3 results

Aquatic Animal Health Subprogram: Identifying the cause of Oyster Oedema Disease (OOD) in pearl oysters (Pinctada maxima), and developing diagnostic tests for OOD

Project number: 2013-002
Project Status:
Completed
Budget expenditure: $262,968.20
Principal Investigator: David Raftos
Organisation: Macquarie University
Project start/end date: 30 Jun 2013 - 29 Jun 2016
Contact:
FRDC

Need

Pearl oyster farming is one of Australia's most successful aquaculture industries, with substantial scope for future growth. Recent data suggest that the pearling industry generates approximately $100 m pa and provides significant employment opportunities in remote areas of Australia. Despite its remarkable success, the viability of Australian P. maxima pearling is compromised by a fatal disease (oyster oedema disease, OOD). If OOD is not controlled, the industry is unlikely to develop as efficiently and cost effectively as required. In some areas, the disease is making it difficult to restock growing areas with hatchery reared spat, and it is significantly decreasing the number of oysters available to produce pearls. OOD also appears to be impacting wild P. maxima populations.

The proposed project is the first step in developing an integrated management strategy to control OOD in the Australian pearling industry. Some progress has been made in studying the disease. We suspect that OOD is initiated by an infectious virus associated with secondary bacterial infection. But we still do not understand:

1. the precise causative agent(s) of OOD, or,

2. how to provide early diagnosis of the disease

These gaps in our knowledge mean that industry does not have sufficient information to establish effective management strategies that can control OOD. Most importantly, we need diagnostic methods to detect the onset of disease before catastrophic outbreaks occur. Such tests could be used to identify disease-free broodstock for hatcheries, find areas where OOD is less prevalent, determine environmental factors that might be associated with infection, and manage the translocation of OOD-affected oysters. Our project addresses these needs in order to identify management practices that can be used to control OOD and secure the Australian pearling industry.

Objectives

1. REVISED PROJECT OBJECTIVE 1. Identify the presence of nucleotide sequences associated with OOD affected oysters using a next generation sequencing approach
1. SUPERCEDED OBJECTIVE 1: Identify the presence of any pathogens associated with OOD-affected oysters using a next generation sequencing approach.
2. SUPERCEDED OBJECTIVE 2: Investigate the association of the pathogens detected by next generation sequencing with the severity of disease in P. maxima using a combination of quantitative (q) PCR, pathology and histopathology (including in situ hybridisation).
2. REVISED PROJECT OBJECTIVE 2: 2. Use quantitative real time PCR to measure the prevalence of these nucleotide sequences in a broad range of oyster samples
3. SUPERCEDED OBJECTIVE 3: Develop diagnostic tests that can detect and identify the causative infectious agent(s) of OOD

Final report

ISBN: 978-0-646-96779-0
Authors: Priscila Goncalves David Raftos David Jones Kelli Anderson Brian Jones & Michael Snow
Final Report • 2017-02-01 • 4.26 MB
2013-002-DLD.pdf

Summary

The goal of this project was to investigate the cause of oyster oedema disease (OOD) in Australian pearl oysters so that diagnostic tests and management practices for the disease can be developed. OOD has been associated with mortalities in some pearl oyster farming areas. However, the cause of these mortalities has remained unknown, hampering efforts to study the disease and develop effective control strategies. The project described in this report was conducted by researchers from Macquarie University, Fisheries Western Australia and the New Zealand Ministry for Primary Industries (Manatū Ahu Matua), working in collaboration with the Australian Pearl Producers Association and the Australian pearling industry. We compared OOD-affected oysters with healthy control oysters to identify any genetic material in the OOD-affected oysters that might come from an infectious agent such as a virus, bacteria or parasite. Our logic was, if OOD is caused by an infectious agent, genetic material (cDNA nucleotide sequences) from that infectious agent should be far more abundant in OOD-affected oysters than in healthy controls. That genetic material would act as a fingerprint for the disease and may provide information about its cause. We found clear differences between the nucleotide sequences present in oysters affected by OOD when compared to healthy controls. A number of nucleotide sequences were strongly associated with OOD and the abundance of some of these sequences was correlated with increasing mortality. None of these nucleotide sequences were closely related to any known infectious agents. However, the strong relationship between these sequences, OOD and mortality means that they may be very useful predictors of mortality. Their lack of resemblance to known infectious agents leaves open the possibility that OOD is not an infectious disease and may have some other cause.

Aquatic Animal Health Subprogram: Development of a DNA microarray to identify markers of disease in pearl oysters (Pinctada maxima) and to assess overall oyster health

Project number: 2008-030.20
Project Status:
Completed
Budget expenditure: $157,480.00
Principal Investigator: David Raftos
Organisation: Macquarie University
Project start/end date: 30 Jun 2008 - 29 Jun 2011
Contact:
FRDC

Need

In October 2006, unexplained high mortalities of Pinctada maxima oysters were reported. The disease associated with these mortalities has been termed Oyster Oedema Disease (OOD). It is likely that OOD is caused by an infectious agent and it is possible to cross-infect oysters with infected tissue. The disease spread rapidly and there are no known control measures, no knowledge of a causative agent, no understanding of how widespread the disease was, and no way to test for it. This proposal seeks to develop DNA microarray technology to detect abnormal levels of stress response genes in pearl oysters. These genes will be used as markers in new, rapid diagnostic tests for diseased pearl oysters. The requirement for such rapid diagnostic tests for the detection of OOD is well acknowledged. The spread of the disease could have been limited had there been a test available to differentiate sick animals from healthy ones. Such assays also have applications in routine translocation testing and the assessment of general oyster health. Translocation samples are treated as high priority and current methods report results after several days. With rapid tests derived from DNA microarray analysis it may be possible to report results within 24 hours. The attraction of molecular stress-response markers is that their expression levels change dramatically during times of stress. This can act as an indicator of disease susceptibility. A DNA microarray to target such stress markers in P. maxima could
also be used to investigate disease in other shellfish and it will be able to detect effects of other pathogens in addition to those involved in OOD. Our main goal is to use the P. maxima microarray to identify key stress-response genes that can be used to develop a new generation of rapid, inexpensive tests of environmental stress, infection and overall oyster health.

Objectives

1. To construct a cDNA library using healthy, stressed and OOD-affected oysters. We will use oysters exposed to a range of environmental conditions to make sure that a broad array of stress-response genes are represented in the cDNA library. Cloned cDNAs will be analyzed by PCR to confirm that a broad range of different sized cDNA is also included in the library.
2. To design and print DNA microarray slides for the analysis of diseased states in pearl oysters (P. maxima). cDNA clones to print will be based on sequence analysis. cDNA's will be printed onto the slides in duplicate or triplicate to increase the statistical robustness of subsequent analyses.
3. To use the DNA microarray to identify molecular markers that differentiate pearl oysters that are diseased (including OOD-affected oysters) from those that appear to be healthy.
4. To use the DNA microarray to test for markers of adverse health in pearl oysters that appear to be affected by environmental stressors other than OOD. This will be done using archived samples and oysters that do not fit the case definition for OOD.

A biochemical, pathological and behavioural study to assess the protective effects of selenium and vitamin E against mercury

Project number: 1981-011
Project Status:
Completed
Budget expenditure: $0.00
Organisation: Macquarie University
Project start/end date: 27 Jun 1986 - 29 Jun 1986
Contact:
FRDC

Objectives

1. Examine the premise that the natural accumulation of methyl mercury in association with selenium and/or vitamin E in fish reduces or abolishes the potential toxicity of methyl mercury in food for mammals
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