View source

'''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. The purpose in using a vaccine to prevent a particular disease is to trigger or boost 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 - the bird will produce antibodies that fight future invasion. Unfortunately the damage done to the bird suffering such disease is usually too great and the bird either dies or becomes unthrifty and non-productive. A natural invasion caused infection will be uncontrolled and has the possibility of causing severe damage. Vaccination is a way of obtaining a controlled result with a minimum of 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. [[Image:Avian influenza 1.jpg|thumb|right|300px|Scientists are developing a vaccine for avian influenza (Birds showing symptoms)  Source: CSIRO]] 

=== Types of vaccine  ===

'''Live vaccine''' - the active part of the vaccine is the live microbe that causes the disease. As such it is capable of producing the disease in birds that have not had previous experience with that microbe (or other organism). Vaccinated birds, in many cases are able to infect non-vaccinated birds if housed together. 

'''Attenuated vaccine''' - with this type the microbe (or other 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 the microbes have been killed and are unable to cause the disease although they retain their ability to trigger the immune system. In many cases, the level of immunity produced by this form of vaccine is weaker than that produced by live and attenuated vaccines. 

Vaccines are produced mainly in three forms: 

#Liquid vaccine - it is in fluid form ready to use. 
#Freeze dried vaccine - the vaccine is stored as one pack of freeze dried material and one pack of diluent, often a sterile saline solution. These have to be combined before use. 
#Dust - where the vaccine is prepared for administration in the dry form.

Vaccines are sold in dose lots, the number of doses being the number of fowls that may be vaccinated with that amount of vaccine when using the recommended technique. In the case of many vaccines there are differences in the disease organism strains that they are effective against. It is important that the correct vaccine strain be used and this can only be determined by veterinary advice. 

=== Handling vaccines on the farm  ===

Vaccines are fragile in many respects and require very careful handling to ensure they retain their potency. Poor handling procedures will, in most cases, result in a rapid decline of potency. 

The important handling requirements on the farm are: 

#On receipt of the vaccine on the farm, check and record: 
##That the vaccine has been transported in the recommended manner - usually in the chilled or frozen state. Prolonged exposure to atmospheric temperature will result in the rapid loss of potency. 
##Type of vaccine - is it the vaccine ordered. 
##The number of doses - has the correct amount been delivered. 
##The expiry date of the vaccine - vaccines have a date when there is significant risk they will no longer retain their potency and will not produce the immunity required. The expiry date is based on the vaccine being handled and stored in the recommended manner. 
#As soon as possible place the vaccine into recommended storage conditions. Read the instructions to find out what these are. However, in the main, freeze dried material should be kept in a temperature below freezing with the diluent just above freezing. Liquid vaccines are generally kept at temperatures just above freezing. 
#Remove the vaccines from storage immediately prior to their being used. Only remove and re-constitute enough for immediate needs and repeat this through the day if more is required. Do NOT mix a days needs at the start of the day and leave it stand until required. 
#Protect the vaccines after mixing by holding them in an ice bath. Place ice in a small esky or similar container and place the container of mixed vaccine in the ice. Some vaccines have a very short life once mixed e.g. Marek’s Disease has a life of about 1.5 hours after mixing IF HELD IN AN ICE BATH. It is much shorter if held in higher temperatures. 
#Use the recommended administration techniques and do not vary these without veterinary advice. 
#Always clean and sterilise the vaccinating equipment thoroughly after use. 
#Always destroy unused mixed vaccines after the task has been completed. Some vaccines have the potential to cause harm if not destroyed properly. 
#Do not vaccinate birds that are showing signs of disease or stress.

=== Vaccination procedures  ===

There are a number of ways that vaccines may be administered to poultry It is very important that the correct method be used for each vaccine. To use the wrong method often results in the vaccine failing to produce the desired immunity. Some of the methods require the operator to handle every bird and, consequently is 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. 

==== Intramuscular injection  ====

This method involves the use of a hypodermic needle or similar equipment to introduce the vaccine into the muscle of the bird - usually the breast muscle. It is large enough to make the technique relatively easy without harming the bird. The task is speeded up greatly by the use of an automatic syringe. 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. Care must be taken also to ensure that other unwanted organisms are not administered to the bird at the same time by contaminating the vaccine or equipment. This problem is prevented by good hygiene and vaccine handling procedures. 

==== Subcutaneous injection  ====

This method involves the use of similar equipment to that used with 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. Do not introduce other 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. The recommended technique observes the following: 

*All equipment used for vaccination is carefully cleaned and free of detergents and disinfectants; 

*Only cold, clean water of drinking quality should be used; 

*Open the stopper of vaccine bottle under water; 

*The water present in the drinking water should be consumed before vaccination; 

*By ensuring that all birds drink during the vaccination phase, all should receive an adequate dose of the vaccine.

==== 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 birds’ 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. The technique is not used, as a rule, 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. 

==== Wing stab  ====

With this method the vaccine is introduced into the wing by a special needle(s). These needles have a groove along their length from just behind the point. When dipped into the vaccine some of the vaccine remains on the needle to fill the groove. The needle(s) are then pushed through the web just behind the leading edge of the wing and just out from its attachment to the body of the bird. Care must be taken to select a site free of muscle and bone to prevent undue injury to the bird. Ensure that the needles penetrate the layers of skin at the ideal site. A common problem is for the vaccine to be brushed from the needles by fluff or feathers before it is brushed into the follicles. 

==== 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. 

=== Monitoring  ===

In the case of some vaccines, an important part of the procedure is to ascertain whether the vaccine has worked or “taken”. A good example of this is fowl pox vaccine administered by wing stab. Within 7 to 10 days after vaccination a “take” should appear at the vaccination site. This is in the form of a small pimple one half to one centimetre in diameter. If the take is larger and has a cheesy core, it indicates that contaminants have been introduced either with the vaccine or with dirty vaccinating equipment. A check for takes would involve inspecting approximately 100 birds for every 10,000 vaccinated. 

Another example of whether the birds are reacting satisfactorily to the vaccination is the systemic reaction found in chickens vaccinated against infectious bronchitis disease. In many cases the birds react approximately 5 to 7 days after vaccination by showing signs if ill health - slight cough, a higher temperature and lethargy. In cases where there are no obvious signs of success, blood samples may be taken and sent to the laboratory for examination. The usual test is for the presence of an adequate number of the appropriate antibodies (called the titre) in the blood. If the vaccination has been unsuccessful, it may be necessary to re-vaccinate to obtain the desired protection. 

Failure to find evidence of success could be because of: 

*Faulty technique resulting in the vaccine not being introduced into the vaccination site. 
*Faulty vaccine - too old or not stored or mixed correctly. It would be unusual but not impossible for the vaccine to be faulty from manufacture. 
*The birds are already immune i.e. the immune system has already been triggered as a result of parental (passive) immunity, previous vaccination or other exposure to the causal organism.

== See also  ==

*[[Rapid tests for poultry diseases]] 
*[[Poultry health management]] 
*[[List of avian diseases]] 
*[[Immune system#Vaccines_and_the_immune_response_to_vaccination|Immune response]]

== External links  ==

*[http://en.wikipedia.org/wiki/Poultry_disease Wikipedia: '''Poultry disease'''] provides a definition of '''Poultry disease'''

[[Category:Bird_health_and_disease]] [[Category:Chicken_meat_industry]] [[Category:Egg_industry]] [[Category:Anatomy_and_physiology]] [[Category: Other poultry species]]