Infectious Bronchitis

Suggested By - Submitted By –Dr A.K. Srivastava Pratiksha SrivastavaDr Neeraj Gangwar 3rd Yr, 6th Semester B.V.Sc & A.H Department Of Veterinary Pathology, DUVASU

Introduction• First reported in 1931 in U.S.A.• Highly infectious & contagious respiratory

disease.• Great economic importance due to adverse

effect on production.• Caused By – IB Virus ( Corona Virus )• Corona Virus – Enveloped, pleomorphic,

Positive Sense ssRNA virus, pear shaped peplomers present on envelope which lacks matrix protein.

• Capsid on virus show crown like pattern.• Helical Symmetry present.

Replication of Coronavirus

Serotypes Of Virus• Massachusetts Affinity for

respiratory Tract• Connecticut• T • Gray Nephrotoxic Nature• Holte

Hosts • Chicken – Naturally infected.• Respiratory form – more severe in chicks.• Nephritic Form – seen in birds under 10

wk of age.

Spread• Direct airborne transmission – most common.• Via Infected Faeces.• Through fomites.• Transmission via egg – exceptional.

Forms Of Disease• Respiratory• Nephritic• Genital• GIT ( Enteropathogenic Form )

PathogenesisVirus readily infects respiratory

tract ,intestinal tract, kidneys and oviducts.New virus start to appear 3 to 4 h after

infection.Maximum output reaches in 12 h.In many cases recovery occurs unless

chickens are very young or air sacculitis develops from secondary bacterial infections.

Air Sacculitis

SignsRespiratory Signs – Rales, gasping, sneezing,

watery nasal discharge, lachrymation & swelling. Chicks huddle under source of light.

Genital Form – Cystic dilatation in oviduct, thin shelled misshaped eggs, Watery albumin, Internal ovulation may occur.

Watery Albumin

Nephritic Form – Marked depression

Enteropathogenic Form - Diarrhoea

LesionsGross – Caseous plug in bronchi at point of entry in

lungs.Air sacs may appear cloudy, may contain yellow

caseous exudate.Bronchial mucosa very much thickened.Ureters filled with white chalky substance

( urates ).Juction of isthmus & magnum get atrophied.

White Caseous Plug in Bronchi Accumulation Of White Urates

Microscopic –Tracheal mucosa – oedematous, loss of cilia,

rounding & sloughing of epithelial cells.Interstitial nephritis in kidney, granular

degeneration, vacuolation & desquamation of tubular epithelium ( prominent in medula ), focal areas of necrosis, ureters distended with urates.

In oviduct – decrease in height & loss of cilia from epithelial cells, dilation of tubular glands.

Oedema in Trachea Ureter distended with Urates

DiagnosisOn the basis of symptoms & lesions.Isolation & Identification of virus.Samples to be collected – trachea, bronchi,

caecal tonsils.9 – 11 days old Embryonated chicken egg

inoculation via allantoic sac route – after 3-4 days curling & dwarfing of embryo is seen.

Tracheal Organ Culture (TOC)Immunoperoxidase AssaysAb detection by – VNT, ID,

Immunoflourescence, ELISA.

Thickened amnion & Allantois Stunting & Curling Of embyoes

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