By P W Cargill, Merial Avian Business Unit UK and Joey
Johnston, Merial Avian Business Unit, USA.
Poor administration is the most common cause of vaccine failure
in poultry. Planning and attention to detail resulting in better
administration will improve disease control and therefore
economic performance of poultry. The following is an overview of
the principles of poultry vaccination.
Flock sizes of commercial poultry operations can be as high as
45,000 birds in a single air space. For this reason it has become
necessary to evolve effective methods of mass vaccination. The
aim is to vaccinate a high enough proportion of the birds in the
flock, to prevent or minimize the effect of a particular disease.
The proportion of the birds that need to be effectively
vaccinated will vary according to the infectious agent involved
and the current epidemiological situation with respect to that
agent.
In many situations, vaccination may only be employed as a means
of minimizing the economic impact of a disease rather than total
prevention in 100% of the flock.
Commercially produced vaccines are available in presentations
tailored to large flock sizes. While the principles of
administration remain the same, the techniques used for the mass
application of vaccines need to be adapted to small flocks of
birds.
There are two main types of vaccines available for poultry:
Again, due to flock size, the most widely used vaccines are
live attenuated virus vaccines which can be administered to birds
by techniques which are practical within the limitations of the
production environment. This is usually by means of the drinking
water or by spray application, though some live vaccines require
individual application by eye drop or administration by injection.
Inactivated vaccines are usually employed in breeding or
laying stock and require individual administration by injection.
All contain some type of adjuvant in order to optimize the immune
response to the antigen. Commonly used adjuvants include mineral
oils and aluminium hydroxide.
- Drinking water.
- Spray/nebulisation - at day of age. Birds in the housed
environment.
- Eye drop.
- Transfixion and scarification (cutaneous route in the wing web
or foot).
- Injection - intramuscular or subcutaneous.
- In-ovo administration.
Drinking water administration is an appropriate method of administration for most live vaccines, particularly for diseases such as infectious bursal disease and avian encephalomyelitis where the target organ is the gut. The presence of a choanal cleft in poultry also allows this route to be employed for most respiratory virus vaccines, vaccine virus gaining entry to the nasal cavity from the mouth via the cleft.
Live vaccines by their nature have a limited lifespan that must be taken into account during administration. As a rough guide 1.5 to 2.0 hours is a typical period of time over which live vaccines should be administered. The aim should be to present the vaccine in the water to all the birds in the colony over this 1.5 to 2.0 hour period.
One of the limitations of this method is that we must be sure
that all the birds in the flock will drink over the period of
time over which the vaccine is presented to them. Various means
are available to encourage this situation such as controlled
lighting, controlled feeding or water deprivation.
Feed and water intake are closely linked in poultry, therefore
presenting food will stimulate water consumption. Water
deprivation can also be useful, however this must be used with
caution as excessive deprivation can stress the birds to a level,
which can predispose disease and adversely influence vaccine
efficacy and feed efficiency. Controlled lighting will affect
water consumption by influencing activity and feeding patterns.
Live vaccines are as susceptible to antiviral agents as field viruses, and it is important to ensure that the vaccine does not come into contact with disinfectant, chlorinated water or water sanitizing materials commonly used on farms.
Basic steps can be taken to minimize the risk of exposure of the vaccine to these chemicals. These include washing hands thoroughly (rinsing soap off thoroughly), only mixing vaccine in a clean area on a clean surface and ensuring that vaccine vials are not placed on surfaces that may carry traces of disinfectants and consequently contaminate the water during mixing.
The volume of the water necessary for the vaccination period
should be calculated and the influx of mains water into the tank
interrupted until the completion of vaccination.
Chlorinated water is hazardous to vaccines and can severely
reduce the amount of vaccine virus presented to the birds.
The addition of skimmed milk powder to all water, which will come into contact with vaccine, is a simple and effective way to overcome the detrimental effects of the chlorine. The milk powder must be mixed at the correct rate of 2-2.5g/litre or 10g/gallon and the powder should be mixed with the water at least 20 minutes prior to the vaccine being added.
With a clean plastic bucket, some of the milk treated water
should be removed from the tank. Remove the metal caps from the
vaccine vials and submerge each bottle in the water before
removing the rubber stopper, rinsing the entire contents of each
vaccine bottle.
Once the vaccine has been added to the water reservoir of the
delivery device, the water should be mixed thoroughly ensuring
even distribution of the vaccine.
It is very important to prime the drinker system, as the
pipework will contain water with no vaccine.
Due to their design, nipple drinker lines will contain large
amounts of water even if they have been drunk dry by the birds.
An additional advantage of using milk powder is that it acts as a
useful visual marker for the vaccine and the drinker lines should
be drained until the milk is visible. Approved dyes may be added
as an indicator.
Once vaccine is presented to the birds, stimulating activity
by increasing light intensity, operating feeders and walking
through the birds are all effective at encouraging drinking.
Bell drinker systems present more difficulties in terms of
priming the drinkers with vaccinated water.
The only practical solution to eliminate unvaccinated water is to
walk through the shed, tipping each drinker until they fill with
water containing milk powder.
An alternative approach is to deliver a measured dose, manually to each drinker in the shed, however the water supply must be treated with milk powder and it is important to ensure adequate mixing of the vaccine in each drinker.
Due to the diversity of drinker system design and plumbing
routes in houses, it is important to tailor the method of
vaccination to the particular equipment in use.
Mock vaccination using special dyes capable of temporarily
staining the bird&rsquos mouth are a useful means of proofing
vaccination technique.
Administration of respiratory virus vaccine by spray is
another very effective method of vaccination. Spray
administration is employed in two situations that are distinctive
for both
practical and technical reasons. These are:
- Spray administration to day old birds in delivery boxes.
- Spray administration to birds in poultry houses.
The day old birds contained in delivery boxes represents the situation where we have most control of the birds in terms of our ability to administer vaccines. Birds are in groups of 80-150 and their close proximity facilitates physical lateral transfer of vaccine.
The physical size of birds does not facilitate the delivery of
vaccine directly to the respiratory system, as no currently
available equipment is capable of producing a consistent particle
size capable of inhalation.
The aim should be to apply vaccine onto the birds, some of which
will enter the eye but most will be taken in orally. Day old
birds will readily take very small drops of water off each other
and the flat surfaces of the box.
The spray employed should be capable of distributing the vaccine evenly over the birds. The volume applied must be accurately determined and repeatable for every box and can range from 7ml to 40ml per 100 birds depending upon the vaccine and particular spray equipment in use.
For practical reasons droplets of 100-300µ diameter are ideal
as they facilitate even coverage of birds. Smaller droplets have
a tendency to drift with air movement and may not reach the box.
Due to the small volumes of water used during spray
administration, all water used for vaccine reconstitution should
be fresh, cool distilled water as water temperature also has an
impact on vaccine life.
Excessively hot water will seriously reduce the titre of the
vaccine. The possible effect of the water chilling the birds must
be taken into consideration when deciding on volumes to be
employed.
From a practical point of view a spray pattern that easily
facilitates coverage of all the birds in the box is ideal.
Equipment designed to administer vaccine by means of a &lsquoflat
fan&rsquo nozzle onto a box on a moving conveyor are usually
more effective in terms of the extent of coverage of the chicks
achieved.
The nozzle should remain vertical above the box during the
procedure and care taken that the entire inside area of the box
is covered.
Some types of spray equipment will measure a pre-determined volume each time it is operated, others must be calibrated on the basis of the volume delivered in a unit time and the dose applied to each box determined by the time that the spray is applied to each box.
Pressurized spray equipment must have the operating pressure maintained and time which the spray is applied should be measured and not guessed if effective application of the vaccine is to be achieved. Compressed air quality must be monitored in order to ensure freedom from bacterial and oil contamination generated in the compressor.
The rapid growth rate of modern poultry breeds means that at
the age where respiratory virus vaccines are required the
physical size of the birds is considerably greater than at day
old.
For this reason it now becomes possible to administer vaccine
directly to the respiratory system if so desired. In practice,
vaccine is usually administered by two main means of producing a
spray.
This consists of a pressure chamber, lance and nozzle. The nozzle and the operating pressure vary the size of the particle produced, but this type of equipment will produce a large range of particle sizes from 50-1000µ in diameter. One of the practical difficulties with this method is that spray particles produced this way will only travel approximately 50cm from the nozzle.
Therefore in order to vaccinate all the birds the nozzle must come within 50cm of every bird in the group. Due to the range of particles produced only a small proportion of vaccine is capable of being inhaled by birds, the remainder is either taken up by the ocular oral route or falls on the ground. A consequence of this is the need to employ relatively large volumes of water to cover the birds, which can be in the order of 15-30 litres per shed of birds.
Spray technology developed for horticultural and insect
control use is directly applicable to poultry vaccination.
These devices are capable of producing a narrow band of particle
sizes in a predetermined range.
The spray is generated by centrifugal force and water is
delivered to a spinning disc on the circumference of which the
spray is formed. The nebulized vaccine can then be blown by means
of a fan, in order to facilitate delivery to the birds. One of
the advantages of this type of equipment is that they are able to
produce a particle size between 80µ and 100µ resulting in
inhalation of the particles and their deposition in the upper
respiratory tract.
This type of equipment also delivers vaccine in a band
approximately 1m in width and 3m in front of the machine that
enables the operator to easily administer vaccine to all the
birds.
The volumes of water required are also relatively small, because
only particles in the desired range are produced by the machine,
this means up to 30,000 birds can be vaccinated with as little as
900ml of water. Again, as water volumes employed are relatively
small, all vaccines should be reconstituted in cool, fresh,
distilled water.
It is advisable to contact the relevant manufacturer for
information regarding the most appropriate spray equipment for
each vaccine.
Again, from a practical point of view it is important to ensure
that all the birds are administered with the spray at the same
time. Shutting down the ventilation system will minimize air
movement in the shed and prevent 'drift' of vaccine.
Reducing the light level until bird movement is minimized is also essential. Once these two measures are taken the spray should be applied to the birds as evenly as possible by following a logical and systematic route through the birds whilst spraying. It is often useful to approach the process by aiming to apply the spray to the entire floor area of the shed, the birds being incidental to the process and the route being determined by the technical attributes of the equipment being employed.
Eye drop administration is probably the most effective (but labor intensive) means of administering live respiratory virus vaccines to birds. Each bird is individually handled and receives a full dose of vaccine. The process facilitates both local and humoral immunity due to the presence of the Harderian gland behind the third eyelid. Eye drop diluent is available from vaccine manufacturers for use with certain vaccines and is presented in an easy to use bottle, which usually contains a dye in order to assess the efficiency of administration. Birds dosed effectively will show staining at the nares shortly after vaccination.
Care must be taken over the process to ensure that the fluid does not 'roll off' the eye due to the surface tension of the droplets. Each bird should be held until it blinks after the droplet is applied and the whole process must not be rushed or birds will be missed.
This method delivers the vaccine into the skin thickness and
is the method used exclusively for fowl pox vaccination, though
avian encephalomyelitis is often combined with the fowl pox
vaccine.
The site most widely used for application is usually the skin of
the wing web (using a special two pronged, grooved applicator)
though scarification of the skin of the thigh and the foot can
also be used.
It is very important to ensure that fowl pox vaccine does not
come into contact with the eyes or mouth of the birds. This can
lead to lesions appearing in these organs.
In practice the most common complication can occur if the vaccine is applied to the skin under the wing where birds occasionally place their head when sleeping. Birds can subsequently develop lesions on the head that may be severe enough to affect the mouth and eyes with subsequent adverse effects on food and water consumption.
Care must also be taken to remove all used vaccine vials and scarifying equipment from the shed after vaccination as birds will peck at these items which can also lead to oral lesions.
Intramuscular or subcutaneous injection is the most common
route of administration employed for oil and aluminium hydroxide
adjuvanted vaccines and some live vaccines.
Vaccine is usually available in 500 or 1000 dose bottles, which
feed an automatic syringe at a preset dosage that facilitates
vaccination of large numbers of birds.
The site of administration is most commonly into the breast or
leg though the lower neck can also be used.
Accuracy of placement of the needle is critical as incorrect
placement can lead to granuloma formation, lameness, head
swelling or liver puncture depending on the injection site.
The method and care of handling birds during this procedure is
also important as this can contribute to lameness in birds.
A 12.5mm (1/2"), 19 gauge needle is suitable for use and
should be changed at least every 200 birds in order to avoid
spread of bacteria and viral contaminants.
Attachments for automatic syringes are now available which
decontaminate needles between each bird and are a useful aid in
minimising the risk of cross contamination.
A needleless injector system is also available for use with some
vaccines, which significantly decreases the possibility of
hygiene complications associated with needles as well as
improving the consistency of the vaccine delivery into the bird.
This is a process by which vaccine is administered into fertile eggs via the air cell at between 17.5 and 19 days of incubation using a special machine.
The system has proved to be effective for the administration
of Marek's disease vaccine, certain types of infectious bursal
disease vaccine and may be appropriate for a number of other
types of live vaccine.
This is a rapidly growing area of vaccine technology which will
generate a number of other vaccines developed specifically for in-ovo
administration.
December 2006