POULTRY MED L6: Infectious Bronchitis (IB)

Avian infectious bronchitis (IB)

is an economically important, highly contagious, acute, upper‐respiratory tract disease of chickens and other fowl

gammacoronavirus

Avian infectious bronchitis (IB) is caused by the avian ___

infectious bronchitis virus (IBV)

causative agent of Avian infectious bronchitis (IB)

inhalation or direct; fomites

The virus is found worldwide and is transmitted by __ or __ contact with infected birds or contaminated litter, equipment, or other __

respiratory

The disease is characterized by __ signs, reduced weight gain, and reduced feed efficiency in meat‐type broiler chickens infected with the virus

airsacculitis, pericarditis, and perihepatitis

Infection also predisposes broilers to secondary opportunistic bacterial infections that can result in __, __, and __

100%

Morbidity is almost always __, but mortality can vary depending on the age and immune status of the birds, the strain of the virus, and if secondary bacterial or viral pathogens are involved.

nephropathogenic

Some strains of IBV are ___ and can cause high mortality due to kidney failure in susceptible birds

70%

In layer and breeder chickens, infection may result in reduced egg production of up to __ and declines in eggshell quality

oviduct

The virus can replicate in the ___ and cause permanent damage in young hens resulting in limited egg production over a prolonged period of time and birds that fail to come into production (false layers).

pale; watery

Eggs from breeds with pigmented shells may become __, and the albumen can have a __ viscosity

chicken

The __ is the major host, but IBV, or IB-like viruses, also infect turkeys, pheasants, peafowl, guinea fowl and probably other galliforms

all ages

Infectious bronchitis is primarily a disease of chickens with __ being susceptible to infection

1. virus strain and type,

2. sex and age of the chicken,

3. immune status (vaccination, immunesuppression, and maternally derived antibodies),

4. coinfections, and

5. environmental circumstances such as climate, dust, ammonia, and cold stress

The pathogenicity of IBV can vary widely between strains. The clinical outcome of an infection in chickens depends on many variables such as these 5 factors

18–36

In susceptible chickens, infection of the upper respiratory tract is seen after an incubation period of ___ hours

10–14

The most common clinical signs include sneezing, coughing, tracheal rales, catarrhal exudate in the trachea, nasal cavity and sinuses, lacrimation, reduced weight gain and morbidity (up to 100%). Some mortality may occur, depending on the incidence of secondary infections. In an uncomplicated infection, recovery occurs within ___ days.

Secondary infections

increase the duration and severity of clinical signs

Colisepticemia

Escherechia coli infections occur in broilers when stocking density is high and when ventilation levels are suboptimal

Good management

is essential to reduce the incidence of colisepticemia

chilling at the brooding stage and immunosuppression

Other important predisposing factors include __ and __

sloughing off

Post-mortem findings include lymphocytic infiltration and edema of the epithelium, deciliation and __ of the tracheal mucosa. Lungs may be congested.

asphyxiation

Airsacculitis, pericarditis and perihepatitis are common following colisepticaemia, and caseous plugs of mucus in the primary bronchi may occur, causing ___.

Poor ventilation

leads to build up of dust and ammonia fumes

Renal infection

Where this occurs it usually follows respiratory infection in broilers, commonly at 3–6 weeks, often affecting only a small percentage of the flock

30%

Clinical signs include depression, scouring, and wet litter as a result of increased water intake. Mortality may be minimal but can reach __.

visceral gout

Kidneys are pale, swollen and blotchy with distended tubules that appear white due to deposition of urates. Deposition of urate crystals on internal organs (__) may occur

egg laying

Respiratory signs may be seen, but more commonly IBV affects ___ performance

70%

Drops of up to __ in egg production may occur in fully susceptible hens, lasting at least 4–6 weeks

cystic oviducts

Infection with some IBV variants at a very young age may result in permanent oviduct damage, including ___ often associated with ‘false layers’

egg peritonitis

The oviduct may appear normal, but deposits of yolk may accumulate in the abdomen - ‘___’

Depigmentation

Poor internal egg quality (watery whites) and poor shell quality (thin, pale, misshapen and cracked eggs) are common. __ of the shell may occur.

oviduct

On post-mortem examination, the __ may appear normal, or may have regressed with metaplasia of the epithelium, glandular dilation, lymphocytic infiltration of the subepithelium, proliferation of lymphoid follicles and fibroplasia.

ovarian follicle

The __ may be flaccid

highly

IBV is __ infectious, only a few virus particles being needed to initiate infection

feces

During clinical infection large quantities of virus are shed from the respiratory tract and via the ___

cecal tonsil

Virus is shed for several weeks after infection and may persist in the intestinal tract, possibly the ___, since the virus has been recovered from experimentally infected chickens for up to a year after infection

lipid solvents, alkalis, many disinfectants, 1% formalin and heating

Outside the host the virus is readily destroyed by ___, ___, many __, and __ at 56°C for 15 min

Clinical Signs / Gross lesions

__ / __ are not definitive

Virus Isolation

Gold Standard (but slow)

RT-PCR, rRT-PCR

modern standard (rapid)

ELISA

most widely used serologic test

1. Newcastle disease

2. LPAI

3. Infectious Laryngotracheitis

4. Infectious Coryza

4 Differential Diagnoses

live and inactivated

Both __ and __ virus vaccines are used for IBV immunization

Live vaccines

__ are used in meat type (broiler) chickens and for the initial vaccination and priming of breeders and layer pullets. Applied by mass application methods. (Coarse spray, aerosol, drinking water).

True

T or F: No specific treatment exists for IB

heat

Provision of additional __ to eliminate cold stress, good air quality, elimination of overcrowding, and attempts to maintain feed consumption to prevent weight loss are flock management factors that may help reduce losses from IB

antibiotics

Treatment with appropriate __ may be used to aid in reducing the losses from airsacculitis resulting from infection by secondary bacterial pathogens

nephritis

In case of clinical ___, a decrease in protein levels in the food and a supply of electrolyte replacers in the drinking water might be helpful to compensate for the acute loss of sodium and potassium and thereby reduce mortality from this condition.

72 mEq

The recommended concentration for treatment is ___ of sodium and/or potassium, with at least one‐third in the citrate or bicarbonate salt form