Abstract: Vaccines play an increasingly large role in the aquaculture industry, with the development of large-scale, industrialization and intensification of the aquaculture industry, the feeding density is getting larger and larger, the circulation range is also getting wider and wider, and the types of diseases are also increasing, which brings great threats to aquaculture production, so the role of vaccines in production is crucial. This article elaborates on the types of vaccines and their applications for the reference of farmers.
The development of the breeding industry and animal epidemic prevention are closely related, weak animal epidemic prevention will cause animal diseases, such as avian influenza, foot-and-mouth disease, blue ear disease, tuberculosis, etc. not only seriously threaten the development of the breeding industry, but also affect the safety of livestock products, a threat to social public health security, so animal epidemic prevention is the key to preventing diseases, vaccines are the basis for animal epidemic prevention, and it is very important to understand the relevant knowledge and application methods of vaccines for breeders.
1 type of vaccine
Vaccines are artificially used in animals for automatic immunization of biological products, is made of pathogenic microorganisms, parasites and their components or metabolites after special treatment of the vaccine according to the different sources of production can be divided into bacteria, vaccines, toxoids, bacteria are made of bacteria, mycoplasma, spirochetes, etc. or their components, vaccines are made of viruses, rickettsia or their components, toxoids is made of certain bacterial exotoxins. According to the composition and research and development methods of vaccines, they are roughly divided into conventional vaccines, genetically engineered vaccines, synthetic polypeptide vaccines, anti-unique antibody vaccines, and viral antibody complex vaccines.
1.1 Routine vaccines
Conventional vaccines are vaccines made from intact microorganisms such as bacteria, viruses, rickettsia, spirochetes, and mycoplasma. Conventional vaccines are common inactivated vaccines, live vaccines and toxoids. Inactivated seedlings are vaccines made by artificially cultivating highly immune bacteria, viruses, etc., inactivated by physical and chemical methods, and then added appropriate adjuvants. It mainly includes two kinds of chicken embryo tissue inactivated seedlings and cell inactivated seedlings. In livestock production, inactivated seedlings of diseased tissue are often made in order to ensure immune effects. The advantages of inactivated seedlings are more prominent, mainly good safety, production preservation and transportation are convenient, but their production costs are high, the immunization period is relatively short, and multiple immunizations are required to induce humoral immunity. Live vaccines are developed using artificially weakened strains, natural weakened strains or non-virulent strains that have lost most of their pathogenicity but still maintain good antigenicity and can reproduce in vivo. This type of vaccine can effectively stimulate the body's immune system, stimulate humoral nucleus cells to produce immunity, long immunity period and good effect is easy to use. Toxoid refers to the biological products made of exotoxins produced by the bacteria through detoxification and purification, and can be produced after inoculating animals with antitoxins, such as tetanus toxins used to prevent tetanus.
1.2 Genetically engineered vaccines
A genetically engineered vaccine is a biotechnological vaccine that uses genetic engineering methods or molecular cloning techniques to isolate a pathogen's protective antigen gene and then transfer it to a human pronuclear or eukaryotic system, and the protective antigen of the pathogen is expressed. Or remove the virulence gene from the pathogen, making it a gene-deletion vaccine without virulence genes. Commonly used genetically engineered vaccines include recombinant live carrier vaccines, genetically engineered subunit vaccines, and gene deletion vaccines. The biggest advantage of genetically engineered vaccines is that they are safe and have low production costs. Genetically engineered vaccines also have deficiencies, such as poor immunogenicity of genetically engineered subunit seedlings, animals that need to be immunized multiple times to have better protection, and some recombinant live carrier seedlings are carcinogenic. However, the advantages and immune effects of genetically engineered vaccines are very obvious, and the prospects for application are relatively broad.
1.3 Synthetic peptide vaccines
Synthetic peptide vaccine is a new type of vaccine, the advantage of this type of vaccine is that it will not be toxic due to mutation, nor will it lose immunogenicity due to excessive weakness, and there is no inactivation incomplete or hidden infection, and there is great potential for development. At present, the most studied synthetic peptide vaccines for foot-and-mouth disease virus, rabies virus and influenza virus have made some progress.
1.4 Anti-unique antibody vaccine
Anti-unique antibody vaccine is also a new type of vaccine, compared with the traditional vaccine, it has many advantages, such as not containing infectious antigens, can avoid potential autoimmune reactions, do not need to purify, etc., but its manufacturing method is very complex, immunogenicity is weak, there are disadvantages such as xeno protein side reactions, it is currently in the research stage, and it still needs a lot of work to be done in the production of promotion.
2 Application of the vaccine
With the rapid development of the aquaculture industry, vaccines have been widely used in the prevention and control of animal diseases. However, in the process of vaccine use, because of the different vaccines and animal breeds, the method of immunization is different. The vaccination methods of animal vaccines currently developed can be divided into injection, nose and eye drops, oral, aerosol, prick and so on.
Injections mainly include subcutaneous injection, intradermal injection, intramuscular injection and intravenous injection, and injection immunization should be based on different vaccines and animal species to choose the appropriate method for injection, for example, diseases that can cause extensive damage to the whole body can be injected subcutaneously; Sheep pox seedlings and diagnostic fluids can be injected intradermally; Pigs, cattle, sheep and other large animals injected with anti-disease serum mostly intravenously.
Nose drops are usually used in poultry, such as chicken infectious bronchitis. Such methods have little stress on poultry and have a significant immune effect. The prescribed dose should be applied according to the requirements of the vaccine when immunization is carried out.
Oral classes are mostly used for herd immunity, especially in poultry. Oral vaccines are generally live vaccines, and when used for immunization, the dose used is larger, generally more than 10 times the injectable dose. Before oral vaccinations, in order to ensure the immune effect, water should be stopped and fed for two hours to ensure that each animal can take an adequate dose. In oral immunity, drinking water immunity is better than mixing feeding immunity, because drinking water not only passes through the digestive tract, but also comes into contact with oral mucosa, tonsils, etc. The lymphoid tissue in these parts is rich and more likely to produce immune responses.
Aerosol immunity is also a more commonly used immune method, suitable for herd immunity, poultry production is more used. For example, The Newcastle disease II, I and IV weakened vaccines are commonly used in this way for infectious bronchial weakening vaccines. Aerosol immunization saves time and effort, and the vaccine immunization effect of invasive respiratory tract is good. However, the stress caused by this immunity is large and can easily induce respiratory diseases.