Infectious Bronchitis R134A_00_1 First reported by Schalk & Hawn in 1931 in North Dakota (USA) in young chicks showing respiratory signs Distribution:

Infectious Bronchitis

R134A_00_1

First reported by Schalk & Hawn in 1931 in NorthDakota (USA) in young chicks showing respiratorysigns

Distribution: Worldwide

Transmission: Horizontal, direct contact

Incubation period: 18 - 36 hours.



R134A_00_2

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.



R134A_00_3

Young birds:• respiratory signs• sneezing, coughing, nasal discharge. Mortality may reach 30%, especially in combination with secondary infections (E. coli, M. gallisepticum).

Adult birds:• respiratory signs• egg drops• alteration in the internal and external quality of eggs (misshapen and soft eggs, watery albumen).


Pathogenesis:


R134A_00_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

?


R134A_00_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.


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בעלי פעילות במצב תקין CILIA( ריסים (


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במצב פגועCILIA( ריסים (


R134A_00_8

Ciliostasis test

10 tracheal rings 3 x top

4 x middle

3 x bottom

Results 0 = 100% cilia moving

1 = 75% cilia moving





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

Antigenic variation


R134A_00_10

Model of the structure of the “S”

protein on the surface of the virus

S1

S2

Virion membrane(Cavanagh, 1983)


R134A_00_11

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 thereforemore relevant to think in terms ofprotectotypes 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.

Cross protection


R134A_00_12

Cross protection studies


R134A_00_13

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

Experimental design


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Challenged with different field isolates 5 weeks of age by eye drop (0.1 ml)

Challenge dose: log10 3.0 CD50

Ciliostasis test 5 to 7 days p. challenge

in all experiments, groups vaccinated and challenged with homologous virus were included

Challenge


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0

10

20

30

40

Novaccine

VaccineA

VaccineB

Example of results

Maximum index = 40

Vaccine A:

- - No protection

Vaccine B:

- - Good protection

Ciliostasis Index


R134A_00_16

0

10

20

30

40

Control Ma5 IB 4/91 Bothvaccines

Protection against: Arkansas

Average ciliostasis index

Vaccines used


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0

10

20

30

40


Protection against: Brazil


Vaccines used


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0

10

20

30

40


Protection against: Honduras


Vaccines used


R134A_00_19

0

10

20

30

40


Protection against: South Africa (890/80)


Vaccines used


R134A_00_20

0

10

20

30

40


Protection against: Taiwan (A1121)


Vaccines used


R134A_00_21

0

10

20

30

40


Protection against: Holland (D274)


Vaccines used


R134A_00_22

0

10

20

30

40


Protection against: Holland (D1466)


Vaccines used


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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


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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

Documents

Infectious Bronchitis R134A_00_1 First reported by Schalk & Hawn in 1931 in North Dakota (USA) in young chicks showing respiratory signs Distribution: