Infectious Bronchitis in Chickens: Causes, Signs & Control

Infectious Bronchitis, also known as gasping disease, is a highly infectious respiratory disease that affects chickens of all ages. This article explores the causes, transmission, clinical signs, and prevention of this disease. Additionally, the economic losses associated with Infectious Bronchitis are discussed.

Causes of Infectious Bronchitis:

Infectious Bronchitis is caused by a virus and can be transmitted through aerosol inhalation or ingestion of contaminated feeds and water. The virus responsible for the disease is known as Coronavirus, which consists of different serotypes with varying antigenic characteristics. It is worth noting that the infectious bronchitis virus is not highly resistant and easily loses its infectivity under adverse conditions.

Transmission of the Disease:

The virus spreads among chicken flocks primarily through inhalation, i.e., aerosol transmission. It can also be transmitted through contaminated equipment and personnel. Egg transmission is not commonly reported. Additionally, the disease can spread between flocks and farms through the air.

Species Affected:

Chickens are the natural hosts for Infectious Bronchitis, and birds under 10-12 weeks of age are generally more severely affected than older birds. Maternal immunity through vaccination provides some protection to birds.

Clinical Signs:

The most common clinical manifestation of Infectious Bronchitis is a respiratory syndrome, which includes symptoms such as rales, gasping, sneezing, and watery nasal discharge.

In young chicks, depression, huddling together under the heat source, reduced feed consumption, and poor feed conversion may be observed.

Laying flocks experience a significant decrease in egg production, often by 50% or more, accompanied by poor egg quality.

Affected birds lose their youthful appearance, exhibit worn-out feathers, and may start molting.

The disease can also manifest as the uraemic form, primarily affecting birds of 3-6 weeks of age, with symptoms including respiratory distress, depression, dehydration, ruffled feathers, and watery diarrhea.

Mortality rates depend on the virulence of the virus serotype and the immune status of the birds.

Summary of Symptoms:

The symptoms of Infectious Bronchitis include gasping and coughing (resembling laryngotracheitis), eye and nose discharges (similar to coryza), and a decline in egg production in laying flocks.

Unlike Newcastle disease, Infectious Bronchitis does not present nervous symptoms. Young chicks are particularly susceptible to high mortality rates.

Egg production in affected laying flocks may drop as low as 5% and remain below normal for about six weeks. The virus also affects the reproductive system, leading to rough egg shells and watery egg whites.

The disease can spread from infected to non-infected birds and may be transmitted through eggs, resulting in unhatched embryos.

Postmortem Lesions:

Postmortem examinations reveal serous exudates in the trachea, hyperaemic tracheal mucosa, nasal passages, and sinuses. Cheesy plugs may be found in the lower trachea or at the bifurcation of the bronchi. Mild air vasculitis and pneumonia may also be observed. Additionally, poor egg quality, watery egg albumin, and permanent damage to the oviducts in birds are common. In cases where nephrotoxic strains affect birds, pale kidneys with distended ureters can be seen, and severe cases may present visceral gout as white chalky material on the liver, heart, and air sacs.

Differential Diagnosis:

In the field, Infectious Bronchitis may resemble Infectious Laryngotracheitis (ILT). Laboratory tests are necessary for accurate diagnosis.

Treatment:

Currently, there is no known cure for Infectious Bronchitis. However, providing a comfortable environment for the affected birds can help reduce stress and alleviate the severity of the infections. It is crucial to isolate infected birds to prevent further spread of the disease.

Additionally, improving ventilation in poultry housing is recommended.

Note: Strict biosecurity measures should be implemented to minimize the risk of introducing the virus to the flock. Antibiotics can be administered to combat secondary bacterial infections, and vitamin supplementation can support quick recovery in affected birds.

Prevention and Control:

An effective vaccination program is essential in preventing Infectious Bronchitis. Good management practices, such as maintaining strict hygiene through regular cleaning and disinfection, are vital in controlling the disease.

Common vaccine strains used include Massachusetts, Connecticut, and Holland, and the vaccination program may vary based on the specific strain prevalent in the area.

Economic Losses of Infectious Bronchitis:

Infectious Bronchitis can lead to significant economic losses in the poultry industry. Infection at an early age can result in damaged oviducts, leading to false layers. Breeding flocks may experience an increase in unsuitable hatching eggs and reduced hatchability.

Commercial layers may suffer from a drop in egg production and poor-quality eggs. In some cases, production levels may never fully recover, necessitating the culling of affected birds.

Broilers may also be adversely affected, exhibiting poor feed conversion and reduced weight gain, potentially leading to condemnations.

Conclusion:

Infectious Bronchitis is a highly contagious respiratory disease that affects chickens of all ages. It is characterized by respiratory symptoms, reduced egg production, and poor egg quality. The virus is easily transmitted through aerosols, contaminated equipment, and personnel.

Effective prevention and control strategies, including vaccination, strict biosecurity, and proper management practices, are crucial in mitigating the impact of the disease on poultry farms.

By understanding the causes, clinical signs, and preventive measures associated with Infectious Bronchitis, poultry farmers can take proactive steps to protect their flocks and minimize economic losses.