Tra basa vaccine under development

The Fish Site
by The Fish Site
28 May 2007, at 1:00am

VIET NAM - RMIT University is using a partnership of talented individuals to develop a vaccine against the Edwardsiella ictaluri bacteria. The development will help to increase the profitability of tra basa catfish farming in Vietnam.

Professor Peter Coloe and Ms. Phan Ngoc Thuy in the lab.

Head of Applied Science at RMIT University, Professor Peter Coloe, said “Aquaculture is a critical element of Vietnam’s globalisation program at the macro level, and the welfare of tens of thousands of households at the micro level is influenced by successful productivity at the farm level,”

“Therefore, RMIT would like to help young scientists from Vietnam to solve problems that challenge farmers and fish producers,” Professor Coloe added.

The intention is to develop a product that would be administered by immersing catfish fingerlings in water containing the vaccine. They would then be put into the ponds, where the protection should last long enough to take them through to harvest.

The researcher strategy is to make vaccine strains that are able to invade the fish and induce immunity but not cause disease. The most effective vaccine is likely to be a live vaccine, because it stimulates all types of immunity and provides with fish longer protection than other methods.

Professor Coloe says this is an established approach and the same type of procedure that is used to develop a salmonella vaccine for chickens - a project that was also undertaken at RMIT.

Professor Coloe and Ms. Phan Ngoc Thuy, a PhD candidate, are working with fish specimens from Vinh Long and Can Tho. They believe that over-stocking of fishponds can contribute to the spread of the bacteria within fish populations.

They compared two separate ponds, stocking 90 and 30 fish per cubic metre respectively, and measured feeding patterns in both.

“It was clear that in the pond with 90 fish per cubic metre the water quality was lower and there was a greater likelihood of fish succumbing to disease. There is likely to be a decrease in nutrient conversion efficacies,” said Ms. Phan.

Professor Coloe and his colleague, Dr. Patrick Griffiths, who works in Vietnam, visited the Thang Hung fish-processing factory in Can Tho, which exports basa and snapper to the Woolworth’s supermarket chain in Australia.

“We’ve consulted people along the production chain, including scientists, industry representatives, processors and farmers,” said Dr. Griffiths “They are all aware that, unless there are vaccines, farmers face risks of fish being rejected by processors at one level, and nations at another.”

Professor Coloe was extremely impressed by the high quality of the Thanh Hung factory. “The processing plant was spotless and highly efficient. The Tra basa are shipped by barge from upstream and arrive in the morning live. They are filleted within seconds of slaughter, and are trimmed and snap-frozen soon after.”

After inspection, the product is shipped by container down the Hau River to Sai Gon Port. It’s about a 15-day journey to Melbourne.