Since Adam’s birth pathogens and living creatures are to be dagger drawn on each other. To take the bull of infection on right its horn and pay back in the same coins is the achievement of vaccination. The main purpose of all vaccines and consequently vaccination is to administer an optimum and safe amount of antigen to elicit immune response in the bird.

Vaccination does not give guarantee that birds are protected. There are number of factors which may furnish the success of a vaccine. It is a worth remembering that antigens or vaccine or vaccination itself does not produce immunity rather it is the bird’s immune system in general and immune cells in particular that provoke the immune response and present the antigen to T lymphocytes and by macrophages and from there it is expressed to b lymphocyte where the immune response initiated in items of antibodies. These antibodies are identical to the antigen of vaccine.

The successful vaccination comes up in terms of higher and stonger immunity. On most of occasions we get proper protection with vaccination but immunity breakdown is usually not known. There current topic highlighted the factors which will come up in term of good immunity.

GENERAL PRINCIPLES OF VACCINATION :

Vaccination involves the administration of antigen to stimulate the immune system to produce specific antibodies against viral, vacterial, and protozoal disease. Vaccination program should be based on the following considerations.
• Diseases prevalent in the urea of operation.
• Risk of exposure.
• Immune status of parent stocks.
• Cost of acquisition and administration of vaccines
• Flock placement programs.
• Availability of specific vaccines.
• Cost benefit ratio associated with vaccination taking into account the risk of infection and financial loses from disease.

PRECAUTION FOR USE OF VACCINES :

1. Do not vaccinate the birds during stress period particularly few days before or after the debeaking, transfer shifting and grading. In these conditions negative Immuno-modulation occur which ended with low level of active immunity.

2. It is not wise to vaccinate the birds during extreme weather, because heat stress on one end affect the bird and on other end effect the vaccine due to high environment temperature.

3. Avoid using metal drinkers and containers for mixing of vaccines, as the metal ions and metals react with the vaccines to inactivate the live vaccines offered through the drinking water. Aluminum and brass containers are not recommended due their maximum inactivation properties. It is recommended to use the PVC or PET containers (Plastic).

4. Use clean equipment and drinkers and sterile syringes, so not use any chemical to disinfect the vaccine utensils because the residues of these chemicals inactivate the vaccines. Rinse the utensils with fresh water to avoid the errors.

5. Always use sterile diluents preferably of the same company for reconstitution of injectable vaccines as the different sources are not synchronized with the optimal requirements. Some diluents contains dyes more than optimum levels which act as sterilizes for diluent and at the same time inactive the vaccine .

6. Do not use waterfor vaccine dilution containing disinfectants, particularly the Bleaching Powder (Chlorine compounds) to avoid the possibility of these chemicals either stop usage of these substances a day earlier the vaccine is offered or two days earlier the vaccine is offered or two days vaccination, enteric forms of vaccines are more sensitive to these type of chemicals.

7. Try to use the vaccines as soon as possible the vaccines are reconstituted, delay to offer by the farmers or sonsumption by the birds leads to temporal decrease in the vaccine tillers.

8. In those areas where the salt concentration is too high preferably vaccine the birds through injection or eye, nose or mouth dropping.

9. Addition of skim milk is recommended, as the particles of vaccines are distributed well in the water. In case milk with fat or fresh milk is used it make aggregates on or near the surface of the container ( due to light weight fat) where the vaccine is mixed, leading to develop different concentration zones in the container.

10. Lower limit of skim milk per liter is fixed but there is no upper limit, the higher the milk concentration the best will be the suspension of vaccine in drinking water, the drinkers should be empty in one hour maximum taking in consideration of temperature of house and feed time, the off water time may be adjusted.

ROUTE OF ADMINISTRATION :

It is emphasized that appropriate control over the reconstitution of live vaccines is required to ensure potency. The actual administration of vaccines of should be monitored by submission of serum samples to diagnostic laboratory for titer assay using ELISA or acceptable technique. Various methods of administrating vaccines are used commercially, including:

1. INTRANASAL: By instillation or dipping the beak up to the naries. In birds nose, mouth and lachrymal duct opened in mouth, therefore, each of the route ended up with the same results with exception of the sensitivity and accommodation by the eyelid epithelium otherwise routes are nearly same. In these route please do not dip the beak for too long short time.

2. INTRAOCULAR: Eye dropping is most popular route of vaccination. There some ereors in the eye dropping made during the vaccination. Eye drop and intranasal routes suitable for hatchery adminstration and during brooding of chicks. In Pakistan the eye droppers are 30ml for 1000 birds, the vaccinator make the vial and drop the birds until and unless the whole of the vaccine is not spent. The too longer time holding the vaccine. In these cases contaminated diluents or vaccines leads to infection of eye and blocked of lachrymal duct and drooling of water from the eye used for vaccination. This reaction may some time normally occur after vaccination of ILT.

3. IN DRINKING WATER: This corresponds to oral and intra nasal administration. Drinking water administration, can be implemented at low cost but it is of limited effectiveness against some infections.

4. INJECTION: Subcutaneous, intra muscular depending on the type of vaccine and the direction of the manufacturer,. Subcutaneous, injection to administer either live or inactivated emulsion vaccines to chicks rearing stocks and breeders.

5. IN OVO VACCINATION: At 18 days of incubation using the patented Inovoject system. Most commonly recommended in the case of Gumboro and Marek’s vaccines.

6. POST-HATCH SPRAY VACCINATION: In cabinets for mass-adminstration of aerosol vaccines to day old chicks. This is mostly employed for ND, IB vaccination on day one in hatchery or farm.

7. WING-WEB STAB: This method is used to administer fowl pox vaccine or other live vaccines directly to each bird. Be careful that eye of the needle carries vaccine each time or not.

8. AEROSOL ADMINISTRATION: Using a knapsack or electric sprayer to deliver vaccines to flocks as a coarse spray.

FAILURE OF VACCINE :

USE OF EXPIRED VACCINE
Vaccines re expired by many ways, among the most common are the expired in storage due to sale, expired in storage due to sale, expired due to less shelf life ( it must be year plus when reached in Pakistan ) expired supply by the manufacturer only with few months in hand.

GENETIC RESISTENCE
The major histocompatibility complex varies from bird to bird and its structure dictates if a bird will respond to an antigen at all. Due to some structural lacks in MHC it is possibility that the birds are recognize the one of the antigens. Therefore that strain of birds might be more susceptible to pathogen.

IMPROPER STORAGE OF VACCINES
This is the most common cause of vaccine failure in routine uses of vaccines. This might be due to transportation from market to farm or from manufacturer to distributor to market, failure of electricity, failure of refrigerators, storage in deep freezers, exposure of sunlight.
Ignoring the use of ice box, coolers or thermos and using the translucent thin membrane shoppers permitting the sunlight exposure.

• Exposure of heat, sunrays, room temperature, brooding house temperature to diluents mixed vaccines. To avoid the damages bottles either packed in cold bucket or use chilled diluents.
• Do not open the lid of vaccine in the open environment as the vaccines are contained in negative pressured bottles. Use disposable syringe to constitute the vaccine or open the bottle lid inside the water to avoid the sudden change in pressure.
• Avoid to use the improper disinfected syringes and needles. Always use wide bore needles for vaccine suction or dilution, narrow bore needle may retained the cell culture vaccines, which make the non uniform mixing of vaccine and lower the antigen amount.
• Exposure to viricidal disinfectants (phenols, alcohol) may be avoided as these chemicals inactivate the vaccinal virus.

HEALTH STATUS OF THE FLOCK
The infectious agents such as Chicken Anemia Agent (Circo virus), Gumboro Disease Virus (Birna virus), Marek’s Disease Virus (Herpes Virus ), REO Virus, Salmonella and Mycoplasma etc. may cause varying degree negative immunomodulation which consequently may lead to vaccinal failure or adverse reaction in the face of these disease.

IMMUNO SUPPRESSION DUE TO DRUGS
Continuous administration of Immuno-suppressive drugs such as chloramphenicol, furazolidone may cause cause poor immunity development.

MYCOTOXINS
Presence of mycotoxin in the feed affect the vaccinal response very badly. Mycotoxin reduce host immunity directly by reducing the Macrophage engulfing tendency and production of toxin, lymphocytes which give poor out put in immunity development. Mycotoxin indirectly affect the bird by producing steroids from the adrenal glands which decrease the lymphocytes and increase the neutrophils by the virtue of increased nutrophil the bird become Immune compromised.

WATER DEPRIVATION AND HEAT STRESS
Due to water deprivation the bird is exposed to heat stress. Due to heat stress lot of steroid production do occur which decrease the lymphocytes produce the antibodies. This is common observation that the dehydrated and heat exposed birds commonly infected with coli septicemia and other diseases.

COLD AND HIGH DENSITY STRESS
These are social stress as well as stress like heat stress and decrease the immunity by decreasing the number of lymphocyte, which is the factory of antibodies.


POOR NUTRITION
Hypoprotenemia especially protein hurt the immune response as antibodies are made up of amino acids. Poor nutrition causes problem with metabolism, protein synthesis and immunity.

PRESENCE OF AMMONIA IN HOUSES
On the port of entry from where the pathogens are entered the body to produce infection there are some host defense mechanism which prevent the entry of pathogens. Hairs cilia moist membranes are among the preventive cushions. The moist membranes of or the mucous membranes among the gut , trachea, nostrils and bronshi produce Immunoglobulin .a through the lymphocytes present on the surface of these organs. This is called secretory immune mechanism and it is watch dog on the port of entry.

If the ammonia levels are high in the house above 30PPM it has bad effect on the birds ability to produce local immunity as the cells on the surface of moist membranes are affected badly with the ammonia because ammonia is water soluble gas. In the absence of the local immunity the bird become susceptible to viral diseases particularly those which proliferates in respiratory tract. Ammonia condentration above 100 PPMm always associated with the respiratory disease. As the ammonia is water soluble gas one can easily felt the ammonia as it dissolved in lachyymal secertion of the eyes .

ADMINISTRATION ERRORS QUALITY OF WATER
Water quality ispoor in most of the areas of Pakistan, particularly in salinity affected areas such as Faisalabad, Sheikhupura and Multan Division, where the salt level is half of the sea water and EC even in Islamabad is 600-2000. Poor water quality and high salt concentration produce ill effect on the vaccine diluted in such kind of water.

MATERNAL ANTIBODIES
High maternal antibodies inhibit the chicken immune response. It has negative feed back effect on B lymphocytes. Moreover high levels of maternal antibodies against infectious agent such as Gumboro, also play a role in neutralizing the vaccinal antigen thus making the vaccine less effective and designing the vaccine program more difficult. Due to high maternal antibodies not only the vaccinal antigen is destroyed but also the maternal antibodies are also destroyed leaving the bird exposed to field challenge if earlier vaccination in high titer is done.

PRESENCE OF VARIANT IN FIELD
It has been observed that with the emergence of new variants the classical vaccines are no more effective to control the disease. Classical vaccine of gumboro is missing the VP-2 protien therefore it is not effective against field variant or strain. The hot intermediate and intermediate plus do have the VP-2 protein and can penetrate up to the site of proliferation. In the same manner classical IB is no more effective against IB variants.

POOR ANTIGENICITY OF VACCINES
Live vaccines must be applied at a level at or above the minimum infective dose. After the live virus has been applied the bird serves as a virus production site. The bird is media in which the initial dose of vaccine can multiply to a level which will stimulate a proper immune response. For potency testing of vaccines, always contact well facilitated Lab. Inactivated vaccines should contain sufficient amount of antigen to stimulate an immune response when applied the bird as there is no multiplication of the virus of bacteria in the bird.

INTERFERENCE
Do not give live respiratory vaccines (IB,ND,ILT) within 3 to 4 days if not combined by the manufacturer in licensed combination. Reation may be too great or response to the later vaccine may be compromised due to interference. This is also true in case of ND and AI vaccine. Do ND vaccine earlier andthan proceed for AI vaccine.

GEONETICS
Means simply the geographical influence on the gentics of local poultry ppulation. The geontical influence may affect the ultimate response of birds to vaccine under indigenous environments and may result in vaccine failure. The difference pay more if they are present in MHC.

VACCINATION REATIONS
Adverse vaccine reaction, however do not serve a useful purpose and should be prevented if at all possible. Several factors can affect the severity of the reaction that occur. These include:

• Chick quality.
• Level of maternal antibodies.
• Vaccine strain.
• Doses of vaccine used.
• Route of application.
• Timing of vaccination.
• Immuno suppression.
• House sanitation.
• Down time.
• Water,litter and air quality.
•
A normal respiratory vaccine reaction in broiler chicks begins about four days post vaccination and lasts about five days. A build up of dust and ammonia often occurs, and will cause respiratory vaccine reactions to be more severe which may never clear completely between vaccinations. A rolling vaccine reaction is one of increased duration and/or intensity compared to what is normally expected. The bacteria or fungus in haled during few hours of life or present in the yolk sac, can complicate vaccination andresult in airaculitis. These birds will react to respiratory vaccines for several days some time during the entire grown out.