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 some infected populations. AVG does not affect human health.
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 3 May 2021 by the CSIRO’s Australian Centre for Disease Preparedness.
AVG detections were also made in NSW but were limited to retail and wholesale outlets. There were no detections in wild abalone.
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.
The national Aquatic Consultative Committee for Emergency Animal Diseases has met and agreed that AVG is endemic to Australia and is not an exotic aquatic disease. AVG is found in south-west Victoria and Tasmania, and is not technically feasible to eradicate from wild abalone populations.
Any future outbreak that occurs in farmed abalone or is detected in a processing facility or retail outlet, may still be considered eradicable by the Aquatic Consultative Committee for Emergency Animal Diseases, in accordance with AQUAVETPLAN.
Disease management in Victoria
Agriculture Victoria completed its delimiting surveillance in the affected areas on 25 June 2021. Out of the 533 samples that were sent for laboratory testing, 96 returned positive. These samples were taken across 21 reefs, of which, 7 have been declared infected with AVG.
The extensive surveillance around the affected coastline in Victoria has identified the affected areas, and enabled Agriculture Victoria to reduce the boundaries of the control area on 26 June 2021. The control area spans from Cape Nelson to Cape Bridgewater (which is the area of coast close to South Australian border) on.
While eradication of the virus in wild abalone is not achievable, Agriculture Victoria together with the Victorian Fisheries Authority and industry, will continue to manage the disease. There will be two phases which involve an interim policy and then a longer-term policy. Both phases will seek to achieve a high level of education, community involvement, and high-risk mitigation through the commercial and recreational sectors which use the affected reefs.
Victoria’s Control Area
Agriculture Victoria further reduced the size of the Control Area where AVG has been detected. It now spans a kilometre west of Cape Bridgewater Lookout to the Cape Grant area in the east.
In the Control Area you cannot:
- take abalone and other shellfish.
- use weighted commercial fishing equipment, commercial abalone equipment, recreation hoop nets, bait traps, hauling nets
- practice either recreational or commercial diving for abalone
- take rock lobster, shellfish, sea urchins and any of the substrate or sea floor
- move any abalone or shellfish out of the control area unless the movement is in accordance with a permit issued by an inspector
- snorkel and dive.
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 conducted surveillance within the seafood industry. Any abalone observed to be unwell during this surveillance was tested for AVG. AVG is not known to occur in wild abalone stock in NSW, and there are no abalone farms.
In total 278 live seafood holding premises were visited, with 30 premises having abalone that tested positive to AVG. All infected premises have been resolved.
NSW DPI has a Biosecurity Control Order in place on abalone allowing the movement of live abalone within NSW and outlining the conditions for any person dealing with abalone or carriers of the virus that causes AVG. The order supports the resumption of movement into NSW of live abalone from Eastern Zone Victoria, Tasmanian land-based farms, and all other Australian jurisdictions. Restrictions continue to apply to Tasmanian and Victorian western and central zone wild caught abalone, and farmed Victorian abalone.
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 because 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.