Aquatic pests: marine and freshwater

White spot disease (WSD) is a highly contagious viral infection that affects crustaceans.

These include:

• prawns
• freshwater crayfish
• crabs.

It can be spread in polychaete worms including those used for bait.

Impact

It poses a major threat to the Australian prawn industry and native crustaceans.

It does not affect humans.

White spot syndrome virus can cause high death rates in farmed prawns.

Current situation

This disease is exotic to Australia and not currently in the Northern Territory (NT).

In 2022, white spot disease was detected in a facility in northern New South Wales (NSW). This was rapidly eradicated.

In February 2023, white spot syndrome virus infected farmed prawns in northern NSW.

It's very different to the Queensland strain, which suggests that these infestations came from different sources.

A source of these infestations has not been identified.

Controls are now in place to prevent white spot disease spreading.

These include stopping the transportation of uncooked prawns and bait from areas where the disease has been detected or is suspected.

What it looks like

Prawns with white spot disease may have a loose shell with white spots. The spots can be 0.5mm to 2mm wide.

They're on the inside surface of the shell with a pink to red discolouration.

Inspection and testing of a prawn infected with white spot disease - photo courtesy of Queensland Department of Agriculture and Fisheries

Help stop its spread

You can take the following steps to stop white spot disease from spreading in the NT:

• don't use prawns meant for human consumption as bait
• don't throw away prawns meant for human consumption in or near waterways
• never throw any seafood waste in waterways.

Report it

If you think you've seen a case of white spot disease, follow these steps:

Step 1. Photograph it - from different angles and with the bag the prawns were purchased in.
Step 2. Record it - make a note of when and where you purchased the prawns including the producer’s name, the trade or common name of the prawns and where they came from.
Step 3. Collect it - keep the whole bag of prawns and freeze it.
Step 4. Report it - call the Fishwatch Hotline on 1800 891 136 or make a report through the Fishing Mate app.

To find out more about the response to this disease, go to the National Pest and Disease Outbreaks website.

History of disease in Australia

An outbreak of white spot disease was confirmed on several prawn farms in south-east Queensland in December 2016.

It triggered a national biosecurity response to contain and eradicate the disease.

In south-eastern Queensland, there is a management zone. There are restrictions on moving untreated prawns and polychaetes out of the area because the disease hasn't been completely eliminated.