1. Infectious Bronchitis
First reported by Schalk & Hawn in 1931 in North
Dakota (USA) in young chicks showing respiratory
signs
Distribution: Worldwide
Transmission: Horizontal, direct contact
Incubation period: hours.

2. Infectious Bronchitis
Agent: Coronavirus (RAN)
Host: Chickens of all ages
Affects:
respiratory tract
uro-genital tract
* The virus can be isolated from different organs up
to ± 50 d.p.i.

3. Infectious Bronchitis
Pathogenesis:
Young birds:
respiratory signs
sneezing, coughing, nasal discharge.
Mortality may reach 30%, especially
in combination with secondary infections
(E. coli, M. gallisepticum).
Adult birds:
egg drops
alteration in the internal and external quality of eggs
(misshapen and soft eggs, watery albumen).

4. ? Why is IB still a problem? Highly infectious Persistent in the birds
Fast dissemination
RNA virus - mutations recombinations
Causes different diseases
Many different serotypes

5. Ciliostasis Test
Tool to measure the effect of a virus on the tracheal mucosa
The tracheal mucosa represents a mechanic barrier
against foreign particles in the respiratory tract
(muco-ciliar apparatus)
Consists of motile structures (cilia) and secretory cells
(Goblet cells). They trap and eliminate foreign particles
(ex. dust and bacteria).
Tracheal rings of vaccinated and/or challenged birds are
prepared and observed under the microscope.

6. ריסים (( CILIAבעלי פעילות במצב תקין

7. ריסים (( CILIAבמצב פגוע

8. Ciliostasis test 10 tracheal rings 3 x top 4 x middle 3 x bottom
Results 0 = 100% cilia moving
1 = 75% cilia moving
2 = 50% cilia moving
3 = 25% cilia moving
4 = 100% cilia moving

9. Antigenic variation New serotypes of IBV
can emerge as a result of few aminoacid changes in the S1 part of the spike genome of the virus

10. Model of the structure of the “S” protein on the surface of the virus
Virion membrane
(Cavanagh, 1983)

11. Cross protection
Cross protection against IB viruses belonging to other serotypes may be due to the fact that most of the virus genome remains unchanged
From a practical point of view it is therefore
more relevant to think in terms of
protectotypes rather than serotypes
There are occasions when existing IB vaccines
do not provide adequate protection against
newly emerging serotypes
With the continual emergence of new serotypes of IBV it seems prudent to evaluate the level of cross protection obtained by the use of currently available vaccines.

12. Cross protection studies

13. Experimental design 4 groups (10 SPF birds)
1 Massachusetts (Ma5) at 1 day
2 4/91 at 14 days
3 Massachusetts (Ma5) at 1 day & 4/91 at 14 days
4 Not vaccinated
Reared in isolators

14. Challenge Challenged with different field isolates
5 weeks of age by eye drop (0.1 ml)
Challenge dose: log CD50
Ciliostasis test 5 to 7 days p. challenge
in all experiments, groups vaccinated and
challenged with homologous virus were included

15. Example of results Maximum index = 40 Vaccine A: - No protection
Ciliostasis Index
Maximum index = 40
Vaccine A:
- No protection
Vaccine B:
- Good protection

16. Protection against: Arkansas
Average ciliostasis index
Vaccines used

17. Protection against: Brazil
Average ciliostasis index
Vaccines used

18. Protection against: Honduras
Average ciliostasis index
Vaccines used

19. Protection against: South Africa (890/80)
Average ciliostasis index
Vaccines used

20. Protection against: Taiwan (A1121)
Average ciliostasis index
Vaccines used

21. Protection against: Holland (D274)
Average ciliostasis index
Vaccines used

22. Protection against: Holland (D1466)
Average ciliostasis index
Vaccines used

23. Conclusions
The increasing prevalence of new serotypes creates difficulties in the design of adequate vaccination programs against IB
It is undesirable and not always necessary to consider developing new live vaccines for each new serotype

24. Conclusions
The concept of protectotypes is more relevant from a practical point of view
The use of IB vaccines belonging to different serotypes may broaden the protection against a wide variety of antigenically different IBV’s