Barramundi farm on Bathurst Island. (Photo: Marine Harvest)
Farmed barramundi industry to get an immunity boost
Friday, August 20, 2010, 00:00 (GMT + 9)
University of Queensland researchers have devised a dependable typing system for infections in barramundi that will allow for the quick implementation of vaccines in the industry.
The barramundi project is being funded by the Fisheries Research and Development Corporation.
Dr Andrew Barnes of the School of Biological Sciences developed the vaccine along with the Darwin Aquaculture Centre and veterinarians Matt Landos, John Humphrey and Suresh Benedict.
“Streptococcus iniae is a bacterium that causes disease in farmed fish similar to meningitis and blood poisoning in humans," Barnes said. “Treating the infection with antibiotics is difficult because antibiotics must be fed to the fish and when the fish are sick, they don't eat the medicated feed.”
“There is a problem of bacteria becoming resistant to antibiotic treatment, and this resistance can be transmitted to other bacteria that may be harmful to humans. For food and safety reasons, farmers may have to abide a ‘withdrawal period' of their stock from market to ensure residue levels of the antibiotics meet required levels. This causes problems for farmers when the fish are close to market size,” he elaborated.
Although vaccinating barramundi to protect it from the bacteria is possible in fish, it has not always been successful, because vaccinated fish do not necessarily recognise new strains of disease.
Barnes explained that the flu shot works in humans because there are only two proteins on the surface of the virus that change, and these can be identified in laboratory tests to be included into each year’s vaccine.
“Typing the surface of S. iniae has been more difficult as it is a polysaccharide. Of more than 20 genes responsible for the surface capsule, changes in five have been attributed to critical changes in the surface,” he told.
“A reproducible and accurate typing system has been developed and a manual drafted and disseminated to veterinary laboratories which will enable accurate detection of any new isolates should they arise in the future," Barnes added.
Thanks to the results of his work, it is now possible to create a generic vaccine for Australian barramundi.
Future work ought to incorporate further typing but will mainly target the testing of the generic vaccine formulations in fish to guarantee cross protection and generating a dossier to allow for registration of the vaccine.
Barramundi is expected to grow strongly as an aquaculture species in Australia.
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By Natalia Real