Abalone Virus Ganglioneuritis
Wild abalone off the coast of Cape Nelson, Victoria have tested positive to a disease called Abalone Virus Ganglioneuritis or AVG. AVG affects the nervous system of abalone which results in the curling of the foot and swelling of the mouth. This leads to weakness and a 90% mortality rate in infected animals.
The detection was made by a diver who is familiar with signs of AVG, and collected a sample which he provided to Agriculture Victoria for testing. The disease was confirmed on 3rd May by the CSIRO’s Australian Centre for Disease Preparedness.
AVG has been detected in Australia before with previous incidents in Tasmania and Victoria. The last recorded instance of disease in Tasmania and Victoria was in 2010. It was eradicated from farmed abalone in Tasmania but in Victoria it is distributed in wild abalone populations along more than 200 km of coastline from Discovery Bay to Cape Otway.
Victoria’s Control Area
Agriculture Victoria declared a Control Area on 4 May 2021 which was extended west on 23 May due to further detections. The Control Area is to assist with limiting the spread of disease.
The new Control Area now spans from past Lower Cape Bridgewater in the east to past Narrawong in the east between two and 10 kilometres offshore.
The disease has also been confirmed from samples collected from the reefs at Murrells and Jones Bay west of Portland, well within the original Control Area.
Surveillance results will shape an understanding of the extent of disease spread, with ongoing dive surveys taking place across many reef areas in the Control Area.
On 23 May the Control Area was amended to allow line fishing without sinker attached. All other restrictions remain in place for the Control Area.
The following is prohibited under the Control Order:
- The taking of abalone and other shellfish.
- The use of weighted commercial fishing equipment, commercial abalone equipment, recreation hoop nets, bait traps, and hauling nets.
- Commercial and recreational diving for abalone.
- The taking of rock lobster, all shellfish, sea urchins and any of the substrate or sea floor.
- Moving any abalone or shellfish out of the control area unless the movement is in accordance with a permit issued by an inspector.
- Boats, vessels and fishing equipment cannot be anchored in the Control Area. However, a vessel can move through the area provided it does not stop. Line fishing from the breakwater is permitted provided anglers are standing on the breakwater.
Activities such as swimming, surfing, paddle boarding and walking along the shore/rocks are allowed. Snorkelling and diving is not allowed.
Special arrangements are in place for boats required to anchor in the Portland anchorage area.
See the Agriculture Victoria website for more details about the outbreak and the restrictions that apply under the Control Order. There are also maps showing the affected area.
Detections in New South Wales
Upon receiving reports of the Victorian outbreak, NSW DPI implemented a compliance action plan to reiterate the importance of good biosecurity, and to undertake surveillance within the seafood industry. Any abalone observed to be unwell during this active compliance was tested for AVG. AVG is not known to occur in wild abalone stock in NSW, and there are no abalone farms.
In mid-May this surveillance resulted in several positive detections so NSW DPI established an Incident Management Team to coordinate actions to minimise the spread and eradicate infection from affected premises.
NSW’s tracing and surveillance activities have identified 30 premises with abalone that have tested positive to AVG. This is out of a total of 286 premises that have dealings with live abalone in NSW. Actions are being implemented at these infected premises to decontaminate infected tanks and equipment under formal Individual Biosecurity Directions.
A Biosecurity Control Order is in place that includes restrictions on abalone coming into and leaving the state, and restricting movements of live abalone within NSW. These restrictions are in place to enable NSW DPI to conduct tracing activities and to better understand the pathways that have potentially introduced the virus, as well as to finalise the decontamination of those premises with infected abalone.
A Group Permit was issued on 31 May that allows movement of live abalone within NSW under strict biosecurity conditions to minimise risk through the identified pathways. This has allowed NSW wild-capture abalone fishers to resume harvest, provided they meet those biosecurity requirements for hygiene and cleaning. The NSW Control Order will continue to be applied to minimise the risk to NSW abalone populations through biosecurity measures applicable to the movements of live abalone, and to the abalone live-holding supply chain.
Agriculture Victoria and NSW DPI are working together in a joint investigation, as the AVG detected in NSW was the Victorian lineage.
No other jurisdictions have reports of the disease in abalone.
South Australia’s interstate movement restrictions
On 27 May 2021 South Australia (SA) introduced temporary restrictions on fresh abalone products coming into SA from interstate, including recreationally caught abalone. These restrictions are aimed at ensuring SA waters remain free of the disease. (There have not been any detections of AVG in South Australia).
Exemptions apply for stock consigned directly to fish processors or retail markets, including restaurants, from accredited abalone farms or from Western Australia, Northern Territory and Queensland which are also regarded as being AVG free. Exemptions also apply for stock consigned to fish processors from AVG affected jurisdictions.
Other SA restrictions include:
- Strict conditions for transporting, keeping and disposing of abalone and abalone waste by fish processors.
- Members of the public are only permitted to bring cooked and/or preserved abalone in sealed packaging into South Australia from interstate.
- No abalone sourced from interstate can enter an aquaculture farm or be deposited in SA waters.
- Abalone cannot be used for bait or berley in SA waters.
There are no food safety and human health issues associated with this virus. Abalone remains safe to eat.
Advice for the abalone industry
The abalone industry needs to make sure there are sound biosecurity measures in place across the whole supply chain.
Biosecurity measures are key and include:
- Do not share equipment between abalone tanks and farms.
- Do not put abalone sourced from different locations in the same tank.
Quarantining newly introduced abalone until you know they’re healthy minimises the risk of introducing the disease onto your farm or processing facility.
- Divers should always clean their equipment with soapy water as soon as they leave the water.
- Know the signs of AVG and report any sick or dead abalone to the Emergency Animal Disease Watch Hotline on 1800 675 888. It is an official notifiable disease that must be reported.
The abalone industry should refer to the detailed guidelines on appropriate abalone farm biosecurity which are available in the National Biosecurity Plan Guidelines for Land Based Abalone Farms.
Fishing and recreation sectors
Recreational water users also need to keep biosecurity in mind when going about their activities. They can inadvertently spread an aquatic disease by moving contaminated boats and equipment from infected areas to other locations where the disease is not present.
- Always clean your boat and equipment straight after leaving the water, and comply with any conditions in a Control Area.
- Do not throw any abalone, including the meat and gut or their shells back into the ocean or any other waterway. And do not use them as fishing bait as this is illegal in most states. Dispose of them in a garbage bin.
More on biosecurity measures is available from the Victorian Fisheries Authority.
AVG is caused by a herpesvirus specific to abalone. It can spread through the water from infected abalone or abalone product like offal, shells or mucus. Fishing equipment including wetsuits, anchors, rock lobster pots and ropes can also spread the disease, along with people who have come into contact with infected abalone.
The disease can cause high mortalities in both farmed and wild abalone populations. To date, species known to be susceptible to AVG in Australia include greenlip abalone, blacklip abalone, hybrids of these two species, and brownlip abalone.
Signs of the disease
In wild abalone there may be high mortality and usually only shells are present because of predators.
In farmed abalone, signs include:
- swollen mouth parts, occasionally with the mouth protruding from under the anterior foot - where it is usually only partially visible
- reduced pedal adhesion to surfaces
- absence of marked foot extension seen in the righting reflex of healthy abalone
- curled mantle edge
- high mortalities of up to 90%.
More detailed information about AVG can be found in the: Aquatic Animal Diseases Significant to Australia: Identification Field Guide 5th edition. This guide is free to download from the Department of Agriculture, Water and the Environment website.
There is no change in Australia’s disease status for AVG as a result of this detection. The Department of Agriculture, Water and the Environment will work with trading partners to manage any market access issues should they arise.
Australia’s largest export markets for abalone are China, Hong Kong and Singapore which were worth $115 million to the Australian economy in 2019-2020. The total value of abalone exports was $144 million for the same period.