RESEARCH & DEVELOPMENT:

PRAWN DISEASE CONTROL

Friday, 15 June 2001

Ref 2001/147 , CSIRO, Australia

Australian prawn farmers will soon be able to use a Virus Test Kit to head off outbreaks of viral prawn diseases.

Viral diseases in prawns, such as gill-associated virus (GAV) and yellow head virus (YHV) have caused over $40m in losses to this fast-expanding industry and devastated prawn farming operations in Asia.

An agreement has been signed between CSIRO Livestock Industries, BIOTEC (the National Centre for Molecular Biology and Biotechnology, Bangkok, Thailand) and Farming IntelliGene (a Taiwan-based company), which will lead to the commercial production and distribution of the Virus Test Kit for GAV and YHV - two of the major viral killers of prawn stocks in Australia and Asia.

The Managing Director of Farming IntelliGene Corporation, Mr Leo Liu is visiting Queensland this week and is participating in a prawn farmers workshop to promote virus detection kits and advise farmers on disease awareness and management.

"GAV poses a major threat to the farmed prawn stocks in Australia. This diagnostic virus test kit offers the farmer the necessary technology to identify its presence in their stocks and manage the disease more effectively," says Mr Liu.

The CSIRO scientists responsible for isolating the virus GAV are delighted to see this groundbreaking technology getting out to prawn farmers in such an easy to use form.

"GAV is a very unusual virus indeed", says CSIRO's Dr Peter Walker, who headed the team called in to tackle the menace.

"It's the first virus of its type known to science, and has drawn the attention of virologists worldwide," he says.

GAV is now known to be present at low levels in healthy prawns without ill effect, but when the prawn is stressed by poor water conditions, overcrowding or other diseases, the virus multiplies and the infection becomes lethal. Although it affects farm production, the virus is not at all harmful to humans.

The research team concluded that GAV and YHV are closely related, but come from two different viral populations. GAV affects Australian prawns while YHV occurs in Asian prawn stocks.

The test for GAV developed by the team in projects supported by the Australian Centre for International Agricultural Research (ACIAR) and the Aquaculture Co-operative Research Centre, revealed it usually infects only the black tiger prawn, not other farmed species like the premium-priced Kuruma prawns that are exported to Japan.

The test also indicates that broodstock from areas such as Carpentaria may be free of the virus, and could in future offer a source of GAV-free farming stock, provided they are also free of other viruses.

"Since GAV is present in almost all farmed black tiger prawns in eastern Australia and there is no easy way to eradicate it, we believe that the answer lies in managing conditions on the farm to avoid stressing the stock and breeding prawns that are virus-free," says Dr Walker.

Guidelines for dealing with GAV have been developed by scientists from CSIRO Livestock Industries and Queensland Department of Primary Industries working within the former Aquaculture Co-operative Research Centre.

The guidelines will assist farmers to deal rapidly and safely with outbreaks of the disease and advise on the cleaning the ponds afterwards to prevent future outbreaks.

The development of this virus testing kit also makes it possible for farmers to keep an eye on other species of farmed prawns to ensure they remain disease-free and to test new sources of broodstock to ensure they are free of the virus.