Valuable oyster estuary closed after deadly QX disease discovered

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Valuable oyster estuary closed after deadly QX disease discovered

A killer oyster disease has been found in one of the largest estuaries in New South Wales.

This is the first time that QX (Queensland unknown) – a seasonal disease affecting Sydney rock oysters – has been found in Port Stephens, but previous outbreaks have crippled growing areas elsewhere.

After a report of poor oyster growth, samples were taken and sent to the Elizabeth MacArthur Agricultural Institute (EMAI) with tests confirming the presence of QX.

Sarah Britton, NSW Senior Veterinarian, said QX was a very complex disease.

“It’s a parasite that has an intermediate host that has a full life cycle that takes place and gets into the shellfish and tends to multiply and multiply and gets into their digestive system and basically prevents them from starving and they don’t do well,” she said.

Dr Britton said QX infections were most likely to occur earlier in the year, around March to April.

“It is possible that we are at the end of the stage where this intermediate host is very active for this disease,” she said.

Sarah Britton, NSW Senior Veterinarian, says QX was very complex.(

ABC: Hugh Hogan


Biosecurity trend restricts oyster movement

The Department of Primary Industries has placed movement restrictions on the Port Stephens oyster industry while investigating the presence of the disease further.

There are concerns that QX’s presence in Port Stephens will have a significant impact on the entire state.

“It’s one of our largest oyster-producing areas and they have hatcheries, nurseries and research facilities, and there’s a lot of stuff going on in that estuary,” Dr. Britton said, adding that farmers in other areas should monitor oysters for any signs of disease.

“There is no risk to human consumption with this particular disease, so the main thing we are trying to do is reduce the risk to other estuaries and keep the disease out of as many estuaries as possible.”

Farmers waiting in a noisy hook

Don Burgoyne, an oyster farmer in Port Stephens, said the potential for the QX “hung over our heads.”

“Every estuary has a chance of something like this happening,” he said.

The estuary is home to over 40 oyster farmers, but stock is also sourced from the area by outside farmers.

“We are all waiting for the severe disagreement to see how things develop,” he said.

Don Burgoyne is standing next to Tilligerry Creek on his oyster farm.
Don Burgoyne said the impact on the local industry could be devastating.(

1233 ABC Newcastle: Robert Virtue


Burgoyne said that given previous QX outbreaks, there could be a significant impact on the region.

“It definitely decimated the industry in the George and Hawkesbury Rivers,” he said. “They couldn’t keep up. Every year it kills 90 percent of your oysters, so you can’t keep going.”

Since those outbreaks, researchers have worked to breed QX-resistant oysters.

Macleay Farms switches to QX-resistant oysters

Three hours north of Port Stephens, David Smith, who farms on the McClei River, knows how difficult a QX outbreak can be.

“It’s a very devastating event that anyone can go through,” he said.

“We heard about the outbreak in Port Stephens on Friday and to be honest, I didn’t sleep all Friday night just worried about these guys.”

Oyster farmer David Smith in front of the water.
Farmer David Smith switched to QX-resistant oysters after losing $500,000 of the crop to the deadly disease in 2020.(

ABC Med North Coast: Hana Palmer


After losing $500,000 worth of QX stock in March 2020, he turned to DPI-developed QX-resistant oysters, and just in time.

“This year the QX is back on our river and it was a direct result of the flooding,” he said.

Smith referred to the devastating virus as a “ramp of hope” that takes years to recover from the outbreak.

“You bring your oysters and whatever sealed thing you assume are alive and you put them back in, and you check them a month or so later, 50 or 60 percent of them are dead,” he said.

“Not only do you lose current year’s oysters, which is your cash flow, but you lose next year’s cash flow as well, because what we saw in oysters less than 12 months away we saw a 70 to 75 percent mortality rate.”

oyster shells;
Farmers say it takes years to recover from losses from QX disease.(

ABC Med North Coast: Hana Palmer


Before QX reached the Macleay River, there were 25 oyster farmers, and Mr. Smith said he is now one of 10 farmers.

“The size of the oyster farms in Port Stephens is off the charts, compared to our river here,” he said.

“My thoughts go to all of these cultivators. It is a mental and physical challenge to deal with this event.


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