6 results

Aquatic Animal Health Subprogram: Determination of susceptibility of various abalone species and populations to the various known AbHV genotypes

Project number: 2013-001
Project Status:
Completed
Budget expenditure: $207,118.00
Principal Investigator: Serge Corbeil
Organisation: CSIRO Australian Animal Health Laboratory
Project start/end date: 30 Jun 2013 - 2 Aug 2015
Contact:
FRDC

Need

With the emergence of AVG in in Victorian abalone in 2005/6, the subsequent discovery of several genetic variants of the causative agent, abalone herpesvirus (AbHV), associated with disease outbreaks in Tasmanian processing plants, and apparent variations in AbHV pathogenicity observed in different abalone species, there is the need to understand what factors promote disease in infected hosts. This project aims to address this knowledge gap and is relevant to all jurisdictions with abalone fisheries. Access to biosecure aquarium facilities, major abalone species and all known AbHV genotypes provides CSIRO-AAHL with a unique capability to investigate what factors influence disease outcomes following infection, including the nature of the AbHV genotype as well as abalone species or origins from locations spanning the primary wild fisheries in Victoria, Tasmania and South Australia. An improved understanding of the susceptibility of of abalone of different species and origins to infection by the various AbHV genotypes, and of whether different genotypes vary in their potential to transition from sub-clinical infection to acute disease is important for instructing fisheries and aquaculture policies and strategies to avoid disease, especially in aquaculture and abalone processing facilities. This project addresses specific priorities detailed in the current FRDC Aquatic Animal Health Subprogram R&D Plan (viz. 6.2.1 Nature of disease and host-pathogen interaction), priorities identified in the National Abalone Health Work Plan developed by a committee of national representatives following the second Abalone Virus Scientific and Management Forum held in Melbourne in 2007, and FRDC’s 2013 Annual Competitive Round Call for Expressions Of Interest (viz. Determining risk factors for AVG).

Objectives

1. Determine the susceptibility of greenlip, blacklip, hybrid and other readily available abalone species to abalone herpesvirus (AbHV) genotypes
2. Determine the complete genome sequences for AbHV Tas3 and Tas4 to gain insights into how and over what timeframe they have arisen, whether genetic recombination is contributing to this variation and which genome regions might affect virulence, as well as instructing on how diagnostic methods for their detection and diffferentiation can be refined.

Final report

Authors: Serge Corbeil Lynette M Williams Jeff A Cowley Nick JG Moody and Mark StJ Crane

Aquatic Animal Health Subprogram: development of improved molecular diagnostic tests for Perkinsus olseni in Australian molluscs

Project number: 2011-004
Project Status:
Completed
Budget expenditure: $305,561.00
Principal Investigator: Nick Gudkovs
Organisation: CSIRO Australian Animal Health Laboratory
Project start/end date: 21 Sep 2011 - 29 Aug 2014
Contact:
FRDC

Need

Improved diagnostic methods for endemic and exotic pathogens of aquatic animals have been identified as a Key Research Area in the 2009-12 FRDC AAHS R&D plan (6.2.3 Endemic and exotic aquatic animal disease diagnostics).

Since Perkinsus olseni was first described in Australian abalone by Lester and Davies in 1981, histology and culture in Ray’s medium have been the most commonly applied diagnostic procedures for detection of Perkinsus sp.. Although these tests are relatively straight forward and practical, they are general in nature and neither identifies or differentiates specific species of Perkinsus. Despite a well developed framework for the molecular characterization of Perkinsus and modern PCR based molecular tests for some of the more commercially important Perkinsus species, these have rarely been applied in Australia. The first attempts to apply molecular methods to a small number (n=40) of Perkinsus infected abalone from disease outbreaks in NSW have already revealed a new variant which probably represents a new previously unrecognized species in Australia (Reece et al. 2010). This fact and the apparent variation in pathogenicity observed with Perkinsus in different areas, has raised several questions about which Perkinsus sp. are present in commercial mollusc populations.

Given that a significant depletion of blacklip abalone (Haliotis rubra) stocks in NSW over the last 20 years has been attributed to infection with Perkinsus (FRDC Project 2004/084) and localized areas of infection occur in a number of Australian states, from South Australia to northern Western Australia, the development and implementation of highly sensitive and rapid PCR based molecular methods to identify specific species of Perkinsus is essential. The development and application of such tests is necessarily underpinned by a detailed understanding of the molecular makeup of Perkinsus in these populations which is the subject of this application.

Objectives

1. Undertake a targeted molecular, histological and cultural examination of known Perkinsus infected wild abalone populations from NSW, SA and WA to compare existing methods of detection.
2. Establish representative axenic (single species) cultures of Perkinsus sp. from infected abalone.
3. Use established PCRs and DNA sequencing methods to confirm the presence of P. olseni and determine the genetic diversity, including other Perkinsus sp. from these populations.
4. Develop and validate qPCR methods for the detection and identification of P. olseni in infected abalone.
5. Compare and evaluate the performance of the Objective 4 qPCR with existing conventional PCR methods for detection of P. olseni.

Final report

ISBN: 978-1-4863-0691-6
Author: Nick N. Godkovs

Aquatic Animal Health Subprogram: Investigations into the genetic basis of resistance to infection of abalone by the abalone herpes-like virus

Project number: 2011-003
Project Status:
Completed
Budget expenditure: $107,439.00
Principal Investigator: Serge Corbeil
Organisation: CSIRO Australian Animal Health Laboratory
Project start/end date: 30 Sep 2011 - 15 Nov 2012
Contact:
FRDC

Need

Of particular interest to both the aquaculture and wild capture industries is whether there are
sub-populations of abalone that demonstrate some innate resistance to infection/disease or that are
capable of developing resistance. Identification of these sub-populations could prove useful to both
the farming and the wild-capture sector.
In a controlled culture population it may be possible to breed for a more AVG-resistant population that
would be able to respond better should a disease outbreak occur. Potential AVG resistance between
different wild populations could also be inferred since the parents of the farmed bred lines have come
from different wild sources and we will be able to use knowledge of their ancestry to determine if there
is any evidence for population differences. In addition, should any zones of the natural population be
at low densities such that re-stocking either from cultured seed or by movement of natural stock from
other zones be required, it will be critical to know if there is innate resistance prior to translocation of
any stocks. If sub-populations in the wild are found to be more resistant and others more susceptible,
this may influence management of these zones and restrict movement of stock within and between
zones. If genetic resistance is identified in greenlips, the next step would be to confirm this in blacklips
and hybrids, and then search for genetic markers associated with resistance/susceptibility to be able
to identify individuals and sub-populations that are more resistant or susceptible. Moreover, this study
will be the first examination of virus resistance in a gastropod and might provide us with information on
future events. Identification of mechanisms of resistance to infection/disease was identified as a
priority in the draft national abalone health work plan. Identification of resistant family line(s) would
allow further research on mechanisms of resistance (future proposal).

Objectives

1. Determine whether there is genetic variation in susceptibility to abalone viral ganglioneuritis in abalone family lines. (If genetic resistance is identified in specific family line(s), a subsequent proposal will be submitted.)

Aquatic Animal Health Subprogram: Characterisation of abalone herpes-like virus infections in abalone

Project number: 2009-032
Project Status:
Completed
Budget expenditure: $401,292.00
Principal Investigator: Mark S. Crane
Organisation: CSIRO Australian Animal Health Laboratory
Project start/end date: 7 Feb 2010 - 29 Oct 2012
Contact:
FRDC

Need

At the National Abalone Health Workplan Priority Setting Workshop held on 18 June 2008 in Melbourne, attended by representatives from DPI Victoria, SARDI, FRDC, VADA, TAC, EZAIA), AAGA, ACA, CSIRO, DPIW Tasmania, RecFish, DAFF and NSW DPI, it was agreed that to address the main epidemiological questions research should be focussed on 4 areas:
1) Development of diagnostics techniques with the highest priorities being:
- Technique to isolate and concentrate the virus from abalone tissues (addressed in FRDC Project 2007/006)
- A rapid and specific diagnostic test-development of a validated PCR-test for the AVG virus (addressed in FRDC Project 2007/006)
- Secondary diagnostic test (ISH development addressed in FRDC Project 2007/006)
- Validation of diagnostic tests (partly addressed in proposed extension of FRDC Project 2007/006 (PCR) and this project (ISH validation))
- Rollout of diagnostic tests across the States (addressed in proposed extension of FRDC Project 2007/006)
- Distribution of infective dose in tissues (to be addressed by this proposal)
2) Disease aetiology and transmission with the highest priorities being:
- Other bio-vectors and abiotic factors (to be addressed by this proposal)
- Determination of the susceptibility of remnant populations following exposure to AVG (to be addressed by this proposal)
3) Virus inactivation with the highest priorities being:
- Determine the viability of the AVG virus, including disinfection efficacy; efficacy of treatments (to be addressed by this proposal)
- Survival of the virus in seawater (to be addressed by this proposal)
- Survival of the virus on fomites (to be addressed by this proposal)
4) Disease surveillance and modelling with the highest priorities being:
- National survey of stocks to determine current distribution of the virus, including latency, and resistance status of stocks (partly addressed by this proposal)
- Determine the mode(s) of spread of the AVG (not addressed)

Objectives

1. Validate the developed in situ hybridisation diagnostic test including roll out to other States
2. Develop a quantitative assay (qPCR) for determining infectious dose for this virus
3. Determine the sensitivity of the virus to physico-chemical conditions including its stability in water/on fomites and its sensitivity to inactivation agents
4. Determine the role of mucus in viral transmission
5. Determine whether a latent stage exists in AVG
6. Determine the susceptibility of remnant populations of abalone previously exposed to AVG and known unexposed wild populations in South Australia

Aquatic Animal Health Subprogram: Development of molecular diagnostic procedures for the detection and identification of herpes-like virus of abalone (Haliotis spp.)

Project number: 2007-006
Project Status:
Completed
Budget expenditure: $344,132.78
Principal Investigator: Mark S. Crane
Organisation: CSIRO Australian Animal Health Laboratory
Project start/end date: 23 Jun 2007 - 30 Sep 2008
Contact:
FRDC

Need

Currently, diagnosis of abalone ganglioneuritis associated with infection by the recently discovered herpes-like virus is dependent on visualisation of gross clinical signs at the macroscopic level, of histological lesions at the light microscopic level and of virus particles at the electron microscopic level. Thus, while detection of diseased abalone is relatively straightforward it is labour-intensive and time-consuming. The purpose of this project is to develop molecular diagnostic procedures for the rapid, sensitive and specific detection and identification of abalone herpes-like virus infections in the presence, or absence, of clinical signs. Thus potential broodstock that are apparently healthy can be screened for the presence of herpes-like virus, sub-clinical, infections prior to on-farm use.

In addition to surveillance tools for detection and identification of sub-clinical infections, better procedures/reagents for overt disease diagnosis are required. While the presence of histological lesions provides a presumptive diagnosis, the development of in situ hybridisation probe(s) and/or diagnostic antiserum for the localisation of abalone herpes-like virus within histological lesions will provide a means for definitive diagnosis to be made with increased confidence.

Furthermore, in addition to providing an enhanced capability and capacity for disease diagnosis (detection and identification of herpes-like virus), development of molecular reagents and procedures will assist future research aimed at better understanding the pathogenesis (e.g. tissue distribution of the virus, effect of host factors such as age) and epidemiology (e.g. determination of host and geographic ranges, modes of transmission) of this disease. Such knowledge is crucial for efficient management of current and future disease outbreaks.

Objectives

1. To purify the herpes-like virus from infected abalone
2. To extract, clone and sequence the entire viral genome and align it to the Ostreid herpesvirus-1 genome
3. To develop a sensitive and specific PCR assay for detection and identification of abalone herpesvirus
4. To develop an in situ hybridisation assay specific for the abalone herpesvirus
5. To document a draft Australian and New Zealand Standard Diagnostic Procedure (ANZSDP) and submit for external review

Final report

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