Transmission of ranavirus between

ectothermic vertebrate hosts

Roberto Brenes1*, Matthew Gray1, Debra Miller1,2,

Rebecca. P. Wilkes2, and Thomas. B. Waltzek3

1Center for Wildlife Health and 2College of Veterinary Medicine,

University of Tennessee

3College of Veterinary Medicine, University of Florida

What is killing the frogs?

• Emerging infectious

diseases (Daszak et al.

2003, Hayes et al. 2010)

• Batrachochytrium

dendrobatidis (Bd): Tropics

• Ranaviruses: North America

and Europe

(Lips et al. 2005, Lips et al.

2006, Kilpatrick et al. 2010)

(Duffus et al. 2008, Gray et al.

2009, Teacher et al. 2010)

Ranavirus Hosts

Poikilothermic Hosts

• Turtles (Johnson et al. 2008, Allender

et al. 2011)

• Snakes (Hyatt et al. 2002)

• Salamanders (Jancovich et al.

2003, Geng et al. 2010)

• Frogs (Green et al. 2002, Miller et al.

2007).

• Fish (Chinchar et al. 2001, Gobbo et al.

2010, Jensen et al. 2011)

Most Reported Die-offs

How Does Ranavirus Persist?

• Environmental persistence (Nazir et al. 2012)

• Post-metamorphic stages (Brunner et al. 2004)

• Ectothermic vertebrates (Jancovich et al. 2011, Grayfer et al. 2012)

– Reservoirs

Community Level Transmission

Fish

Reptile

Can ranavirus move among host species?

Sympatric Ectothermic Vertebrate Species

Pathogen

Amphibian

Objective

• Test whether a FV3-like

ranavirus could be

transmitted between

ectothermic vertebrate

hosts

Three Suitable Hosts

0

10

20

30

40

50

60

70

80

90

100

Cope's Gray tree frog Red-eared slider Mosquito fish

Mo

rtal

ity

(%)

85% mortality

Hoverman et al. (2011)

40% mortality

Waltzek et al. (unpub.data)

10% mortality

Brenes et al. (unpub.data)

Susceptibilities tested

during single challenge

experiments

Treatments

1. Exposed turtle and unexposed

tadpole

2. Exposed tadpole and unexposed

turtle

3. Exposed fish and unexposed

tadpole

4. Exposed tadpole and unexposed

fish

5. Exposed tadpole and unexposed

tadpole

The control treatments were unexposed turtle and fish, turtle and tadpole, fish and

tadpole, and tadpole and tadpole

Experiment

• Direct exposure

– Exposed to 103 PFU/mL

– 3 days

• 12-L containers divided in

half by a 2000 µm plastic

mesh

• Different species in each

side of the container

Infection Results

• Turtles infected

amphibians

• Amphibians infected

turtles

• Fish infected Amphibians

• Amphibians did not

infected fish

50%30%10%

0

10

20

30

40

50

60

70

80

90

100

R | A F | A A | R A | F

Infe

cted

(%

)Treatment

Direct

Indirect

*

*

20% 50%

30% Cleared the infection after 28 days

Mortality Results

• Not all species caused mortality

• Turtles caused mortality in amphibians

• Amphibians did not cause mortality in turtles

• Fish caused mortality in Amphibians

• Amphibians did not caused mortality in fish

50%10%

0

10

20

30

40

50

60

70

80

90

100

R | A F | A A | R A | FM

ort

alit

y (%

)Treatment

Direct

Indirect

**

28 Days

12% Amphibians and 100% turtles infected survived5% Amphibians infected survived20% infected turtles survived20% infected Fish survived

Turtle and Fish Results

• All classes tested can

transmit the virus

• Turtles infected tadpoles

– 50% mortality

• Fish infected tadpoles

– 10% mortality

50%

10%

Amphibian Results

• Indirect mortality only in

amphibians

• Amphibians did not cause

fish or turtle mortality

• High indirect mortality

New Findings

• Previous studies

– Fish susceptible to amphibian ranavirus (Jensen et al. 2011, Moody

and Owens 1994)

– Turtle hatchlings susceptible to amphibian ranaviruses (Ariel 2007)

– Amphibian susceptible to fish ranavirus (Bailey et al. 2013)

• All previous studies

– Direct exposure to ranavirus

– Laboratory experiments

• These is the first study to document:

– Indirect transmission between ectothermic classes

– Transmission between reptiles and fish

Conservation Implications

• Interclass transmission can occur among ectothermic

hosts

• Reptiles and fish can present asymptomatic infections

– Pass the infection to amphibians

– Clear the infection

• Fish and turtles could act as reservoirs of ranavirus when

amphibians are absent

• Interclass transmission can contribute to pathogen

persistence and explain reoccurrence of die-offs

Acknowledgments

• UT Institute of Agriculture

– UT AgResearch Grant

– UT College of Veterinary Medicine

– Access and Diversity Fellowship (UT AgResearch)

– Hazelwood Scholarship (CASNR)

– UT-ESPN Scholarship (CASNR)

– Society of Wetland Scientists Student Research Grant

• Drs. Melissa Kennedy (CVM)

• Dr. Mark Campbell and Roger Long (JARTU)

• Jen Tucker

• Technicians and Volunteers

Questions??

Contact:

rbrenes@utk.edu

mgray11@utk.edu

dmille42@utk.edu