![]() ![]() ![]() Immersion vaccination involves immersion of fish in water containing vaccine antigens. Immersion vaccination is more applicable compared to injection vaccination, but the method suffers from a low potency, due primarily to inefficient uptake of antigens across mucosal membranes. Inactivated vaccines based on either killed pathogens or isolated pathogen subunits are, in many cases, weakly immunogenic with low vaccine efficacies. Traditionally, vaccines comprise either live, attenuated, replicating or non-replicating pathogens, inactivated pathogens or their subunits. Treatment of fish diseases with antimicrobials may have negative impacts on the aquatic environment and human health. Electrostatic coating with positively charged chitosan to obtain mucoadhesive vaccines and a more efficient delivery of inactivated vaccines has also been successful.ĭisease prevention by vaccination is, on economic, environmental and ethical grounds, the most appropriate method for pathogen control currently available to the aquaculture industry. Examples are booster vaccination, administration of immunostimulants/adjuvants, pretreatment with low frequency ultrasound, use of live attenuated and DNA vaccines, preincubation in hyperosmotic solutions, percutaneous application of a multiple puncture instrument and application of more suitable inactivation chemicals. Therefore, during recent years, several studies have focused on different ways to augment the efficacy of these vaccines. Inactivated vaccines are, in many cases, weakly immunogenic, resulting in low protection after immersion vaccination. However, injection is problematic in small fish, and fry as small as 0.5 gram may be immersion vaccinated when they are considered adaptively immunocompetent. In most cases, immersion vaccination is inferior to injection vaccination with regard to achieved protection. Administration of vaccines depends on the size of the fish. The lack of classical secondary responses following repeated immersion vaccination may partly be explained by the limited uptake of antigens by immersion compared to injection. During immersion vaccination the antigens are taken up by the skin, gills or gut and processed by the immune system, where the resulting response may lead to protection. Immersion vaccines are used for a variety of aquacultured fish to protect against infectious diseases caused by bacteria and viruses. ![]()
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