Infectious bronchitis

• Infectious bronchitis (IB) is a viral d2 affecting chickens of all ages world wide
• Chickens are the only sps reported to be naturally affected
• highly infectious and contagious respiratory d2
• Great economic imp due to adverse effect on production

    Etiology :

                      IB virus (coronavirus)

• Enveloped , pleomorphic , +ve sense ssRNA virus , pear shaped peplomers present on envelopes which lack matrix proteins.
• Vaccine and field strains of IBV may persist in caecal tonsils of intestinal tract and can be excreted in faeces for weeks or longer in clinically normal chicken

  Transmission:

• Ib is highly contagious
• IP = 18 – 36 hrs
• O2 spreading through on entire flock within one or two days

a. Horizontal :-

• Aerosol transmission (sneezing)
• Contaminated organic material ,drinking water and equipment

b. Vertical :

• It  has been shown to be imp 
• However ,surface contamination of eggs with IB virus is a possible way by which virus can be spread in hatcheries or egg packing stations.

Forms of disease :

• Respiratory = more severe in chicks
• Nephritic =  seen under 10 week of age
• Genital
• GIT [enteropathogenic form]

Pathogenesis:-

• IBV internally infects and reproduces in URT causing loss of productive calls lining sinuses and trachea.

                ⬇

   blood[brief viremia]

                ⬇

Virus can be detected in kidneys , reproductive tract and caecal tonsils

• Some strains of IBV ,referred to as nephropathology, are known to cause lesions in kidneys.
• Renal damage associated with different IB stains is an increasingly important feature of IB infection especially in broilers.
• In many cases recovery occurs unless chickens are very young or air saccilims develops from secondary bacterial infections.
• Most severe clinical sign are seen in chick younger than 6 weeks of age

Clinical sign :-

• Young chickens are depressed and huddle under heat source

a. Respiratory signs :-

• Gasping
• Coughing
• Tracheal rules
• Nasal discharge
• Lacrimation and swelling

b. Urinary form :- water intake , depression , scouring .wet litter

c. Genital form :-

• Cystic dilation in oviduct
• Thin shelled misshapen egg
• Watery albumin
• Internal ovulation may occur

d. Enteropathogenic form :- DIarrhoea

 PM Lesions

• lesions are found in respiratory tract and urinary tract

a. Respiratory :

• air savvusins serious or caseous exudate in trachea , nasal passage and sinus
• Bronchial mucosa are very much thickened
• Cloudy air sac which may contain yellow caseous exudate
• Pneumonia

 b. Urogenital:-

• Swollen, pale kidneys, with distended tubules and ureters containing urate crystal in neuropathologic forms
• Fluid yolk material may be found in abdomen of birds in production
• Degeneration of ovary and swollen oviducts
• Junction of isthmus and magnus get atrophied

MICROSCOPIC:-

• Tracheal mucosa : edematous , loss of cilia , rounding and sloughing of epithelial cells
• Interstitial nephritis in kidneys, granular degeneration vacuolation and desquamation of tubular epithelium ( prominent in medulla ), focal areas of necrosis , ureters distended with urates
• Oviduct = decrease in height and loss of cilla from epithelial cells dilation of tabular glands

 DIAGNOSIS

• Symptoms and lesions
• Isolation and identification of virus
• Tracheal organ culture
• Tmmunoperoxidate assays
• Ab detection = VNT ,ID ,immunofluorescence , ELISA
• Virus neutralization

DDX

• Newcastle disease
• Mycoplasmosis
• Vaccinal rxn
• Avian influenza
• laryngotracheitis