New technology combats marine biosecurity threat

Original story by Aaron Fernandes, ScinceNetwork Western Australia

THE exotic fish trade presents an ongoing challenge for bacteriologists working to keep harmful pathogens out of WA water ways, but experts say the state’s biosecurity efforts are among the best in the country.

The importation of exotic aquarium fish into Australia is worth around $350 million annually, with 15.5 million fish being imported in 2005.

However, these animals can be a source of exotic pathogens, bacteria and disease that cause havoc in Australia’s freshwater and marine eco-systems.

Fish imported into Australia are subject to Department of Agriculture Fisheries and Forests (DAFF) biosecurity conditions and on arrival are held in quarantine for inspection.

In WA, fish showing signs of disease are sent to the Fish Health Unit at the Department of Fisheries, before bacteriology is conducted at the Department of Agriculture’s Animal Health Laboratories.

Animal Health Laboratories expert Dr Nicky Buller says she regularly receives samples of suspected exotic pathogens which are then subjected to state-of-the-art technology for culturing and identification.

“When DAFF Biosecurity officers observe significant deaths among quarantined fish, we are supplied tissue samples for identification,” she says.

“We perform traditional culture procedures and DNA-based methods, but we also have introduced the matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF) for identifying samples,” Dr Buller says.

“This technology utilises the proteins on the cell wall which are ionized by a laser beam and separated under vacuum.

“The mass is recorded on a detector, and the resulting spectrograph is compared to the database to determine a probability whether high or low of it being a certain organism.

“In the last year we have had a few exotic pathogens detected in quarantine and we have been able to identify them through both traditional methods and with this new technology.”

“Culturing” involves growing the bacteria for further study, a process that can present several challenges for researchers.

Bacteria from marine fish need to be cultured in media containing NaCl, or magnesium and potassium ions, whereas bacteria from freshwater fish do not required added NaCl.

“It is a challenging task. You have to be able to recognise potential cases of exotic disease among the endemic cases; bacteria that you wouldn’t normally see in everyday diagnostics,” Dr Buller says.

“There are also specific temperature and media requirements for different bacteria, and that means knowing what temperature is optimum for culturing.”

Dr Buller is urging West Australians to help reduce the risk to Australia’s native fish with practices like disposing of dead aquarium fish in bleach in the household rubbish, rather than flush them down the toilet.