How vaccines function in poultry
Vaccination works by exploiting the most natural of bodily reactions.When a bird meets an infection, the body’s defenses (the immune system) reacts on two levels. First, it mobilizes cells and chemicals to kill the invading organism and stop disease occurring. Secondly, it triggers a memory system in the body to respond quickly should the bird meet that infection again at some time in the future.
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This can be by priming cells to fight infection or by the production of antibodies which are complex proteins circulating in the bloodstream. Antibodies will neutralize infections which have managed to reach the bloodstream. As an added bonus in breeding chickens, these antibodies can be passed to the newly hatched chick via the yolk sac and protect the chick for the first few weeks of life from the bugs that the parent hen has been previously exposed to.
These protective measures provided by the immune system are highly specific, i.e they will only protect the bird against the specific organism they have been previously exposed to. We use vaccination to exploit this mechanism by "priming" the bird to a range of diseases which might be a risk to them in later life.
Vaccines can now be produced against a wide range of organisms, and poultry vaccines are currently available against viral, bacterial and some parasitic diseases.
TYPES OF VACCINE FOR POULTRY
Vaccines available for poultry fall into two broad categories:
• Live vaccines: These are modified version or naturally occurring mild strains of the disease organism. This type of vaccine will trigger the birds’ immune system to produce antibodies but without causing disease in the bird. Examples of this type of live vaccine include Infectious Bronchitis, Infectious Bronchitis variant vaccines, Newcastle disease vaccine, coccidiosis vaccine and Mareks disease vaccine.
• Killed or inactivated vaccines: These vaccines, as their name suggests, are killed infectious organisms which can trigger birds’ immune system to respond. Many of these require previous priming with a live vaccine to produce the best immune response in the bird.
HOW ARE VACCINES GIVEN TO THE BIRD?
The main methods of vaccine administration are:
1) By injection
2) Via drinking water
3) By spray application
4) By eye drop and mouth drop
5) By spray on feed.
6) In ovo administration into the egg prior to hatching.
The last two methods are not commonly used for vaccination of laying flocks.
Vaccine administration
Vaccine must be administered to the birds in such a way that the whole flock can respond in the most efficient manner.
Inactivated (killed) vaccines
Injection is the usual route for killed vaccines as these vaccines don’t spread from bird to bird so one needs to be certain each bird gets its own individual dose. These vaccines can be given under the skin (subcutaneously) or into the leg or breast muscle (intramuscularly).
Vaccines are usually administered by well trained and highly skilled vets, and if you have any vaccinations
As this type of vaccination involves sticking a needle into the bird and breaking the skin, it is imperative that the highest standards of hygiene and cleanliness are observed during the vaccination process.
Live vaccines
Live vaccines are, in many ways, easier to administer and are ideal for mass administration to large flocks as they can be given via drinking water or by spray or, in some cases, by individual eye drop.
Common examples of live vaccines include Infectious Bronchitis, Newcastle Disease, TRT, ILT and AE vaccines.
Live vaccines are often given to act as primers during the early part of the rearing period to stimulate the birds’ immune system so that when the bird receives a killed vaccine prior to transfer to the laying site, the immune system is primed to give good antibody response so that the bird has a long lasting immunity.