Amphibian ranavirus disease dynamics in an industrially altered landscape
1. Amphibian ranavirus dynamics in
an industrially altered landscape
Danna M. Schock
2nd International Symposium on Ranaviruses
Knoxville TN, 27-29 July 2013
2.
3. Map from the Washington Post
Fort McMurray, Alberta
Oilsands, boreal forest, big money & big politics
4. RV dynamics like prevalence
& frequency of outbreaks
Habitat
characteristics, Wetland
classification
Contaminant levels in
amphibian tissues
and breeding ponds
Population biology &
biomarkers of (chronic)
stress
Proximity to disturbancesCan wood
frogs be used
to monitor
ecosystem
health in the
oil sands?
5. Establishing field sites – 2012 & 2013
1)Wood frogs breeding at the site
2)In close proximity to air monitoring
stations
3)Geographically representative of the
landscape*
4)Safe to work
Priority placed on identifying wetlands suitable for long-term
monitoring of the oil sands region of Alberta.
6. Atmospheric deposition and pulses of contaminants into amphibian
breeding ponds in the spring
Photo: Dave Cooper, Calgary Herald
Snow sampling March 2013
8. Ranaviruses detected widely in
wood frogs
12/27 (44%) sites positive at
least once from 2010 – 2013
Positive wetlands from Fort
Resolution to Fort McMurray
● PCR and/or characteristic
lesions and carcasses
(~2,200 samples still to
screen, including most
samples from 2013)
9. Ranaviruses detected widely in
wood frogs
Ranavirus-related die-offs at
remote sites (helicopter access
only) and highly disturbed sites
Die-offs take place last week of
June/first week of July
● irrespective of type of site
● irrespective of spring thaw
10. Ranaviruses detected widely in
wood frogs
The majority of carcasses are
tadpoles Gosner stages 37 - 40
All positives sequenced to date are
FV3-like
● MCP4/5 primers
● but see Schock et al. 2008 Copeia
re “hidden” variability of northern
isolates
● additional characterization in
progress by J. Brunner
11.
12.
13. Data collected
Basic information
• Species
• Snout-Vent-Length
• Gosner stage (tadpoles), weight (terrestrials)
• Physical abnormalities
Tissue samples
• toe/tail clips (several times/year, screen for
RV, Bd)
• lethal whole body, once/year, screen for
contaminants and evidence of stress
Water quality
• pH & conductivity (handheld meters)
• In-depth analysis (3x per active season)
including hardness, and 26 metals, 74
PAH, and 60 NA
14. Narratives of 3 wetlands
• Jetliner – loss of entire age class
• Tower Road – repeated die-offs, no apparent change in
population biology (yet?)
• Gateway – why hasn’t ranavirus been detected here (yet)?
Results – an evolving story
15. Distribution of mass of
terrestrial wood frogs in
2013 at 6 intensively
studied sites.
Mass (g)
Jetliner
#ofindividuals
26. Size at metamorphosis is another indication of population health
Snout-vent length (mm) of Gosner Stage 44
wood frogs in 2013
F5,159 = 17.287, P < 0.01a
a
b
27. A role for environmental transmission?
Unrelated 2011 lab study:
Only wood frog tadpoles in reference wetland
water and aged tap water became infected.
FV3: apparently “killed” by something in the
OSPM water?
Tadpoles in the OSPM water: 85%+ survival Gateway
28. A role for invertebrates in ranavirus transmission?
• Impede transmission by scavenging carcasses quickly?
• Facilitate transmission or persistence – leeches ?
29. What about nutrient/energy cycles in these wetlands?
• Die-off years vs non-die-off years?
• Different invertebrate species assemblages?
30. Data to come:
PCR screening of 2,200+ tissue
samples for ranavirus
Water and tissue contaminant
analyses
Bio-markers of (chronic) stress –
metabolomics, CORT
Other fitness correlates –
triglycerides & glycogen
PCA and Regression analyses
