Vaccination plays an important part in the health management of the poultry flock. There are numerous diseases that are prevented by vaccinating the birds against them. A vaccine helps to prevent a particular disease by triggering or boosting the bird’s immune system to produce antibodies that in turn fight the invading causal organisms.
A natural invasion that actually causes the disease will have the same result as the bird will produce antibodies that fights the current invasion as well as to prevent future invasions by the same causal organisms. Unfortunately birds that become diseased usually become unthrifty, non-productive or even die.
An infection caused by natural invasion will be uncontrolled and therefore has the possibility of causing severe damage, however vaccination provides a way of controlling the result with minimal harm to the birds.
Vaccines are generally fragile products, some of which are live but in a state of suspended animation. Others are dead. All have a finite life that is governed by the way they are handled and used. Handling and administration procedures also influence the potency of many vaccines and consequently the level of immunity the bird develops.
Live vaccine – the active part of the vaccine is the live organism that causes the disease. As such, it is capable of inducing the disease in birds that have not had previous contact that organism. Vaccinated birds, in many cases are able to infect non-vaccinated birds if housed together.
Attenuated vaccine – with this type of vaccine the organism has been weakened by special procedures during manufacture so that it has lost its ability to cause the serious form of the disease. At worst, the birds may contract a very mild form of the disease, however, the vaccine still has the ability to trigger the immune system to produce antibodies.
Killed vaccine – with this type of vaccine the organism has been killed and is unable to cause the disease, although the ability to trigger the immune system remains. In many cases, the level of immunity produced by this form of vaccine is weaker than that produced by live and attenuated vaccines.
Vaccination procedures
There are a number of ways that vaccines may be administered to poultry and it is very important that the correct method be used for each vaccine. To use the wrong method will often result in failure of the vaccine to produce the desired immunity. Some of the methods require the operator to handle every bird and, consequently are time consuming and stressful to the birds and operator. Other methods involve administration by methods much less stressful and time consuming. These methods include administration via the drinking water or as an aerosol spray. The different ways that the vaccines may be administered to poultry are below.
In-ovo vaccination
Using the method of in-ovo vaccination, the vaccine is administered into the embryo before hatch. In general, vaccines can be applied to five different areas of the egg: the air cell, the allantoic sac, the amniotic fluid, the body of embryo and the yolk sac.
Intramuscular injection
This method involves the use of a hypodermic needle or similar equipment to introduce the vaccine into the muscle (usually the breast muscle) of the bird. The task is sped up greatly by the use of an automatic syringe which makes the technique relatively easy and doesn’t harm the bird. Care must be taken to ensure that the correct dose is administered to each chicken and the equipment should be checked regularly to ensure this.
Care must be taken to ensure that the needle does not pass through into a key organ and that other unwanted organisms are not administered to the bird at the same time by contaminated vaccine or equipment. Contamination can be prevented by good hygiene and vaccine handling procedures.
Subcutaneous injection
This method involves the use of similar equipment to that used for the intramuscular technique. The main difference between the two techniques is that, in this case, the vaccine is injected under the skin, usually at the back of the neck, and not into the muscle. Care must be taken to ensure that the vaccine is injected into the bird and not just into the feathers or fluff in the case of very young chickens. The dose being administered should be checked for accuracy frequently. Maintain good hygiene practices to limit introducing contaminating organisms during the procedure.
Ocular
This method involves the vaccine being put into one of the bird’s eyes. From here the vaccine makes its way into the respiratory tract via the lacrimal duct. The vaccine is delivered through an eyedropper and care must be taken to ensure that the dropper delivers the recommended dose. If it is too little, the level of immunity may be inadequate, while if too much, the vaccine may not treat the total flock but will run out beforehand.
Nasal
This method involves introducing the vaccine into the birds’ nostrils either as a dust or as a drop. Always ensure that the applicator delivers the correct dose for the vaccine being used.
Oral
With this method the vaccine dose is given in the mouth. From here it may make its way to the respiratory system or it may continue in the digestive tract before entering the body.
Drinking water
With this method the vaccine is added to the drinking water and, as a consequence, is less time consuming and is significantly less stressful on the birds and operator. Take care to ensure the vaccine is administered correctly as there is much scope for error.
Cloacal
This method involves the introduction of the vaccine to the mucus membranes of the cloaca with an abrasive applicator. The applicator is firstly inserted into the vaccine and then into the bird’s cloaca and turned or twisted vigorously to cause an abrasion in the organ. The vaccine enters the body through the abrasion. The technique is time consuming and stressful to the birds and care must be taken to ensure no contamination is introduced with the vaccine particularly from bird to bird. As a rule, the technique is not used on commercial farms.
Feather follicle
With this method the vaccine is introduced into the feather follicles (the holes in the skin from where the feathers grow). The technique involves the removal of a group of adjacent feathers or fluff in young chickens, and the brushing of the vaccine into the empty follicles with a short, stiff bristled brush. Good hygiene is necessary to prevent the introduction of contaminant organisms with the vaccine.
Spray
With this method the vaccine is sprayed onto the chickens (or into the air above the chickens) using a suitable atomiser spray. The vaccine then falls onto the chickens and enters the body of other chickens as they pick at the shiny droplets of vaccine. A small quantity may be inhaled as well.
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