Maintaining an Environmentally Sustainable Australia

One of the main objectives of the ARC Network for Parasitology will be the generation of both knowledge about and practices for the management of terrestrial and marine ecosystems.

The combined expertise of the Network will begin by assessing the susceptibility to, and monitoring the prevalence of, parasitic disease in wildlife by:

• Assessing parasite diversity in Australian fauna; and
• Ensuring the sustainability of wildlife and ecosystem health.

Case Study : QX Disease Resistance in Sydney Rock Oysters

Dr Robert Adlard, Senior Curator (Parasitology), Queensland Museum.

Australia's oysters are world famous. However there is a disease that is threatening the very existence of the industry.

Scientists at the Queensland Museum have been conducting a three-year study using DNA testing to determine where the QX Disease is prevalent.

QX outbreaks in south-east Queensland, northern NSW and the Georges River have cut oyster production significantly in those areas.

The three-year study revealed not only where the disease was causing problems - but also identified those estuaries where the disease agent occurs but was not causing significant disease.

In this way, the researchers, headed by Dr Robert Adlard, Senior Curator (Parasitology) at the Museum, can determine ways to minimise the impact of any disease outbreaks and provide a factual basis for disease risk management.

There were concerns that the disease was spreading south from Queensland, putting at risk the lucrative Sydney rock oyster market. However Dr Adlard and his team allayed fears that the disease was working its way down the New South Wales coast.

"The DNA testing has shown us that the disease is not necessarily spreading, but with the extreme sensitivity of such tests the pattern we are now seeing is more likely to be the true distribution of the disease agent. We are now thinking that the disease only becomes active when the oyster's immune defences are depressed," Dr Adlard said.

"We are only just starting to properly understand the true nature of the QX parasite. Previously there were limited diagnostic tools and sampling was not comprehensive. However, using a combination of DNA diagnostic techniques and by conducting a comprehensive study covering all the major oyster growing areas, we have been able to capture more accurate data and provide results that make this project very exciting scientifically."

The QX organism was first detected in Queensland in the 1970's and has been affecting oyster culture in Queensland and northern New South Wales for decades. It was discovered 450 kilometres further south in the Georges River, Sydney in 1994 by Dr Adlard.

The QX parasite, Marteilia sydneyi, is a protozoan organism which develops in the oyster's digestive gland and effectively starves the oyster to death within 2-3 months. There are no human health issues associated with the syndrome.

Dr Adlard and his team at the Queensland Museum have been working with Macquarie Univerity, New South Wales Fisheries, Queensland Department of Primary Industries and the Federal Government's Fisheries Research and Development Corporation (Aquatic Animal Health Subprogram) to unravel the mystery of the QX parasite.

In late March, the team will again head to select locations on the NSW and Southern Queensland coasts including a total of 21 estuaries, to collect oyster samples for study. Sampling has been conducted in NSW since 2001 and in Queensland since 2002.

Current Project Funding