White spot disease
White spot disease is a highly contagious viral infection that affects crustaceans.
Three prawn farms along the Logan River have returned to production. Biosecurity Queensland is working closely with the farms to monitor production as they progress.
The farmers have received technical advice on a range of enhanced biosecurity measures that are being applied throughout their production cycle. This will reduce the risk of a disease recurrence.
These measures include finalising and implementing an on-farm biosecurity plan to manage disease risks, and to having systems in place so any suspect signs of disease can be reported immediately.
The national Aquatic Consultative Committee on Emergency Animal Diseases continues to meet, and provides technical and expert advice to Queensland.
Biosecurity Queensland completed another round of white spot surveillance on the Logan and Brisbane Rivers and within the Moreton Bay region. All tests for white spot syndrome virus from this surveillance round have returned negative results.
All jurisdictions including the Department of Agriculture which is responsible for Commonwealth prawn fisheries, have collected samples as part of the national surveillance program. To date, all samples that have been collected and tested within other states and territories, have returned negative results.
The national two-year surveillance program is relevant to demonstrate that other areas in Australia remain disease free.
Keep Australia's fishing spots free from disease
Everyone who uses our waterways has a role in keeping them free from disease. Regardless of where you are in Australia you need to take some simple steps to prevent the spread of aquatic diseases or the transfer of marine pests.
Diseases and pests that affect aquatic animals can easily spread between waterways by the movement of contaminated bait and fishing equipment.
Disease outbreaks can cause major social and economic damage to Australia’s seafood industries.
Tips to keep your favourite fishing spot disease free
- When you are selecting your bait, use local and reputable bait shops or source your own bait from local waterways.
- Do not use seafood meant for human consumption as bait.
- Make sure you put all unwanted seafood in the rubbish bin.
- Keep your fishing gear, boat and trailer clean. Make sure that any debris and seaweed is removed. In particular, check wheel arches on trailers, boat propellers, fishing tackle and footwear.
- Use soapy water to clean your boat and trailer, fishing rods and other equipment, and allow them to dry completely before using them at another location, even if it is on the same day.
The Movement Restriction Area in Queensland will remain in place, and the Queensland Department of Agriculture and Fisheries (QDAF) does not anticipate any change to this in the foreseeable future. These movement restrictions are to contain white spot disease and prevent new outbreaks.
The restrictions prohibit the movement of high-risk animals such as prawns, yabbies and marine worms out of the white spot restricted area that extends from Caloundra to the NSW border and west to Ipswich.
To provide a level of protection to prawn farms, QDAF has introduced fishing restrictions within 100 metres of the inlet and outlet channels, and in all prawn farm drainage channels in the Logan River region.
An exemption exists for low-risk species: spanner crabs, three spotted crabs, blue swimmer crabs, mud crabs, red champagne lobster, slipper lobster, tropical rock lobster, red claw and bugs. They can now be moved out of the restricted area raw, however anyone wishing to move these species out of Queensland must check the importation requirements of the destination state before doing so.
The movement restrictions do not apply to molluscs (oysters and mussels).
To find out more about the current movement restrictions in Queensland and to download the map, see the QDAF website.
Restrictions that apply in other states and territories
The NSW Department of Primary Industry has issued two Importation Orders.
Primary Industries and Regions South Australia has restrictions that apply to bait/berley.
How to report white spot disease
White spot disease can only be diagnosed through appropriate laboratory testing. Infected prawns and yabbies may not display any symptoms. In some cases, white spots can appear on them because of freezer burn or bacterial and fungal infections.
If you suspect that you have purchased prawns with white spot disease symptoms, do not use them or throw them away. Keep them refrigerated and phone the Emergency Animal Disease Watch Hotline from anywhere in Australia on 1800 675 888. You will be connected to your local department of primary industries or fisheries, and provided with further advice.
Information for prawn farmers
The information below provides advice on how to prevent a disease incursion on your farm.
Prawn farmers need to ensure appropriate biosecurity measures are in place on their farm which includes sourcing disease free stock and animal feed.
Make sure livestock, water, visitors and staff, and equipment that are coming onto, and leaving the farm are clean. Equipment and footwear should be disinfected in addition to being cleaned.
The Department of Agriculture offers a free guide to help farmers develop biosecurity plans. This template can be easily adapted to your specific aquaculture sector (for example, prawn or abalone farming) or for specific production systems (for example, recirculation finfish aquaculture).
All aquaculture farms should have a Disease Management Plan including standard operating procedures that can be implemented in the event of a disease outbreak.
About white spot disease
White spot disease is a highly contagious viral disease of decapod crustaceans including prawns, crabs, yabbies and lobsters. The disease is caused by white spot syndrome virus.
White spot disease - Aquatic Animal Diseases Significant to Australia: Identification Field Guide
How to identify white spot disease
Photos courtesy of the Queensland Department of Agriculture and Fisheries
Prawns with white spot disease may have a loose shell with numerous white spots (0.5-2.0 mm in diameter) on the inside surface of the shell and a pink to red discolouration.
Signs to look for include:
- unusual mortality
- prawns coming to the edge or water surface of the pond
- prawns demonstrating unusual swimming patterns
- reduced feeding and failure to thrive.
How the disease can spread
The disease is primarily spread through the movement of infected animals or contaminated water. Birds that feed on and move infected animals can spread the disease.
The disease effect on other species
Fin fish are not affected by the disease and are not a carrier of the disease.
Decapod crustaceans including, but not limited to, prawns, lobsters and crabs are susceptible to the infection. Marine worms are also considered to be carriers of the disease.
The white spot disease detected in south east Queensland is not the same disease that can infect ornamental/aquarium fish. White spot in aquarium fish is a parasitic skin infection and not related to white spot disease.
Where white spot disease is found
White spot disease is widespread throughout prawn farming regions in Asia and the Americas where it has caused severe losses on prawn farms.
Australia is one of the few countries in the world with a prawn farming industry that has remained free of white spot disease.
Food safety and information for consumers
Consumers should be aware that white spot disease does not pose a threat to human health or food safety.
White spot disease can only be diagnosed through appropriate laboratory testing. Infected prawns and yabbies may not display any symptoms and white spots may appear for a range of reasons including, salt crystallisation, freezer burn and bacterial or fungal infections.
The most common reason you will see white spots on prawns that you have purchased is due to the crystallisation of salt under the shell of the prawn. This is because prawns are frozen quickly in a concentrated saltwater immersion process, during which the prawns pass through a saline brine tank. Some salt is then absorbed by the prawns as they freeze. This salt can crystallise under the shell while the prawns are frozen which causes white mottling to appear under the shell of the prawn. This mottling can be found on the body and head and becomes more noticeable as the prawns defrost.
With white spot disease, prawns are likely to have a loose shell with white spots that are 0.5 to 2 millimetres in diameter on the inside surface of the shell and a pink to red discolouration.
The photos below show the difference between white spots caused by white spot disease and white mottling caused by salt crystallisation.
Photos courtesy of Queensland Department of Agriculture and Fisheries - White Spot Disease lesions and prawn with salt crystallisation
It is unlikely that white spot disease could be detected by consumers in imported prawns. The disease is not visible in prawns that do not have a head or shell. Prawns imported to Australia are required to be de-headed, and most that are supplied to retail outlets are de-shelled.
Review of import conditions
The Australian Government Department of Agriculture put in place enhanced import conditions in July 2017 to allow for the safe trade in prawns and prawn products to Australia.
The department has indicated that if the biosecurity risks for these products change, then the enhanced import conditions may be amended to ensure that Australia’s appropriate level of protection continues to be met.
On 27 July 2018, the department released a Biosecurity Advice outlining the new enhanced import conditions for breaded, battered and crumbed (BBC) prawns.
From 28 September 2018, all imported BBC prawns will need an additional par-cooking step during processing to ensure the coating solidifies and adheres to the prawn.
The department is also undertaking a comprehensive review of the biosecurity risks and import conditions for prawns and prawn products imported for human consumption. This review was announced by the Director of Biosecurity in May 2017. The first round of stakeholder consultation closed on 2 July 2018. The department is currently considering submissions provided in preparing the draft report. If you would like further information on the review of import conditions for prawns, contact the department by emailing: Prawn review.
Find out about interstate movement conditions and other white spot disease information that relates to your state or territory:
- Queensland Department of Agriculture and Fisheries
- NSW Department of Primary Industries
- Reporting in NSW:
Aquatic Pest & Disease 24 hour recorded reporting line: (02) 4916 3877 or email Aquatic Pests
- Department of Primary Industries and Regions South Australia
- Department of Fisheries Western Australia
WA FishWatch 24 hour hotline on 1800 815 507
- Department of Agriculture and Food Western Australia (import conditions)
- Northern Territory Government
- Australian Prawn Farmers Association