Coryza in Chickens: Keeping Our Flocks Healthy This Fall

Since fall is here (in the United States) and winter is approaching, it’s a good time to address coryza in chickens. Unfortunately, I have seen many posts about sick chickens in the forums I follow.

I am passionate about poultry health and don’t want anyone to feel overwhelmed and alone while caring for ill chickens! So, let’s dig into this week’s topic: coryza in chickens.

Coryza is a term that many backyard poultry enthusiasts dread hearing. It refers to a highly contagious bacterial infection that affects chickens and can devastate flocks if not appropriately managed.

The name might sound fancy, but if you own chickens or are considering raising them, it’s crucial to understand coryza, its symptoms, and the best ways to treat and prevent it.

Close up of rooster waiting for vaccine from veterinarian

What is Coryza?

The bacteria Avibacterium paragallinarum causes coryza in chickens. It targets the respiratory system of chickens, leading to severe facial swelling, nasal discharge, and breathing difficulties.

Coryza spreads quickly among poultry, especially those kept in close quarters, making it a notable concern for chicken keepers worldwide.

Coryza tends to happen on small farms or in backyards in older birds, especially in groups of chickens of different ages. The other issue is that there can be co-occurring infections, which can make the chicken ill longer. But, several antibiotics work well against the bacteria that cause coryza in chickens.

Mortality rates (aka death rates) tend to be around 20% but can be as high as 50% within flocks. The preventative measures and treatments I will discuss below can help lower your flock’s death rates.

The good news is that even though many birds get sick from this disease, few die from it unless they develop different infections caused by other bacteria. Coryza in chickens generally lasts 7-11 days if other infections are absent.

Another critical thing to know is that recovered chickens can still spread coryza. They can become carriers.

Infection carriers are animals with a disease, though they might not show signs of being sick. Yet, they can still spread the disease to others. Think of them like someone carrying a full backpack but not showing any struggle – they may not look affected, but they can still pass something to others.

Symptoms of Coryza

Identifying coryza early can make a significant difference in managing the disease. Here are the primary symptoms to watch out for:

  • Facial Swelling: Swelling of the chicken’s face, particularly around the eyes, is a distinct symptom of coryza. This can become so pronounced that the eyes are swollen closed. Wattles can also swell in some cases.

  • Nasal and Eye Discharge: A thick, sticky, foul-smelling discharge often accompanies facial swelling.

  • Sneezing and Coughing: As with many respiratory conditions, affected chickens sneeze and cough.

  • Difficulty Breathing: Chickens with coryza may have labored breathing or make a gurgling sound when breathing.

  • Reduced Egg Production: Hens infected with coryza often show a decrease in egg production. This can be a concern for farmers relying on egg sales.

  • Sluggishness and Reduced Appetite: Sick birds might become less active and show little interest in food.

To be sure you are dealing with coryza in chickens, it’s important to tell it apart from other chicken diseases. Some diseases and conditions have symptoms like coryza.

Chronic breathing issues, fowl cholera, fowl pox, ornithobacteriosis (another type of bacterial infection sometimes called “swollen head syndrome”), or lack of vitamin A have similar symptoms.

Veterinarians can take from nasal discharge or any large sores (lesions) to check for the bacteria Avibacterium paragallinarum, which causes infectious coryza in chickens.

Hand holding a sick chicken infected with infectious coryza

Treatment of Coryza

If you suspect your chickens have coryza, it’s essential to act fast:

  • Isolation: Immediately separate any symptomatic birds from the rest of the flock. Isolation helps limit the spread of the disease to healthy birds.

  • Veterinary Care: Always consult a veterinarian with poultry disease experience. They can prescribe antibiotics that are effective against the bacteria causing coryza. Prescribed antibiotics include erythromycin, sulfonamides, or tetracycline.

  • Supportive Care: Make sure your infected birds have easy access to clean water and nutritious food. This helps bolster their immune system and aids in recovery.

  • Cleanliness: Clean and disinfect the chicken coop and all equipment. Coryza bacteria can survive a few days outside the host chicken, so thorough cleaning can help reduce the risk of further infections. Temperatures between 113-131 degrees can kill the bacteria. When cleaning, keep items at those temperatures for at least 10 minutes.

  • Culling: Culling might be necessary in severe outbreaks, especially in commercial settings. While this is a tough decision, it can be the fastest way to eradicate the disease from a flock.

Hen with Infectious Coryza


Prevention is always better than cure. Here are some steps to help keep coryza in chickens at bay:

  • Biosecurity: Limit the introduction of new birds to your flock. If you must introduce new chickens, keep them separated for at least 30 days before they mix with your existing flock. For more tips we have an article on biosecurity here.

  • Regular Monitoring: Watch your birds for signs of illness and act if symptoms of coryza or any other disease appear.

  • Vaccination: In areas where coryza is prevalent, consider vaccinating your chickens. Speak with a veterinarian about the best vaccines and vaccination schedules. Merck has a vaccine called Corvac-3 for the prevention of coryza in chickens. It can be administered to chickens as young as five weeks old.

  • Good Hygiene: Regularly clean and disinfect the chicken coop, feeding equipment, and waterers. Maintaining a clean environment can reduce the chances of disease outbreaks.

In good news, coryza in chickens is not contagious to humans. And, if cooked well, you can eat eggs and meat from infected birds. But, if you treat your flock with antibiotics, read the labels and follow the guidelines for withdrawal times (in other words, how long it takes for the medicine to leave the chicken’s body).

Veterinarian with stethoscope holding and examining chicken


Coryza can be a significant concern for chicken keepers. Understanding this disease, managing it, and using preventive measures can make a world of difference. You can protect your flock with prompt attention, good hygiene, and diligent monitoring. You can make sure they remain healthy and productive.

Let me know in the comments if this article was helpful. Or drop me a line and let me know what topics you’d like to read in future posts.


Infectious Coryza (IC): Frequently asked questions (FAQs) (FS-1131) | University of Maryland Extension (

INFECTIOUS CORYZA IN POULTRY – Small and backyard poultry (

Chris Lesley Bio Picture
Chris Lesley has been Raising Chickens for over 20 years and is a fourth generation chicken keeper. She can remember being a young child when her grandad first taught her how to hold and care for chickens. She also holds a certificate in Animal Behavior and Welfare and is interested in backyard chicken health and care.


  1. How do I manage an aggressive rooster? His poor hands lost their shutters on their back and on their sides. I did get jackets for them, but he still was too rough. He’s the sweetest rooster I’ve ever had and IHow do I manage an aggressive rooster? His poor hands lost their shutters on their back and on their sides. I did get jackets for them, but he still was too rough. He’s the sweetest rooster I’ve ever had and I don’t want to get rid of them, I have him in his old coop. Is that cruel?

    • we have a black Australorp that will have to go. Our hens are suffering, like 15 of them- and he attacks us. We have used spray bottles, sticks, and whatever to avoid him—he attacks me when i’m vulnerable- picking up eggs or bent over picking something up. My wife jokes he will wind up in a pot- but we can’t kill him, we raised him from a day old baby but wow he has got to settle down. At first we thought he is young, but now is 2 yrs old and nothing has changed. Its no fun to not allow kids around the chickens because of him potentially attacking them.

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