Western Meeting of Poultry

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Monitoring Vaccine Spray Distribution Using Water-Sensitive Paper

Dr. Douglas Grieve

Hy-Line International

Introduction

The administration of live vaccines to poultry by the aerosol or spray route has been widely used for many years and is increasingly popular as the size of pullet and laying flocks increase. Spray administration is effective in delivering live respiratory vaccines (i.e. Newcastle and bronchitis) to the immune tissues associated with the head and the upper respiratory tract. The natural route of infection for many poultry disease pathogens is through the respiratory tract, therefore establishing good mucosal immunity in the head and upper respiratory tract is critical in the protection of the bird. The poultry vaccines which have been administered as a spray are Newcastle, bronchitis, Gumboro, coccidiosis, laryngotracheitis and avian encephalomyelitis. Spray application offers the advantages of mass application, which require less time and labor for administration, minimal bird stress, and stimulation of good mucosal immunity, while the chief disadvantages are inconsistencies of vaccine dosage depending upon the spray exposure of each bird, and the potential for some birds to receive no vaccine at all. Spray also circumvents some of the water quality problems associated with water administration.

The efficacy of spray vaccination programs is the result of the interaction of vaccine, vaccination technique, and bird related factors (Table 1). Problems in any of these areas can result in vaccine failures.

Table 1

Factors Affecting Spray Vaccination

A wide variety of sprayers are used by poultry producers to administer vaccines. Some of these sprayers are designed for poultry vaccine administration while others are designed for other agricultural uses (i.e. orchard sprayers, cleaning sprayers, paint sprayers). The wide variety of sprayers used for vaccination and the many factors that can affect sprayer performance give much variability to the results seen from spray administered vaccine.

The even distribution of the spray throughout the cage rows is very important to prevent the situation, which can lead to post-vaccination, or "rolling" vaccine reactions. Bronchitis and Newcastle vaccines are particularly prone to cause bird health problems due to this rolling reaction. The bronchitis virus is genetically unstable and can easily reassort and mutate their genetic material that might change the pathogenic and virulence factors of the original vaccine virus. The uneven distribution of the spray within the house can allow large numbers of birds to be not adequately exposed to the vaccine. These unvaccinated birds can be subsequently infected by other vaccinated birds, which are shedding the virus. This bird-to-bird passage can cause the original vaccine virus to "heat up" or become more pathogenic causing the "rolling" post-vaccination reaction. Post-vaccination reactions may also result from a spray, which is too fine (small spray droplets) in young birds. These small spray droplets penetrate deeply into the lungs and airsacs where vaccine strain in a young previously unexposed bird (i.e., LaSota, Newcastle, or Arkansas, bronchitis) might also cause an adverse post-vaccination reaction.

The important factors that maximize the even distribution of the vaccine spray within the house are: 1. Steady even paced walking of the sprayer down the cage row, 2. Dimming of the lights to prevent spray avoidance by the birds, 3. Reduction of the airflow within the house during the application of the spray, 4. Proper positioning of the spray nozzle so the spray is delivered at head level, 5. Proper function of the sprayer.

Factors relating to the sprayer which may affect its performance are: 1) the sprayer flow rate, 2) sprayer pressure, 3) excessive dust which suppresses spray distribution, 4) low relative humidity which decreases droplet size through evaporation, 5) sprayer nozzle problems (i.e. corrosion, caked with residue, wear, heat damage, accidental damage to nozzle or orifice). Spray nozzle tips, depending on the amount of usage, should be changed every six months to one year.

Water-sensitive paper strips (CIBA-GEIGY Ltd., available through spraying Systems Co., Wheaton, IL) are widely used in agronomy to monitor the distribution of herbicide/pesticide spray in fields. The water-sensitive paper is a rigid paper with a special coated surface designed to stain blue when the paper is contacted with water droplets. The paper can be used to check the vaccine spray distribution within a caged flock. The droplet density at the target areas can be evaluated. Also, a rough visual estimate of the droplet size and the uniformity of the spray droplets can be evaluated. The strips need to be handled carefully after removing them from their package. Plastic gloves are helpful to prevent the moisture on fingertips from leaving marks upon the paper. Houses with high relative humidity can also affect the paper by diffusely changing the paper strips blue. The strips of paper should be retrieved as soon as the spray has dried and evaluated. The strips can be stored in a clear plastic folder to be examined later.

The procedure is to place strips of water-sensitive paper within empty cages at selected locations within the house. The paper can be woven between the wires of hung from the top of the cage. The selection of cages to be used during the evaluation can be random or according to a predesigned pattern. The important point is that cages at all levels (upper, middle, bottom) and positions within a cage row (front, middle, back) be evaluated. It is also advisable that the person actually spraying the vaccine not be aware of the exact position of the test cages to prevent an unintentional bias in the spray technique.

The examination of the paper strips can reveal if large sections of the cage row are being missed. The use of sprayers having multiple spray nozzles can be evaluated to establish if the spray nozzles are properly positioned at each cage level. The target area of a spray should be head level to the bird. It is common to find sprays that are directed too low and are spraying the legs and feet of the birds. Sprayers with a single want (back pack type sprayers) are easier to apply unevenly because the wand is hand held and the applicator may not consistently apply the spray in the same way.

Another common problem encountered is that the total numbers of vaccine doses are unevenly applied in the house. The last cage row sprayed is often the area shorted of vaccine. Simply adding more water to the remaining vaccine solution in order to finish the last cage row only dilutes the vaccine. And, in extreme cases, might dilute the vaccine below an immunizing dose. A remedy for this is to divide the total doses of vaccine and mix only the vaccine required for half of the house, and mix a fresh solution with the other half of the vaccine to finish the house. This approach would avoid large mistakes in vaccine distribution. There is also the advantage in keeping the vaccine solution fresh and high titered.

House lights should be dimmed to prevent the birds from avoiding the spray. It is not necessary to make the house completely dark, but dim the lights enough so that the birds stay evenly distributed within the cages. Birds under dim light conditions seem to be curious of the sound made by the sprayer and will hold their heads high and pointed toward the spray.

Doubling the spray volume to allow two passages of the spray over the flock would provide the most complete coverage. This method is not popular because of the extra time and labor involved, but might be considered when complete coverage is vital (revaccination in the fact of an outbreak with ILT vaccine).

High quality (distilled, bottled or known good quality) water should be used for mixing vaccine solution. Good quality water is particularly important for spray vaccination because dried skimmed milk cannot be used to protect the vaccine as is often used for drinking water vaccination. The water used should be free of chlorine or other substances, which might adversely affect the vaccine. The reconstituted vaccine solution should be used immediately within two hours. The vaccine titers of liable vaccines such as bronchitis and AE can deteriorate quickly after reconstitution in water.

In conclusion, spray administration of vaccine is not an exact science and it is often the proficiency and experience of the vaccinator and sprayer function which most determines success. Water-sensitive paper appears to be a useful tool to monitor the spray vaccination protocol.

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Last modified: 5/28/2009