scholarly journals Differential Mortality and High Viral Load in Naive Pacific Oyster Families Exposed to OsHV-1 Suggests Tolerance Rather than Resistance to Infection

Pathogens ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1057
Author(s):  
M. Victoria Agnew ◽  
Carolyn S. Friedman ◽  
Christopher Langdon ◽  
Konstantin Divilov ◽  
Blaine Schoolfield ◽  
...  
Keyword(s):  
Pacific Oyster ◽  
High Viral Load ◽  
The United States ◽  
Differential Mortality ◽  
Breeding Programs ◽  
Pacific Oysters ◽  
Copy Numbers ◽  
Resistance To Infection ◽  
Ostreid Herpesvirus 1 ◽  
Tomales Bay

Pacific oysters, Crassostrea gigas, are one of the most productive aquaculture species in the world. However, they are threatened by the spread of Ostreid herpesvirus-1 (OsHV-1) and its microvariants (collectively “µvars”), which cause mass mortalities in all life stages of Pacific oysters globally. Breeding programs have been successful in reducing mortality due to OsHV-1 variants following viral outbreaks; however, an OsHV-1-resistant oyster line does not yet exist in the United States (US), and it is unknown how OsHV-1 µvars will affect US oyster populations compared to the current variant, which is similar to the OsHV-1 reference, found in Tomales Bay, CA. The goals of this study were to investigate the resistance of C. gigas juveniles produced by the Molluscan Broodstock Program (MBP) to three variants of OsHV-1: a California reference OsHV-1, an Australian µvar, and a French µvar. This is the first study to directly compare OsHV-1 µvars to a non-µvar. The survival probability of oysters exposed to the French (FRA) or Australian (AUS) µvar was significantly lower (43% and 71%, respectively) than to the reference variant and controls (96%). No oyster family demonstrated resistance to all three OsHV-1 variants, and many surviving oysters contained high copy numbers of viral DNA (mean ~3.53 × 108). These results indicate that the introduction of OsHV-1 µvars could have substantial effects on US Pacific oyster aquaculture if truly resistant lines are not achieved, and highlight the need to consider resistance to infection in addition to survival as traits in breeding programs to reduce the risk of the spread of OsHV-1 variants.

scholarly journals First evaluation of resistance to both a California OsHV-1 variant and a French OsHV-1 microvariant in Pacific oysters

BMC Genetics ◽  
2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Konstantin Divilov ◽  
Blaine Schoolfield ◽  
Benjamin Morga ◽  
Lionel Dégremont ◽  
Colleen A. Burge ◽  
...  
Keyword(s):  
United States ◽  
Genetic Correlations ◽  
Genetic Selection ◽  
The United States ◽  
Plate Assay ◽  
Pacific Oysters ◽  
Significant Heritability ◽  
Ostreid Herpesvirus 1 ◽  
Tomales Bay ◽  
Us West

Abstract Background Variants of the Ostreid herpesvirus 1 (OsHV-1) cause high losses of Pacific oysters globally, including in Tomales Bay, California, USA. A suite of new variants, the OsHV-1 microvariants (μvars), cause very high mortalities of Pacific oysters in major oyster-growing regions outside of the United States. There are currently no known Pacific oysters in the United States that are resistant to OsHV-1 as resistance has yet to be evaluated in these oysters. As part of an effort to begin genetic selection for resistance to OsHV-1, 71 families from the Molluscan Broodstock Program, a US West Coast Pacific oyster breeding program, were screened for survival after exposure to OsHV-1 in Tomales Bay. They were also tested in a quarantine laboratory in France where they were exposed to a French OsHV-1 microvariant using a plate assay, with survival recorded from three to seven days post-infection. Results Significant heritability for survival were found for all time points in the plate assay and in the survival phenotype from a single mortality count in Tomales Bay. Genetic correlations between survival against the French OsHV-1 μvar in the plate assay and the Tomales Bay variant in the field trait were weak or non-significant. Conclusions Future breeding efforts will seek to validate the potential of genetic improvement for survival to OsHV-1 through selection using the Molluscan Broodstock Program oysters. The lack of a strong correlation in survival between OsHV-1 variants under this study’s exposure conditions may require independent selection pressure for survival to each variant in order to make simultaneous genetic gains in resistance.

Pacific oyster mortality syndrome: a marine herpesvirus active in Australia

2016 ◽  
Vol 37 (3) ◽  
pp. 126 ◽  
Author(s):  
Richard Whittington ◽  
Paul Hick ◽  
Olivia Evans ◽  
Ana Rubio ◽  
Navneet Dhand ◽  
...  
Keyword(s):  
Pacific Oyster ◽  
Case Fatality ◽  
Marine Bivalve ◽  
Base Pairs ◽  
Pacific Oysters ◽  
Oyster Mortality ◽  
The Family ◽  
High Infection ◽  
Herpesvirus 1 ◽  
Ostreid Herpesvirus 1

Genotypes of Ostreid herpesvirus 1 (OsHV-1) known as microvariants cause the disease Pacific oyster mortality syndrome (POMS). Since its appearance in NSW in 2010, OsHV-1 microvariant has prevented the farming of Pacific oysters (Crassostrea gigas) in the affected estuaries near Sydney, following the initial massive outbreaks1,2. The arrival of the disease in southeast Tasmania in January 2016 has put the entire $53M industry in Australia in jeopardy3. The virus is a member of the Family Malacoherpesviridae4, which includes several invertebrate herpesviruses. The OsHV-1 genome consists of 207 439 base pairs, with organisation similar to that of mammalian herpesviruses. However, OsHV-1 contains two invertible unique regions (UL, 167.8 kbp; US, 3.4 kbp) each flanked by inverted repeats (TRL/IRL, 7.6 kbp; TRS/IRS, 9.8 kbp), with an additional unique sequence (X, 1.5 kbp) between IRL and IRS4. Unlike many herpesviruses which are host specific, OsHV-1 strains have been transmitted between marine bivalve species5 and the virus is transmitted indirectly. The virus may have relatively prolonged survival in the environment, has extremely high infection and case fatality rates, and latency is unproven. Along with pilchard herpesvirus6–8 and abalone ganglioneuritis virus9,10, it is part of a dawning reality that marine herpesviruses are among the most virulent of pathogens. Finding solutions for industry requires more than laboratory-based research.

scholarly journals Ostreid Herpesvirus 1 Infection among Pacific Oyster (Crassostrea gigas) Spat: Relevance of Water Temperature to Virus Replication and Circulation Prior to the Onset of Mortality

2014 ◽  
Vol 80 (17) ◽  
pp. 5419-5426 ◽  
Author(s):  
Tristan Renault ◽  
Anne Lise Bouquet ◽  
Julien-Thomas Maurice ◽  
Coralie Lupo ◽  
Philippe Blachier
Keyword(s):  
Water Temperature ◽  
Crassostrea Gigas ◽  
Pacific Oyster ◽  
Mortality Rates ◽  
Mass Mortality ◽  
Content Type ◽  
Pacific Oysters ◽  
The Pacific ◽  
Herpesvirus 1 ◽  
Ostreid Herpesvirus 1

ABSTRACTA number of bivalve species worldwide, including the Pacific oyster,Crassostrea gigas, have been affected by mass mortality events associated with herpesviruses, resulting in significant losses. A particular herpesvirus was purified from naturally infected larval Pacific oysters, and its genome was completely sequenced. This virus has been classified asOstreid herpesvirus 1(OsHV-1) within the familyMalacoherpesviridae. Since 2008, mass mortality outbreaks amongC. gigasin Europe have been related to the detection of a variant of OsHV-1 called μVar. Additional data are necessary to better describe mortality events in relation to environmental-parameter fluctuations and OsHV-1 detection. For this purpose, a single batch of Pacific oyster spat was deployed in 4 different locations in the Marennes-Oleron area (France): an oyster pond (“claire”), a shellfish nursery, and two locations in the field. Mortality rates were recorded based on regular observation, and samples were collected to search for and quantify OsHV-1 DNA by real-time PCR. Although similar massive mortality rates were reported at the 4 sites, mortality was detected earlier in the pond and in the nursery than at both field sites. This difference may be related to earlier increases in water temperature. Mass mortality was observed among oysters a few days after increases in the number of PCR-positive oysters and viral-DNA amounts were recorded. An initial increment in the number of PCR-positive oysters was reported at both field sites during the survey in the absence of significant mortality. During this period, the water temperature was below 16°C.

scholarly journals Investigation of an EHV-1 Outbreak in the United States Caused by a New H752 Genotype

Pathogens ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 747
Author(s):  
Nicola Pusterla ◽  
Samantha Barnum ◽  
Julia Miller ◽  
Sarah Varnell ◽  
Barbara Dallap-Schaer ◽  
...  
Keyword(s):  
Early Stage ◽  
Clinical Signs ◽  
Amino Acid Position ◽  
High Viral Load ◽  
The United States ◽  
Neurological Deficits ◽  
Diagnostic Challenge ◽  
Genotype I ◽  
Flunixin Meglumine ◽  
Nasal Secretions

Here we report on an EHV-1 outbreak investigation caused by a novel genotype H752 (histidine in amino acid position 752 of the ORF 30 gene). The outbreak involved 31 performance horses. Horses were monitored over a period of 35 days for clinical signs, therapeutic outcome and qPCR results of EHV-1 in blood and nasal secretions. The morbidity of the EHV-1 outbreak was 84% with 26 clinically infected horses displaying fever and less frequently anorexia and distal limb edema. Four horses showed mild transient neurological deficits. Clinically diseased horses experienced high viral load of EHV-1 in blood and/or nasal secretions via qPCR, while subclinically infected horses had detectable EHV-1 mainly in nasal secretions. The majority of infected horses showed a rise in antibody titers to EHV-1 during the outbreak. All 31 horses were treated with valacyclovir, while clinically infected horses further received flunixin meglumine and sodium heparin. This investigation highlights various relevant aspects of an EHV-1 outbreak caused by a new H752 genotype: (i) importance of early detection of EHV-1 infection; (ii) diagnostic challenge to assess H752 genotype; (iii) apparent benefit of valacyclovir use in the early stage of the outbreak; and (iv) weekly testing of blood and nasal secretions by qPCR in order to monitor individual infection status and lift quarantine.

scholarly journals Distribution, Condition and Gonad Maturity of the Invasive Pacific Oysters (Crassostrea Gigas, Thunberg 1793) in Cimanuk Delta, Indramayu, West Java, Indonesia

Omni-Akuatika ◽  
2017 ◽  
Vol 13 (2) ◽  
Author(s):  
Selia Hermawati ◽  
Sulistiono Sulistiono ◽  
Agustinus M Samosir
Keyword(s):  
Distribution Pattern ◽  
Crassostrea Gigas ◽  
Brackish Water ◽  
Pacific Oyster ◽  
Condition Factor ◽  
Maturity Stage ◽  
West Java ◽  
Gonad Maturity ◽  
Pacific Oysters ◽  
The Pacific

Pacific oyster (Crassostrea gigas) is an invasive species which is able to adapt a wide range of environmental conditions. The study was conducted from August to October 2014. Objective of this study was to asses the distribution pattern, condition and gonad maturity length (Lm 50%) of the Pacific oysters in mangrove ecosystem of Cimanuk Delta, Indramayu, West Java, Indonesia.  This study was conducted in two adjacent areas:  Pabean Ilir and Pagirikan subdeltas. The oysters were collected from the estuary, brackish water ponds and the coastal flat, and  observed for their abundance, total length (mm) and weight (g). Morphological and histological methods were used to estimate the gonad maturity stage. Analysis were carried out to estimate distribution pattern and condition factor. According to the study, the Pacific oyster distribution pattern was clumped. The condition factor of the oyster was higher in the brackish water pond and estuary than in the coastal flat.  The Pacific oyster was found in gonad maturity stage (GMS) I – IV. The oyster was hermaprodit protandry and had length maturity (Lm 50%) of 47,46-48,43 mm (male) and 75,27-75,50  mm (female). 

Spatial Distribution of Pacific Oyster (Crassostrea gigas) Population Related Environment Factor in Coastal Water of Pabean Ilir, Indramayu

2020 ◽  
Vol 4 (1) ◽  
pp. 38-47
Author(s):  
Risma Qurani ◽  
Fredinan Yulianda ◽  
Agustinus Mangaratua Samosir
Keyword(s):  
Spatial Distribution ◽  
Coastal Water ◽  
Crassostrea Gigas ◽  
Pacific Oyster ◽  
Oyster Population ◽  
Pacific Oysters ◽  
The Pacific ◽  
Arc Gis ◽  
Environment Factor ◽  
Spatial Condition

Pacific oysters (Crassostrea gigas, Thunberg, 1793) is a benthic organisme that tend to live and settle in the bottom. One of the pacific oyster habitat is Coastal Water of Pabean Ilir, Indramayu. The purpose of this study was to map spatial condition of the population related habitat of the oyster (Crassostrea gigas). The mapping were done with laptop, using Arc GIS. There were 15 points of sampling. The oyster population in Pabean Ilir can be categorized into three categories: low, medium, and high density. Based on the similarity of environmental characteristics the habitat were divided into four groups. Condition Coastal Water of Pabean Ilir such as temperature, salinity, pH, BOD, TSS, TDS, COD, and composition of substrate indicated Coastal Water of Pabean Ilir have compatibility optimum sufficient habitat to support the growth of pacific oyster

Limitations of the A-IM Method for Fecal Coliform Enumeration in the Pacific Oyster (Crassostrea gigas)

1987 ◽  
Vol 70 (3) ◽  
pp. 535-537
Author(s):  
Charles A Kaysner ◽  
Stephen D Weagant
Keyword(s):  
Escherichia Coli ◽  
Positive Reaction ◽  
Crassostrea Gigas ◽  
Water Samples ◽  
Fecal Coliform ◽  
Pacific Oyster ◽  
Food Products ◽  
Fecal Coliforms ◽  
Pacific Oysters ◽  
The Pacific

Abstract Use of the A-IM method, which was originally devised for testing water samples, has recently been extended for enumeration of fecal coliforms and Escherichia coli in shellfish and other food products. Results of our study indicate that while this method is reliable for analysis of growing waters, the use of the A-IM method for testing Pacific oysters may be less reliable because bacteria not belonging to the coliform group but which are sometimes present in these animals also give a positive reaction.

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