Infectious bronchitis In Poultry

Infectious bronchitis is a sudden, rapid, highly contagious disease of chickens characterized by abnormal respiratory sounds, coughing, and sneezing. It is an important disease of young chicks, causing high mortality. The virus may also affect kidneys. In laying birds, the disease causes great economic loss through reduced egg production and poor eggshell quality. Both in broilers and layers, infection causes poor weight gain and feed efficiency. Birds of all ages are susceptible but the disease is most common in young chicks, causing some mortality.

Cause

A virus - called coronavirus. The virus survives outside the bird under farm conditions for weeks to months. However, it is rapidly killed by common disinfectants.

Spread

I. By the air. As the virus is easily spread by air, inhaling infected air is the most important means of

spread. However, spread through infected faeces may also be important.

2. Spread by people and virus-contaminated materials can occur.

3. Carriers (birds which carry infection without showing symptoms) also spread the disease. Birds may shed the virus for up to 4 weeks after recovery.

Symptoms

I. The respiratory form is the most common in birds of all ages. The symptoms include abnormal respiratory sounds, severe respiratory distress, gasping and sneezing, watery nasal discharge, and sometimes eye discharge and facial swelling.

2. In the reproductive form, there is reduced egg production. Drop in production may sometimes be more than 50%. Egg production may become normal after 3-4 weeks, but there is a fall in egg quality. Eggs may be smaller, deformed, shell-less , or have calcium containing deposits on the surface. Inside, the albumen loses its viscosity. That is, the albumen is thin and watery, without clear-cut demarcation between the thick and thin albumen of the normal fresh egg.

3. In the kidney form, there is marked depression usually with respiratory symptoms, and mortality as high as 30% in the severe form.

Postmortem Findings

In the mild respiratory form, there is excess mucus in the respiratory tract. In the more severe form, a

caseous plug may be found in the lower trachea or bronchi of chicks that die. In the kidney form, the kidneys are swollen and pale. The ureters are distended with urates. In some birds there is visceral gout, in which case white granular material (urates) may coat the internal organs (see 'visceral gout').

Diagnosis

I. Symptoms and postmortem findings may be suggestive, but are not diagnostic.

2. Infectious bronchitis must be differentiated from Ranikhet disease and infectious coryza. Ranikhet disease is more severe, and in layer flocks drop in egg production is more than with infectious bronchitis. Infectious coryza can be differentiated on the basis of facial swelling which occurs only rarely in infectious bronchitis.

Treatment

There is no specific treatment for infectious bronchitis. In mixed infections, use antibiotics against E. coli and mycoplasma. In the kidney form of disease, administer electrolytes in the drinking water.

Control

I. Management can be helpful if proper attention is given to maintaining proper ventilation of chicks.

2. As treatment is of no value and because this virus is so commonly present everywhere and spreads rapidly, control depends on increasing resistance of flocks by vaccination. Both live and killed vaccines are available and both have been shown to be of value.