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Avian encephalomyelitis (AE) vaccination

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Avian encephalomyelitis (AE) vaccination

  1. 1. Avian Encephalomyelitis (AE) Vaccination
  2. 2. Plan of Talk  Immunity against AE  Aim of vaccination  Types of vaccine – Live vaccine – Inactivated vaccine  Choosing the right vaccine
  3. 3. Plan of Talk  Immunity against AE  Aim of vaccination  Types of vaccine – Live vaccine – Inactivated vaccine  Choosing the right vaccine
  4. 4. Immunity Cheville, and later Westbury and Sinkovic, clearly showed that humoral, but not cellular, immunity was important in curtailing infection.
  5. 5. Active Immunity  Data from Calnek et al. suggested that chicks from eggs laid 11 days after exposure and carries passively acquired antibodies were resistant to contact exposure after hatching.  Positive VN tests can be found 11—14 days PI.  Positive immunodiffusion (ID) tests as early as 4—10 days PI.  Flocks of chickens with positive serology rarely, if ever, have recurrent outbreaks of AE.
  6. 6. Passive Immunity  Antibodies are transferred to progeny from the dam via the embryo and can be demonstrated in egg yolk.  Birds from immune dams were not fully susceptible to oral inoculation until 8—10 weeks of age, and antibodies were demonstrated in the serum until 4—6 weeks of age.  Passively acquired antibodies can prevent development of disease and prevent or reduce the period of virus excretion in feces.
  7. 7. Plan of Talk  Immunity against AE  Aim of vaccination  Types of vaccine – Live vaccine – Inactivated vaccine  Choosing the right vaccine
  8. 8. Aim of Vaccination Control of AE is achieved by vaccinating breeder flocks during the growing period to; 1. Protect the bird from AE infection and in turn prevent vertical transmission. 2. Protect progeny against AE during the critical first 2—3 weeks. 3. Prevent a temporary drop in egg production associated with AE.
  9. 9. Cont. … Vaccines used to control AE in chickens have been shown to be efficacious in turkeys as well.
  10. 10. Plan of Talk  Immunity against AE  Aim of vaccination  Types of vaccine – Live vaccine – Inactivated vaccine  Choosing the right vaccine
  11. 11. Types of Vaccines The development of AE vaccination strategies has been detailed by Calnek.
  12. 12. Types of Vaccines Live Vaccines  Most flocks are vaccinated with a live, embryo-propagated virus, such as strain-1143, which can be administered by naturally occurring routes such as via drinking water or by spraying.  Vaccination by wing-web inoculation of AEV is also practiced in many flocks but this method may carry some risk of clinical signs.
  13. 13. Vaccination Live Vaccines - Spread  Live virus vaccines are similar to field virus in that they spread readily within a flock.  This allows for oral administration to a small percentage of the birds in a flock, which then spread infection to others, although this method is generally unsatisfactory for birds in wire cages.  Shafren et al. found that serologic responses to vaccine administered ocularly to 10% of a flock were as good as those following drinking water administration of virus to the entire flock.
  14. 14. Types of Vaccines Inactivated Vaccines Inactivated vaccines have been developed and may be useful in flocks in production or where the use of a live virus is contraindicated.
  15. 15. Plan of Talk  Immunity against AE  Aim of vaccination  Types of vaccine – Live vaccine – Inactivated vaccine  Choosing the right vaccine
  16. 16. Choosing the Right Vaccination  A.E. vaccines are produced in chicken embryos.  The continuous propagation of virus in chicken embryos makes the virus adapt to the nervous tissue.  In order to prevent the virus from becoming adapted to the chicken embryos, occasionally the virus needs to be passaged back into chickens.
  17. 17. Cont. … It is very important that embryo adaptation of strains used for live virus vaccines does not occur because : 1. Adapted virus loses its ability to infect via the intestinal tract and is, therefore, no longer efficacious when administered by naturally occurring routes. 2. Adapted virus can cause clinical disease when administered by the wing-web route.
  18. 18. Cont. … Glisson and Fletcher observed clinical encephalitis in broiler breeder pullets given embryo-propagated AEV vaccine by the wing-web route and concluded that the most probable explanation was that the vaccine virus was inadvertently adapted during manufacture.
  19. 19. Cont. … Adaptation is detected by careful monitoring of inoculated embryos used in the production of vaccine for characteristic signs, and any adapted virus can be eliminated from vaccine seed virus stocks by passage in susceptible chicks inoculated orally.
  20. 20. Cont. …  The level of embryo adaptation of a vaccine can be determined by increase incidence of muscular dystrophy that the virus produces in inoculated chicken embryos.

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