1. Infectious bronchitis
Dr. Latif Ahmad-PhD,
Assistant Professor

2. Infectious bronchitis: Definition
Acute/subacute, highly infectious & contagious dis of chickens characterized by:
Resp. symptoms,
High mortality in young chicks (25-30%),
Dec. egg prod. &
Deteriorated egg quality in layers
The dis. common in Northern areas of Pakistan

3. Etiology Gamma coronavirus/IB virus);
Alpha/Beta (mammals);
Delta (wild birds, pigs).
Non-segmented, +ve-sense, single-strndd RNA
Sensitivity: 56°C 15 min, at room temp. 2-3 days, Common detergents destroy
Many strains (differ in antigenic properties, virulence), mutations, recombination

4. Epizootology IBV infects Air-borne route common
chickens of all ages (meat/egg type),
pheasants;
Air-borne route common
Mechanical transfer possible,
Vertical transmission if egg breakage in hatchery
Within a day dis. spreads whole flock
Persists months, shed for 4-9 wks
Mat. abs. control inf. 3 wks;
> severe IBV induced resp. dis., if other pathogens (e.g., bacteria) producing chronic complicated air-sacculitis.

5. Clinical Signs Incubation period: Resp. signs: severe in young chicks
Natural: 3-8d; Experimental: hrs
Resp. signs: severe in young chicks
Suffocation
Cough, rales, sternutation/sneezing, nasal discharge
Mortality (Young: 30%; 60% if complicated; Growing: 10%; Adults: usually nil)
Drop of lay (<20% within 2wks), false layers
Inferior eggs; Reduced hatchability, Chick mortality
IB in young chicks damages their oviducts
Clinical signs last for 10 – 14 days

7. Transmission Horizontal spread
Rapid spread – high concentration of animals
Vertical transmission – not demonstrated
Virus replicates in epithelial and subepithelial cells of repiratory tract and kidney (nefropathogenic strains)
Virus persistence and long term shedding

8. Postmortem Lesions Respiratory System
Acute catarrhal tracheitis, bronchitis, sinusitis/rhinitis, air sacculitis, local pneumonia (Massachusetts, Connecticut)
Sub-epi. oedema, cilia lost, epi. hyperplasia/metaplasia
> lymphocytes, monocytes in L.P.; distorted muc. glands

9. Kidneys Nephritis, (Gray, Holte, Australian and T starins)
Off-white kidneys; urates, necrotic material in lumen

10. Oviducts Degen. ovary; atrophic, haem. follicles;
Salpingitis (European Strains e.g., D-207, D-212, D-41)
Degen. ovary; atrophic, haem. follicles;
In false layers: short/narrow/ impacted/
partially closed oviduct

11. Diagnosis
Tracheal swabs – till 14 days in chicken, 7-10 days in older, 2-3 weeks in nefropat. strains
Virus isolation in acute phase of the disease
CAM (2-3 passages)
tracheal explantates (ciliostasis in 2-3 days)
Variant strains and Ag mutants – sentinel SPF animals

12. Differential Diagnosis
ND: In ND nervous signs are usual, mortality is much higher than in IB and birds may go completely out of lay in ND, but rarely so in IB.
ILT: There are haem. trachitis & severe dyspnoea & spread of ILT is slower through the flock than IB.
Mycoplasmosis also spreads slowly than IB.
Facial swelling in inf. coryza, not evident in IB.
Nephrosis in IB resembles the terminal renal picture in IBD, IBH, intoxications, dehydration and nutritional deficiencies etc.

13. MCQs
Choose the MOST CORRECT or THE ONLY CORRECT answer for the following questions:
1. In chickens affected with IB, the virus can be isolated from which of the following organs/tissues?
A. trachea
B. lungs
C. trachea and lungs
D. trachea and cecal tonsils
E. trachea, lungs and cecal tonsils

14. 3. The emerging of antigen-variant strains is most significant with which of the following viruses?
2. Which of the following viruses does express haemagglutination activity following treatment with the enzyme neuraminidase?
A. IBV
B. IBDV
C. IBV and IBDV
A. IBDV
D. IBV, IBDV and MDV
B. IBV
E. IBV, IBDV, MDV and haemorrhagic enteritis virus
C. ILTV
D. AEV
E. Reovirus

15. 4. Natural infection with IBV ocuurs in chickens and
A. In some birds, there are white foci in liver
B. In some birds, spleen may be enlarged
A. turkey
C. In some birds, there is diffuse consolidation in one ore both lungs.
B. duck
C. pigeon
D. quial
D. Major frequent lesion include excess mucous in the trachea with thickening and roughening of the tracheal mucosa
E. none of the above choices
5. Which of the following is NOT true about the gross lesions in quails affected with quail bronchitis?
E. None of the above choices.

16. 7. The HA test can be used to distinguish NDV and
6. A virus was isolated from resp. tract of broiler chicken with resp. disease. Negative contrast microscopy showed that the virus had club- shapped surface projections. The virus could be:
7. The HA test can be used to distinguish NDV and
A. ILTV
B. IBV and ILTV
C. IBV and EDS
D. ILTV and EDS
E. None of the above 4 choices
A. AIV
B. NDV
C. IBV
D. ILTV
E. adenovirus

17. 9. Which of the following changes does characteristically occur in chick embryos innoculated with IBV?
8. Which of the following organs/tissues are preffered for virus isolation from chicken infected 3 weeks ago with IBV?
A. Pneumonia
B. Diffuse haem. in trachea
A. trachea
B. air-sacs
C. Necrotic foci in liver
C. lungs
D. Stunting and curling of the embryos
D. nasal passages
E. Pocks on the chorio- allantoic membranes
E. Cecal tonsils

18. 10. Which of the following sequence is true with respect to the degree of virulence of Holland, Massachusetts and Connecticut vaccine strains of IBV?
11. The HI test can be used to determine the humoral immune status to which of the following viral diseases? ND
ND and EDS
ND and IB
A. H120<Conn<Mass
ND, EDS and IB
B. H120<Mass<Conn
ND, EDS and IBD
C. Conn<Mass<H120
D. Conn<H120<Mass
E. Mass<Conn<H120

19. 12. Production of mis- shapen eggs in chickens is a feature associated with which of the following viral diseases?
13. Which of the following is NOT among the suggested causes of urolithiasis among commercial layers?
A. AE
A. Inf. With certain strains of IBV
B. EDS
B. Inf. With IBDV
C. IB
C. Certain mycotoxins
D. IB an EDS
D. High Ca++ diet during growing period
E. IB and AE
E. Water deprivation

20. 14. Quail bronchitis is caused by:
15. Layer and breedr flocks are sometimes boosted during egg production with live ND, and live IB vaccines. To maintain a protective level of immunity and also to avoid vaccine-induced drop in egg- production, it is recommended that the boosters be given every:
14. Quail bronchitis is caused by:
A. Adenovirus
B. Coronavirus
C. Herpesvirus
D. orthomyxovirus
E. paramyxovirus
2-4 weeks
4-6 weeks
8-10 weeks
12-14 weeks

21. E. Chicken inf. Anemia virus
16. In the serologic diagnosis of IB in the field, which of the following serologic test can be used with confidence to detrmine the serotype of the virus?
17. Certain strains of which of the following avian viruses are nephropathgenic?
A. ILTV
B. IBV
A. immuno-diffusion and ELISA
C. NDV
D. AEV
B. HI test and virus neutralization (VN) test
E. Chicken inf. Anemia virus
C. Immuno-diffusion, HI and VN tests
D. ELISA, HI and Virus neutralization (VN) tests
E. None of the above (A-D)

22. 18. Which of the following lesions usually occur in the reproductive organs of mature chickens infected during 1st wk of life with IBV.
19. Which of the following viruses is not enveloped and, therefore, may not be inactivated by detergents:
A. AIV
A. hypoplastic inactive ovaries
B. IBDV
C. IBV
B. Hypoplastia of the oividucts
D. ILTV
E. NDV
C. Thickening of the wall of the oviduct
D. Mis-shappen discolored ova
E. None of the above (A-D)

23. 20. Newly hatched chicks may be vaccinated in the hatchery with live vaccines for which of the following diseases?
A. ND
B. ND and IB
C. ND and ILT
D. IB and AE
E. ND, IB and AE

24. KEY to MCQs
1. E
2. B
3. D
4. E
5. C
6. C
7. B
8. E
9. D
10. C
10. C
11. D
12. C
13. A
14. A
15. C
16. E
17. B
18. B
19. B
20. B

25. False Layers
The term false layer has been used to describe a bird that has characteristics of bird in prod., visiting the nest regularly but not laying eggs.
Bird has normal-appearing ovary & oviduct, but after ovulation, infundibulum fails to engulf ovum.
At necropsy: excessive amounts of orange- colored fat & liq. Yolk/coagulated yolk in b. cavity.
Defect may result as a sequel to IB at early age