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Ruiz VL, Robert J. The amphibian immune system. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220123. [PMID: 37305914 PMCID: PMC10258673 DOI: 10.1098/rstb.2022.0123] [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: 02/05/2023] [Accepted: 04/16/2023] [Indexed: 06/13/2023] Open
Abstract
Amphibians are at the forefront of bridging the evolutionary gap between mammals and more ancient, jawed vertebrates. Currently, several diseases have targeted amphibians and understanding their immune system has importance beyond their use as a research model. The immune system of the African clawed frog, Xenopus laevis, and that of mammals is well conserved. We know that several features of the adaptive and innate immune system are very similar for both, including the existence of B cells, T cells and innate-like T cells. In particular, the study of the immune system at early stages of development is benefitted by studying X. laevis tadpoles. The tadpoles mainly rely on innate immune mechanisms including pre-set or innate-like T cells until after metamorphosis. In this review we lay out what is known about the innate and adaptive immune system of X. laevis including the lymphoid organs as well as how other amphibian immune systems are similar or different. Furthermore, we will describe how the amphibian immune system responds to some viral, bacterial and fungal insults. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
- Vania Lopez Ruiz
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
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Brunner JL, Olson DH, Gray MJ, Miller DL, Duffus AL. Global patterns of ranavirus detections. Facets (Ott) 2021. [DOI: 10.1139/facets-2020-0013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ranaviruses are emerging pathogens of poikilothermic vertebrates. In 2015 the Global Ranavirus Reporting System (GRRS) was established as a centralized, open access, online database for reports of the presence (and absence) of ranavirus around the globe. The GRRS has multiple data layers (e.g., location, date, host(s) species, and methods of detection) of use to those studying the epidemiology, ecology, and evolution of this group of viruses. Here we summarize the temporal, spatial, diagnostic, and host-taxonomic patterns of ranavirus reports in the GRRS. The number, distribution, and host diversity of ranavirus reports have increased dramatically since the mid 1990s, presumably in response to increased interest in ranaviruses and the conservation of their hosts, and also the availability of molecular diagnostics. Yet there are clear geographic and taxonomic biases among the reports. We encourage ranavirus researchers to add their studies to the portal because such collation can provide collaborative opportunities and unique insights to our developing knowledge of this pathogen and the emerging infectious disease that it causes.
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Affiliation(s)
- Jesse L. Brunner
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Deanna H. Olson
- USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR 97331-8550, USA
| | - Matthew J. Gray
- Department of Forestry, Wildlife and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, TN 37996-4563, USA
| | - Debra L. Miller
- College of Veterinary Medicine, University of Tennessee Institute of Agriculture, Knoxville, TN 37996-4563, USA
| | - Amanda L.J. Duffus
- Department of Natural Sciences, Gordon State College, Barnesville, GA 30204, USA
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Common midwife toad ranaviruses replicate first in the oral cavity of smooth newts (Lissotriton vulgaris) and show distinct strain-associated pathogenicity. Sci Rep 2019; 9:4453. [PMID: 30872735 PMCID: PMC6418247 DOI: 10.1038/s41598-019-41214-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 02/28/2019] [Indexed: 11/08/2022] Open
Abstract
Ranavirus is the second most common infectious cause of amphibian mortality. These viruses affect caudates, an order in which information regarding Ranavirus pathogenesis is scarce. In the Netherlands, two strains (CMTV-NL I and III) were suspected to possess distinct pathogenicity based on field data. To investigate susceptibility and disease progression in urodeles and determine differences in pathogenicity between strains, 45 adult smooth newts (Lissotriton vulgaris) were challenged via bath exposure with these ranaviruses and their detection in organs and feces followed over time by PCR, immunohistochemistry and in situ hybridization. Ranavirus was first detected at 3 days post infection (p.i.) in the oral cavity and upper respiratory mucosa. At 6 days p.i, virus was found in connective tissues and vasculature of the gastrointestinal tract. Finally, from 9 days p.i onwards there was widespread Ranavirus disease in various organs including skin, kidneys and gonads. Higher pathogenicity of the CMTV-NL I strain was confirmed by higher correlation coefficient of experimental group and mortality of challenged animals. Ranavirus-exposed smooth newts shed virus in feces intermittently and infection was seen in the absence of lesions or clinical signs, indicating that this species can harbor subclinical infections and potentially serve as disease reservoirs.
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Pathogen Risk Analysis for Wild Amphibian Populations Following the First Report of a Ranavirus Outbreak in Farmed American Bullfrogs ( Lithobates catesbeianus) from Northern Mexico. Viruses 2019; 11:v11010026. [PMID: 30609806 PMCID: PMC6356443 DOI: 10.3390/v11010026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 11/29/2018] [Accepted: 12/24/2018] [Indexed: 01/20/2023] Open
Abstract
Ranaviruses are the second deadliest pathogens for amphibian populations throughout the world. Despite their wide distribution in America, these viruses have never been reported in Mexico, the country with the fifth highest amphibian diversity in the world. This paper is the first to address an outbreak of ranavirus in captive American bullfrogs (Lithobates catesbeianus) from Sinaloa, Mexico. The farm experienced high mortality in an undetermined number of juveniles and sub-adult bullfrogs. Affected animals displayed clinical signs and gross lesions such as lethargy, edema, skin ulcers, and hemorrhages consistent with ranavirus infection. The main microscopic lesions included mild renal tubular necrosis and moderate congestion in several organs. Immunohistochemical analyses revealed scant infected hepatocytes and renal tubular epithelial cells. Phylogenetic analysis of five partial ranavirus genes showed that the causative agent clustered within the Frog virus 3 clade. Risk assessment with the Pandora+ protocol demonstrated a high risk for the pathogen to affect amphibians from neighboring regions (overall Pandora risk score: 0.619). Given the risk of American bullfrogs escaping and spreading the disease to wild amphibians, efforts should focus on implementing effective containment strategies and surveillance programs for ranavirus at facilities undertaking intensive farming of amphibians.
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Ranavirus genotypes in the Netherlands and their potential association with virulence in water frogs (Pelophylax spp.). Emerg Microbes Infect 2018; 7:56. [PMID: 29615625 PMCID: PMC5882854 DOI: 10.1038/s41426-018-0058-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/04/2017] [Accepted: 02/25/2018] [Indexed: 12/15/2022]
Abstract
Ranaviruses are pathogenic viruses for poikilothermic vertebrates worldwide. The identification of a common midwife toad virus (CMTV) associated with massive die-offs in water frogs (Pelophylax spp.) in the Netherlands has increased awareness for emerging viruses in amphibians in the country. Complete genome sequencing of 13 ranavirus isolates collected from ten different sites in the period 2011–2016 revealed three CMTV groups present in distinct geographical areas in the Netherlands. Phylogenetic analysis showed that emerging viruses from the northern part of the Netherlands belonged to CMTV-NL group I. Group II and III viruses were derived from the animals located in the center-east and south of the country, and shared a more recent common ancestor to CMTV-amphibian associated ranaviruses reported in China, Italy, Denmark, and Switzerland. Field monitoring revealed differences in water frog host abundance at sites where distinct ranavirus groups occur; with ranavirus-associated deaths, host counts decreasing progressively, and few juveniles found in the north where CMTV-NL group I occurs but not in the south with CMTV-NL group III. Investigation of tandem repeats of coding genes gave no conclusive information about phylo-geographical clustering, while genetic analysis of the genomes revealed truncations in 17 genes across CMTV-NL groups II and III compared to group I. Further studies are needed to elucidate the contribution of these genes as well as environmental variables to explain the observed differences in host abundance.
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HIGH PREVALENCE OF INTESTINAL ADENOCARCINOMA IN A CAPTIVE POPULATION OF AMAZON MILK FROG (TRACHYCEPHALUS RESINIFICTRIX). J Zoo Wildl Med 2017; 47:1061-1068. [PMID: 28080918 DOI: 10.1638/2016-0037.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
: A series of eight cases of intestinal adenocarcinoma in Amazon milk frog (Trachycephalus resinifictrix) is described. All cases presented with signs of inappetence and weight loss, and evidence of large intestinal distention on gross postmortem, with six of the eight cases showing a grossly visible large intestinal mass. Histologic examination identified the mass as an intestinal adenocarcinoma in all cases. No specific etiologic agent could be identified. This is the first report of neoplasia in the Amazon milk frog, and the first reported series of amphibian gastrointestinal neoplasia.
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Soto-Azat C, Peñafiel-Ricaurte A, Price SJ, Sallaberry-Pincheira N, García MP, Alvarado-Rybak M, Cunningham AA. Xenopus laevis and Emerging Amphibian Pathogens in Chile. ECOHEALTH 2016; 13:775-783. [PMID: 27682604 DOI: 10.1007/s10393-016-1186-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 08/31/2016] [Accepted: 09/08/2016] [Indexed: 06/06/2023]
Abstract
Amphibians face an extinction crisis with no precedence. Two emerging infectious diseases, ranaviral disease caused by viruses within the genus Ranavirus and chytridiomycosis due to Batrachochytrium dendrobatidis (Bd), have been linked with amphibian mass mortalities and population declines in many regions of the globe. The African clawed frog (Xenopus laevis) has been indicated as a vector for the spread of these pathogens. Since the 1970s, this species has been invasive in central Chile. We collected X. laevis and dead native amphibians in Chile between 2011 and 2013. We conducted post-mortem examinations and molecular tests for Ranavirus and Bd. Eight of 187 individuals (4.3 %) tested positive for Ranavirus: seven X. laevis and a giant Chilean frog (Calyptocephallela gayi). All positive cases were from the original area of X. laevis invasion. Bd was found to be more prevalent (14.4 %) and widespread than Ranavirus, and all X. laevis Bd-positive animals presented low to moderate levels of infection. Sequencing of a partial Ranavirus gene revealed 100 % sequence identity with Frog Virus 3. This is the first report of Ranavirus in Chile, and these preliminary results are consistent with a role for X. laevis as an infection reservoir for both Ranavirus and Bd.
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Affiliation(s)
- Claudio Soto-Azat
- Facultad de Ecología y Recursos Naturales, Centro de Investigación Para la Sustentabilidad, Universidad Andres Bello, Republica 440, Santiago, Chile.
| | - Alexandra Peñafiel-Ricaurte
- Facultad de Ecología y Recursos Naturales, Centro de Investigación Para la Sustentabilidad, Universidad Andres Bello, Republica 440, Santiago, Chile
| | - Stephen J Price
- UCL Genetics Institute, Gower Street, London, WC1E 6BT, UK
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK
| | - Nicole Sallaberry-Pincheira
- Facultad de Ecología y Recursos Naturales, Centro de Investigación Para la Sustentabilidad, Universidad Andres Bello, Republica 440, Santiago, Chile
| | - María Pía García
- Facultad de Ecología y Recursos Naturales, Centro de Investigación Para la Sustentabilidad, Universidad Andres Bello, Republica 440, Santiago, Chile
- Molecular Virology Laboratory, Fundación Ciencia & Vida, Av. Zañartu 1482, Ñuñoa, Chile
| | - Mario Alvarado-Rybak
- Facultad de Ecología y Recursos Naturales, Centro de Investigación Para la Sustentabilidad, Universidad Andres Bello, Republica 440, Santiago, Chile
| | - Andrew A Cunningham
- Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK
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Rijks JM, Saucedo B, Spitzen-van der Sluijs A, Wilkie GS, van Asten AJAM, van den Broek J, Boonyarittichaikij R, Stege M, van der Sterren F, Martel A, Pasmans F, Hughes J, Gröne A, van Beurden SJ, Kik MJL. Investigation of Amphibian Mortality Events in Wildlife Reveals an On-Going Ranavirus Epidemic in the North of the Netherlands. PLoS One 2016; 11:e0157473. [PMID: 27315226 PMCID: PMC4912076 DOI: 10.1371/journal.pone.0157473] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 05/30/2016] [Indexed: 12/15/2022] Open
Abstract
In the four years following the first detection of ranavirus (genus Ranavirus, family Iridoviridae) infection in Dutch wildlife in 2010, amphibian mortality events were investigated nationwide to detect, characterize and map ranaviruses in amphibians over time, and to establish the affected host species and the clinico-pathological presentation of the disease in these hosts. The ultimate goal was to obtain more insight into ranavirus disease emergence and ecological risk. In total 155 dead amphibians from 52 sites were submitted between 2011 and 2014, and examined using histopathology, immunohistochemistry, virus isolation and molecular genetic characterization. Ranavirus-associated amphibian mortality events occurred at 18 sites (35%), initially only in proximity of the 2010 index site. Specimens belonging to approximately half of the native amphibian species were infected, including the threatened Pelobates fuscus (spadefoot toad). Clustered massive outbreaks involving dead adult specimens and ranavirus genomic identity indicated that one common midwife toad virus (CMTV)-like ranavirus strain is emerging in provinces in the north of the Netherlands. Modelling based on the spatiotemporal pattern of spread showed a high probability that this emerging virus will continue to be detected at new sites (the discrete reproductive power of this outbreak is 0.35). Phylogenetically distinct CMTV-like ranaviruses were found in the south of the Netherlands more recently. In addition to showing that CMTV-like ranaviruses threaten wild amphibian populations not only in Spain but also in the Netherlands, the current spread and risk of establishment reiterate that understanding the underlying causes of CMTV-like ranavirus emergence requires international attention.
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Affiliation(s)
- Jolianne M. Rijks
- Dutch Wildlife Health Centre, Utrecht University, Utrecht, The Netherlands
- * E-mail:
| | - Bernardo Saucedo
- Dutch Wildlife Health Centre, Utrecht University, Utrecht, The Netherlands
- Department of Pathobiology, Utrecht University, Utrecht, The Netherlands
| | | | - Gavin S. Wilkie
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Alphons J. A. M. van Asten
- Dutch Wildlife Health Centre, Utrecht University, Utrecht, The Netherlands
- Department of Pathobiology, Utrecht University, Utrecht, The Netherlands
| | - Jan van den Broek
- Department of Farm Animal Health, Utrecht University, Utrecht, The Netherlands
| | | | - Marisca Stege
- Department of Pathobiology, Utrecht University, Utrecht, The Netherlands
| | | | - An Martel
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Merelbeke, Belgium
| | - Frank Pasmans
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Merelbeke, Belgium
| | - Joseph Hughes
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Andrea Gröne
- Dutch Wildlife Health Centre, Utrecht University, Utrecht, The Netherlands
- Department of Pathobiology, Utrecht University, Utrecht, The Netherlands
| | | | - Marja J. L. Kik
- Dutch Wildlife Health Centre, Utrecht University, Utrecht, The Netherlands
- Department of Pathobiology, Utrecht University, Utrecht, The Netherlands
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Abstract
Pathogenic fungi and viruses cause mortality outbreaks in wild amphibians worldwide. In the summer of 2012, dead tadpoles and adults of the European common frog Rana temporaria were reported in alpine lakes in the southwestern Alps (Mercantour National Park, France). A preliminary investigation using molecular diagnostic techniques identified a Ranavirus as the potential pathogenic agent. Three mortality events were recorded in the park, and samples were collected. The amphibian chytrid fungus Batrachochytrium dendrobatidis was not detected in any of the dead adult and juvenile frogs sampled (n=16) whereas all specimens were positive for a Ranavirus. The genome sequence of this Ranavirus was identical to previously published sequences of the common midwife toad virus (CMTV), a Ranavirus that has been associated with amphibian mortalities throughout Europe. We cultured virus from the organs of the dead common frogs and infecting adult male common frogs collected in another alpine region where no frog mortality had been observed. The experimentally infected frogs suffered 100% mortality (n=10). The alpine die-off is the first CMTV outbreak associated with mass mortality in wild amphibians in France. We describe the lesions observed and summarize amphibian populations affected by Ranaviruses in Europe. In addition, we discuss the ecologic specificities of mountain amphibians that may contribute to increasing their risk of exposure to and transmission of Ranaviruses.
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Stöhr AC, Papp T, Marschang RE. Repeated Detection of an Invertebrate Iridovirus in Amphibians. ACTA ACUST UNITED AC 2016. [DOI: 10.5818/1529-9651-26.1-2.54] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Anke C. Stöhr
- 1. Fachgebiet für Umwelt- und Tierhygiene, Universität Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
| | - Tibor Papp
- 2. Institute for Veterinary Medical Research, Centre for Agricultural Research of the Hungarian Academy of Science, H-1143 Budapest, Hungária krt. 21, Hungary
| | - Rachel E. Marschang
- 1. Fachgebiet für Umwelt- und Tierhygiene, Universität Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany
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Stöhr AC, López-Bueno A, Blahak S, Caeiro MF, Rosa GM, Alves de Matos AP, Martel A, Alejo A, Marschang RE. Phylogeny and differentiation of reptilian and amphibian ranaviruses detected in Europe. PLoS One 2015; 10:e0118633. [PMID: 25706285 PMCID: PMC4338083 DOI: 10.1371/journal.pone.0118633] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 01/21/2015] [Indexed: 11/23/2022] Open
Abstract
Ranaviruses in amphibians and fish are considered emerging pathogens and several isolates have been extensively characterized in different studies. Ranaviruses have also been detected in reptiles with increasing frequency, but the role of reptilian hosts is still unclear and only limited sequence data has been provided. In this study, we characterized a number of ranaviruses detected in wild and captive animals in Europe based on sequence data from six genomic regions (major capsid protein (MCP), DNA polymerase (DNApol), ribonucleoside diphosphate reductase alpha and beta subunit-like proteins (RNR-α and -β), viral homolog of the alpha subunit of eukaryotic initiation factor 2, eIF-2α (vIF-2α) genes and microsatellite region). A total of ten different isolates from reptiles (tortoises, lizards, and a snake) and four ranaviruses from amphibians (anurans, urodeles) were included in the study. Furthermore, the complete genome sequences of three reptilian isolates were determined and a new PCR for rapid classification of the different variants of the genomic arrangement was developed. All ranaviruses showed slight variations on the partial nucleotide sequences from the different genomic regions (92.6–100%). Some very similar isolates could be distinguished by the size of the band from the microsatellite region. Three of the lizard isolates had a truncated vIF-2α gene; the other ranaviruses had full-length genes. In the phylogenetic analyses of concatenated sequences from different genes (3223 nt/10287 aa), the reptilian ranaviruses were often more closely related to amphibian ranaviruses than to each other, and most clustered together with previously detected ranaviruses from the same geographic region of origin. Comparative analyses show that among the closely related amphibian-like ranaviruses (ALRVs) described to date, three recently split and independently evolving distinct genetic groups can be distinguished. These findings underline the wide host range of ranaviruses and the emergence of pathogen pollution via animal trade of ectothermic vertebrates.
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Affiliation(s)
- Anke C. Stöhr
- Fachgebiet für Umwelt- und Tierhygiene, Universität Hohenheim, Stuttgart, Germany
| | - Alberto López-Bueno
- Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid, Spain
| | - Silvia Blahak
- Chemisches und Veterinäruntersuchungsamt Ostwestfalen Lippe (CVUA-OWL), Detmold, Germany
| | - Maria F. Caeiro
- Centro de Estudos do Ambiente e do Mar (CESAM) Lisboa, Lisbon, Portugal
- Departamento de Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Gonçalo M. Rosa
- Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, United Kingdom
- Institute of Zoology, Zoological Society of London, Regent’s Park, London, United Kingdom
- Centre for Ecology, Evolution and Environmental Changes (CE3C), Faculty of Sciences, University of Lisbon, Lisbon, Portugal
| | - António Pedro Alves de Matos
- Centro de Estudos do Ambiente e do Mar (CESAM) Lisboa, Lisbon, Portugal
- Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Monte de Caparica, Portugal
| | - An Martel
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Alí Alejo
- Centro de Investigación en Sanidad Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Valdeolmos, Spain
| | - Rachel E. Marschang
- Fachgebiet für Umwelt- und Tierhygiene, Universität Hohenheim, Stuttgart, Germany
- Laboklin GmbH & Co. KG, Laboratory for Clinical Diagnostics, Bad Kissingen, Germany
- * E-mail:
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First evidence of amphibian chytrid fungus (Batrachochytrium dendrobatidis) and ranavirus in Hong Kong amphibian trade. PLoS One 2014; 9:e90750. [PMID: 24599268 PMCID: PMC3944218 DOI: 10.1371/journal.pone.0090750] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 02/03/2014] [Indexed: 11/19/2022] Open
Abstract
The emerging infectious amphibian diseases caused by amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) and ranaviruses are responsible for global amphibian population declines and extinctions. Although likely to have been spread by a variety of activities, transcontinental dispersal appears closely associated with the international trade in live amphibians. The territory of Hong Kong reports frequent, high volume trade in amphibians, and yet the presence of Bd and ranavirus have not previously been detected in either traded or free-ranging amphibians. In 2012, a prospective surveillance project was conducted to investigate the presence of these pathogens in commercial shipments of live amphibians exported from Hong Kong International Airport. Analysis of skin (Bd) and cloacal (ranavirus) swabs by quantitative PCR detected pathogen presence in 31/265 (11.7%) and in 105/185 (56.8%) of amphibians, respectively. In addition, the water in which animals were transported tested positive for Bd, demonstrating the risk of pathogen pollution by the disposal of untreated wastewater. It is uncertain whether Bd and ranavirus remain contained within Hong Kong's trade sector, or if native amphibians have already been exposed. Rapid response efforts are now urgently needed to determine current pathogen distribution in Hong Kong, evaluate potential trade-associated exposure to free-ranging amphibians, and identify opportunities to prevent disease establishment.
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