Ranaviral disease pathology and physiology


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2013 International Symposium on Ranaviruses
by Debra Miller

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  • Degeneration of hepcytes with loss of membrane integrityWidespread pyknosis and karyorrhexis (Hematopoietic and sinusoidal endothelial cell)
  • Low power kidney
  • Ranaviral disease pathology and physiology

    1. 1. Ranaviral Disease Pathology and Physiology Debra L. Miller, DVM, PhD Center for Wildlife Health and Department Biomedical and Diagnostic Sciences, University of Tennessee, Knoxville, TN http://scienceblogs.com/tetrapodzoology/wp- content/blogs.dir/471/files/2012/05/i- ef0fe026ef8adf268fbce8dda99e3d45- Uroplatus_fimbriatus_Piotr-Naskrecki_April-2010.jpg Photo: Blind Pony Hatchery Photo: N Haislip Photo: N Haislip
    2. 2. What information do we get when we identify lesions (pathology)?  Presence of disease (response of the individual to a pathogen/agent)  NOT exact etiology (generally not) but often a ‘list of differentials (possible causes)’  Insight into what might be happening to function (organ, system) within the individual (physiology)
    3. 3. Ranavirus  Amphibians: Anurans and Caudates  Reptiles: Turtles, Lizards, Snakes  Fish: Boney fish 3 Classes
    4. 4. Gross changes  Lesions can look similar across classes (amphibian, reptile, fish) – Hemorrhage, swelling and necrosis (tissue death) are common gross changes W. Sutton N. Haislip T. Waltzak
    5. 5. Amphibians: larvae Photo: J. Chaney Boreal Toad Photo: Nathan Haislip Bullfrog affected unaffected Photo: N. Haislip Bullfrog Photo: N. Haislip Wood frog
    6. 6. Amphibians: metamorphs Photo: Jordan Chaney Boreal Toad
    7. 7. Amphibian: adults Common frog (Rana temporaria) Photos: Amanda Duffus ulceration Midwife toad (Alytes obstetricans) Photos: Amanda Duffus ulceration Eastern spotted newt (Notophthalmus viridescens) Photo: Betsie B. Rothermel Hemorrhage Friable spleen Hemorrhage Gopher frog Photos: B Sutton and R Hardman
    8. 8. Is this ranaviral disease? Cryptobranchus alleganiensis alleganiensis Photo: Dale McGinnity and Sherri Reinsch
    9. 9. Photo: B Sutton and R Hardman And what role do ectoparasites (leeches) play?
    10. 10. Bullfrog (~10%; 0% FV3) Cope’s Gray tree frog (~70% RI; ~40% FV3) Wood frog (~ 100% for both) Varies by host (species)-susceptibility & isolate (mortality: RI [ranaculture isolate] vs FV3 = Amphibian isolates)
    11. 11. Necrotic (white ) areas inside the mouth (circles and arrows). Upper photo with mouth opened. Lower photo with mandible removed Photo: Mark Ruder Photo: Mark Ruder Photo: Mark Ruder Reptiles Similar reports in snakes and lizards (including being off feed, weight loss, dermatitis) Eastern Box Turtle (West Virginia) (Terrapene carolina carolina) Eastern Box Turtle (Kentucky) (Terrapene carolina carolina)
    12. 12. Blue arrows = left lung Yellow arrows = necrosis Liver Intestine Stomach Ocular discharge Ranavirus-Negative Herpesevirus-Negative Mycoplasma-POSITIVE (M. agassizzi) Ranavirus-POSITIVE Herpesvirus-Negative Mycoplasma-Negative Determining etiology Oral mucosal necrosis Photo: Mark Ruder Lung necrosis Photo: Mark Ruder Eastern Box Turtle (Virginia) (Terrapene carolina carolina) Eastern Box Turtle (Kentucky) (Terrapene carolina carolina)
    13. 13. Fish Photo: Emilie Travis Photos: Tom Waltzek Photo: Ted Henry
    14. 14. Histology
    15. 15. Histology  Lesions can look similar across classes (amphibian, reptile, fish) – Cellular necrosis of the hematopoietic tissue, vascular endothelium and epithelial cells and intracytoplasmic inclusion bodies are common microscopic lesions Endothelium Endothelial necrosis Spleen Necrosis
    16. 16. Amphibians
    17. 17. FV3 Box turtle isolate Pallid sturgeon isolate Ranaculture isolate Wood Frog Spleen
    18. 18. Reptiles
    19. 19. Pallid isolate; bath exposure
    20. 20. Pallid isolate; bath exposure
    21. 21. vasculitis Myofibers disrupted Ulcerated crust on oral mucosa Disrupted muscle fibers Photos: Mark Ruder
    22. 22. Fish
    23. 23. Photo: Emilie Travis
    24. 24. Hematopoietic necrosis; tubular epithelial necrosis Endothelium Endothelial necrosis Photo: Tom Waltzek
    25. 25. Visualizing the virus
    26. 26. Concurrent Infections
    27. 27. Concurrent infections Photo: Betsie B. Rothermel
    28. 28. Ranavirus-positive animals plus: Parasites increased In Tennessee: Die-off in L. clamitans, L. catesbeianus, N. viridescens Concurrent infections
    29. 29. Concurrent infections URTI Gopher Tortoise (Gopherus polyphemus) Photo: Jess Gonynor McGuire Eastern Box Turtle (Terrapene carolina carolina)
    30. 30. Concurrent infections  Parasitism – Soft shells (adults)  Spirorchid eggs (often systemic)  Entomeoba spp trophozoites (intestines only)  Bacterial Enteritis – Sliders (adults, not pictured)
    31. 31. Conclusions
    32. 32. Eastern spotted newt Notophthalmus viridescens American bullfrog Lithobates catesbeiana Creek chub Semotilus atromaculatus affected unaffected Eastern box turtle (Terrapene carolina carolina) Photo: Mark Ruder Red-eared slider (Trachemys scripta elegans) Pallid sturgeon Scaphirhynchus albus Photo: Tom WaltzekPhoto: Emilie Travis Photo: Betsie B. Rothermel CONCLUSIONS 1. Lesions can look similar across classes 2. Multiple age groups are affected 3. Interclass transmission is possible
    33. 33. Conclusions  Isolates from culture facilities appear to have considerably high virulence  Host susceptibility varies (and thus community composition may matter in epizootics) Pallid sturgeon isolate Ranaculture isolate Bullfrog (~10%; 0% FV3)Cope’s Gray tree frog (~70% RI; ~40% FV3) Wood frog (~ 100% for both)
    34. 34. Ranaviral Disease Pathology and Physiology  Current research directives: – characterizing the pathogenesis of ranaviral disease among virus isolates and among hosts (including lizards and snakes) – Elucidating the effects of concurrent pathogens on disease progression (chytrid and ranavirus; other viruses; mycoplasma)  In situ hybridization and immunohistochemistry are being used to visualize the virus within the tissues. Optimization for detecting multiple ranaviruses is being explored.
    35. 35. Acknowledgements  Matt Gray  Tom Waltzek  Bill Sutton  Jordan Chaney  Rachel Marschang  Becky Hardman  Rachel Goodman  Julia Lankton  Sharon Schlosshan and UT histology laboratory Histology Funding:  UT CVM Faculty Education and Research (FEAR) Fund  UT CVM Center of Excellence
    36. 36. Questions?