISAV-HPR∆ viruses in Chile on segment 6 is not related to these viruses on segment 5 (Figure 6).

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