Infectious Bronchitis Virus IBV Group 3 coronavirus

Infectious Bronchitis Virus (IBV) • Group 3 coronavirus • Main cause of economic loss in poultry farms • • • Young chickens Broiler chickens Layers healthy chicks IBV-infected egg defect IBV-infected embryo normal embryo

Infectious Bronchitis • An acute, highly contagious respiratory disease of chickens. • All ages infected; particularly a problem in laying flocks. • Chicks - growth suppression & predisposition to other diseases. • Hens - variable production loss and affects egg quality. • Turkeys resistant.

Etiology • Coronavirus - The positive sense RNA - heat sensitive. • Many serotypes and strains with great antigenic variation have been identified. • Mass 41 & Conn 46 are used as vaccine and protect against closely related serotypes. • Different strains affect different organ systems: respiratory, renal, reproductive. • Some important field strains are JMK, Ark. 99, Fla. 88, Holland, 072, GA variant, and many others. • The QX type virus causes a severe disease including nephritis in young birds, high mortality, respiratory distress in broilers and drops in egg production in breeders and layers (false layer syndrome). • In Iraq CH Baghdad F 1 2013, CH Babylon F 2 2013 were genetically close related with variant strain IB Egypt 12177. 1 FSP 1 and IS/885 and IS/1494/06.

Taxonomy of the IBV • • Infectious bronchitis virus belongs to the order Nidovirales. family Coronaviridae. genus Gammacoronavirus. The Coronaviridae comprises two genera, Corona virus and Toro virus. • Corona viruses are divided in to three groups, IBV is placed in group three.

Incubation Period • 18 -36 hours - used in diagnoses. • Rapid spreading and highly contagious.

Course of Disease 1 -2 weeks, secondary problems can linger. Predisposes birds to chronic respiratory problems.

Method of Spread Airborne aerosol from infected birds ( respiratory tract). Direct contact with short time carriers. fecal transmission and fomites. Virus shedding lasting for several weeks after infection and persistent carriers may be present. • Disease also transmitted through materials, equipment and movement of field worker from the infected flocks to health farm also movement of live birds. • Wild birds may play a crucial role as reservoirs and long-distance carriers of IBV. • •

Mortality • Respiratory IB usually not significant but in recent year high mortality nots - although tracheal plugs at the bifurcation cause asphyxiation. • Some serotypes can cause serious airsacculitis. • Depends on secondary infection such as Mycoplasma. • Nephrotropic strains may cause high mortality in chicks and layers. Causes urolithiasis. • Nephrotropic strains include Holt and Gray.

Clinical Signs CHICKS – The nature and severity of the disease are influenced by the age and immune status of the flock and virulence of the causal strain. The main clinical signs were restless and huddled together, difficult in breathing, gasping, coughing, sneezing, tracheal rales, nasal discharge, wet eye and swollen sinus, ruffled feathers, morbidity up to 100% • Facial swelling may also occur occasionally, particularly with concurrent bacterial infection of the sinuses. • Depressed and cold decrease of feed intake and conversion, loss of body weight • increased water intake, wet droppings, depression, lethargy and poor growth in broilers

Nephropathogenic strains can produce interstitial nephritis with high mortality (up to 60%) in young chickens. In most outbreaks, although secondary bacterial infections may cause higher losses.

Clinical Signs LAYERS • Rales and seldom have nasal or ocular discharge. • Egg production may drop 20 -50%. • mainly affects egg quality (thin, rough, fragile, misshapen egg shells and thin watery egg) and causes decrease in egg production In some cases the virus infection may cause severe damage to the oviduct and result in decreased or permanent loss of egg production

Postmortem Lesions CHICKS AND BROILERS • Infected chickens have serous, catarrhal or caseous exudates may be seen in the trachea, nasal cavity and sinuses • Congested blood vessels in trachea and caseous plugs of mucus in the primary bronchi (Tracheal plugs at the bifurcation)may followed secondary infection and cause asphyxiation. Lungs may appear congested and airsacculitis is common Slight airsacculitis - severity varies with serotype of IBV. Ark causes airsacculitis. • Nephropathogenic strains, the kidneys become pale and swollen and urate deposits may form in the kidneys and ureters

Postmortem Lesions PULLETS AND LAYERS • Hyperemia of trachea • Serous & catarrhal exudate of trachea • the ovarian follicle may be flaccid, Deposition of yolk material in the peritoneal cavity (egg peritonitis) is common Salpingitis & permanently damaged oviduct. • Infection of 2 -3 week old pullets with IBV may cause infertility, salpingitis, and internal laying. • Swollen kidneys with urates • Necropsy finding of bird infected with QX strain frequently showed either cystic oviduct with watery contents that could exceed one liter or partially atrophic oviduct with large cystic dilatation.

Differential Diagnosis • • • Newcastle Disease Laryngotracheitis (ILT) - slow moving Infectious Coryza(Haemophilus gallinarum) - swollen head Avian Influenza turkey rhinotracheitis (TRT) also causes a swollen head syndrome

Diagnosis • History of fast spreading respiratory disease • ELISA - uses Mass. antigen but get cross reaction with other serotypes. • HI - IBV is treated with neuraminidase enzyme before testing because IBV is not naturally hemagglutinating. • VN - rises in titer between paired serum samples (2 wks. apart) • Agar-gel precipitation test (AGPT)

Diagnosis • Isolation and identification of virus- embryonating eggs – stunting, curled, and hemorrhagic - vaccine strains are embryo adapted and often affect embryos on the 1 st or 2 nd passage whereas field strains may require additional passages before lesions appear. • Identification of IBV serotype - PCR, monoclonal antibody test, etc. • Detection of virus genome (RT-PCR)

Stunted, Curled Embryos

Prevention Establish and enforce a biosecurity program. Vaccination - complete prevention of IB is difficult because of variation of field strains and the ability of the virus to change. There is little cross protection between serotypes.

Prevention (Cont. ) VACCINES: LIVE - Monovalent - usually Mass Bivalent - Mass. & Connecticut Other attenuated strains such as Holland and. Ark. 99 are used as vaccines.

Prevention (Cont. ) VACCINES: KILLED - used in breeders and layer pullets to prevent production losses and produce consistently high antibody titers.

Prevention (Cont. ) • Management Procedures • Ideal management includes strict isolation, high biosecurity, and repopulation with only day-old chicks following the cleaning and disinfection of the poultry house and equipment in contact with poultry or poultry litter and removal of the feces from the premises.

Treatment: § None for the virus (acyclovir, amantadine) § Broad spectrum antibiotics for secondary bacterial involvement