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Infectious Bronchitis

Other Names: Avian Infectious Nephrosis

Infectious bronchitis (IB) is a widespread rapidly spreading, highly contagious respiratory infection caused by a coronavirus. It primarily affects the chicken's upper respiratory tract, although sometimes it spreads to the renal and reproductive systems. There are several types of vaccines available, however the emergence of multiple strands of the virus have made control difficult.

Outbreaks of infectious bronchitis frequently occur worldwide, even in vaccinated flocks. The disease spreads rapidly among chickens in a flock, resulting in all birds eventually becoming infected, in a short period of time. Susceptible birds placed with infected chickens usually develop clinical signs of illness within 24–48 hours. Chickens of all ages and breed types are susceptible to IBV infection, but the extent and severity of the disease is pronounced in young chicks, compared to adults. Similarly, resistance to infection was suggested to increase with increasing age

What are the Signs of Infectious Bronchitis?


Infectious bronchitis predominately infects the upper respiratory system, resulting in sneezing, gasping, coughing, tracheal rales, nasal discharge, sometimes wet eyes, and occasionally swollen sinuses. Chicks may appear depressed and be seen huddled under a heat source. Laying chickens affected will show a drop in egg production for about two weeks. The eggs often have irregular and roughened eggshells with watery albumin. Watery albumen with yolk separated from thick album (eggs). Infectious bronchitis resembles several other acute respiratory diseases such as Newcastle disease, infectious laryngotrancheitis, low pathogenicity avian influenza, and infectious coryza.

What are the potential complications of infectious bronchitis?


  • Secondary bacterial infections: IBV damages the chicken's respiratory epithelium, often predisposing young chicks to secondary infections with pathogenic bacteria, such as Escherichia coli and Mycoplasma spp. Two of the most common secondary manifestations resulting from E. coli infection in chickens, following IBV infections are airsacculitis and systemic colibacillosis.
  • Kidney damage: Some strains of IBV are nephrogenic, meaning that after replicating in the bird’s trachea (and causing respiratory disease), the virus will then spread to the kidneys (causing nephritis—or inflammation of the kidneys). Nephritis results in damage to the kidneys which often leads to renal failure and increases the risk of birds developing gout. Typical signs of renal failure include: increased water intake, rapid weight loss, and diarrhea in affected birds.
  • Reproductive system damage: In both immature and adult egg laying hens, if the virus replicates in the oviduct, they are at risk of reproductive system damage. Affected hens may have reduced lifelong egg production and/or resulting in abnormal eggs that differ in shape (misshapen), size (smaller), internal egg yolk quality (watery), egg shell quality (rough or soft-shelled)

How Infectious Bronchitis is Diagnosed


Infectious bronchitis can be confirmed through several tests offered by most veterinary diagnostic laboratories. It consists of taking a simple swab from the chicken's trachea, and mailing it to the lab. Diagnostic tests include virus neutralization, haemagglutination inhibition and ELISA tests.

Transmission of Infectious Bronchitis Virus


The virus is transmitted via the respiratory secretions, as well as faecal droplets from infected poultry. Contaminated objects and utensils may aid transmission and spread of the virus from one flock to another. Recovered chickens can also spread the disease, as birds may shed the virus for up to 20 weeks after recovery from the infection.

Treatment of Infectious Bronchitis


Although infectious bronchitis is highly transmissible, most chickens will recover with supportive care. Since it's a virus, there is no treatment. However, antibiotics can help control secondary bacterial infections.

Clinical Signs

Sneezing
Coughing
Gasping
Tracheal rales
Nasal discharge
May have wet eyes
Swollen sinuses (occasionally)
Reduced egg production
Chicks may appear depressed and huddled under heat source
Irregular and roughened eggshells with watery albumin

Diagnosis

  • History
  • Clinical Signs
  • Laboratory testing

Treatment

NameSummary
Supportive careMost birds will recover with supportive treatment. Isolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress.
AntibioticsMay be indicated to control secondary bacterial infections.

Support

Prevention

  • IBV inactivated vaccine: Given as an intramuscular injection at 16-18 weeks of age
  • IBV live attenuated vaccines : Given by a coarse spray upon hatching and again at 2 to 3 weeks later
  • Biosecurity

Scientific References

Good Overviews

Age Range

All ages are susceptible but the disease is more severe in young chicks less than 6 weeks old.

Risk Factors

  • Poor biosecurity
  • Stressed and overcrowded birds
  • Lack of sunlight