Tools and solutions to enhance shellfish aquaculture ... page/extension_conf/Jun… · 2010....
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Tools and solutions to enhance shellfish aquaculture production in the face of the emerging Ostreid herpes virus pathogens: OsHV-1 & OsHV-1 µvar National Aquaculture Extension Conference in Boise, June 5-9, 2017
Transcript of Tools and solutions to enhance shellfish aquaculture ... page/extension_conf/Jun… · 2010....
Tools and solutions to enhance shellfish aquaculture production in the face of the emerging Ostreid herpes virus pathogens: OsHV-1 & OsHV-1 µvar
National Aquaculture Extension Conference in Boise, June 5-9, 2017
Goals• The main aim of this proposal is to:
– Arm the shellfish industry with options and tools to prepare for the introduction and or spread of the lethal Ostreid herpes virus -1 and its variants:
• We will provide educational materials and training to help prevent OsHV-1 spread.
• In addition, we will provide:– Diagnostic tools, – Identify oyster herpesvirus-resistant oyster lines/species, – And determine relative risk of disease transmission among
life stages.
Importance of Oyster Culture• In the US, oysters represent
important economic and ecological species:
• In 2013 sales from 483 farms were worth $180M.
• The US West Coast leads US shellfish aquaculture with >$100M (56%) produced annually; $24M (16%) and $50M (28%) are grown along the Gulf and East coasts, respectively.
• The Pacific oyster, Crassostreagigas, dominates oyster culture value (48%).
• We address “Emerging and Re-emerging Diseases Affecting Aquaculture Production”
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Pacific Northwest Oyster Culture
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Oyster aquaculture production along the US west coast (Pacific Northwest) (www.fao.org)
Oyster mortalities in Tomales Bay
• The Oyster Herpesvirus (OsHV) was first detected in 2002 & via examination of archived samples is known to have been present as early as 1995
• Initially no disease agent was identified
• Short pulses of mortality of juvenile Pacific oysters have occurred nearly annually since 1993 (up to 90% )
• OsHV is non-culturable and is difficult to detect with traditional methods – Need rapid molecular assays
• OsHV-1-induced Pacific oyster losses in TB closure of oyster farms and establishment of oyster farms in other embaymentsto reduce losses due to OsHV-1 and expand the US west coast shellfish aquaculture industry
Presenter
Presentation Notes
Tools developed herein will focus on emergency preparedness allowing prompt decisions on the movement of oysters in the US (i.e. rapid molecular assays to quantify and distinguish OsHV-1 variants) and provide a rapid response for the industry (i.e. by determining family lines or species resistant to the virus), a goal strongly supported by our industry partners.
Oyster herpesvirus: 1993-2002
OsHV-1 detection
Presenter
Presentation Notes
When I started working on my PhD in the Fall of 2002, information about the virus was contained to France and New Zealand where mortalities associated with the virus started in the early 1990’s. The virus was known to cause mortality in larval and juvenile bivalves, a phenomnom particularly well-studied in Pacific oysters. In the fall of 2002, we first detected OsHV-1 in Tomales Bay, California, an area hampered by large scale mortalities of seed oysters. Around the same time, the virus was detected in oysters from Japan, Korea, and China
Oyster herpesvirus: 2008-2016
OsHV-1 detection OsHV-1 µvar or microvariant detection
Presenter
Presentation Notes
The disease has been described as the most problematic emerging disease in oysters for the last 40 years!! France: 2008: with increased mortalies & more life stages affected. Moved within Europe likely with oyster shipments in many cases-Ireland, Spain, UK, Italy; no evidence of this in Portugal, Netherlands, Norway and Sweden. Ireland: 3 bays 2008, 16 2009 & 29 out of 30 in 2012; all 30 bays declared positive 2010 in New Zealand and Australia. Moved within New Zealand with animal transfers. In Australia, became endemic to two estuaries where unable to now culture, and moved without animal transfers to Tasmania in 2016 After the initial emergence of OsHV-1 µvar in France, OsHV-1 µvar or microvariants and mortalities have been reported to spread geographically in Europe (first date of detection) including Spain (2008; (Roque et al., 2012), Italy (2010; (Dundon et al., 2011)), Ireland (2008; (Morrissey et al., 2015), United Kingdom (2008; (Peeler et al., 2012)), the Netherlands (2011; (Gittenberger et al., 2016), Portugal (2011; (Batista et al., 2015)), Sweden (2014; (Mortensen et al., 2016)), and Norway (2014; (Mortensen et al., 2016)). Though specific regulatory frameworks exist in Europe to control movements of live animals and trade (reviewed in (Pernet et al., 2016), shipments of Pacific oysters from France into several of these countries coincides with detection of an OsHV-1 microvariant genotype including Spain (Roque et al., 2012), Ireland (Morrissey et al., 2015), the United Kingdom (Peeler et al., 2012), and Italy (Dundon et al., 2011). In contrast, in other locations, no evidence was presented for introduction of OsHV-1 µvar or microvariants with live animal shipments including wild C. angulata in Portugal and feral C. gigas in the Netherlands/Scandanavia. Interestingly, OsHV-1 microvariants were detected in both Norway and Sweden prior to OsHV-1 associated mortalities in 2014, but cooler water temperatures may have limited viral infection and spread (Mortensen et al., 2016). OsHV-1 microvariants causing C. gigas mortalities were first detected in 2010 in both New Zealand (Bingham et al., 2013, Keeling et al., 2014) and Australia (Jenkins et al., 2013). In New Zealand, OsHV-1 has only been detected to date in the North Island, and likely spread between farms through animal transfers (Bingham et al., 2013). Though OsHV-1 microvariants have spread in Australia, both within New South Wales and in 2016 to Tasmania (~850 km from New South Wales) both initial emergence and spread has not been linked to animal transfers. Though OsHV-1 microvariants have been described in Asia (South Korea, China, and Japan), routine monitoring of OsHV-1 has not been conducted and reports are limited. Recent reports from China (Bai et al., 2015) and Japan (Shimahara et al., 2012) indicate the presence of OsHV-1 microvariants in both countries. In South Korea, a recent report indicated OsHV-1 involved in mortalities in an oyster hatchery (Hwang et al., 2013). DOUBLE CHECK ALL LOCALS.
Project Background• OsHV-1 µvar’s ability to kill seed and adults heightens concern
over this variant relative to its progenitor, OsHV-1, which is lethal to larvae and young oysters.
• OsHV-1 resistance has been shown to confer resistance to µvarin field trials in France.
– In addition, these resistant oysters were able to both limit infection loads and eliminate virus from their tissues.
• In New Zealand, oysters susceptibility to µvar decreased over time providing hope for development of resistance.
• Collectively this suggests that selection for resistance is possible and that preparing for OsHV-1 µvar is prudent.
2016 PCSGA Shellfish Health & Disease Panel
Major focus of questions:OsHV-1 and OsHV-1 μvars, NSGO funds proposal for additional work
California Sea Grant New Data• We have demonstrated increased resistance to
OsHV-1 in some US west coast Pacific oyster lines
• Summer 2015, we identified two hybrid Pacific oyster lines from an industry breeding program (Taylor Hybreed) with differential survival
• One line (10-15:58x19) experienced moderate (47%), and a second line (10-15:12x52) experienced low (25%), survival after OsHV-1 exposure in TB
• Whole body burden of OsHV-1was 1.5x higher on average in the family with low survival relative to that with higher survival
• The survival of line 10-15:58x19 was considered exceptional given the young age and very small size (~5 mm) of these spat
• Susceptibility to OsHV-1 is inversely proportional to size
Figure 2. Differential performance of seed from two hybrid Pacific oyster families planted in Tomales Bay summer 2015. A. Body burden (log10 copies of OsHV-1 DNA per oyster). B. Oyster survival.
Body burden of OsHV-1 DNA per oyster
Oyster survival
Presenter
Presentation Notes
Seed were planted 2 weeks prior to 9/10/15 on 8/27/15
OsHV-1 in California
MORTALITY
TEMPERATUREOsHV-1
PACIFIC OYSTERS
Role of alternate hosts?
Disease resistance?
Tools: qPCR; RT qPCR; OsHV-1 transcriptome & genome
Host physiology & susceptibility?
Presenter
Presentation Notes
My attempt at a simple model of this system: Temperature is clearly linked with disease, in years we’ve monitored mortalities occur after non-lethal temperatures. Data indicate that naïve individuals only contact the virus after a temperature increase, perhaps from a latent virus infections from previous years surivvors leading to mass mortalities—up to nearly 100% in certain groups, though it appears to have a genetic and size component. We are currently looking at this using families of Pacific oysters, planted over time followed by a paired genotype by sequencing and transcriptomic response. We don’t currently know much about reservoirs but data indicate that other species may have low level infections by using PCR as a proxy.
OsHV-1 µvar replicates & kills QUICKLY!Vi
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In order to reach our objectives (described below), we will test the following hypotheses:
• H1: Species and family lines will demonstrate differential survival in the face of OsHV-1 and OsHV-1 µvar exposure.
• H2: Oyster families or species resistant to OsHV-1 are also resistant to OsHV-1 μvar.
• H3: Genome variation of viral strains (i.e. the California OsHV-1 and OsHV-1 μvar strains) can explain differences in virulence.
Objectives: • Objective 1: Develop a (multi-plex) real-time,
quantitative polymerase chain reaction (qPCR) assay.
• Objective 2: Conduct field trials to oyster families/species with differential susceptibility to OsHV-1.
• Objective 3: Conduct laboratory trials to examine differential seed survival to OsHV-1 µvar.
• Objective 4: Sequence the viral genomes used in infection trials (California OsHV-1 and OsHV-1 µvars strains)
Presenter
Presentation Notes
Year 3 Uvar sequence vs OsHV-1 = large deletion in France in 2008-2010 and most locations but local variation: deletions, insertions (indels). OIE: seq variation in microsatellite locus upstream of ORF 4 and, within ORFs 4, 42 and 43 vs OsHV-1 ref sequence (Saggarra et al. 2010) Europe, NZ, Australia and Asia.
Conclusions
• OsHV-1 and its µvars are serious pathogens of oysters
• Our goal is to limit spread by education and outreach
• We aim to develop tools (molecular assays and oyster lines) to better enable management of this disease, early detection and adaptive management of our oyster stocks
