VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

VACCINES

• Use of vaccines have become one of the major approaches to combat fish diseases in recent years and have made a major contribution to improvements of fish health in aquaculture.
• Developing fish vaccine could potentially improve the aquaculture produce by preventing diseases and decrease antibiotic usage, making a safer, more environmentally friendly consumer product.
• Vaccines are helpful mostly in protecting diseases in finfishes which have immunological memory.
• Vaccines cannot confer protection effectively against diseases in shellfishes like shrimp, crab and oysters which have very less or no immunological memory.

Characteristics of an ideal vaccine

An ideal vaccine should

• confer maximum protection to the fish against the disease. 
• be safe for the fish, the person(s) vaccinating the fish, and the consumer. 
• provide long-lasting protection (till the end of the production cycle) 
• be in a form that can be easily administered.
• be cost effective.

TYPES OF IMMUNIZATION

There are two types of immunization procedures to protect the fishes from diseases namely,

• Passive immunization
• Active immunization

Passive immunization

• It involves the immunity that is conferred by administration of preformed antibodies or cells from one animal to other. The antibodies may be produced in a donor by active immunization and that these antibodies be given to susceptible animals in order to confer immediate protection. These antibodies may be raised in animals of any species and against a wide variety of pathogens. Monoclonal antibodies represent a potential source of passive protection

Active immunization

• It involves the immunity produced as a result of administration of an antigen. The advantage of active immunization over passive immunization is the prolonged duration of protection and boosting the protective response by repeated administration of antigen .
• Vaccines are used for active immunization of hosts in order to protect them from diseases.
• An ideal vaccine to be used for active immunization should be cheap, stable and adaptable to mass vaccination.
• It should give prolonged strong immunity with an absence of adverse side effects and ideally should stimulate an immune response distinguishable from that due to natural infection so that vaccination does not interferes with diagnosis.
• If an living organism must be used as a vaccine, they have to be treated in such a way that they lose their disease causing ability. The process of loss of virulence is called attenuation. The commonly used methods of attenuation involve adapting organisms to unusual environmental conditions so that they loose the ability to replicate uncontrollably in their unusual host. Viruses may also be attenuated by growing in abnormal conditions, cell lines etc.