University of Tennessee 1 Center for Wildlife Health 2 CVM Department of BDS Debra L. Miller 1,2 and Matthew J. Gray 1 A Pathogen Lurking in the Darkness: Global Emergence of Ranavirus in Ectothermic Vertebrates M. Niemiller 26 September 2014, 12:00 PM University of Georgia
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University of Tennessee 1Center for Wildlife Health2CVM Department of BDS
Debra L. Miller1,2 and Matthew J. Gray1
A Pathogen Lurking in the Darkness: Global Emergence of Ranavirus
in Ectothermic Vertebrates
M. Niemiller
26 September 2014, 12:00 PM University of Georgia
Outline
I. Ranavirus Characteristics and Die-offs
II.II. Pathology of RanavirusesPathology of Ranaviruses
III.III. Learning about Ranavirus (FV3) EcologyLearning about Ranavirus (FV3) Ecology
IV. Can Ranaviruses Contribute to Declines?
Ranavirus Characteristics•dsDNA, 150-280K bp
•120-300 nm in diameter (3x smaller than bacteria)
•Icosahedral Shape (20)
Family: Iridoviridae
Virion
Chinchar et al. (2011)
Iridovirus, Chloriridovirus, Ranavirus, Megalocytivirus, and Lymphocystivirus Genera:
Brunner et al. (2004), Harp & Petranka (2006), Brunner et al. (2007), Hoverman et al. (2010), Robert et al. (2011)
Routes of Transmission
Indirect Transmission
Skin, Gills, Intestines
(epithelial cells)
(3 hrs viral transcription)
Water or
Sediment
Ingestion
Incidental, Necrophagy, Cannibalism,
Predation
(Mortality 2X Faster)
Direct Contact
One Second Skin Contact
Ranaviral DiseaseRanaviral Disease
Gross changesGross changes
Lesions can look similar across classes (amphibian, reptile, fish)Lesions can look similar across classes (amphibian, reptile, fish)– Hemorrhage, swelling and necrosis (tissue death) are common gross Hemorrhage, swelling and necrosis (tissue death) are common gross
Common frog (Rana temporaria)Photos: Amanda Duffus
ulceration
hemorrhage
Brazil : 2 Brazil : 2 presentations: presentations:
tadpoles vs tadpoles vs adultsadults
(Mazzoni, in prep)(Mazzoni, in prep)
Edema and Hemorrhages
Neurologic: vestibular syndrome
Hemorrhage and necrosis
Photos: R. Mazzoni
Is this Is this ranaviral ranaviral disease in disease in hellbendershellbenders?? Ozark hellbender (K. Irwin)
Ozark hellbender (K. Irwin)
It is in Chinese Giant Salamanders! (Y. Geng)
How about this?How about this?
Cryptobranchus alleganiensis alleganiensisPhoto: Dale McGinnity and Sherri Reinsch
And what role do And what role do ectoparasites (leeches) play?ectoparasites (leeches) play?
Photos: B Sutton and R Hardman
Bullfrog (~10%; 0% FV3)
Cope’s Gray tree frog (~70% RI; ~40% FV3)
Wood frog (~ 100% for both)
Varies by host-susceptibil i ty & virus isolateVaries by host-susceptibil i ty & virus isolate(mortality: RI [ranaculture isolate] vs FV3)(mortality: RI [ranaculture isolate] vs FV3)
Are isolates from captive (culture) facil i t ies more virulent?
Necrotic (white ) areas inside the mouth (circles and arrows). Upper photo with mouth opened. Lower photo with mandible removed
Photo: Mark RuderPhoto: Mark Ruder
Photo: Mark RuderPhoto: Mark Ruder
Photo: Mark RuderPhoto: Mark Ruder
Reptiles(most often chelonian reports)Similar reports in snakes
HistologyHistology Lesions can look similar across classes (amphibian, reptile, fish)Lesions can look similar across classes (amphibian, reptile, fish)
– Cellular necrosis of the hematopoietic tissue, vascular endothelium and Cellular necrosis of the hematopoietic tissue, vascular endothelium and epithelial cells and intracytoplasmic inclusion bodies are common epithelial cells and intracytoplasmic inclusion bodies are common microscopic lesionsmicroscopic lesions
Endothel ium
Endothel ial necrosis
Spleen Necrosis
AmphibiansAmphibians
Vestibular hemorrhage and necrosis(Mazzoni, in prep)
•Transmission is efficient – Multiple Routes •Environmental Persistence is long (1 – 3 mo)
•Anthropogenic Stressors and Pathogen Pollution contribute to Ranavirus Emergence
Ranaviruses represent a significant threat to the global biodiveristy of ectothermic vertebrates
What can we do?
•Establish surveillance programs (broad then focus on hotspots, >40% infection)
•Identify mechanisms of emergence(natural, stressors, novel strains)
•Identify and implement intervention strategies(break host-pathogen cycle, reduce stressors,
biosecurity precautions)
Gray and Miller (2013)
World Organization for Animal Health
Chytridiomycosis Ranaviral disease
2008
OIE Aquatic Code International Transport of
Animals
•Bleach >4%•EtOH >70%•Virkon >1%
•Nolvasan >0.75%
$75/ bottle
Notifiable Diseases
Schloegel et al. (2010)
Certification for Shipment
Disinfection: Johnson et al. (2003), Bryan et al. (2009), Gold et al. (2013)
Global Ranavirus Consortiumhttp://fwf.ag.utk.edu/mgray/ranavirus/ranavirus.htm
The goal of the GRC is to facilitate communication and collaboration among scientists and veterinarians conducting research on ranaviruses and diagnosing
Invited Talks and Poster SessionDirected Topic Discussions
WorkshopsField Trips
Presentation Contributors:
A. Balseiro, SERIDAM. Brand, University of TennesseeR. Brenes, Carroll University J. Chaney, University of TennesseeA. Duffus, Gordon CollegeR. Goodman, Hampden-Sydney CollegeR. Hardman, Laboklin GmbH & Co KGR. Hill, University of TennesseeJ. Hoverman, Purdue UniversityA. Kouba, Memphis ZooJ. Lankton, USGS NWHCR. Mazzoni, Universidade Federal de GoiásD. McGinnity, Nashville ZooP. Reilly, University of TennesseeM. Ruder, USDAS. Schlosshan, UT Histology (CVM)B. Sutton, Tennessee State UniversityT. Waltzek, University of FloridaB. Wilkes, UT Virology (CVM)