Incorporation of Transgenic Microalgae Harbouring Vaccines into Feed to Improve the Efficacy of Oral Vaccination: A Review

The aquaculture industry has been rapidly progressive and is contributing to economic growth in many countries worldwide. However, one of the factors that is affecting the aquaculture industry are diseases caused by pathogens such as bacteria, viruses, fungi, and parasites. The utilization of antibiotics has been one of the measures taken in controlling fish diseases. However, continuous treatment with antibiotics for a long period of time will lead to the development of antibiotic-resistant pathogens which can cause harm to the well-being of humans, animals, and the environment as well. An alternative method in combating fish diseases is through vaccination. Vaccination for fish is commonly done by injection and is known to be very effective in protecting fishes from various ailments. However, this method is labour intensive, costly, stressful to the fish and not suitable for juvenile fish. Therefore, other methods are necessary to be performed for vaccinating the fish. This review aims to demonstrate effective methods of delivering vaccine to the fish using transgenic microalgae, specifically via oral vaccination. This review article summarizes the challenges faced in the aquaculture industry which could be mitigated via improved vaccination procedures. In addition to that, the potentials of incorporating transgenic microalgae whole cells into fish feed formulation as an alternative method of disease control is also outlined.