Vibrio tubiashii and Pacific oyster disease susceptibility
1. Vibrio tubiashii : disease and pathogenicity to
Pacific oyster larvae
Pacific Coast Shellfish Growers Association Annual Meeting
September 26, 2012
Elene Dorfmeier, Carolyn Friedman, Steven Roberts
University of Washington | School of Aquatic & Fishery Sciences
2. Pacific Northwest
Shellfish Industry
Photo: OSU
• USD100 million industry (~3000 jobs)
• Large-scale production reliant on
shellfish hatcheries
• Oysters account for ~76% of shellfish
production
Google Maps
4. The Pathogen:
Vibrio tubiashii (Vt)
Gram-negative, facultative anaerobe
Causative agent of vibriosis in early stage shellfish
Pathogenic to a variety of marine invertebrates,
including Pacific oyster
Photo: Phetsouvanh et al. 2008
5. Disease
Vibriosis:
Characterized by bacterial swarming, loss of
motility, soft tissue necrosis, and mortality
Larval mortality within 24 hours of exposure to
the most pathogenic strains
Management of bacterial disease has been
historically problematic
Re-emergent in the Northwest
Larvae Photo: Lisa Crosson
Bacteria Photo: Dartmouth EM Facility
6. Environmental Change:
Ocean Acidification
The chemical changes associated with the increase
of CO2 in the oceans.
• increases aqueous CO2
• lower seawater pH
• decreased carbonate ion (aragonite, calcite)
availability
7. Acidification of Northwest Waters
SUMMER 2009:
Dabob Bay
Totten Inlet
Map: R. Jacobsen Graphs: Simone Alin et al. NOAA
8. Impact of Ocean Acidification on
Marine Calcifiers
Effects of ocean acidification on calcifying
organisms:
Growth and development
Energy allocation
Metabolic depression
Photo: Emma Timmons-Shiffman
9. Environmental Shifts and
Shellfish Aquaculture
1. Re-emergent bacterial disease
Vibrio tubiashii
2. Host response to environmental shifts
high pCO2 and temperature
Photo credit: Steve Ringman, Seattle Times
10. Research Goals
Investigate the influence of elevated pCO2
on Vibrio tubiashii growth
Determine the impact of elevated pCO2 on
Pacific oyster larval susceptibility disease
Photo: Norbert Dankers
11. Investigate the influence of
elevated pCO2 on Vibrio tubiashii
growth
Photo: Dartmouth Electron Microscope Facility
17. Total Abundance
*
*
p = <0.001
*
Error Bars = 95% CI
Stationary Phase
18. Summary: Vt Growth
At 16°C, Vt grew faster and reached higher
abundance at elevated pCO2
Enhanced Vt growth under acidified conditions may
lead to outbreaks of vibriosis in hatcheries
Why? / How?
Enhanced gene expression of cell division when exposed to lower
pH (cadA, toxR, rpoS)?
Photo: Dartmouth Electron Microscope Facility
19. Determine the impact of elevated
pCO2 on Pacific oyster larval
susceptibility disease
Photo: Virginia Sea Grant
20. Vt Disease Challenge
Temperature:
16°C
pCO2:
Disease
Ambient (7.9 pH) agent:
750 ppm (7.8 pH) V. tubiashii
2000 ppm (7.4 pH) RE22
Vt doses (102 – 106 CFU/ml)
LD50 at 24, 48, and 72 hrs
Photo: Ghent University
21. Overview: Vt Disease Challenge
Early stage Prodissoconch I
D-veliger veliger
3 days old 10 days old
Photo: FAO
22. Results: Larval Disease Challenges
Larval survival after 48 hours Vt exposure
Late Stage
Early stage
ND ND
Error Bars: 95% CI
p-values >> 0.05
23. LD50 Results
Early stage
Late Stage
LD50 reported in CFU/ml of V. tubiashii
Logistic curve: Pi = 1 / (1 + e –(a + b * x))
24. LD50 Results
Early stage
Late Stage
LD50 reported in CFU/ml of V. tubiashii
Logistic curve: Pi = 1 / (1 + e –(a + b * x))
25. LD50 Results
Early stage
Late Stage
LD50 reported in CFU/ml of V. tubiashii
Logistic curve: Pi = 1 / (1 + e –(a + b * x))
26. Larval Disease Challenge
No detectable difference in Pacific oyster susceptibility
to vibriosis at elevated pCO2.
Considerations:
• Length of exposure to experimental conditions
• Conditions throughout early shell development is
important to overall survival
• Vt culture conditions
27. Summary: Disease and OA
Elevated pCO2 does not affect Vt pathogenicity, but Vt
growth under acidified conditions may facilitate
outbreaks of vibriosis
Higher temperature exacerbates growth
Still many unanswered questions
Rearing oysters at lower temperatures when higher
pCO2 levels exist may have lower risk of vibriosis
Trade-off less disease / slower oyster growth
28. Saltonstall-Kennedy Program (NOAA)
UW School of Aquatic & Fishery Sciences
Generous student support provided by NOAA
NSA – Pacific Coast Section
Ed and Vicky Jones
Taylor Shellfish Hatchery
Washington Sea Grant
NOAA PMEL
Joth Davis - Taylor Resources
Emma Timmons-Shiffman
Mackenzie Gavery
Sammi Brombacker
Robyn Strenge
Alex Rutherford
Notas do Editor
Washington state is a large producer of molluscan shellfish larvae for export to growers both in the US and abroadProduction of shellfish in the US has increased dramatically in recent years
In the past few decades, the PNW has encountered a number of serious problems concerning natural bivalve populations and hatchery propagation of several bivalve species. Some of these problems include…it is critical to examine the problems facing bivalve larvae from a regional perspective by systematically assessing how the environment influences such as OA and pathogens, like VT, and the spread of disease can affect organismal processes of both pathogen and host.
Natural processes can accelerate acidification of coastal watersIn the PNW, environmental affects of OA are evident. Seasonal coastal upwelling events along the continental shelf of the Pacific coast cause major shifts in pH in the Sound. The 2 graphs on the right, summer pH measurements from Dabob Bay and Totten Inlet, were data collected by Simone Alin. The graphs illustrate a strong fluctuation in pH in both areas that dive as low as 7.4 at both locations. Recent data from NOAA surveys show a range of pH of Pacific coastal areas ranging from 7.2 – 9.0 pH units! The levels seen here influence our selection of experimental pCO2 levels used.Local processes that contribute to acidification of water in the Sound exacerbate acidification conditions that.
The affects of OA on calcifying organisms have been an extensive area of study in recent years. Some of the major findings of many of these studies include slower growth and development, shifts in energy allocation and metabolic depression as a result of environmental stress. What we don’t know yet is how environmental shifts will impact pathogen-host interactions or disease susceptibility in early life stage bivalve larvae. Especially in the economically important pacific oyster.
Recruitment failures in both natural populations and hatchery propagated bivalve populations
Within the hatchery, high potential for Vt blooms given higher temperaturesMore fuel to obtain maximum bacterial growth mortality!
In summary, there was no detectable difference in oyster susceptibility to vibriosis at elevated pCO2 or larval stage.Why might this be?There are a few things that I have considered that may affect susceptibility of host that are difficult to account for.Intrinsic variation of larval populations from week to week may account for some of the variability seen in this experiment.Length of exposure to low pH – Larvae were spawned in the hatchery and acutely exposed to low pH. Mortality was determined after exposure. What if larvae were spawned under low pH?The saturation state of calcium carbonate minerals and carbonate ion availability – Recently published research by Gazeau at al. has shown that growth and developmental success of oysters to be sensitive carbonate ion availability, not pH directly.Vt culture conditions – how does elevated pCO2 affect virulence factors of Vt? – that’s next!
Difference of proportion power calculation for binomial distribution (arcsine transformation) h = 0.8 n = 24sig.level = 0.05 power = 0.7914094 alternative = two.sided
