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Infectious Bronchitis

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Presentation on theme: "Infectious Bronchitis"— Presentation transcript:

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

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