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Brunner JL, Olson AD, Rice JG, Meiners SE, Le Sage MJ, Cundiff JA, Goldberg CS, Pessier AP. Ranavirus infection dynamics and shedding in American bullfrogs: consequences for spread and detection in trade. DISEASES OF AQUATIC ORGANISMS 2019; 135:135-150. [PMID: 31392966 DOI: 10.3354/dao03387] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
American bullfrogs Lithobates catesbeianus are thought to be important in the global spread of ranaviruses-often lethal viruses of cold-blooded vertebrates-because they are commonly farmed, dominate international trade, and may be 'carriers' of ranavirus infections. However, whether American bullfrogs are easily infected and maintain long-lasting ranavirus infections, or are refractory to or rapidly clear infections, remains unknown. We tracked the dynamics of ranavirus in American bullfrogs through time and with temperature in multiple types of samples and also screened shipments from commercial suppliers to determine whether we could detect subclinical infections. Collectively, we found that tadpoles and juveniles were commonly infected at moderate doses, and while some died, others controlled and appeared to clear their infections. Some individuals, however, harbored subclinical infections for up to 49 d, suggesting that American bullfrogs may be important carriers. Indeed, tadpoles and metamorphosed frogs from 2 of 5 commercial suppliers harbored subclinicial infections. Juveniles at warmer temperatures had less intense but still persistent infections. Because diagnostic performance was strongly related to infection intensity, non-lethal samples (i.e. tail or toe clips, swabs, and environmental DNA) had only a moderate chance of detecting subclinical infections. Even internal tissues may fail to detect subclinical infections. However, viral shedding was correlated with the intensity of infection, so while subclinically infected tadpoles shed virus for 35-49 d, the low levels might lead to little transmission. We suggest that a quantitative focus on virus dynamics within hosts can provide a more nuanced view of ranavirus infections and the risk presented by American bullfrogs in trade.
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Affiliation(s)
- Jesse L Brunner
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
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Maclaine A, Forzán MJ, Mashkour N, Scott J, Ariel E. Pathogenesis of Bohle Iridovirus (Genus Ranavirus) in Experimentally Infected Juvenile Eastern Water Dragons ( Intellagama lesueurii lesueurii). Vet Pathol 2019; 56:465-475. [PMID: 30686212 DOI: 10.1177/0300985818823666] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Juvenile eastern water dragons ( Intellagama lesueurii lesueurii) are highly susceptible to infection with Bohle iridovirus (BIV), a species of ranavirus first isolated from ornate burrowing frogs in Townsville, Australia. To investigate the progression of BIV infection in eastern water dragons, 11 captive-bred juveniles were orally inoculated with a dose of 104.33 TCID50 and euthanized at 3, 6, 8, 10, 12, and 14 days postinfection (dpi). Viral DNA was detected via polymerase chain reaction (PCR) in the liver, kidney, and cloacal swabs at 3 dpi. Mild lymphocytic infiltration was observed in the submucosa and mucosa of the tongue and liver at 3 dpi. Immunohistochemistry (IHC) first identified viral antigen in foci of splenic necrosis and in hepatocytes with intracytoplasmic inclusion or rare single-cell necrosis at 6 dpi. By 14 dpi, positive IHC labeling was found in association with lesions in multiple tissues. Selected tissues from an individual euthanized at 14 dpi were probed using in situ hybridization (ISH). The ISH labeling matched the location and pattern detected by IHC. The progression of BIV infection in eastern water dragons, based on lesion severity and virus detection, appears to start in the spleen, followed by the liver, then other organs such as the kidney, pancreas, oral mucosa, and skin. The early detection of ranaviral DNA in cloacal swabs and liver and kidney tissue samples suggests these to be a reliable source of diagnostic samples in the early stage of disease before the appearance of clinical signs, as well as throughout the infection.
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Affiliation(s)
- Alicia Maclaine
- 1 College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
| | - María J Forzán
- 2 Cornell Wildlife Health Lab, Department of Population Medicine, Animal Health Diagnostic Center, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | - Narges Mashkour
- 1 College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
| | - Jennifer Scott
- 1 College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
| | - Ellen Ariel
- 1 College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia
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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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Forzán MJ, Jones KM, Ariel E, Whittington RJ, Wood J, Markham RJF, Daoust PY. Pathogenesis of Frog Virus 3 (Ranavirus, Iridoviridae) Infection in Wood Frogs (Rana sylvatica). Vet Pathol 2017; 54:531-548. [DOI: 10.1177/0300985816684929] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Wood frogs ( Rana sylvatica) are highly susceptible to infection with Frog virus 3 (FV3, Ranavirus, Iridoviridae), a cause of mass mortality in wild populations. To elucidate the pathogenesis of FV3 infection in wood frogs, 40 wild-caught adults were acclimated to captivity, inoculated orally with a fatal dose of 104.43 pfu/frog, and euthanized at 0.25, 0.5, 1, 2, 4, 9, and 14 days postinfection (dpi). Mild lesions occurred sporadically in the skin (petechiae) and bone marrow (necrosis) during the first 2 dpi. Severe lesions occurred 1 to 2 weeks postinfection and consisted of necrosis of medullary and extramedullary hematopoietic tissue, lymphoid tissue in spleen and throughout the body, and epithelium of skin, mucosae, and renal tubules. Viral DNA was first detected (polymerase chain reaction) in liver at 4 dpi; by dpi 9 and 14, all viscera tested (liver, kidney, and spleen), skin, and feces were positive. Immunohistochemistry (IHC) first detected viral antigen in small areas devoid of histologic lesions in the oral mucosa, lung, and colon at 4 dpi; by 9 and 14 dpi, IHC labeling of viral antigen associated with necrosis was found in multiple tissues. Based on IHC staining intensity and lesion severity, the skin, oral, and gastrointestinal epithelium and renal tubular epithelium were important sites of viral replication and shedding, suggesting that direct contact (skin) and fecal-oral contamination are effective routes of transmission and that skin tissue, oral, and cloacal swabs may be appropriate antemortem diagnostic samples in late stages of disease (>1 week postinfection) but poor samples to detect infection in clinically healthy frogs.
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Affiliation(s)
- M. J. Forzán
- Canadian Wildlife Health Cooperative, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - K. M. Jones
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - E. Ariel
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia
| | - R. J. Whittington
- School of Life and Environmental Sciences, Faculty of Veterinary Science, University of Sydney, Camden, New South Wales, Australia
| | - J. Wood
- Pisces Molecular LLC, Boulder, CO, USA
| | - R. J. Frederick Markham
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - P.-Y. Daoust
- Canadian Wildlife Health Cooperative, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
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Forzán MJ, Smith TG, Vanderstichel RV, Hogan NS, Gilroy CV. Hematologic reference intervals for Rana sylvatica (Lithobates sylvaticus) and effect of infection with Frog Virus 3 (Ranavirus sp., Iridoviridae). Vet Clin Pathol 2016; 45:430-43. [PMID: 27564850 DOI: 10.1111/vcp.12393] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Although the Wood Frog, Rana sylvatica, is used in research on infectious diseases of amphibians, hematologic RIs or response to infection have not been established. OBJECTIVES The purpose of the study was to determine hematologic RIs for adult Wood Frogs and alterations associated with infection with Frog Virus 3 (FV3, Ranavirus sp.). METHODS Blood was collected from 40 wild-caught adult Wood Frogs that had been in captivity for 6 months. Complete (Natt-Herrick solution hemocytometry) and differential (Wright-Giemsa-stained smears) WBC, RBC, and thrombocyte cell counts, PCV, and automated total cell counts (WBC+RBC+thrombocytes, Sysmex particle counting) were determined. Concordance correlation coefficients determined agreement between hemocytometric and automated total cell counts. Thirteen frogs were orally infected with a lethal dose of 10(4.43) plaque-forming units of FV3 and terminally sampled 4, 9, or 14 days postinfection (dpi). Pre- and postinfection variables for each frog were compared. RESULTS Leukocyte morphology was similar to that of other amphibians and mammals. Lymphocytes were the most numerous WBC. PCV and RBC counts were similar to other frogs in the same family. Agreement was good between hemocytometry and automated total cell counts. Infection with FV3 caused neutrophilia, increase in undifferentiated blast-like cells, and reduction in the percentage of basophils. Lymphocytes decreased at 4 and 9 dpi but increased at 14 dpi. From 9 dpi onwards, nuclear deterioration and mild toxic change were present in neutrophils; viral cytoplasmic inclusion bodies were observed in lymphocytes, monocytes, neutrophils, and eosinophils. CONCLUSION We provide hematology RIs for Rana sylvatica, and report hematologic changes associated with a lethal FV3 infection.
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Affiliation(s)
- María J Forzán
- Canadian Wildlife Health Cooperative, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada. .,Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada.
| | - Todd G Smith
- Department of Biology, Acadia University, Wolfville, NS, Canada
| | - Raphaël V Vanderstichel
- Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | - Natacha S Hogan
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada
| | - Cornelia V Gilroy
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
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García‐Díaz P, Ross JV, Woolnough AP, Cassey P. Managing the risk of wildlife disease introduction: pathway‐level biosecurity for preventing the introduction of alien ranaviruses. J Appl Ecol 2016. [DOI: 10.1111/1365-2664.12749] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Pablo García‐Díaz
- School of Biological Sciences and Centre for Conservation Science and Technology (CCoST) The University of Adelaide North Terrace SA 5005 Australia
| | - Joshua V. Ross
- School of Mathematical Sciences NHMRC Centre of Research Excellence in Policy Relevant Infectious Diseases Simulation and Mathematical Modelling (PRISM2) Centre for Conservation Science and Technology (CCoST), and ARC Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS) The University of Adelaide North Terrace SA 5005 Australia
| | - Andrew P. Woolnough
- Department of Economic Development, Jobs, Transport and Resources 475‐485 Mickleham Road Attwood Vic. 3049 Australia
| | - Phillip Cassey
- School of Biological Sciences and Centre for Conservation Science and Technology (CCoST) The University of Adelaide North Terrace SA 5005 Australia
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Huang X, Fang J, Chen Z, Zhang Q. Rana grylio virus TK and DUT gene locus could be simultaneously used for foreign gene expression. Virus Res 2016; 214:33-8. [PMID: 26806670 DOI: 10.1016/j.virusres.2016.01.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 01/15/2016] [Accepted: 01/15/2016] [Indexed: 10/22/2022]
Abstract
Ranaviruses (family Iridoviridae, genus Ranavirus) have been recognized as emerging infectious pathogens and caused a great loss to the global biodiversity. Thymidine kinase (TK) and deoxyuridine triphosphatase (dUTPase, DUT, encoded by ORF 67R) are ubiquitous, existing in iridoviruses and other organisms. Previous studies showed that TK and DUT could be individually knocked out without impeding viral replication. In this study, we tried to insert two fluorescence genes into the above loci. We started with Δ67R-RGV, a recently generated recombinant Rana grylio virus (RGV) with the whole DUT replaced by enhanced green fluorescence protein (EGFP) gene. Then, a red fluorescence protein (RFP) gene initiated by RGV immediate-early (IE) ICP18 gene promoter was inserted into TK locus through homologous recombination. A novel recombinant virus, ΔDUT, TK-RGV, was generated by nine successive rounds of plaque isolation using RFP selection. All of the plaques produced by this recombinant virus could emit both green and red fluorescence. Furthermore, one-step and multiple-step growth curves of ΔDUT, TK-RGV were similar to those of wt-RGV and Δ67R-RGV. In conclusion, a novel dual-fluorescence labeled recombinant iridovirus in which DUT and TK gene locus were simultaneously used for foreign gene expression was constructed.
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Affiliation(s)
- Xing Huang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China
| | - Jin Fang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China
| | - Zhongyuan Chen
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China
| | - Qiya Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Wuhan 430072, China.
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