Dr Sarah Britton, NSW Department of Primary Industries' chief veterinary officer, said routine lab testing at the Elizabeth Macarthur Agricultural Institute had confirmed the presence of QX in samples from Port Stephens.

"The oysters submitted to NSW Department of Primary Industries were in poor condition and exhibiting poor shell growth," Dr Britton said.

"Samples were sent to the Elizabeth Macarthur Agricultural Institute and the positive result was confirmed. QX poses no risk to human health and all seafood in the market place remains safe to eat."

QX, which stands for Queensland Unknown, affects Sydney Rock Oysters and is caused by a protozoan, or single-celled, parasite. Signs that oysters are infected include lack of growth and loss of condition.

Dr Britton said NSW DPI will be deploying "significant resources to bear" in the effort to manage the detection.

"We have activated an Incident Management Team and we expect to announce a number of biosecurity measures in the coming days, we will continue to work closely with the local oyster industry in response to this threat," she said.

"Port Stephens is a vital oyster producing estuary and the second most valuable NSW oyster production estuary in NSW.

"Oyster production in NSW is estimated to be worth $58.2 million and oyster producers, particularly Port Stephens oyster producers, are still recovering from flooding in March."

Dr Britton urged Sydney Rock Oyster producers to be vigilant and to report anything unusual with their stock.

"It's vital that any producer who sees anything out of the ordinary reports it to the NSW Biosecurity Hotline on 1800 680 244," she said.

For more information on DPI's incident response, Port Stephens oyster growers are encouraged to call 1800 801 738.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can access our trusted content: