"عسى أن تكون علما ينتفع به"

1. Avian Encephalomyelitis (AE)
Vaccination

2. Plan of Talk
 Immunity against AE
 Aim of vaccination
 Types of vaccine
– Live vaccine
– Inactivated vaccine
 Choosing the right vaccine

3. Plan of Talk
 Immunity against AE
 Aim of vaccination
 Types of vaccine
– Live vaccine
– Inactivated vaccine
 Choosing the right vaccine

4. Immunity
Cheville, and later Westbury and Sinkovic, clearly showed that
humoral, but not cellular, immunity was important in curtailing
infection.

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. 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. Plan of Talk
 Immunity against AE
 Aim of vaccination
 Types of vaccine
– Live vaccine
– Inactivated vaccine
 Choosing the right vaccine

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. Cont. …
Vaccines used to control AE in chickens have been shown to be
efficacious in turkeys as well.

10. Plan of Talk
 Immunity against AE
 Aim of vaccination
 Types of vaccine
– Live vaccine
– Inactivated vaccine
 Choosing the right vaccine

11. Types of Vaccines
The development of AE vaccination
strategies has been detailed by Calnek.

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. 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. 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. Plan of Talk
 Immunity against AE
 Aim of vaccination
 Types of vaccine
– Live vaccine
– Inactivated vaccine
 Choosing the right vaccine

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. 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. 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. 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. 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.