Infectious Coryza

Infectious Coryza, commonly known as simply Coryza, is a bacterial disease of the respiratory system that is highly contagious and largely incurable.   Facial swelling, discharge from the eyes and nose, and a characteristic offensive odor from this discharge are key signs of a Coryza infection.   This disease is very serious and largely incurable since birds remain carriers.  Depopulation is strongly recommended, however since the bacteria does not survive long outside the host, after a few weeks the flock can be repopulated.  Treatment is not very effective and must be combined with sound management. 


Who:  Affects both wild and domesticated birds.  

  • Chickens 
  • Possibly Pheasants & Guineas

Note:  There is disagreement from reputable sources as to whether Pheasants and Guineas actually contract IC, or another disease with similar symptoms that has a different cause. 

Where:  Worldwide, with the vast majority (>90%) in temperate climates during fall & winter months; occurrence is infrequent, but more common in hobby and backyard flocks. 

When:  > 1 month; most frequently in adolescent or mature birds

Why:  Bacteria; Hemophilus gallinarum

  • How: 
  • Most common cause is from the introduction of carriers to a flock.
  • Spread by carriers via water, bedding or feed. 
  • Spread by airborne dust and exhaled droplets. 
  • Survivors remain carriers.   All birds within an affected flock are considered carriers. 
  • Symptoms can be brought on by general stress or drafty coops which presumably compromise the immune system.
  • Secondary infections, particularly other respiratory diseases are common.
  • Infectious Coryza can last much longer when infected simultaneously with Mycoplasma Gallisepticum (MG)


            Common Symptoms:

  • Swollen in face
  • Strong unpleasant odor from reddish nasal discharge
  • Nasal discharge is thick and sticky
  • Often one eye is stuck shut due to discharge
  • Sneezing
  • Watery discharge from eyes
  • Decreased egg production
  • Decreased food & water consumption
  • Labored wheezing
  • Lack of Energy

            Other Symptoms:

  • Loose stools
  • Stunted growth in when illness lingers


Treatment:  Culling is recommended.   Disease may reoccur following treatment.   Drugs only are insufficient for control. 

  • Erythromycin
  • Fluoroquinolones (Merck manual)
  • Macrolides (Merck manual)
  • Streptomycin
  • Sulfa drugs


  • "All-in/All-out" depopulation and repopulation is recommended. 
  • Birds from flocks that have been infected should never be taken to swaps, shows or auctions.   They should be culled, or the flock should remain isolated. 
  • Proper flock management is crucial.  If outbreak occurs, depopulate, disinfect the coop & leave unoccupied for several weeks before reintroduction of birds. 
  • The bacteria cannot last long outside the host, and is susceptible to disinfectants, so depopulation followed by disinfection is the surest way to restore health.  

Vaccine:  Yes, but typically only used in commercial populations: 

  • Typically used in commercial flocks where prior outbreaks are recorded. 
  • Used when introducing commercial layers into a flock.  


Also Known As: 

  • Coryza
  • IC
  • Cold
  • Roup

Affects:  Respiratory system

Clinical Diagnosis:  Observation of distinctive nasal discharge with offensive odor; observation of facial swelling particular to Coryza; confirmation by blood testing in a lab. 

Diseases with similar symptoms: 

  • Avian influenza
  •  Fowl cholera (also has swelling of the face and wattles)
  • Infectious bronchitis
  • Laryngotracheitis (LT)
  • Mycoplasmosis
  • Newcastle disease
  • Swollen head syndrome (ornithobacterosis)
  • Vitamin A deficiency.

Note:  The characteristic offensive odor of Coryza is key to identification.

Duration of symptoms:  A few days, up to 3 months. 

Incubation:  As little as a few hours, up to 3 days. 

Morbidity:  High (>50%) 

Mortality:  Up to 50%, but usually 20% or less. 

Transmission to people:  No known cases. 


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A righteous man cares about his animal's health...

Proverbs 12:10a