Definition

The immune protection against animal diseases can be obtained actively by applying vaccines or passively by the use of serum. The application of vaccines needs the organic reaction which is conditioned by the own characteristics of the vaccine, the application method and organic circumstances of the immunized animal.

Vaccines are prepared antigens to be used for preventing of diseases caused to birds and cattle by bacteria, viruses, fungi, mycoplasma, protozoa and parasites.

The type of vaccine is established depending on the type of antigen which determines the method of elaboration.

In this article we will describe those aspects which influence on vaccine’s characteristics (antigens, inactivators, preservatives, excipients, adjuvants and elaboration and distribution processes), its application (via and contraindications) and those that affects the animal organism which receives the vaccine.

Components and types of vaccines:

1.-Components: The veterinary vaccines are composed of Active Ingredients (antigens) and other components which affect the velocity of liberation (adjuvants) or are used to obtain proper forms (inactivators, preservatives and excipients).

a)Antigens: The essential component of any vaccine is the antigen which consists of biologic units, usually proteins or infectious agents, and produce, when in contact with animals, the formation of antibodies, substances of protein nature, capable of react especially against its antigen.

1. Alive without being modified: They are biological units which are administered without intervening over its structure. It basically consists of provoking the disease under control. The use of this kind of antigen is frequent in antiprotozoal vaccines and avian viral vaccines. In the first case, its efficacy depends on the quantity and the increasing pace of application. One example of this type of vaccine is the vaccine used to prevent avian coccidiosis for Eimeria. On the second example, we can mention vaccines with turkey herpes virus to vaccinate hens against Marek’s disease.

2. Attenuated alive: They are biological units which have been intervened by reducing its pathogenicity by successive passes in animals or cultivating microorganisms in swine reproductive conditions. The degree of attenuation is directly proportionally related to with the number of passes done. These methods of attenuation are mainly used on viruses such as avian infectious bronchitis (ovoculture) and swine plague virus (lapinized).

3. Modified or recombined alive: They are genetically modified biological units with the aim of avoiding to express some own proteins or expressing strange ones. In the first case they achieve attenuated live antigens irreversibly or fractions which do not interfere with diagnostic techniques or both characteristics at unison (virus of Aujeszky’s disease).The modified live antigens do not present at short term the possibility to become in pathogens but if they keep the possibility at long term they can become pathogens by natural recombination .The recombined live antigens present advantages from the industrial point of view as they use bacteria and yeasts which are easier to cultivate than the donor microorganism generally of viral origin. The vaccine with mixomatosis virus of rabbit which has received genetic material from viral haemorrhage virus is an example of recombined vaccine.

4. Inactivated: They are biological units, some toxins included, which have been killed by the action of physic or chemical agents or both at the same time. They preserve part of the chemical structure capable of provoking immune response. Bacterins and toxoids correspond to this type of antigen which constitutes the most secure antigen in its application.

5. Subunits: They are fragments of biological units that due to its composition can provoke immune response. Generally these subunits are inactivated subsequently. Some components in these subunits have been eliminated despite of getting immune response, as they can interfere with the subunit. This kind of antigen is frequent in vaccines for swine atrophic rhinitis and colibacillosis.

6. Synthetics: They are units or subunits obtained by chemical synthesis. The difficulty of their use is that the three-dimensional disposition of amino acids is not identical to the original antigen; therefore their immune response isn’t identical either.

7. Antidiotipos: They are obtained by biological mediums due to its lack synthetic antigens. They are biological units obtained as antibodies of original antigen’s antibody to which replaces them. The original antigen is inoculated and the antibodies produced are called idiotype. When this idiotype inoculates in another animal some antibodies are obtained (antiidiotipo), which three-dimensional structure is identical to the natural antigens’ one. Its elaboration is difficult but presents the advantage of acting immunologically as an alive microorganism without being a microorganism.

b) Adjuvants: They are chemical substances, materials of microbiological origin or mixtures which administered together with the antigen contribute to the production of a better immune response.

1. Aluminium and calcium salts: They delay the liberation of antigen from the point of inoculation and permit to obtain prolonged immune responses. The most common salts are calcium phosphate and aluminium phosphate and hydroxide.

2. Immunostimulants: They increase or recover the immune defenses and they can be materials of biological or chemical origin.

• Bacterial fractions

• Vegetable substances

• Chemical

3. Freund’s adjuvant is an emulsion of water-oil and complete mycobacterium or a fraction called muramyl dipeptide.

4. Liposomes

c) Inactivators: They are substances that remove the pathogen capacity of the antigens. They can be used alone or combined with the action of physical agents such as the heat.

1. Formol: It is the commonest inactivator in the elaboration of anatoxins. Its maximum quantity in the final product is limited by Pharmacopoeia to avoid its action on animal tissues.

2. Alkylating: They are substances that lead to the formation of bonds between nucleic acid’s bonds. As they react with the superficial proteins of the microorganism, this one keeps its antigenic power. The commonest alkylatings are the ethylene oxide, Beta-propiolactone and ethylenaimin.

d) Preservatives: They are substances which they incorporate to inactivated vaccines to avoid further pollutions during the handling in farm. Fenol is the commonest preservative in the elaboration of inactivated vaccines. Its content in the final product is limited by the monographies of every vaccine described in Pharmacopoeia.

e) Excipients: They are liquid or solid diluents that permit to obtain the concentration of antigens in the final product in order to give doses easily.

1. Physiologic serum

2. Skimmed milk

2.-Types of vaccines:

1. Live vaccines: They are elaborated with not modified live antigens, attenuated live antigens and modified live antigens. This kind of vaccine provides fast immunity but they are only suitable in contaminated environment.

2. Dead vaccines: They are elaborated with inactive antigens. It provides slow immunity and most of them require the incorporation of a coadjuvant. They are indicated in healthy environment for its harmlessness.

3. Design vaccines: They are elaborated with subunits, synthetic antigens and antiidiotypes.

Elaboration and control of veterinary vaccines

The elaboration of a veterinary vaccine is a complex procedure based on many steps and variables depending on the antigen used. The work procedures must adjust to the international recommendations about GMP and the quality of raw materials described by European Pharmacopoeia, National Pharmacopoeia and the technical profile recognised.

Its facilities and equipment used in elaboration of veterinary vaccines must adjust its construction and materials to the European and National rules. The rule 81/851/CEE and the Real Decree 109/1995 constitute the existing legal body regulator of the requirements that these facilities must accomplish.

Regarding the constructions we must take into account the following:

1. The circulation of vaccine’s components is done in a direction which avoids the crossing among ingredients, intermediate products and final products.

2. The circulation of people and their clothing is also done in a determinate direction to avoid crossings.

3. The circulation and quality of air avoids pollution from outside. The packing is realised under sterile conditions and positive pressure.

4. In cleanness procedures we must avoid the formation of convex right angles of difficult access.

Regarding the materials we must take into account the following:

1. In order to avoid the filtration of microorganisms and organic material, they cannot be porous.

2. Easily washable.

Facilities will be divided into the following parts; raw material’s warehouse, area for elaboration of intermediate products, mixing area, packing, warehouse of quarantine, laboratory of analysis, labelling area, final product’s warehouse and expedition area. Equipment used will be made of glass or stainless steel and will be easy to access and clean.

As didactic purposes, we will briefly describe the steps of a bacterin or an inactivated bacterial vaccine:

1. Elaboration of manufacturing sheet: it consists of a sheet where can be found the quantities and identification codes of all materials used. This sheet must accompany the ingredients during the entire process.

2. Preparation of starting materials: it takes place in the raw material’s warehouse from already analysed products and declared suitable for its adecuacy to the characteristics mentioned in the European Pharmacopoeia and own technical profile. In the case of vaccines it exists an exceptional starting material called working seed. It is a culture prepared in the microorganism’s warehouse.

3. Elaboration of intermediate products: intermediate products can be defined as those mixtures of starting materials which constitute parts of the elaboration of the final product. The suspension of microorganisms constitutes the main intermediate product in the elaboration of bacterin. It consists of microorganisms produced by fermentation from the inoculum of the working seed in large fermenters. The content of these fermenters is concentrated through tangential filtration. Both the suspension of the microorganisms and the solution of toxins are inactivated by the use of inactivator products mentioned above (formol and others) and storage refrigerated until its use in elaboration of final product

4. Elaboration of the final product: it is done by mixing of several intermediate products (microorganisms and toxins) with starting material such as adjuvants, preservatives and excipients. The product obtained is packaged in sterile atmosphere in sterile flasks which are blocked, sealed and stored in the area of quarantine.

5. Once the final mixture is done, it must be analysed before the liberation to the market. For this reason, a refrigerated warehouse (4-8ºC) will be necessary.

6. Quality control for final products: the controls on final product must be done accordant to the monograph of the product described by the European Pharmacopoeia, National Pharmacopoeia and the internationally recognised technical profile. Despite of the existence of particularities, the final product must be basically subjected to the following controls:

• Physical-chemical characteristics

• Power: it basically consists of administering to a group of animals vaccine doses and subsequently realise a confrontation with microorganisms of the antigen but lives and pathogens. If the vaccine has the necessary power, animals will survive.

• Safety and abnormal toxicity: It basically consists of administering a dose of vaccine higher than recommended to a batch of animals. Animals cannot present symptoms of disease and local reaction during a period of observation determined.

• Direct validity and validity after reconstitution: This process is compulsory and takes place during the process of registration of the specialty but is advisable its realisation sporadically in manufacturing batches or when by technologic reasons some stage or material has been modified. The validity tests are used to determine for how long they can maintain the power under a determinate temperature and light conditions.

• Security and absence of strange pathogenic agents.

7. Labelling: Established the aptitude of the product by analysis described in early chapters, they proceed to label the product and provide them with informative material that permits its right application. The analytic and performance data of the manufacturing are added to the manufacturing sheet. The manufacturing sheet together with the tests is stored for at least 3 months after the expiry date of its manufactured batch. The final product is sent to the warehouse of final products awaiting for its distribution.

8. Final product warehouse and expedition area: We can underline that both areas must count with refrigeration and an informatics or manual system which permit to know when, how and where every single manufactured batch has been sent. This information is very valuable in case of detecting adverse reactions of the product once it has been released to the market.

Distribution

Heat and sunlight make that vaccines lose its efficacy. The distribution of veterinary vaccines is regulated by the Real decree 109/1995 which obliges to dispose of adequate places as well as the services of a pharmaceutical technical director. Refrigeration within 2-8ºC is usually necessary but they cannot be frozen unless in some specific vaccines where the freezing in liquid nitrogen or dry ice (Marek’s disease) is necessary. Apart from the corresponding cold chain, it is necessary the realisation of monitoring the inputs and outputs of the product batches through corresponding document registrations.

Administration

Veterinary vaccines are administered by different ways depending on the type of antigen and the breeding system of the targeted animals.

1. Orally: This way of administration is used in live vaccines destined to birds. This practice permits a massive vaccination, as it is really fast and does not need many personnel to leave the antigen in drinking water. Only a few precautions are necessary such as having restricted drinking water during 10-12 hours before, using water without disinfectants and dissolving skimmed milk in powder with the antigen in order to increase its viability.

2. Air way: It is frequent in viral and bacterial live vaccines destined to birds and swine. This way permits a massive vaccination although it requires proper premises and equipment in order to produce nebulisation. The size of the droplets is important as they must be suspended enough time in the air to be breathed in by animals.

3. Cutaneous way: It is used for any type of administration of antigens, especially inactivated ones. This way of administration requires more personnel and more time than the administration ways above mentioned and causes discomfort to animals. On the contrary, it guarantees the most adequate administration to every animal. Syringes used must not be disinfected with alcohol or other disinfectants as they may inactivate live antigens. We must pay particularly attention in vaccinations without needle in order they are administered in the proper tissue. Among the most used, we can find the subcutaneous and intramuscular although some vaccines are administered by specific ways such as intraskin and intravenous.

4. External way: This way of administration is used for live viral antigens in nasal mucosa and eye conjunctival.

Factors related to the organism to immunize

1. Before the administration: It is necessary to plan the manipulation of animals in order to avoid unnecessary discomfort on them. It is also necessary to know the pathological antecedents of population or individuals who will be vaccinated. We also need to take into account that we must avoid vaccination in pregnant females during its first month or birds during periods of peak egg laying. Administration of vaccines is not indicated for ill animals, with feverish, treated with corticosteroids or those who are receiving immunosuppressor medicines. It must be taken into account that vaccinating with strains of herpes virus, for its latent infectious power, as one vaccine can be apathogenic for a determinate age but can trigger a disease in younger animals.

2. During the vaccination

3. After the vaccination: keep the animals in mild environmental conditions.