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Battle against white spot disease in Australian prawns

By Darius Koreis

June 19, 2018

Black tiger prawns in hand
Black tiger prawns.

DECEMBER is normally peak business for the Australian prawn industry, with locals savouring the aquatic crustaceans for their Christmas and Boxing Day lunches.

2016 was different. Prawn farmers located on the Logan River, south of Brisbane, were left reeling from the discovery of white spot disease in their stock. Lethal only to crustaceans, with no effect on humans, the highly pathogenic virus leads to multiple organ failure in prawns.

While the cause of the viral outbreak into Moreton Bay’s wild prawns is unconfirmed, the most prevalent theory was the use of imported uncooked prawns as bait from countries where the disease is endemic.

Matt West, President of the Australian Prawn Farmers Association, says a race was suddenly on to stop the disease, with biosecurity measures hitting the Logan farms like a sledgehammer, which produce around 40 per cent of Australia’s farmed prawns.

“To be honest, no one was prepared. It devastated us,” West says.

“The industry tried to work with government to reduce the risk of spread in that locality, but it was like playing Russian roulette where every week one of our mates, one of our colleagues received the ‘death card.’”

prawns with white spot
Prawns with white spot disease: Image: Queensland Department of Agriculture and Fisheries

West, a prawn farmer himself who runs a commercial operation an hour south of Mackay, was thankfully spared from the outbreak occurring around 900km southwards.

To try to stop the spread of the virus, all of the prawn farmers along the Logan River saw millions of dollars’ worth of their stocks systematically euthanased just weeks before they were to be harvested.

Chlorine was poured into the ponds, eradicating both the prawns and the virus. Losses hit the farmers hardest, but downstream freight companies, power companies and fishermen were all financially impacted, as well as fish markets due to the public’s false perception of human health risk.

While this was occurring, CSIRO’s Australian Animal Health Laboratory in Geelong, Victoria, worked around the clock – even over Christmas – to continually test some 21,000 samples and help to determine the extent of the outbreak. But CSIRO suddenly found itself on the front line in another, more dire way.

Outbreak hits home for CSIRO

The Bribie Island Research Centre, shared with the Queensland Department of Agriculture and Fisheries, is located at the top of Moreton Bay – where white spot disease was running wild.

CSIRO research group leader for Northern Aquaculture, Dr James Kijas, says the facility was caught in the Moreton Bay exclusion zone, and the stakes could not have been higher.

“Bribie Island is CSIRO’s only dedicated aquaculture facility. It’s a vital component to our national aquaculture research, studying animals such as Atlantic salmon, barramundi, and indeed prawns,” Dr Kijas says.

The facility sources its water from seawater pumped from around 200 metres offshore, and water was filtered down to 400 microns (0.4mm).

“If white spot was detected at the facility, Biosecurity Queensland would have asked for the eradication of all animals on the site, which would have put all of our work in jeopardy,” he says.

“Aquaculture sites were going down one by one, so we quickly instigated a UV treatment of the seawater as a stop-gap measure before a more permanent solution could be implemented.”

Work at the facility is of particular interest to the prawn industry, where it is the home of research into NovacqTM prawn feed.

Dr Matthew Briggs, ‎Technical Project Manager at Ridley AgriProducts that sells the NovacqTM product, says the recent signing of a research alliance between CSIRO and Ridley would have been dealt a blow if the facility was shut down.

“This facility is essential for us, and if it went down our work would be significantly impacted,” Dr Briggs says.

“The five year alliance between Ridley and CSIRO is vital for us to achieve the best diet we can in our aqua feeds, which create healthier and larger prawns and in turn makes the most money for farmers.

“White spot, while devastating, is really the tip of the iceberg, and globally there are new diseases coming each year. The measures you have to take against white spot will help against the vast majority of those as well.”

A responsibility to the prawn industry

Dr Kijas explains that it quickly became apparent that work at the facility into nutrition, breeding, production systems, disease and health was vital for the prawn industry, and the site could not be compromised.

“If we don’t have this site and the capability to run animal-based trials, much of our external co-investment and our ability to deliver to clients wouldn’t be possible,” he says.

“There was also wider risk mitigation to consider, and the industry is also looking to us to assist them to get back online.”

water treatment plant
New water treatment infrastructure at Bribie Island.

That led to the installation of a new five stage seawater treatment process that filters water down to as small as five microns – or the width of a human blood cell, as well as ozone treatment to neutralise any organic compounds, such as viruses.

Other biosecurity features were also significantly tightened to reduce the risk of contaminants entering the facility in other ways.

“These systems and protocols give us biosecurity measures on par with the best aquaculture facilities in Australia, and we are able to continue our work with the prawn industry,” Dr Kijas says.

Getting back on their feet

Prawn farming on the Logan River was scheduled to resume in May 2018, though most farmers are looking to recommence farming later this year. They were recently dealt a blow, with news that white spot disease continues to be detected in wild Moreton Bay prawns, which has extended the duration of the existing restrictions on the movement of prawns.

Matt West says that his own farm is having biosecurity updates installed, such as improved filtration systems. It is a measure being replicated across the entire industry.

“We hope that this breach is a wakeup call to change how we look at biosecurity in general,” he says.

“It’s a big call to start running again after not having any income for essentially two years. But our farmers are resilient, and the Logan River guys are implementing increased biosecurity measures to try.”

He also recognises the work that CSIRO does to support the industry, and the time spent with farmers to understand the issues they face.

“The industry is able to compete on a world scale because of excellent science backing us up to enable us to deliver exceptional quality prawns in an efficient manner,” West says.

“The game has now changed, and we are going to be more reliant on R&D agencies like CSIRO to back us even more. We need to now move faster than ever before but it is comforting to know that a research agency like CSIRO has our back,” he says.

This work includes development of Shrimp MultiPath, an innovation that detects 13 commercially relevant prawn pathogens in a single test. It will enable for the first time a cost-effective and highly accurate means to test for multiple pathogens, with prawns often harbouring multiple pathogens at any one time. CSIRO is accelerating the Shrimp MultiPath test to market through their ON Accelerate commercialisation program in 2018.

CSIRO also has experience in selective prawn breeding programs, in breeds such as the Black Tiger prawn, which help to identify positive traits for consumers and boost profits for farmers. However, industry recognises it must move away from wild-caught broodstock – a practice which accentuated the scale of the original outbreak.

“Transitioning towards domesticated broodstock is an absolute must, but we can’t do this alone,” West says.

“We need good geneticists, like the expertise within CSIRO, to help with this challenge.”

One comment on “Battle against white spot disease in Australian prawns

  1. Ted woodham says:

    What is the life span of small prawns in the wild that carry the disease ( white spot )

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