White spot disease
White spot disease is a highly contagious viral infection that affects crustaceans.
In April 2020, white spot disease was confirmed on 2 prawn farms on the Logan River and in wild caught prawns and crabs from Moreton Bay.
The farms are among the seven prawn farms that that were affected with white spot disease during the 2016/17 outbreak.
Before this detection, there had been no evidence of the disease in the previous production season or in the previous three rounds of surveillance in wild crustaceans in the region.
This detection does not change Australia’s animal health status. There is no change to our import requirements designed to keep white spot out of Australia.
The Queensland Department of Agriculture and Fisheries (QDAF) continues to lead the response and has worked closely with the Logan River prawn farms in recent years as they returned to production.
Movement controls have been in place since the 2016/17 outbreak which have been effective in preventing spread to other states/locations. These will remain.
The national Aquatic Consultative Committee on Emergency Animal Diseases continues to meet, and provides technical and expert advice to Queensland.
Surveillance of wild crustaceans for the virus that causes white spot disease in South East Queensland continues. In the latest round in March 2020, low levels of the virus were detected in a number of mangrove swimming crabs and prawns collected over two sites. Both detections were from the sites in the northern part of Moreton Bay which previously tested positive for the virus in March 2018.
Surveillance of wild crustaceans in the Logan River recorded negative results. Crustacean and crab samples remain to be tested from the March 2020 sampling round.
All jurisdictions including the Department of Agriculture, Water and the Environment 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 the rest of Australia, outside the movement restriction area in south east Queensland, is 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 a rubbish bin, not in the ocean or waterways.
- Keep your fishing gear, boat and trailer clean. Make sure that any bait, 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 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.
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).
QDAF introduced fishing restrictions within 100 metres of the inlet and outlet channels, and in all prawn farm drainage channels in the Logan River region.
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 issued two Importation Orders.
Primary Industries and Regions South Australia has restrictions that apply to bait/berley.
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, Water and the Environment 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.
If you suspect disease on your farm, phone the Emergency Animal Disease Watch Hotline from anywhere in Australia on 1800 675 888.
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.
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
- 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 may 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.
Australia’s import conditions
The Australian Government Department of Agriculture, Water and the Environment continues to monitor and enforce stringent import conditions to manage the biosecurity risk associated with imported prawns and to safeguard our valuable fisheries and aquaculture industries.
Pre-border and border disease testing, retail testing, and working with exporting countries are being undertaken to ensure Australia's import conditions are being met.
The department is undertaking a review of all import conditions and biosecurity risks for prawns to ensure that risk management measures continue to meet Australia's appropriate level of protection.
Enforcement action will continue to be taken against importers who are found to be deliberately non-compliant with import requirements.
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