A good vaccination program, along with proper flock management and biosecurity, plays a key role in the health and productivity of broiler breeders. The use of bacterins has been shown to lessen the effects of certain diseases by giving the bird resistance to harmful pathogens, but the success of vaccination lies with the skill and technique used by the vaccination crew.
It is advised to administer bacterins using either subcutaneous (SQ) or intramuscular (IM) injections, however, care must be taken to ensure that birds receive a full dose of vaccine. With SQ injections, do not vaccinate too close to the head, base of the neck, or neck bones. With IM injections, do not vaccinate too close to the keel bone or too deep into the breast muscle. With either type of injection, it is imperative that personnel handle equipment safely to avoid self-injury.
Things to consider when administering bacterins are:
- Use only bacterins that have been provided by a veterinarian.
- Ensure correct storage and handling of vaccines. Plan ahead and allow bacterins to come to room temperature before vaccination.
- Vaccine should only be administered by trained personnel who have full knowledge of correct techniques.
- Tissue reactions at the injection site are the birds immune system responding to the vaccine.
- Visual inspection of the vaccination technique at the injection site is the best method to determine accuracy of the injection.
- The ultimate goal of any vaccination program is high, uniform, and long-lasting antibody titers.
- Ensure that no birds are skipped or missed. A bird that is not injected is not protected.
The use of vaccination programs in commercial poultry production is fundamentally important to the growth, welfare, and success of the flock. When used in conjunction with good management practices and biosecurity, vaccines can help to prevent or reduce the harmful effects of diseases and provide the flock with protection against infection.
Bacterins are a critical component of breeder vaccination programs and are used to stimulate high levels of immunity. These bacterins or inactivated bacterial vaccines are used to induce immune response to bacteria protecting the bird from pathogens like Salmonella spp., Pasteurella multocida (Cholera), Escherichia coli (E. coli), Avibacterium paragallinarum (Coryza), and in some countries, Ornithobacterium rhinotracheale (ORT). If administered correctly and at the proper times, bacterins can provide bird resistance to these harmful agents; however, if given incorrectly, they can have potential negative effects. The focus of this article is to provide a description of bacterins, the correct bird age and procedure for administration, auditing of the immune response, and troubleshooting potential issues.
Characteristics of bacterins
Bacterins generally consist of two components, a liquid and adjuvant phases, which are blended into a solution called emulsion. The liquid phase contains the antigen and the adjuvant generally enhances the bird’s response to the antigen. The antigen can be part of the bacteria or components of it. In the case of the adjuvant, aluminum hydroxide and mineral oil are commonly used. These oil emulsion vaccines can be single or double emulsions. Single emulsions consist of a liquid phase surrounded by a continuous oil phase and are referred to as a water in oil (W/O) emulsion. Consequently oil in water (O/W) emulsions have water as the continuous phase. Double emulsions (W/O/W) are manufactured by dispersing water into oil and then dispersing this W/O emulsion into water.
The level of antibody response and subsequent immunity is dependent on the level of tissue reaction and the antigenic concentration of the vaccine. In general, the tissue reaction following injection of oil emulsion bacterins is much more severe than the reaction to the injection of inactivated viral oil-emulsion vaccines, this is true due to the fact that the emulsion of inactivated toxic bacterial cell constituents (especially lipopolysaccharides or endotoxins) in mineral oil creates a very potent immunizing agent.
Most commercially available bacterins are mineral oil based particularly with Fowl Cholera, Salmonella and Coryza oil emulsion bacterins the tissue reaction at the site of injection is usually more severe when compared with aluminum hydroxide inactivated vaccines, thus inducing higher antibody levels.
Age to administer bacterins
Unless the field challenge is high, in which case a review of the biosecurity program is critical, it is advisable not to expose very young birds to the aggressive effect of bacterins. A comprehensive vaccination plan will allow for bacterins to be given at 8-10 weeks of age so that birds are conditioned in terms of body mass to respond to and assimilate the vaccine. Inactivated vaccines require two doses for best results and this is especially true for bacterins. Due to the reaction caused by bacterins, it is recommended for broiler breeders that the last application be given at 18-19 weeks of age, thus giving the bird enough time to recover from the injection before onset of egg production. If the injections are too close together or too close to onset of egg production, the onset of lay and peak egg production could be compromised.
Procedure for bacterin administration
Vaccination Technique. Delivering bacterins by means of SQ or IM injection is a very precise and demanding task, only to be performed by trained individuals within a vaccine crew. These individuals are able to ensure accuracy when vaccinating thousands of birds at a time. Correctly training the vaccination crew can be challenging when dealing with employee turnover, labor cost, and personnel availability, but it is a critical factor for optimum results.
Auditing of the immune response
Visual inspection of the vaccination technique and deposition of the vaccine at the correct site is the best method to determine accuracy of the injection. With the SQ injection in the neck, the feathers at the site of injection can be separated to allow visualization of the vaccine under the skin (Fig. 6). Wet feathers indicate that the vaccine was poorly administered and either full or partial dose ended up in the feathers due to anticipated or delayed expulsion of the vaccine from the syringe. Inspection timing is important; make sure the examination is done within an hour of vaccination. Unannounced visits to evaluate the vaccination crew technique are preferable to get a true picture of the job being done. To visually evaluate the vaccination procedure for the purpose of properly training the vaccination crew on IM injections, some sex slips (sex errors) can be euthanized to inspect the site of injection.
The ultimate goal of a well planned vaccination protocol is high, uniform and long-lasting immunity measured in antibody titers. However, results may not be as expected due to several factors related to the method of application and/or the technical skill of the operators. The immune response to bacterins is dose related. Therefore, when a large percentage of the birds are missed or partially vaccinated, a poor flock immune response is expected. Vaccines are no good if they do not get into the birds.
It is very difficult to determine how many birds within a flock received less than a full dose of vaccine or actually missed being vaccinated. Therefore it is extremely important to implement a monitoring procedure of the vaccination program. Commonly, serological testing is used to indirectly assess the accuracy rate of vaccination. Usually, a minimum of 23 blood samples per group are used with various serological tests such as Enzyme-Linked Immunosorbent Assay (ELISA), which is considered to be specific, sensitive and repeatable. Bad vaccine application could produce serological titers that are not uniform (high %CV) but are also below the expected average (low mean titers). This result could indicate a large percentage of the birds were missed or did not receive the full dose.
Troubleshooting
If there is an indication that the use of the bacterins is causing problems to the birds or the serological results, the following signs or findings should be considered:
Bird discomfort due to the tissue reaction. Particularly with neck injections, some pullets may appear depressed and lethargic, affecting feed consumption for a few days. Because inflammation at the injection site is an energy demanding process diverting body resources for developing good immunity, a higher demand for nutrients may be needed to overcome the tissue reaction. It is recommended that feed be adjusted accordingly during this period. Pullet flock uniformity can be heavily affected by exacerbated tissue reactions.
Missing birds. A bird that is not injected is not protected. Inspection at the site of injection in sex errors and culls will help training the vaccination crew.
Dose of bacterins. The bird’s immune system does not recognize bacterial antigens in the same way it recognizes viral antigens, thus it is recommended bacterins be applied twice before moving the birds to production.