Transmission of ranavirus between ectothermic vertebrate hosts
1. 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
2. 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)
3. 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
4. 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
6. Objective
• Test whether a FV3-like
ranavirus could be
transmitted between
ectothermic vertebrate
hosts
7. Three Suitable Hosts
0
10
20
30
40
50
60
70
80
90
100
Cope's Gray tree frog Red-eared slider Mosquito fish
Mortality(%)
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
8. 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
9. 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
10. 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
Infected(%)
Treatment
Direct
Indirect
*
*
20% 50%
30% Cleared the infection
after 28 days
11. 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 | F
Mortality(%)
Treatment
Direct
Indirect
*
*
28 Days
12% Amphibians and 100% turtles infected survived5% Amphibians infected survived20% infected turtles survived20% infected Fish survived
12. Turtle and Fish Results
• All classes tested can
transmit the virus
• Turtles infected tadpoles
– 50% mortality
• Fish infected tadpoles
– 10% mortality
50%
10%
13. Amphibian Results
• Indirect mortality only in
amphibians
• Amphibians did not cause
fish or turtle mortality
• High indirect mortality
14. 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
15. 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
16. 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
