Training Manual Application of Genetics and Biotechnology in ...

By definition, an immunostimulant is a chemical, drug, stressor, or action that
elevates the non-specific defence mechanisms or the specific immune response.
Immunostimulants can be given to activate non-specific defence mechanisms or they
may be administered with a vaccine for enhancing specific immune response.
Research on immunostimulants is being intensified particularly in the areas of cancer
and acquired immunodeficiency syndrome (AIDS). Veterinary practitioners are
interested in the use of immunostimulants for activation and early protection against
diseases in domestic animals. Although lot of reports on development of
imrnunostimulants in fish in abroad are emerging daily, in India, we have a long way
to go.
Before a year or so, there was not even a single recommended
immunostimulant for Indian major carps, which constitute one of the major
components of Indian fish farming. Although few substances have been
recommended for use in aquaculture abroad, it cannot be recommended to Indian
carps because of many reasons. If the dose is not appropriate, it may even lead to
immunosuppression. Each species has got its own nutritional requirements. Similar
substances may not be effective for all species. Other problems are time, duration of
feeding, cost, over-dose and under- dose problems.
The study and use of immunostimulants in Indian carps first started at CIFA
with the aim of standardizing low-cost, locally available, cost-effective, user-friendly
substances to be used in freshwater aquaculture species particularly for Indian major
carps. Now-a-days, only a few laboratories have taken up work on these lines.
Immunostimulants will be most effective for short-lived fish, living in
cool/cold waters as the development of a specific immune response is temperaturedependent.
Among the non-specific defence mechanisms, the barriers in fish are
skin and scales, lytic enzymes of mucus and sera and cellular changes are observed in
monocytes, macrophages, neutrophils and cytotoxic cells. The specific immune
response is induced by immunogenic stimulation with production of antibodies,