White spot disease is a highly contagious viral disease of decapod crustaceans. These include prawns, crabs, yabbies and lobsters.
White spot syndrome virus (WSSV) causes the disease.
White spot disease does not pose a threat to human health or food safety.
Detection in Australia
White spot disease was detected in black tiger prawns (Penaeus monodon) in 3 farms on the NSW north coast in early 2023.
On 12 February, a producer reported dead prawns with white spots in a single grow-out pond. On 13 February, a small number of prawns across 4 grow-out ponds were sick or dead.
On 24 February, a 2nd farm in the area reported lethargic prawns.
Between 11 and 13 April, prawn samples were collected from a 3rd farm in that area, even though there were no signs of disease. This was part of the active response surveillance. On 21 April, WSSV was confirmed in all ponds sampled on the 3rd farm.
The Australian Centre for Disease Preparedness (ACDP) confirmed WSSV on the 3 farms on 14 and 28 February, and 21 April.
On 3 May, ACDP confirmed the WSSV strains detected at the 3 farm locations are:
- strongly similar to the WSSV detected in NSW in August 2022
- different lineage to the Queensland strain detected in 2016-2020.
Investigations have not been able to determine the origin of the infection.
NSW Department of Primary Industries (NSW DPI) is leading the response to this outbreak. It set up an Incident Management Team (IMT) on 13 February. The IMT coordinates investigation, surveillance and response activities. This includes communication with industry stakeholders. The team also supports infected properties going through the destruction and decontamination processes.
The IMT formally stood down on 30 June. The emergency response has now transitioned to the management phase.
National response arrangements are set out in AQUAVETPLAN. It provides technical guidance on destruction, disposal and decontamination activities.
The national Aquatic Consultative Committee on Emergency Animal Diseases (AqCCEAD) provides technical advice on the response.
The control order:
- establishes a control zone around the Clarence River area in NSW
- restricts moving raw, uncooked prawns, decapod crustaceans and polychaete worms
- supports risk management, surveillance and tracing activities to inform future management approaches.
Uncooked decapod crustaceans, limited to certain crab and lobster species, may be exempt from the control order. They can be moved out of the Clarence River Control Zone for human consumption only. They must be cooked as soon as possible upon arrival at the destination.
Testing and surveillance
Wild prawns and crustaceans in the control zone, including adjacent offshore areas, have been tested for WSSV.
Initial surveillance conducted within the Clarence River control zone in February 2023 found trace levels of WSSV DNA in a small number of samples.
Surveillance and tracing at prawn farms in the Clarence River, coastal and offshore areas will continue. This includes further testing of wild crustaceans.
NSW DPI is working with prawn farmers, fishers and the bait industry to manage the impact of this order.
NSW DPI issued the 3 infected farms with Individual Biosecurity Directions. NSW DPI is working with each of the affected farms to:
- decontaminate and disinfect farm facilities and pond water
- discharge pond water that is tested and considered to be safe for the environment
- finalise the on-farm eradication program
- continue post-control surveillance activities.
What you must do to stop the spread of white spot disease.
Report anything unusual, even if you’re not sure.
If you suspect disease on your farm, call the Emergency Animal Disease Hotline on 1800 675 888. You’ll be directed to your state or territory government.
Follow the rules
White spot disease spreads between waterways through contaminated bait and fishing equipment.
You can help prevent the spread of white spot disease. Make sure you’re aware of restrictions in place or actions you can take to reduce risks.
NSW movement restrictions
Movement of decapod crustaceans or polychaete worms from the Clarence River control zone is currently restricted under NSW’s control order. While there are some exemptions, most decapod crustaceans are considered high-risk and can’t be moved out of the control zone. High-risk decapod crustaceans include, but are not limited to, raw prawns, yabbies and pink nippers.
Queensland has a movement regulated area (MRA) in place. WSSV has established in some populations of wild crustaceans within the MRA. The MRA extends from Caloundra to the NSW border and west Ipswich.
You cannot move high-risk aquatic animals out of this area. This includes uncooked prawns, yabbies and marine worms.
You also need to be aware of fishing restrictions in this area.
A national surveillance program that commenced in 2017 demonstrated that all areas of Australia, outside of the MRA, have remained free from the virus.
Other states and territories
Check for entry restrictions into other states and territories.
Prawn and seafood farmers
Make sure that appropriate biosecurity measures are in place on your farm. This includes sourcing disease-free stock and animal feed.
All livestock, water and people coming in and out of your farm must be clean. Clean and disinfect all equipment and footwear.
Recreational and commercial fishers
Steps to keep your favourite fishing spot disease free:
- Do not use seafood meant for human consumption as bait.
- Use local and reputable bait shops or source your own bait from local waterways.
- Put all unwanted seafood in a rubbish bin, not in the ocean or waterways.
- Keep your fishing gear, boat and trailer clean. Make sure that you remove bait, debris and seaweed. Check, clean and dry wheel arches on trailers, boat propellers, fishing tackle and footwear.
- Use soapy water to clean your boat and trailer, fishing rods and other equipment. Allow them to dry completely before using them at another location, even if it is on the same day.
Import conditions for prawns
The Australian Government Department of Agriculture, Fisheries and Forestry (DAFF) conducted a review of prawn import conditions. This was the ‘Review of the biosecurity risks of prawns imported from all countries for human consumption’.
DAFF released the final report of the prawn review on 5 June 2023.
The final report determined that:
- prawns and prawn products can be safely imported into Australia under the enhanced import conditions implemented since 2017
- additional strengthened import conditions were recommended for uncooked and cooked prawns.
DAFF will start to implement changes to the import conditions for prawns and prawn products for human consumption from 30 October 2023.
See more on the review of prawns and prawn products.
Measures to ensure Australia’s import conditions are being met include pre and post border disease testing, retail testing, and working with exporting countries.
DAFF will continue to:
- monitor and enforce import conditions
- work with Australia’s trading partners and importers
- manage market access
- respond to systemic or non-compliance issues with appropriate enforcement actions.
About the disease
White spot disease is widespread in prawn farming regions in Asia and the Americas. The disease has caused severe losses on prawn farms in these regions.
What to look for
Prawns with white spot disease may have a loose shell with many white spots on the inside surface. The spots have a pink to red discolouration and are 0.5-2.0 mm in diameter.
More reliable signs to look for include:
- unusual mortality
- prawns coming to the edge or water surface of the pond
- prawns demonstrating unusual swimming patterns or lethargy
- reduced feeding and failure to thrive.
Animals infected with the virus may show one or more of these distinctive signs. Or they may not show these signs at all, and the virus may still be present.
White spot disease can be confused with spots of crystallised salt under the shell. Prawns absorb salt as they are frozen in a saline solution. This can crystallise under the shell which causes white mottling to appear. This mottling can be found on the body and head and becomes more noticeable as the prawns defrost.
You can use the aquatic animals identification guide (agriculture.gov.au)
If you’re not sure, you can get advice from the Emergency Animal Disease Hotline on 1800 675 888.
How it spreads
The disease is spread by:
- infected aquatic animals, including prawns, freshwater crayfish, crabs and polychaete worms
- contaminated equipment or water
- birds that feed on and move infected animals.
Effect on other species
Finfish are not affected by the disease and are not a carrier of the disease.
White spot in aquarium fish is a parasitic skin infection. It is not related to white spot disease of crustaceans.
In 2016, white spot disease was detected in 7 prawn farms on the Logan River in Southeast Queensland. In 2017 it was found in wild populations of crustaceans in the northern part of Moreton Bay, Southeast Queensland.
Prawns on the infected farms were destroyed and 5 farms resumed production in 2017.
In August 2022, WSSV was detected at a biosecure prawn hatchery in northern NSW. It was contained and eradicated from the facility. Extensive investigations were unable to determine the origin of the outbreak.
See more on the response and how you can manage the risk of white spot disease.
- White spot disease response in NSW (NSW DPI)
- White spot disease response in Queensland (Qld DAF)
- White spot disease information guide PDF (Qld DAF)
- How to develop your aquaculture farm biosecurity plan (agriculture.gov.au)
- What you can do to Protect Australia's Aquatic Animal Health (agriculture.gov.au)
- Aquatic health plans and guidelines (agriculture.gov.au)
- Make ‘clean’ part of your routine (NSW DPI)
- White spot disease movement restrictions video with Scott Hillier (Biosecurity Queensland)
- Biosecurity Basics (Marine pests website)