The barren ponds that lay dormant along the once-thriving aquaculture hub of the Logan River, south of Brisbane, is a telling sign of Australia's first outbreak of white spot syndrome virus.

One year ago Ian Rossman received the news no prawn farmer ever wants to hear — his farm was infected.

Overnight, his family's future changed irrevocably.

Instead of spending the next month harvesting his crop ahead of the lucrative Christmas market, he watched on as biosecurity authorities killed his prawns and emptied his contaminated ponds.

Those authorities today are still unable to tell prawn farmers like Mr Rossman how or why white spot disease struck.

Farmers are not confident white spot has been eradicated in the wild. ( Supplied: Biosecurity Qld )

A Senate committee report recently concluded the pathogen pathway may never be known.

The uncertainty has taken its toll on Mr Rossman. Listen Duration: 26 minutes 27 seconds 26 m Listen Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen to Ian Rossman, Dr Ben Diggles, Senator Anne Ruston and the Australian Prawn Farmers' Nick Moore on the Country Hour ( Charlie McKillop ) Download 12.1 MB

He and his brother Geoff have opted not to re-stock when the fallow period ends next year because they consider the risks too great.

The extra biosecurity measures needed on the farm, including bird and crab netting ponds, drum filtering and ozonating every drop of water, would cost at least $1 million and give no guarantee against future outbreaks.

And in contrast to the emergency response by authorities to the first outbreak, prawn farmers would bear the full cost of any future decontamination and de-stocking effort.

"The way forward is a very expensive one," Mr Rossman said.

"The unfortunate part about this is we can spend all this effort and money on biosecuring the farm and we can still succumb to white spot again.

"We're not confident it's completely eradicated from the wild."

Prawn imports a 'smoking gun'

In July, the Federal Government ended a six-month ban on uncooked prawns entering the country, based on strict measures it said were designed to help safeguard Australia's $3 billion fisheries and aquaculture industries.

It was a move the commercial fishing and prawn farming sector labelled premature.

A Senate inquiry investigating the biosecurity risks associated with raw prawn import did not definitively answer the question of how the virus entered the Logan River.

But one of Australia's leading experts in diseases in crustacea, Ben Diggles, maintained imported prawns used as bait were the most likely cause.

"It's a smoking gun I suppose in relation to the most likely pathway, but we will never know for sure," Dr Diggles said.

"We do know that up to between 60-80 per cent of the prawns that were on sale in our supermarkets last year were actually positive for white spot virus.

"It is a highly-contagious disease and the virus does survive freezing, and we do know that some people were using those frozen supermarket prawns as bait, so there was a direct pathway from our supermarkets into our environment."

Biosecurity measures put to the test

The federal Department of Agriculture and Water Resources committed in June to ensuring all future imports of uncooked prawns — including marinated, breaded, battered and crumbed prawns — would be subject to 100 per cent inspection (for white spot disease and a separate virus called yellowhead disease) at the source country and the border to ensure they complied with import conditions.

Since trade resumed, samples from three of 115 consignments have tested positive to white spot disease after entering the country under the enhanced import conditions.

A total 85 tested negative and 28 are currently being held until test results have been confirmed.

A department spokesperson said the results supported the effectiveness of biosecurity measures.

But Dr Diggles said questions remained about whether the aquaculture and fisheries industry was adequately protected.

Marine biologist Ben Diggles questions if biosecurity is taken as seriously for aquaculture and fisheries as it is with other primary industries. ( ABC Rural: Jennifer Nichols )

He warned pressure was mounting with the increased volume of trade and pressure to secure more free trade agreements.

"If they're saying that biosecurity should be based on allowing diseases into our country and then trying to keep them out of our farms, I think that's not the arrangement that Australia would tolerate as a country," he said.

"We look at other production industries, certainly our beef cattle industry for example wouldn't like the idea of foot and mouth infected product being allowed to be sold into the country in the hope that they can keep their farms clear of it."

Apart from the seven farms at the epicentre of the outbreak, the bait industry and some wild prawn trawler operators have been crippled by a ban on exporting raw product beyond the south-east corner.

Statewide surveillance by Queensland's Department of Agriculture and Fisheries has returned negative results in all samples tested for the virus, but the control order will remain in place until two years of consecutive negative testing shows the disease is no longer present in the wild.

Mud crabs on the Logan River can carry the white spot disease ( ABC Rural: Marty McCarthy )

Prawn importers 'victims' too

Australia's inspector-general of biosecurity is also finalising a review of the import risk assessment (IRA) and the import conditions for prawns and prawn producers.

But in its submission to a Senate inquiry, the Seafood Importers Association of Australia said it supplied more than two-thirds of Australia's seafood needs.

Australian businesses — importers, wholesalers and food service outlets — had also all been victims of the white spot outbreak.

The association's executive director Norm Grant said importers had no qualms being subjected to the most rigorous tests applied anywhere in the world.

But the success of those tougher conditions would depend on compliance and enforcement action by federal authorities.

A prawn pond on the Logan River wiped out by white spot disease. ( ABC Rural: Marty McCarthy )

Mr Grant said so far the response had focused only on the risk posed by imported product, not the diverse range of pathways for the disease.

"Our main aim in this is it never happens again," Mr Grant said.

"We don't ever want to see a repeat of this, which means the Government and industry needs to look right across the spectrum of biosecurity risks.

"That would include looking at exclusion zones around the farms, and for the farms themselves looking at their own biosecurity and ensuring they meet international standards to prevent another incursion from any source."

Mr Grant said he was aware of reports some import permits had been revoked from "rogue" operators, who federal Agriculture Minister Barnaby Joyce sensationally accused of being akin to drug cheats in sport.

But one year on since Operation Cuttai was launched, importers are still waiting for the wrongdoers who have tarnished the reputation of an entire $1.3 billion industry to be punished.

"While they originally talked about 25 or 30 companies being under scrutiny, that appears not to have been fruitful," Mr Grant said.

"And so we don't know. We are left high and dry and we're as keen to find out what's going on as anyone."

The federal agriculture department said it was taking action against nine importers who accounted for about 70 per cent of Australia's raw prawn imports in 2016.

It declined to comment further on its ongoing investigation, but confirmed one brief of evidence had been provided to the Commonwealth director of public prosecutions for consideration.

