Ranaviral disease pathology and physiology

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

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)

Ranavirus

Amphibians: Anurans and Caudates

Reptiles: Turtles, Lizards, Snakes

Fish: Boney fish

3 Classes

Gross changes

Lesions can look similar across classes (amphibian, reptile, fish)

– Hemorrhage, swelling and necrosis (tissue death) are common gross

changes

W. Sutton N. HaislipT. Waltzak

Amphibians: larvae

Photo: J. ChaneyBoreal Toad

Photo: Nathan HaislipBullfrog

affected

unaffectedPhoto: N. HaislipBullfrog

Photo: N. HaislipWood frog

Amphibians: metamorphs

Photo: Jordan ChaneyBoreal Toad

Amphibian: adultsCommon 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 frogPhotos: B Sutton and R Hardman

Is this ranaviral disease?

Cryptobranchus alleganiensis alleganiensisPhoto: Dale McGinnity and Sherri Reinsch

Photo: B Sutton and R Hardman

And what role do ectoparasites (leeches) play?

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)

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

ReptilesSimilar 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)

Blue arrows = left lungYellow arrows = necrosis

LiverIntestine

Stomach

Ocular discharge

Ranavirus-NegativeHerpesevirus-NegativeMycoplasma-POSITIVE (M. agassizzi)

Ranavirus-POSITIVEHerpesvirus-NegativeMycoplasma-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)

Fish

Photo: Emilie Travis

Photos: Tom Waltzek

Photo: Ted Henry

Histology

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

Amphibians

FV3 Box turtle isolate

Pallid sturgeon isolate Ranaculture isolate

Wood Frog Spleen

Reptiles

Pallid isolate; bath exposure

Pallid isolate; bath exposure

vasculitis

Myofibers disrupted

Ulcerated crust on oral mucosa

Disrupted muscle fibers

Photos: Mark Ruder

Fish

Photo: Emilie Travis

Hematopoietic necrosis; tubular epithelial necrosis

Endothelium

Endothelial necrosis

Photo: Tom Waltzek

Visualizing the virus

Concurrent Infections

Concurrent infections

Photo: Betsie B. Rothermel

Ranavirus-positive animalsplus: Parasites increased

In Tennessee: Die-off in L. clamitans, L. catesbeianus, N.

viridescens

Concurrent infections

Concurrent infections

URTI

Gopher Tortoise (Gopherus polyphemus)Photo: Jess Gonynor McGuire

Eastern Box Turtle(Terrapene carolina carolina)

Concurrent infections

Parasitism

– Soft shells (adults) Spirorchid eggs (often systemic)

Entomeoba spp trophozoites(intestines only)

Bacterial Enteritis

– Sliders (adults, not pictured)

Conclusions

Eastern spotted newtNotophthalmus viridescens

American bullfrogLithobates catesbeiana

Creek chubSemotilus

atromaculatus

affected

unaffected

Eastern box turtle

(Terrapene carolina carolina)

Photo: Mark Ruder

Red-eared slider (Trachemys scripta elegans)

Pallid sturgeonScaphirhynchus

albusPhoto: 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

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)

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.

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

Questions?