Infectious Bronchitis Virus (IBV) Group 3 coronavirus Main cause of economic loss in poultry farms Young chickens Broiler chickens Layers healthy chicks Signs occur after an incubation period of 18-48 hr. Spread to other birds is rapid, and morbidity may be nearly 100%. The nature and severity of the disease are influenced by the age and immune status of the flock and virulence of the causal strain. Young chickens cough, sneeze, and have tracheal rales for 10-14 days. Wet eyes and dyspnea may be seen, and facial swelling may also occur occasionally, particularly with concurrent bacterial infection of the sinuses. In broiler chickens, IBV infection is a major cause of poor feed conversion, reduced growth rate, and condemnation of meat at processing. Nephropathogenic strains can produce interstitial nephritis with high mortality (up to 60%) in young chickens. In most outbreaks, however, mortality is 5%, although secondary bacterial infections may cause higher losses. In layers, egg production may drop 5-50%, and eggs are often misshapen, thin-shelled, and contain watery albumen. Egg production and egg quality generally return to near normal levels in most birds on recovery. IBV-infected embryo normal embryo IBV-infected egg defect

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 - 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.

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

Taxonomy of the IBV The virus is a member of the genus Gamma coronavirus, subfamily Coronavirinae, family Coronaviridae, in the order Nidovirales.

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

Method of Spread Airborne aerosol from infected birds. Direct contact with short time carriers Contaminated premises

Mortality Respiratory IB usually not significant - 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. Young chickens cough, sneeze, dyspnea and have tracheal rales for 10-14 days. Wet frothy eyes with conjunctivitis - swollen Harderian gland. Facial swelling may also occur occasionally, particularly with concurrent bacterial infection of the sinuses. Depressed and cold Swollen head syndrome - the virus gets into the harderian gland located in the eyelid near the medial canthus. Secondary E. coli is involved.

TRT also causes a swollen head syndrome. Spread to other birds is rapid, and morbidity may be nearly 100%. In broiler chickens, IBV infection is a major cause of poor feed conversion, reduced growth rate, and condemnation of meat at processing. Nephropathogenic strains can produce interstitial nephritis with high mortality (up to 60%) in young chickens. In most outbreaks, however, mortality is 5%, although secondary bacterial infections may cause higher losses.

Clinical Signs LAYERS - Rales - snicks. Seldom have nasal or ocular discharge. Egg prodaction may drop 20-50%. Soft, misshapen and or rough surfaced shells. Shell problems may persist due to prior oviduct infection.

Postmortem Lesions CHICKS AND BROILERS Hyperemia of trachea Serous exudate in trachea Slight airsacculitis - severity varies with serotype of IBV. Ark causes airsacculitis. Tracheal plugs at the bifurcation

Postmortem Lesions PULLETS AND LAYERS Hyperemia of trachea Serous & catarrhal exudate of trachea Egg yolk peritonitis Salpingitis & permanently damaged oviduct. Infection of 2-3 week old pullets with IBV may cause infertility, salpingitis, and internal laying. Swollen kidneys with urates

Differential Diagnosis Newcastle Disease Laryngotracheitis - slow moving Infectious Coryza - swollen head Avian Influenza 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 - less cross reaction early in an outbreak but difficult to interpret later. VN - rises in titer between paired serum samples (2 wks. apart)

Diagnosis Isolation and identification of virus- embryonating eggs – stunting, curled, and hemorrhagic - vaccine strains are embryo adapted and often affect embryos on the 1st or 2nd 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, Ark. 99 and Fla 88 are used as vaccines. It is normal after administration of a live vaccine to have a reaction 5 days later. This reaction should be resolved within 5 days.

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

Prevention (Cont.) Parental antibody influences success of vaccination in young birds. High maternal antibody may block the viremia from the 1-day-old vaccination but the Harderian gland is exposed and produces local protection. It is often applied in a spray cabinet. Chick will rub eye on vaccine moistened feathers. Therefore most breeders should have consistent antibody titers. These titer levels can be used as a guide for proper vaccination time in the progeny.

Prevention (Cont.) This involves a series of live and/or killed vaccines or a live vaccine every other month throughout the lay cycle. Progeny can be vaccinated at 2 wks. of age no matter what the parental antibody titers are at hatching. Even chicks that had high maternal antibody at 1-day of age will be susceptible. Those who responded to the 1-day vaccination may have a buffered vaccine response.

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