All You Need To Know About Coryza in Chickens

Coryza in Chickens Featured Image
Infectious coryza, simply known as coryza, is a chronic respiratory disease in chickens caused by bacteria called Avicabacterium paragallinarum. The disease poses a significant poultry health risk since it causes slow growth in chicks, and a substantial decrease in egg production.

Numerous states have reported an increase in infection rates in flocks this year, so understanding it is vital to diagnosing, preventing, and treating it effectively.

Here’s everything you need to know about coryza in chickens:

What Is Infectious Coryza?

Let’s find out more about infection coryza in chickens. Earlier names for this disease include Uncomplicated Coryza, Cold, Roup, Hemophilus Infection, Catarrh, and Infectious Catarrh.

Infectious coryza is a chronic upper respiratory disease in chickens triggered by Avicabacterium paragallinarum. Other names for these bacteria include Hemophilus gallinarum and Haemophilus paragallinarum.

Although it is most common in California and the Southern States in the United States, infectious coryza affects chickens globally.

Coryza typically starts suddenly, with all vulnerable birds displaying signs and symptoms of the disease within 24 to 72 hours after infection exposure.

The most common signs and symptoms of the disease include facial swelling and nasal discharge that gradually produces a foul smell. Roosters may experience swollen wattles.

A hen with Infectious Coryza

Chickens may also have watery eyes and noticeable conjunctivitis. Infected chickens may partly or completely close their eyes because of excessive eye discharge.

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In less severe cases, the disease course is typically 7 to 11 days. However, the disease can be complicated by other infections, which can make it last a month or even longer.

Clinical Signs of Infectious Coryza in Chickens

While coryza in chickens is a respiratory infection, it can be difficult to pinpoint the exact cause. The disease leads to circulatory system problems, respiratory infections, and digestive system diseases in infected poultry.

There are many signs of infectious coryza in chickens that can be mistaken for another health issue. But if you notice all the following clinical signs, there’s no room for guesswork.

These signs and symptoms are:

1. Facial swelling

This is one of the most common signs of infectious coryza in chickens. The swelling usually appears around the eyes and under the cheeks.

2. Nasal Discharge

This is another noticeable sign of coryza in birds. There’s ocular and nasal discharge because of swollen infra-orbital sinus. The birds will cough and sneeze regularly. This may be the reason why the disease spreads so fast.

3. Conjunctivitis

Another noticeable sign is the appearance of bubbles in the corner of the infected bird’s eyes.

4. Swollen/Pale Comb

The comb may become swollen and pale as well.

5. Breathing Problems

The chickens face breathing difficulties and start wheezing. They also open their mouth while breathing.

6. Lower Respiratory Tract Also Affected

While infectious coryza is an upper respiratory tract infection, it can also affect the lower respiratory tract. You can tell this if there breathing sounds such as rales.

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7. Loss of Appetite

There’s a change in your chicken’s appetite and drinking habits.

8. Depression/lethargy

The birds become weak and have trouble walking.

9. Reduced Egg Production

Hens with infectious coryza will have a reduced egg production rate of about 10-40%. Also, the egg shell may be fragile.

10. Eyelids

The birds’ eyelids become crusty or stuck together.

11. Diarrhea

Some chickens with coryza will experience diarrhea.

Foul smell

The bird may also produce foul smell.

Other signs and symptoms include:

  • Swollen wattles
  • Irregular breathing sounds
  • Coughing
  • Change in the voice
  • Open mouth breathing
  • Elevated respiratory rate
  • Head shaking
  • Gurgling
  • Loss of appetite
  • Diarrhea
  • Weight loss
  • Reduced egg production
  • Ruffled feathers

The death rate is low unless other contaminations occur. The illness can persist for 7 days to 11 days or even longer if other infections occur.

How infectious Coryza Is Spread

The main way in which infectious coryza is spread between flocks of chicken is by eating contaminated feed and getting into contact with clothing.

Infected animals like rodents and wild birds can also spread the disease to chickens. Disease microbes may also be passed from flock to flock through shared items.

rodents eating chicken eggs in nesting box

Insects like mosquitoes, beetles, and flies are known carriers of disease-causing microorganisms, as well.

Contact with any infected chicken can also spread the disease to backyard chickens that are reared in close proximity.

Contaminated drinking water has also proven to be a source of diseases, so water sanitation is vital to preventing and controlling infections.


The presence of the aforementioned signs and symptoms is not a surefire way of diagnosing infectious coryza in chickens. You need to provide a vet with dead chickens for postmortem examination.

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The most common signs at postmortem analysis include grey exudates in the infraorbital sinus, extreme changes in the air sacs, bronchi, and trachea.

A conclusive diagnosis is only reached by identifying the pathogen from the lab samples.

When it comes to direct isolation, the organism should be isolated from cotton swabs after examining the air sacs, bronchi, and trachea. For a conclusive diagnosis, the organism should be isolated in the severe phase of infection (during the incubation stage).

PCR testing is also available and offers quick results, usually within 6 hours.

The presence of other organisms can make the diagnosis of coryza in chickens more complicated.


The good news is that antibiotics are available to treat the infection once the offending pathogens are identified by a proper diagnosis by a veterinarian.


In cases where the illness is widespread, infected flocks are usually depopulated to prevent the disease from spreading.

Once the infected flocks are depopulated, the coops musty be cleaned, sanitized and allowed to remain idle for around 21 days before welcoming new flocks into the premises.

As with all infections, the best control and prevention method is by taking stringent measures. The best thing to do if you suspect your chickens have infectious coryza is to contact a vet as soon as possible.


Infectious coryza in chickens is severe even though it has a low mortality rate. It is a serious disease, particularly for older birds. So your chickens may require antibiotics, isolation, and improved care throughout their lifetime.

Patrick Anampiu

Patrick is an avid pet lover and passionate writer who enjoys crafting stories and feels most alive when telling stories about people whose lives have been enriched by their pets. He enjoys adding more chickens to his flock and loves sharing insights on how to take better care of pets and other animals in our lives. When not writing and raising chickens, Patrick enjoys traveling and exploring nature in all its beauty.

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