vaccination

Question 1

why we need to vaccinate

Answer 1

• Infectious agents can lead to significant economic losses to the producer
• Infectious agents can be a serious threat to a supply-managed system (e.g. infection with IBV at < 2 weeks of age)
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  1. To reduce losses due to morbidity and mortality caused by infectious agents
• Many infectious diseases are ubiquitous (e.g. Marek’s)
• Airborne pathogens are difficult to control even with good biosecurity (e.g. IBV)
• There is a high risk of horizontal transmission of pathogens, especially if farmer compliance is poor (e.g. not changing footwear, “industry on wheels”)
  2. To protect layer and breeder birds against diseases causing egg production drops and eggshell deformities
  3. To prevent dissemination of zoonotic pathogens (e.g. Salmonella enterica)

Question 2

FACTORS TO CONSIDER for designing your vaccination program

Answer 2

• Disease challenges on the farm and in the region
• Cost and benefits of vaccination vs. potential loss
• Short- or long-lived birds
• Protection of progeny
• Ease of administration
• Comfort with administration method and equipment

Question 3

GOAL OF VACCINATION for broilers, breeds, and layers

Answer 3

• Achieve immunity in the majority of the birds in the flock to prevent or minimize the effect of disease in or from that flock
• Broilers and turkeys – need adequate immunity throughout the grow-out period to maximize performance (e.g. FCR)
• Breeders – need a high level of immunity so that maternal antibodies are passed on to the progeny (passive immunity)
• Layers – need a high level of immunity because of their long production cycle

Question 4

live vaccine properties, administration, handling

Answer 4

• Usually contain one antigen or agent
• Unmodified (e.g. Eimeria spp.)
• Mild strain (e.g. B1 strain of NDV)
• Modified/attenuated (e.g. IBV)
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• Most are administered by mass application techniques, such as by spray (aerosol) or via drinking water
• May be administered by eye drop, or in some cases by injection
• Require special care and handling (temperature, light, etc.)

Question 5

killed vaccine properties, efficacy, admin?

Answer 5

• Often contain more than one inactivated antigen (multivalent)
  > Combined with an oil emulsion or aluminum hydroxide adjuvant
• Give high and prolonged levels of immunity, especially after priming with live vaccine
• Must be injected

Question 6

METHODS OF ADMINISTRATION – IN-OVO
- how it works, what disease common

Answer 6

• 18 day embryonated egg
• Done at the hatchery
• Marek’s disease (MD) and some recombinants

Question 7

METHODS OF ADMINISTRATION – SPRAY IN HATCHERY
- how it works, what disease common

Answer 7

• Infectious bronchitis virus (IBV)
• Coccidiosis
  > Keep chicks in holding area under bright lights to encourage preening and oocyst ingestion

Question 8

METHODS OF ADMINISTRATION – SPRAY ON-FARM
- main considerations

Answer 8

• Particle size is an important consideration
• Coarse spray (>100 microns)
• Fine spray (50-100 microns)
• Aerosol (<50 microns)
• Finer particle size reaches deeper into respiratory tissues, which can induce a better response
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• Walking pattern and coverage are critical
• Keep a vaccine-exclusive sprayer
• Dim lights before spraying
• Turn off ventilation before spraying (don’t forget to turn it back on!)

Question 9

METHODS OF ADMINISTRATION - WATER
- when is this most useful
- how to do it

Answer 9

• Used for enteric and respiratory viruses
• Convenient
• No chlorine, medication, or disinfectants for 48 hours prior to vaccination
• Tanks must be clean
• Flush lines 24 hours prior to vaccination
• Withhold water for 2 hours prior to vaccination to encourage drinking
• Use vaccine stabilizers and tablets to deactivate chorine
• Bypass filters

Question 10

METHODS OF ADMINISTRATION – INJECTION
- when is this used?

Answer 10

SQ in hatchery
* MD (1-day-old layer chicks)
* Automated
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IM/SQ on-farm
* Labour-intensive
* Often used for inactivated vaccines
* Water/Oil emulsion
* Water carries vaccine, oil stimulates immune response
* IM - thigh, wing muscle, tail, (breast)
* SQ–backofneck

Question 11

METHODS OF ADMINISTRATION – WING WEB
- when is this used? how?

Answer 11

• Principal method administration of fowl pox (FP)
• Often combined with avian encephalomyelitis (AE) using a two- pronged applicator
• Labour-intensive
• Two-pronged needle directed into skin of wing web

Question 12

METHODS OF ADMINISTRATION – EYE DROP
- when is this used? how?

Answer 12

• Used for respiratory viruses
• Live vaccines
  > Infectious laryngotracheitis virus (ILTV)
• Labour-intensive
• Targets Harderian gland, which
  produces local antibodies
• Excess is swallowed or inhaled, producing more local response

Question 13

EVALUATING EFFICACY - SEROLOGY
how to do it

Answer 13

• Collect blood from 20 birds per flock
• Send sera to lab for titres
• Evaluate geometric mean titres and coefficient of variation
• For each pathogen, understand what constitutes low, medium, and high titres
• Establish baseline titres, then use these to determine whether changes to your vaccination program have been effective
• AHL usually provides titre groups – a numeric value assigned to a range of titres

Question 14

EVALUATING EFFICACY – VACCINATION AUDIT
- what is this?

Answer 14

• Verify that the cold chain (2-7°C) has been maintained before and during vaccination
• Check expiry dates
• Verify use of distilled water and proper mixing (water and spray)
• Measure water temperature used for stock solution
• Evaluate spray pattern (hatchery spray cabinet, on-farm backpack sprayer)
• Evaluate method of rounding-up birds for injection (no missed birds)
• Determine how often needles are changed (no more than 100 birds/needle)
• Ensure there has been good uptake of the vaccine. Randomly select 100 birds and look for:
• dye in the mouth (coccidiosis in hatchery, water on farm)
• blue dye under the skin after injection (SQ and WW)
• a slightly raised and swollen area 5-7 days post-injection (WW)

Question 15

EVALUATING EFFICACY – PAST VS. PRESENT

Answer 15

• Evaluate historical data (production records, necropsy findings, lab results, condemnation reports) from previous flocks in the barn and compare to data from flocks housed in the same barn after making changes to the vaccination program
• For example, if you recommended the addition of an in-ovo infectious bursal disease virus (IBDV) vaccine, has there been a reduction in clinical disease, mortality, and/or condemnations in subsequent flocks?