Infectious bronchitis

Occurrence: Worldwide.
Species affected: Chickens only.
Age affected: All, young are most susceptible.
Causes: Infectious bronchitis virus is a coronavirus, and is the most contagious viral respiratory disease in poultry.
Effects: Sneezing and watery eyes are seen early on, followed by depression, coughing and nasal discharge. Producing birds exhibit drop in egg production or weight gain. Eggs have poor shell quality and watery albumin. Layers also have ruffled feathers and wet droppings. Tracheal rales, gasping and urate diarrhoea are also seen.

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Causes

It is caused by a coronavirus.

Mode of transmission

Very contagious and spreads rapidly by aerosol. Contaminated faeces, litter and fomites spread the virus. It is one of the most contagious viral respiratory diseases in poultry.

Clinical signs

Sneezing and watery eyes are seen early on, followed by depression, coughing and nasal discharge. Poor egg shell quality, watery albumen, ruffled feathers and wet droppings are seen in laying birds. A drop in egg production and weight gain, tracheal rales, gasping and urate diarrhoea are also seen.

Infectious bronchitis

Postmortem lesions

Exudate in trachea, nasal turbinates, air sacs thickened or frothy and pneumonia can be seen. In young birds misshapen (nonpatent and hypoglandular) ova and oviduct, and yolk in abdominal cavity. Occasionally swollen pale kidneys with urates are found.

Diagnosis

Virus neutralisation,  HI or ELISA  test  for measuring antibody are helpful.  Virus isolation in embryos or chicken kidney cell cultures and/ or PCR are necessary for a definitive diagnosis. Curling, stunting and death of embryos can be seen in inoculated embryonating eggs. Respiratory signs and lesions with kidney lesions give a presumptive diagnosis. 

Treatment & control

Prevention
Vaccinate birds with multiple serotypes (depending on region) for broad spectrum protection.
Internationally, generally single vaccines are used (H120 or cloned type MA5) or Mass-Conn. In the US various vaccines contain the Ga or Ark subtypes as well. They are administered by spray at day of age in the hatchery or in the field by drinking water or spray. The viruses can be subtyped by real time PCR or using monoclonal antibodies and ELISA.