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Coutinho CD, Ford CE, Trafford JD, Duarte A, Rebelo R, Rosa GM. Non-Lethal Detection of Ranavirus in Fish. Viruses 2023; 15:471. [PMID: 36851684 PMCID: PMC9964643 DOI: 10.3390/v15020471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/01/2023] [Accepted: 02/06/2023] [Indexed: 02/10/2023] Open
Abstract
Emergent infectious diseases have an increasing impact on both farmed animals and wildlife. The ability to screen for pathogens is critical for understanding host-pathogen dynamics and informing better management. Ranavirus is a pathogen of concern, associated with disease outbreaks worldwide, affecting a broad range of fish, amphibian, and reptile hosts, but research has been limited. The traditional screening of internal tissues, such as the liver, has been regarded as the most effective for detecting and quantifying Ranavirus. However, such methodology imposes several limitations from ethical and conservation standpoints. Non-lethal sampling methods of viral detection were explored by comparing the efficacy of both buccal swabbing and fin clipping. The study was conducted on two Iberian, threatened freshwater fish (Iberochondrostoma lusitanicum and Cobitis paludica), and all samples were screened using qPCR. While for C. paludica both methods were reliable in detecting Ranavirus, on I. lusitanicum, there was a significantly higher detection rate in buccal swabs than in fin tissue. This study, therefore, reports that fin clipping may yield false Ranavirus negatives when in small-bodied freshwater fish. Overall, buccal swabbing is found to be good as an alternative to more invasive procedures, which is of extreme relevance, particularly when dealing with a threatened species.
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Affiliation(s)
- Catarina D. Coutinho
- Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Charlotte E. Ford
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Joseph D. Trafford
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
- Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
| | - Ana Duarte
- Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisboa, Portugal
- Instituto Nacional de Investigação Agrária e Veterinária, I.P. (INIAV), 2780-157 Oeiras, Portugal
| | - Rui Rebelo
- Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Gonçalo M. Rosa
- Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
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Strachinis I, Marschang RE, Lymberakis P, Karagianni KM, Azmanis P. Infectious disease threats to amphibians in Greece: new localities positive for Batrachochytrium dendrobatidis. DISEASES OF AQUATIC ORGANISMS 2022; 152:127-138. [PMID: 36519684 DOI: 10.3354/dao03712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
In the early 2000s, numerous cases of European amphibian population declines and mass die-offs started to emerge. Investigating those events led to the discovery that wild European amphibians were confronted with grave disease threats caused by introduced pathogens, namely the amphibian and the salamander chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal) and ranaviruses. In Greece, Bd was previously documented among wild amphibian populations in 2 different locations and 3 different species. However, no disease-related mass declines or mortality events have been reported. In this work, we build upon previous findings with new, subsequently obtained data, resulting in a 225-sample dataset of 14 species from 17 different locations throughout Greece, in order to examine the occurrence status of all 3 pathogens responsible for emerging infectious diseases in European amphibians. No positive samples for Bsal or ranavirus were recorded in any location. We confirmed the presence of Bd in 4 more localities and in 4 more species, including 1 urodelan (Macedonian crested newt Triturus macedonicus) and 1 introduced anuran (American bullfrog Lithobates catesbeianus). All insular localities were negative for Bd, except for Crete, where Bd was identified in 2 different locations. Again, no mass declines or die-offs were recorded in any Bd-positive area or elsewhere. However, given the persistence of Bd across Greece over the past ~20 yr, monitoring efforts should continue, and ideally be further expanded.
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Affiliation(s)
- Ilias Strachinis
- Department of Genetics, Development and Molecular Biology, School of Biology, Faculty of Natural Sciences, Aristotle University of Thessaloniki, 54636, Greece
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Ford CE, Brookes LM, Skelly E, Sergeant C, Jordine T, Balloux F, Nichols RA, Garner TWJ. Non-Lethal Detection of Frog Virus 3-Like (RUK13) and Common Midwife Toad Virus-Like (PDE18) Ranaviruses in Two UK-Native Amphibian Species. Viruses 2022; 14:v14122635. [PMID: 36560639 PMCID: PMC9786228 DOI: 10.3390/v14122635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/18/2022] [Accepted: 11/23/2022] [Indexed: 11/29/2022] Open
Abstract
Ranaviruses have been involved in amphibian mass mortality events worldwide. Effective screening to control this pathogen is essential; however, current sampling methods are unsuitable for the detection of subclinical infections. Non-lethal screening is needed to prevent both further spread of ranavirus and losses of at-risk species. To assess non-lethal sampling methods, we conducted two experiments: bath exposing common frogs to RUK13 ranavirus at three concentrations, and exposing common toads to RUK13 or PDE18. Non-lethal sampling included buccal, digit, body and tank swabs, along with toe clips and stool taken across three time-points post-exposure. The presence/load of ranavirus was examined using quantitative PCR in 11 different tissues obtained from the same euthanised animals (incl. liver, gastro-intestinal tract and kidney). Buccal swab screening had the highest virus detection rate in both species (62% frogs; 71% toads) and produced consistently high virus levels compared to other non-lethal assays. The buccal swab was effective across multiple stages of infection and differing infection intensities, though low levels of infection were more difficult to detect. Buccal swab assays competed with, and even outperformed, lethal sampling in frogs and toads, respectively. Successful virus detection in the absence of clinical signs was observed (33% frogs; 50% toads); we found no difference in detectability for RUK13 and PDE18. Our results suggest that buccal swabbing could replace lethal sampling for screening and be introduced as standard practice for ranavirus surveillance.
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Affiliation(s)
- Charlotte E. Ford
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
- UCL Genetics Institute, University College London, Gower Street, London WC1E 6BT, UK
- Correspondence: or
| | - Lola M. Brookes
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
- RVC Animal Welfare Science and Ethics, The Royal Veterinary College, Hawkshead Lane, Hatfield AL9 7TA, UK
| | - Emily Skelly
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
| | - Chris Sergeant
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
| | - Tresai Jordine
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
| | - Francois Balloux
- UCL Genetics Institute, University College London, Gower Street, London WC1E 6BT, UK
| | - Richard A. Nichols
- School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Trenton W. J. Garner
- Zoological Society of London, Institute of Zoology, Nuffield Building, Outer Circle, London NW8 7LS, UK
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Tian Y, De Jesús Andino F, Khwatenge CN, Li J, Robert J, Sang Y. Virus-Targeted Transcriptomic Analyses Implicate Ranaviral Interaction with Host Interferon Response in Frog Virus 3-Infected Frog Tissues. Viruses 2021; 13:v13071325. [PMID: 34372531 PMCID: PMC8309979 DOI: 10.3390/v13071325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/02/2021] [Accepted: 07/06/2021] [Indexed: 11/30/2022] Open
Abstract
Ranaviruses (Iridoviridae), including Frog Virus 3 (FV3), are large dsDNA viruses that cause devastating infections globally in amphibians, fish, and reptiles, and contribute to catastrophic amphibian declines. FV3’s large genome (~105 kb) contains at least 98 putative open reading frames (ORFs) as annotated in its reference genome. Previous studies have classified these coding genes into temporal classes as immediate early, delayed early, and late viral transcripts based on their sequential expression during FV3 infection. To establish a high-throughput characterization of ranaviral gene expression at the genome scale, we performed a whole transcriptomic analysis (RNA-Seq) using total RNA samples containing both viral and cellular transcripts from FV3-infected Xenopus laevis adult tissues using two FV3 strains, a wild type (FV3-WT) and an ORF64R-deleted recombinant (FV3-∆64R). In samples from the infected intestine, liver, spleen, lung, and especially kidney, an FV3-targeted transcriptomic analysis mapped reads spanning the full-genome coverage at ~10× depth on both positive and negative strands. By contrast, reads were only mapped to partial genomic regions in samples from the infected thymus, skin, and muscle. Extensive analyses validated the expression of almost all of the 98 annotated ORFs and profiled their differential expression in a tissue-, virus-, and temporal class-dependent manner. Further studies identified several putative ORFs that encode hypothetical proteins containing viral mimicking conserved domains found in host interferon (IFN) regulatory factors (IRFs) and IFN receptors. This study provides the first comprehensive genome-wide viral transcriptome profiling during infection and across multiple amphibian host tissues that will serve as an instrumental reference. Our findings imply that Ranaviruses like FV3 have acquired previously unknown molecular mimics, interfering with host IFN signaling during evolution.
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Affiliation(s)
- Yun Tian
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Boulevard, Nashville, TN 37209, USA; (Y.T.); (C.N.K.); (J.L.)
| | - Francisco De Jesús Andino
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA;
| | - Collins N. Khwatenge
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Boulevard, Nashville, TN 37209, USA; (Y.T.); (C.N.K.); (J.L.)
| | - Jiuyi Li
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Boulevard, Nashville, TN 37209, USA; (Y.T.); (C.N.K.); (J.L.)
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA;
- Correspondence: (J.R.); (Y.S.); Tel.: +1-585-275-1722 (J.R.); +615-963-5183 (Y.S.)
| | - Yongming Sang
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, 3500 John A. Merritt Boulevard, Nashville, TN 37209, USA; (Y.T.); (C.N.K.); (J.L.)
- Correspondence: (J.R.); (Y.S.); Tel.: +1-585-275-1722 (J.R.); +615-963-5183 (Y.S.)
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Tian Y, Khwatenge CN, Li J, De Jesus Andino F, Robert J, Sang Y. Targeted Transcriptomics of Frog Virus 3 in Infected Frog Tissues Reveal Non-Coding Regulatory Elements and microRNAs in the Ranaviral Genome and Their Potential Interaction with Host Immune Response. Front Immunol 2021; 12:705253. [PMID: 34220869 PMCID: PMC8248673 DOI: 10.3389/fimmu.2021.705253] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 06/03/2021] [Indexed: 12/21/2022] Open
Abstract
Background Frog Virus 3 (FV3) is a large dsDNA virus belonging to Ranaviruses of family Iridoviridae. Ranaviruses infect cold-blood vertebrates including amphibians, fish and reptiles, and contribute to catastrophic amphibian declines. FV3 has a genome at ~105 kb that contains nearly 100 coding genes and 50 intergenic regions as annotated in its reference genome. Previous studies have mainly focused on coding genes and rarely addressed potential non-coding regulatory role of intergenic regions. Results Using a whole transcriptomic analysis of total RNA samples containing both the viral and cellular transcripts from FV3-infected frog tissues, we detected virus-specific reads mapping in non-coding intergenic regions, in addition to reads from coding genes. Further analyses identified multiple cis-regulatory elements (CREs) in intergenic regions neighboring highly transcribed coding genes. These CREs include not only a virus TATA-Box present in FV3 core promoters as in eukaryotic genes, but also viral mimics of CREs interacting with several transcription factors including CEBPs, CREBs, IRFs, NF-κB, and STATs, which are critical for regulation of cellular immunity and cytokine responses. Our study suggests that intergenic regions immediately upstream of highly expressed FV3 genes have evolved to bind IRFs, NF-κB, and STATs more efficiently. Moreover, we found an enrichment of putative microRNA (miRNA) sequences in more than five intergenic regions of the FV3 genome. Our sequence analysis indicates that a fraction of these viral miRNAs is targeting the 3'-UTR regions of Xenopus genes involved in interferon (IFN)-dependent responses, including particularly those encoding IFN receptor subunits and IFN-regulatory factors (IRFs). Conclusions Using the FV3 model, this study provides a first genome-wide analysis of non-coding regulatory mechanisms adopted by ranaviruses to epigenetically regulate both viral and host gene expressions, which have co-evolved to interact especially with the host IFN response.
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Affiliation(s)
- Yun Tian
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, Nashville, TN, United States
| | - Collins N. Khwatenge
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, Nashville, TN, United States
| | - Jiuyi Li
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, Nashville, TN, United States
| | - Francisco De Jesus Andino
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, United States
| | - Yongming Sang
- Department of Agricultural and Environmental Sciences, College of Agriculture, Tennessee State University, Nashville, TN, United States
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Campbell LJ, Pawlik AH, Harrison XA. Amphibian ranaviruses in Europe: important directions for future research. Facets (Ott) 2020. [DOI: 10.1139/facets-2020-0007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ranaviruses are an emerging group of pathogens capable of infecting all cold-blooded vertebrates. In Europe, ranaviruses pose a particularly potent threat to wild amphibian populations. Since the 1980s research on amphibian-infecting ranaviruses in Europe has been growing. The wide distribution of amphibian populations in Europe, the ease with which many are monitored, and the tractable nature of counterpart ex situ experimental systems have provided researchers with a unique opportunity to study many aspects of host–ranavirus interactions in the wild. These characteristics of European amphibian populations will also enable researchers to lead the way as the field of host–ranavirus interactions progresses. In this review, we provide a summary of the current key knowledge regarding amphibian infecting ranaviruses throughout Europe. We then outline important areas of further research and suggest practical ways each could be pursued. We address the study of potential interactions between the amphibian microbiome and ranaviruses, how pollution may exacerbate ranaviral disease either as direct stressors of amphibians or indirect modification of the amphibian microbiome. Finally, we discuss the need for continued surveillance of ranaviral emergence in the face of climate change.
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Affiliation(s)
- Lewis J. Campbell
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53711, USA
| | - Alice H. Pawlik
- Centre for Ecology and Conservation, University of Exeter, Penryn, Cornwall TR10 9FE, UK
| | - Xavier A. Harrison
- Centre for Ecology and Conservation, University of Exeter, Penryn, Cornwall TR10 9FE, UK
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Harrison XA, Price SJ, Hopkins K, Leung WTM, Sergeant C, Garner TWJ. Diversity-Stability Dynamics of the Amphibian Skin Microbiome and Susceptibility to a Lethal Viral Pathogen. Front Microbiol 2019; 10:2883. [PMID: 31956320 PMCID: PMC6951417 DOI: 10.3389/fmicb.2019.02883] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/29/2019] [Indexed: 12/20/2022] Open
Abstract
Variation among animals in their host-associated microbial communities is increasingly recognized as a key determinant of important life history traits including growth, metabolism, and resistance to disease. Quantitative estimates of the factors shaping the stability of host microbiomes over time at the individual level in non-model organisms are scarce. Addressing this gap in our knowledge is important, as variation among individuals in microbiome stability may represent temporal gain or loss of key microbial species and functions linked to host health and/or fitness. Here we use controlled experiments to investigate how both heterogeneity in microbial species richness of the environment and exposure to the emerging pathogen Ranavirus influence the structure and temporal dynamics of the skin microbiome in a vertebrate host, the European common frog (Rana temporaria). Our evidence suggests that altering the bacterial species richness of the environment drives divergent temporal microbiome dynamics of the amphibian skin. Exposure to ranavirus effects changes in skin microbiome structure irrespective of total microbial diversity, but individuals with higher pre-exposure skin microbiome diversity appeared to exhibit higher survival. Higher diversity skin microbiomes also appear less stable over time compared to lower diversity microbiomes, but stability of the 100 most abundant ("core") community members was similar irrespective of microbiome richness. Our study highlights the importance of extrinsic factors in determining the stability of host microbiomes over time, which may in turn have important consequences for the stability of host-microbe interactions and microbiome-fitness correlations.
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Affiliation(s)
- Xavier A Harrison
- Institute of Zoology, Zoological Society of London, London, United Kingdom.,Centre for Ecology and Conservation, University of Exeter, Exeter, United Kingdom
| | - Stephen J Price
- Institute of Zoology, Zoological Society of London, London, United Kingdom.,UCL Genetics Institute, University College London, London, United Kingdom
| | - Kevin Hopkins
- Institute of Zoology, Zoological Society of London, London, United Kingdom
| | - William T M Leung
- Institute of Zoology, Zoological Society of London, London, United Kingdom
| | - Chris Sergeant
- Institute of Zoology, Zoological Society of London, London, United Kingdom
| | - Trenton W J Garner
- Institute of Zoology, Zoological Society of London, London, United Kingdom
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