udrey Tan writes in Singapore’s Straightstimes.com that, when it comes to putting healthy fish on the dinner table, experts believe vaccination is the way to go. But it is a laborious process. Workers at fish farms have to manually inject young fish with the vaccine one by one in order to protect them against specific diseases.
To develop an easier process, scientists at Temasek Polytechnic (TP) are working with an Israeli partner that will allow farmers to mix the vaccine into the fish feed. The oral vaccine against fish iridovirus — a common disease in farmed fish that can kill them — was developed by inserting parts of the iridovirus into a special type of microalgae, which are then mixed with feed and fed to the fish.
For the Temasek Polytechnic scientists, the key to developing the oral microalgal vaccine was finding a substance that could encapsulate the biological compounds in a way that would prevent it from being destroyed by fish stomach acids.
They worked with Israeli biotechnology company TransAlgae to develop a novel algae-based technology that allows for the oral delivery of protein-based drugs, such as vaccines, to animals. This method uses a strain of algae that can withstand acids in the fish’s digestive tract.
Dr. Ofra Chen, vice-president of research and development at TransAlgae Israel, told The Straits Times: “The specific algae cell wall… protects the vaccine from degradation in the animal digestive system and enables its delivery in its intact and functional form.”
While antibiotics are chemical compounds designed to kill bacteria, vaccines are preventive. They contain biological compounds that boost the fish’s own immune system against the virus. Vaccinating fish against specific diseases reduces the need to treat them with antibiotics when they are sick.
When humans consume antibiotics-fed fish, there is the possibility of residual traces of the drug passing through the food chain and ending up in the bellies of humans, which could build up a resistance to antibiotics.
The hope is that this would encourage wider adoption of vaccines here when rolled out commercially by 2021, reducing farmers’ reliance on antibiotics and leading to healthier fish, said team lead Dr. Diana Chan, head of the Centre for Aquaculture and Veterinary Science at Temasek Polytechnic’s School of Applied Science.
A spokesman for the Agri-Food and Veterinary Authority (AVA) said fish vaccines have helped to reduce disease occurrence in farmed fish, and contributed to the sustainable growth of aquaculture in many countries.
She noted several advantages of oral vaccinations for fish. “It is a quick and easy way to vaccinate a large number of fish, causes less stress to the fish, requires less time and effort to administer, and can be given to fish of all sizes, including those too small to be handled for injections,” said the spokesman.
She added that farms should choose the vaccine administration method that suits them best. “For example, farmers can choose to vaccinate smaller fish with oral vaccines and subsequently boost their immunity with repeated doses of the same oral vaccine, or an injectable version of the vaccine.”