Infectious Bronchitis(IB) is present worldwide, it is a highly contagious, acute, and economically important disease. IB is caused by an Avian Coronavirus. In the field, several different IB serotypes have been identified including the classic Massachusetts type and a number of variants such as IB 4/91, QX, Arkansas and Connecticut.
Transmission
The virus is transmitted rapidly from bird to bird through the airborne route. The virus can also be transmitted via the air between chicken houses and even from farm to farm. The incubation period is only 1-3 days.
Species affected by Infectious Bronchitis
Chickens are the primary poultry species that is susceptible to IB-virus, but quail and pheasants can be affected. Recent discovery of IB virus in other species without clinical signs indicates that other species may act as vectors.
Clinical signs of Infectious Bronchitis
In young chickens the respiratory form appears with gasping, sneezing, tracheal rales and nasal discharge. Generally chicks are depressed and show reduced feed consumption. Mortality in general is low unless infection gets complicated with secondary bacterial infections (like E.coli).
In case of a nephropathogenic type of IB virus generally birds, after initial respiratory signs, are more depressed, show wet droppings resulting in wet litter, increased water intake and increased mortality. In adult “laying” birds (layers and breeders) after initial respiratory signs the affected flocks show a drop in egg production and a loss of egg quality (shell deformation and internal egg changes) resulting in more second class eggs, affecting the hatchability rate of fertile eggs and day-old chick quality.
A specific condition, called “false layers” is related to the QX type of IB; usually flocks do not peak in egg production and many birds show a “penguin-like posture” .
Post mortem lesions
In young chicks a yellow cheesy plug at the tracheal bifurcation is indicative of IB infection. In case of nephropathogenic infections pale and swollen kidneys and distended ureters with urates are found In older birds mucus and redness in the trachea, exudate in the air sacs, and various changes in the oviduct depending on the time and severity of infection. In case of “false layers” permanent lesions in the oviduct make egg production impossible. The oviduct will be blocked and filled with fluid (cysts) or never developed into an active oviduct.
Diagnosis
Clinical signs and post mortem lesions in a flock followed by laboratory confirmation based on virus isolation and identification with PCR. Serology based on paired blood samples using HI, Elisa or VN tests.
Treatment
There is no treatment for Infectious Bronchitis (IB).
Antibiotics are used to control secondary bacterial infections.
Prevention
Vaccination with strain specific or cross protective live vaccines, and for layers and breeders the addition of inactivated vaccines at point of lay to induce long lasting systemic immunity.
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Recommended Vaccines for Infectious Bronchitis (IB)
