Immunostimulant diets and oral vaccination in fish

An immunostimulant (IS) is a natural or chemical substance that stimulates the immune system by specific (vaccines or antigens) or non-specific (irrespective of antigenic specificity) routes. This chapter provides some insight into the target tissue of many IS diets; the fish mucosa. The use of IS-containing diets in aquaculture is widespread and encompasses a wide diversity of products that range from large feed producers using yeast extracts to more local custom production often using traditional remedies and extracts. Oral vaccines have huge potential that needs to be exploited as the method of delivering protection is highly desirable within aquaculture production systems. The development of new methods for the production and encapsulation of antigen that improve delivery, therefore creating a long-term response, is essential. Underlying these efforts are the continuing research that will provide a better understanding of the immune response following oral vaccination and therefore be able to drive and direct formulation strategies.