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Rounsville TF, Polinski MP, Marini AG, Turner SM, Vendramin N, Cuenca A, Pietrak MR, Peterson BC, Bouchard DA. Rapid differentiation of infectious salmon anemia virus avirulent (HPR0) from virulent (HPRΔ) variants using multiplex RT-qPCR. J Vet Diagn Invest 2024; 36:329-337. [PMID: 38212882 PMCID: PMC11110766 DOI: 10.1177/10406387231223290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024] Open
Abstract
Infectious salmon anemia virus (ISAV; Isavirus salaris) causes an economically important disease of Atlantic salmon (Salmo salar L.). ISA outbreaks have resulted in significant losses of farmed salmon globally, often with a sudden onset. However, 2 phenotypically distinct variants of ISAV exist, each with divergent disease outcomes, associated regulations, and control measures. ISAV-HPRΔ, also known as ISAV-HPR deleted, is responsible for ISA outbreaks; ISAV-HPR0, is avirulent and is not known to cause fish mortality. Current detection methodology requires genetic sequencing of ISAV-positive samples to differentiate phenotypes, which may slow responses to disease management. To increase the speed of phenotypic determinations of ISAV, we developed a new, rapid multiplex RT-qPCR method capable of 1) detecting if a sample contains any form of ISAV, 2) discriminating whether positive samples contain HPRΔ or HPR0, and 3) validating RNA extractions with an internal control, all in a single reaction. Following assay development and optimization, we validated this new multiplex on 31 ISAV strains collected from North America and Europe (28 ISAV-HPRΔ, 3 ISAV-HPR0). Finally, we completed an inter-laboratory comparison of this multiplex qPCR with commercial ISAV testing and found that both methods provided equivalent results for ISAV detection.
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Affiliation(s)
- Thomas F. Rounsville
- Pest Management Unit, University of Maine Cooperative Extension Diagnostic and Research Laboratory, Orono, ME, USA
| | - Mark P. Polinski
- National Cold Water Marine Aquaculture Center, U.S. Department of Agriculture–Agricultural Research Service, Franklin, ME, USA
| | - Alyssa G. Marini
- Pest Management Unit, University of Maine Cooperative Extension Diagnostic and Research Laboratory, Orono, ME, USA
- University of Maine School of Biology and Ecology, Orono, ME, USA
| | - Sarah M. Turner
- Aquatic Animal Health Laboratory, University of Maine Cooperative Extension Diagnostic and Research Laboratory, Orono, ME, USA
| | - Niccolò Vendramin
- Unit for Fish and Shellfish Diseases, National Institute of Aquatic Resources, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Argelia Cuenca
- Unit for Fish and Shellfish Diseases, National Institute of Aquatic Resources, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Michael R. Pietrak
- National Cold Water Marine Aquaculture Center, U.S. Department of Agriculture–Agricultural Research Service, Franklin, ME, USA
| | - Brian C. Peterson
- National Cold Water Marine Aquaculture Center, U.S. Department of Agriculture–Agricultural Research Service, Franklin, ME, USA
| | - Deborah A. Bouchard
- Aquatic Animal Health Laboratory, University of Maine Cooperative Extension Diagnostic and Research Laboratory, Orono, ME, USA
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Strube LF, Elgart S, Childs LM. Infection-induced increases to population size during cycles in a discrete-time epidemic model. J Math Biol 2024; 88:60. [PMID: 38600396 PMCID: PMC11006791 DOI: 10.1007/s00285-024-02074-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/11/2023] [Accepted: 02/18/2024] [Indexed: 04/12/2024]
Abstract
One-dimensional discrete-time population models, such as those that involve Logistic or Ricker growth, can exhibit periodic and chaotic dynamics. Expanding the system by one dimension to incorporate epidemiological interactions causes an interesting complexity of new behaviors. Here, we examine a discrete-time two-dimensional susceptible-infectious (SI) model with Ricker growth and show that the introduction of infection can not only produce a distinctly different bifurcation structure than that of the underlying disease-free system but also lead to counter-intuitive increases in population size. We use numerical bifurcation analysis to determine the influence of infection on the location and types of bifurcations. In addition, we examine the appearance and extent of a phenomenon known as the 'hydra effect,' i.e., increases in total population size when factors, such as mortality, that act negatively on a population, are increased. Previous work, primarily focused on dynamics at fixed points, showed that the introduction of infection that reduces fecundity to the SI model can lead to a so-called 'infection-induced hydra effect.' Our work shows that even in such a simple two-dimensional SI model, the introduction of infection that alters fecundity or mortality can produce dynamics can lead to the appearance of a hydra effect, particularly when the disease-free population is at a cycle.
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Affiliation(s)
- Laura F Strube
- Department of Mathematics, Virginia Tech, 225 Stanger St, Blacksburg, VA, 24061, USA
- Department of Immunology, University of Pittsburgh Medical School, The Assembly, 5051 Centre Avenue, Pittsburgh, PA, 15213, USA
- Department of Computational and Systems Biology, University of Pittsburgh Medical School, 800 Murdoch I building, 3420 Forbes Avenue, Pittsburgh, PA, 15213, USA
| | - Shoshana Elgart
- Laurel Springs School, 302 El Paseo Rd, Ojai, CA, 93023, USA
| | - Lauren M Childs
- Department of Mathematics, Virginia Tech, 225 Stanger St, Blacksburg, VA, 24061, USA.
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3
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Nylund A, Kloster-Jensen T, Mohammadi F, Lagadec E, Plarre H. Genotyping tool for salmonid gill pox virus (SGPV) obtained from farmed and wild Atlantic salmon (Salmo salar). Arch Virol 2023; 168:249. [PMID: 37684418 PMCID: PMC10491535 DOI: 10.1007/s00705-023-05866-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 07/30/2023] [Indexed: 09/10/2023]
Abstract
Poxviruses are common viruses found in vertebrate species. In 2006, the first poxvirus associated with salmon, salmonid gill poxvirus (SGPV), was identified during an outbreak of gill disease at a smolt production site in northern Norway and at two marine farms in western Norway. Poxviruses had previously been detected in ayu (Plecoglossus altivelis) and koi carp (Cyprinus carpio). In all three fish species, poxviruses are associated with gill disease. It has not been possible to culture SGPV from Norway, and little is known about its virulence. However, the association between SGPV and gill disease in salmon has shown the need for molecular tools to identify reservoirs and transmission routes. Sequencing the genome of a second isolate of SGPV has made it possible to compare variable regions between two strains of the virus, showing the presence of a large number of variable regions that exhibit both variable numbers of tandem repeats and intra-ORF variation. We present eight regions that are suitable for distinguishing strains of SGPV and determining their phylogenetic relationship, and these were used to compare SGPV isolates obtained from both farmed and wild salmon in fresh and sea water. The prevalence of the virus was found to be higher in wild salmon in rivers than in returning wild salmon collected from traps in Norwegian fjords. Genotyping based on the eight selected variable regions, suggests the presence of geographically distinct isolates in freshwater among both farmed and wild salmon, while SGPV from marine farms shows high local diversity and a wide geographical distribution of similar strains of the virus.
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Affiliation(s)
- Are Nylund
- Fish Diseases Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Thomas Kloster-Jensen
- Fish Diseases Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Faezeh Mohammadi
- Fish Diseases Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Erwan Lagadec
- Fish Diseases Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway.
| | - Heidrun Plarre
- Fish Diseases Research Group, Department of Biological Sciences, University of Bergen, Bergen, Norway
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Aunsmo A, Martinsen L, Bruheim T, Sekkelsten-Kindt MM, Sandtrø A, Gaasø S, Braaen S, Rimstad E. Triploid Atlantic salmon (Salmo salar) may have increased risk of primary field outbreaks of infectious salmon anaemia. JOURNAL OF FISH DISEASES 2022; 45:1733-1743. [PMID: 35914108 PMCID: PMC9805046 DOI: 10.1111/jfd.13695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 07/17/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
The impact that escaped farmed fish may have on wild populations is of major concern for Atlantic salmon (Salmo salar) farming. Triploid fish, being infertile, were originally introduced to mitigate the genetic impact of escaped fish. In the recent years, an increase in the number of infectious salmon anaemia (ISA) outbreaks in Norway has been observed, mainly in the northern parts, which is also where farming of triploid fish has been licensed. The present study investigated the susceptibility of triploid Atlantic salmon to ISA both by field observations and experimental infections. Based on field observations, we found an increased susceptibility, with 9.4 increased odds to primary ISA outbreaks in triploid fish versus diploid fish at production-site level, and a tendency of increased odds (3.4) of ISA in triploid fish at individual cage level at sited with primary outbreaks. At some sites, ISA outbreaks were only diagnosed in cages with triploid fish and not in cages with diploid fish. Primary ISA outbreaks are the source for further spread of the disease, and it is noteworthy that in an experimental trial we found significantly more viral RNA in non-ISA-vaccinated triploid than in non-ISA-vaccinated diploid fish at the peak of the infection. Interestingly, the notable differences of susceptibility to ISA for non-ISA vaccinated diploid and triploid fish observed in field were not repeated experimentally. The possible increased risk of ISA should be considered when evaluating the costs and benefits of triploid salmon in farming. It is recommended to keep triploid and diploid fish in biosecure separated sites, or that triploid fish are not farmed at all.
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Affiliation(s)
- Arnfinn Aunsmo
- Department of Production Animal Clinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
- Laxar Fiskeldi, Reykjavik, Iceland
| | | | | | | | - Ane Sandtrø
- PHARMAQ, Skogmo Industriområde, Overhalla, Norway
| | | | - Stine Braaen
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Ås, Norway
| | - Espen Rimstad
- Department of Paraclinical Sciences, Norwegian University of Life Sciences, Ås, Norway
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Meyers TR, Hickey N. A Perspective: Molecular Detections of New Agents in Finfish-Interpreting Biological Significance for Fish Health Management. JOURNAL OF AQUATIC ANIMAL HEALTH 2022; 34:47-57. [PMID: 35384072 DOI: 10.1002/aah.10155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 12/31/2021] [Accepted: 03/31/2022] [Indexed: 06/14/2023]
Abstract
The increased sensitivity of advanced molecular techniques greatly exceeds the sensitivities of traditional detection methods for infectious agents. This sensitivity causes difficulty in interpreting the biological significance of such detections in fish (and shellfish), especially when the agent(s) cannot be cultured in the laboratory. In the Pacific Northwest, including Canada and Alaska, molecular detections of "new" (unknown or known but discovered in a different geographic location or fish host) potentially infectious agents in fish have received extensive media attention and misinterpretation that call for resource agencies to change current fish health surveillance practices or policies to include these agents. Fish health specialists from several of these agencies and organizations (see Acknowledgments) advise that any policy changes should be made only after further investigations to avoid wasting resources to conduct surveillance for organisms that are not significant to fish health or for noninfectious genetic material that does not represent a viable agent. Molecular detection is not proof of agent viability within or on host tissues and requires further investigation regarding the agent's ability to replicate and evidence that the agent causes substantial risk of disease to exposed fish populations. This document provides examples of molecularly detected agents causing public concern that were accompanied by little or no data to provide context and assessment of biological significance, highlights important questions to be answered regarding these detections, and provides a suggested pathway of investigative criteria to determine viability and pathogenicity of such agents that are necessary for consideration of any changes to aquatic animal health practices and policies.
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Affiliation(s)
- Theodore R Meyers
- Alaska Department of Fish and Game, Commercial Fisheries Division, Post Office Box 115526, Juneau, Alaska, 99811, USA
| | - Nora Hickey
- Northwest Indian Fisheries Commission, 6730 Martin Way East, Olympia, Washington, 98516, USA
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Dean KR, Oliveira VHS, Wolff C, Moldal T, Jansen MD. Description of ISAV-HPRΔ-positive salmon farms in Norway in 2020. JOURNAL OF FISH DISEASES 2022; 45:225-229. [PMID: 34585395 DOI: 10.1111/jfd.13538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 06/13/2023]
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Christiansen DH, Petersen PE, Dahl MM, Vest N, Aamelfot M, Kristoffersen AB, Jansen MD, Matejusova I, Gallagher MD, Jónsson G, Rodriguez E, Fosse JH, Falk K. No Evidence of the Vertical Transmission of Non-Virulent Infectious Salmon Anaemia Virus (ISAV-HPR0) in Farmed Atlantic Salmon. Viruses 2021; 13:v13122428. [PMID: 34960697 PMCID: PMC8708482 DOI: 10.3390/v13122428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 11/30/2022] Open
Abstract
The nonvirulent infectious salmon anaemia virus (ISAV-HPR0) is the putative progenitor for virulent-ISAV, and a potential risk factor for the development of infectious salmon anaemia (ISA). Understanding the transmission dynamics of ISAV-HPR0 is fundamental to proper management and mitigation strategies. Here, we demonstrate that ISAV-HPR0 causes prevalent and transient infections in all three production stages of Atlantic salmon in the Faroe Islands. Phylogenetic analysis of the haemagglutinin-esterase gene from 247 salmon showed a clear geographical structuring into two significantly distinct HPR0-subgroups, which were designated G2 and G4. Whereas G2 and G4 co-circulated in marine farms, Faroese broodfish were predominantly infected by G2, and smolt were predominantly infected by G4. This infection pattern was confirmed by our G2- and G4-specific RT-qPCR assays. Moreover, the HPR0 variants detected in Icelandic and Norwegian broodfish were never detected in the Faroe Islands, despite the extensive import of ova from both countries. Accordingly, the vertical transmission of HPR0 from broodfish to progeny is uncommon. Phylogenetic and statistical analysis suggest that HPR0 persists in the smolt farms as “house-strains”, and that new HPR0 variants are occasionally introduced from the marine environment, probably by HPR0-contaminated sea-spray. Thus, high biosecurity—including water and air intake—is required to avoid the introduction of pathogens to the smolt farms.
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Affiliation(s)
- Debes Hammershaimb Christiansen
- National Reference Laboratory for Fish and Animal Diseases, Faroese Food and Veterinary Authority, 110 Torshavn, Faroe Islands; (P.E.P.); (M.M.D.); (N.V.)
- Correspondence:
| | - Petra Elisabeth Petersen
- National Reference Laboratory for Fish and Animal Diseases, Faroese Food and Veterinary Authority, 110 Torshavn, Faroe Islands; (P.E.P.); (M.M.D.); (N.V.)
| | - Maria Marjunardóttir Dahl
- National Reference Laboratory for Fish and Animal Diseases, Faroese Food and Veterinary Authority, 110 Torshavn, Faroe Islands; (P.E.P.); (M.M.D.); (N.V.)
| | - Nicolina Vest
- National Reference Laboratory for Fish and Animal Diseases, Faroese Food and Veterinary Authority, 110 Torshavn, Faroe Islands; (P.E.P.); (M.M.D.); (N.V.)
| | - Maria Aamelfot
- Norwegian Veterinary Institute, 0454 Oslo, Norway; (M.A.); (A.B.K.); (M.D.J.); (J.H.F.); (K.F.)
| | | | - Mona Dverdal Jansen
- Norwegian Veterinary Institute, 0454 Oslo, Norway; (M.A.); (A.B.K.); (M.D.J.); (J.H.F.); (K.F.)
| | - Iveta Matejusova
- Marine Scotland Science, Marine Laboratory, Aberdeen AB11 9DB, UK;
| | - Michael D. Gallagher
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH8 9YL, UK;
| | - Gísli Jónsson
- Icelandic Food and Veterinary Authority, 220 Hafnarfjordur, Iceland;
| | | | - Johanna Hol Fosse
- Norwegian Veterinary Institute, 0454 Oslo, Norway; (M.A.); (A.B.K.); (M.D.J.); (J.H.F.); (K.F.)
| | - Knut Falk
- Norwegian Veterinary Institute, 0454 Oslo, Norway; (M.A.); (A.B.K.); (M.D.J.); (J.H.F.); (K.F.)
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Islam SS, Wringe BF, Bradbury IR, Fleming IA. Behavioural variation among divergent European and North American farmed and wild Atlantic salmon (Salmo salar) populations. Appl Anim Behav Sci 2020. [DOI: 10.1016/j.applanim.2020.105029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Synthetic Peptides as a Promising Alternative to Control Viral Infections in Atlantic Salmon. Pathogens 2020; 9:pathogens9080600. [PMID: 32717804 PMCID: PMC7459813 DOI: 10.3390/pathogens9080600] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/14/2020] [Accepted: 07/17/2020] [Indexed: 01/07/2023] Open
Abstract
Viral infections in salmonids represent an ongoing challenge for the aquaculture industry. Two RNA viruses, the infectious pancreatic necrosis virus (IPNV) and the infectious salmon anemia virus (ISAV), have become a latent risk without healing therapies available for either. In this context, antiviral peptides emerge as effective and relatively safe therapeutic molecules. Based on in silico analysis of VP2 protein from IPNV and the RNA-dependent RNA polymerase from ISAV, a set of peptides was designed and were chemically synthesized to block selected key events in their corresponding infectivity processes. The peptides were tested in fish cell lines in vitro, and four were selected for decreasing the viral load: peptide GIM182 for IPNV, and peptides GIM535, GIM538 and GIM539 for ISAV. In vivo tests with the IPNV GIM 182 peptide were carried out using Salmo salar fish, showing a significant decrease of viral load, and proving the safety of the peptide for fish. The results indicate that the use of peptides as antiviral agents in disease control might be a viable alternative to explore in aquaculture.
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Rimstad E, Markussen T. Infectious salmon anaemia virus-molecular biology and pathogenesis of the infection. J Appl Microbiol 2020; 129:85-97. [PMID: 31885186 DOI: 10.1111/jam.14567] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 12/20/2019] [Accepted: 12/23/2019] [Indexed: 11/29/2022]
Abstract
Aquaculture has a long history in many parts of the world, but it is still young at an industrial scale. Marine fish farming in open nets of a single fish species at high densities compared to their wild compatriots opens a plethora of possible infections. Infectious salmon anaemia (ISA) is an example of disease that surfaced after large-scale farming of Atlantic salmon (Salmo salar) appeared. Here, a review of the molecular biology of the ISA virus (ISAV) with emphasis on its pathogenicity is presented. The avirulent HPR0 variant of ISAV has resisted propagation in cell cultures, which has restricted the ability to perform in vivo experiments with this variant. The transition from avirulent HPR0 to virulent HPRΔ has not been methodically studied under controlled experimental conditions, and the triggers of the transition from avirulent to virulent forms have not been mapped. Genetic segment reassortment, recombination and mutations are important mechanisms in ISAV evolution, and for the development of virulence. In the 25 years since the ISAV was identified, large amounts of sequence data have been collected for epidemiologic and transmission studies, however, the lack of good experimental models for HPR0 make the risk evaluation of the presence of this avirulent, ubiquitous variant uncertain. This review summarizes the current knowledge related to molecular biology and pathogenicity of this important aquatic orthomyxovirus.
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Affiliation(s)
- E Rimstad
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
| | - T Markussen
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
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