Infectious bronchitis (IB) is a highly contagious respiratory disease in chickens caused by an avian coronavirus called infectious bronchitis virus (IBV)

1. INFECTIOUS BRONCHITIS

2. DEFINATION
 Acute or subacute, highly infectious and
contagious viral upper respiratory disease
Characterized by
 Tracheal rales
 Coughing
 Sneezing
 Nephritis
 Drop in egg production & quality in laying
flocks

3. HISTORY
 1930 ----- Firstly observed in North Dakota
(U.S.A.) as respiratory disease of young
chicks
 1940s ---- Egg production declines in laying
flock was reported to be associated with IB
 1960s -----Kidney lesions in IB were reported

4. ETIOLOGY
 Infectious bronchitis virus
 Family: Coronaviridae
 Genus: Coronavirus
 Characterstics:
 RNA virus (SS +ve)
 Enveloped
 Sensitive to common disinfectants
 Three major virus specific proteins; Spike(S), Membrane glycoprotein
(M) & Internal nucleoprotein (N)
 Strain classification is based on Spike(S) protein
 Serotypes:
 Maasachusetts
& Connecticut Proclivity for respiratory tract
 T, Gray & Holte Nephrotropic

5. ETIOLOGY
 Coronavirus "sun like" appearance under the
microscope.
 The virus possesses a positive stranded RNA
genome that encodes phosphorylated
nucleocapsid protein (N), membrane
glycoprotein (M), spike glycoprotein (S) and
small membrane protein (E).

6. TRANSMISSION
 Sick bird excretes virus through
 Respiratory system
 Faeces
 Horizontal
 Aerosol
 Faecal contamination
 Contamination of personal or equipment
 Vertical: Not reported
 Infectious bronchitis virus is highly contagious and spreads rapidly among
chickens in a flock
 The disease has a short incubation period: Susceptible birds placed with
recently infected chickens usually develop clinical signs within 24–48
hours

7. SYSTEMS INVOLVED
• It affects the
• Respiratory,
• Renal (kidney) and
• Reproductive systems
• Morbidity 100%
• Mortality 25-30%
• Incubation period
• Natural :- 3-10 days
• Exp:- 18-36hrs

8. CLINICAL SIGNS
 Characteristic respiratory signs in chicks
 Gasping, coughing, sneezing, tracheal rales & nasal discharge
 Depressed, huddled under the heat source
 Decreased feed consumption & weight gain
 Renal signs (Nephritis)
 Reproductive signs (in layers)
 In laying flock, decline in egg production (decrease 50%) &
quality
 Hatchability decreases
 Soft shelled, misshapen & rough shelled eggs
 Thin & watery albumin (ca deposition in the egg may be
disrupted)
 Blind or false layers

9. PATHOGENESIS
 Virus can replicate in tissues of respiratory tract (bronchits,
pneumonia), intestinal tract, kidneys and oviduct.
 Virus replication in kidney produced necrosis of tubular cells-----
gout
 Virus replication in oviduct produced atrophy of epithelium.
 Replication occurs in cytoplasm.
 Virion formation occurs by budding process at the membranes of
the endoplasmic reticulum, not at the cell surface.
 Virion accumulate in smooth vesicles, but the mechanism for
their release from the cell is unknown.

10. GROSS LESIONS
Respiratory system:-
 Serous, catarrhal or caseous exudate in the trachea, nasal
passages & sinuses
 Air sacs may appear cloudy or contain a yellow caseous
exudate
 A caseous plug in the lower trachea or bronchi of dead birds
 Pale kidneys often distended with urates
 (urolithiasis may be seen)

11. Microscopic changes
 Trachea and bronchi: inflammation and degeneration changes
 Air sacs: edema, epithelial desquamation, fibrinous exudate
 Oviduct: epithelial damage, dilatation of tubular glands,
infiltration of inflammatory cells, proliferation of lymphoid
follicles
 Cystic oviduct
Uremic form:-
 Kidney: interstitial nephritis, degenerative changes, urolithiasis,
urates in ureter
 Egg yolk peritonitis (fluid yolk material may be found in the
coelomic (abdominal) cavity).

12. Thickening of air sacs walls with heterophils and macrophages present
in the airsac lumen. Peripheral to the airsac, edema and inflammation.

13. Tubulointerstitial nephritis

14. Kidney slides

15. DIAGNOSIS
 Clinical history & gross lesions
 Isolation & identification of the causative organism
 Site for sample collection
 Trachea, caecal tonsils
 Serology
 ELISA
 HI
 Immunodiffusion
 Virus neutralization
 RT-PCR

16. DIFFERENTIAL DIAGNOSIS
 ND: Nervous signs are observed; drop in
egg production in laying flocks may
be greater than IB
 ILT: It spreads more slowly & respiratory
signs may be more severe with IB
 Infectious coryza: Facial swelling is
commonly seen
 EDS: Internal egg quality is not affected
in EDS

17. TREATMENT AND CONTROL
 ONLY SUPPORTIVE THERAPY
 Biosecurity AND the service of
diagnostics, utilizing qualified veterinary
supervision and laboratory support
 The virus, which may survive 4 weeks
in premises, is sensitive to solvents,
heat (56°C for 15 mins), alkalis,
disinfectants (Formal 1% for 3 mins).

18. CONTROL
 Strict isolation
 Biosecurity
 Proper disinfection & cleaning of poultry
house
 Immunization
 Live vaccine for broilers & for initial vaccination in
breeders and layers
 Inactivated oil-emulsion vaccines are used at time
of laying in layers and breeders

19. vaccination
 BOOSTER SHOT
AT DAY 10,
AND DAY 21

20. Abundant mucus secretion in the trachea of a broiler chicken with
infectious bronchitis.

21. Nonfunctional ovary, full of clear fluid, in a mature laying hen