I am often asked if ex-bats require vaccination? I guess this is because we are all so used to our dogs and cats having routine boosters.
All commercial laying hens are vaccinated as path of the course when they are usually just day old chicks. Hens need to have protection from diseases that can be fatal to them in their early development, for example, Mareks disease and Gumboro disease. Vaccines also protect against diseases that can affect egg production and shell quality if the hen becomes infected in lay, for example, Infectious Bronchitis and Mycoplasma gallisepticum. We also have to consider disease that has public health significance such as Salmonella.
Vaccination works by exploiting the most natural of bodily reactions. When a bird meets an infection, the body’s defences (the immune system) reacts on two levels. First, it mobilises 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. This can be by priming cells to fight infection or by the production of antibodies. Antibodies will neutralise 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 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.
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.
As you might imagine vaccinating thousands of chicks at one time is not easy. How is it done? Mainly by spray application or via drinking water, but other methods include eye drops or injection and sometimes as a feed additive.
Increasingly, spray vaccination is used during the laying period to provide “top-up” vaccination against Infectious Bronchitis and Infectious Bronchitis variants as these virus infections are a common cause of problems with egg production and shell quality. To date, there has been no evidence that we have reached any sort of “overload” of the system in the range of vaccines administered to laying flocks.
Do your hens need a booster? Most small animal veterinary surgeons do not keep vaccines in small enough quantities to give booster vaccines to ex-bats and backyard flocks. It is not normally feasible to do this.
If you would like to ask Gaynor a hen health question please email firstname.lastname@example.org or call Hen Central on 01884 860084.