JCU project to help safeguard prawn industry

In a landmark Queensland project, researchers will use environmental DNA (eDNA) samples taken from water in prawn farm ponds to test for the presence of viruses that can cause growth deformities and occasional mass mortality in tiger prawns and banana prawns.

Funded through agrifood industry body Food Agility CRC, the two-year study by JCU’s AquaPATH lab will be conducted at Australian Prawn Farms and Seafarms’ prawn ponds in north Queensland.

“It’s significantly less expensive for a farmer to use eDNA samples and it’s a lot quicker to collect them,” project lead and AquaPATH lab Senior Scientist Dr Kelly Condon said.

“The alternative is catching prawns, taking tissue samples, preserving the tissues, and then disinfecting all of the equipment before moving to the next pond. The tissue analysis only provides information after an infection occurs whereas eDNA allows detection of the pathogen in the environment.

“We saw great benefit using eDNA in sewerage treatment plants for the early detection of COVID and this is applying a similar approach to prawn farming.”

Researchers estimate a saving of $484 per prawn pond in pathogen surveillance compared to the more time-consuming tissue sampling that can cost up to six times as much.

Dr Condon said the eDNA sampling method can effectively act as an early warning system to identify the presence of viruses before a wider - and financially devastating - outbreak can occur.

In the longer term, the eDNA approach allows scientists to investigate the pond conditions that avoid a disease outbreak.

“We don’t get a disease outbreak every time a pathogen is present in a farm, but we don’t understand enough about why a disease outbreak occurs in some situations but not others,” Dr Condon said.

“From a scientific point of view, this method allows us to collect a lot more samples so we can get a weekly indication of how prevalent a pathogen is across a farm and really drill into the pond factors that lead to a disease outbreak versus those that don’t.

“We can get a much more comprehensive picture of how pathogens are getting into the farm, how often they are present in intake water and where we might detect something early on that is yet to affect prawns at that farm.”

The start of the project follows the results of a pilot study conducted by the JCU team earlier this year which demonstrated proof of concept in using eDNA as a viable testing method in prawn ponds - but with a twist.

“In a normal eDNA analysis you would filter water through a machine and then analyse the filter discs. In aquaculture, that’s not easy to do because prawn ponds get a strong algal bloom and the filters will clog up all the time,” Dr Condon said.

“So, we’re trying a way where we put an incubating filter in the water and it relies solely on the water currents for the viruses to bind to our filter, rather than us trying to push it through with a pump.

“The incubate and collect approach of eDNA sampling significantly reduces the time investment required by farms to conduct surveillance to the extent a whole farm can be sampled in one day rather than two to three days.”

Dr Condon said if the project proved to be successful, the sampling method had the ability to become an essential aspect of biosecurity in farmed prawns.

“It’s definitely going to make biosecurity a lot more economically viable for farmers and also provide a tool for scientists to understand some of the farming practises that can reduce the likelihood of disease if a pathogen enters the farm,” she said.