Infectious Coryza
Infectious Coryza is a respiratory disease of chickens caused by the bacteria, Avibacterium paragallinarum. It leads to rapid onset of upper respiratory signs and can severely impact egg production.
Quick Facts
Avibacterium paragallinarum is a bacteria
Highly contagious; spreads quickly in a flock
Birds that recover often remain carriers
Does not spread to or infect humans
Affects chickens of all ages; especially severe in multi-age flocks
What is Infectious Coryza?
Infectious coryza is a respiratory disease of chickens caused by the bacterium Avibacterium paragallinarum. It causes rapid onset of upper respiratory signs and can significantly reduce egg production. The disease spreads quickly through direct contact with infected or carrier birds and contaminated environments. Birds that recover may remain carriers and spread the bacteria again, especially during stress. Antibiotics can reduce clinical signs but do not eliminate carrier birds. Strong biosecurity practices are the most effective way to prevent and control disease.
Signs of Infectious Coryza
Infectious coryza develops quickly and gives birds a very distinct swollen-face appearance. Common signs include:
- Facial swelling (puffy eyes and face from inflamed sinuses)
- Conjunctivitis (red, watery, or irritated eyes)
- Swollen wattles, especially in roosters
- Nasal discharge (watery to thick, sometimes foul-smelling)
- Reduced feed and water intake
- Drop in egg production (often 10–40%)
Infectious coryza is often more serious when birds are also infected with other respiratory diseases, such as Mycoplasma, Newcastle disease, or infectious bronchitis. Co-infection can lead to worse swelling, heavier discharge, longer recovery, and greater production losses.
How does Infectious Coryza Spread?
Infectious coryza spreads quickly through a flock, mainly by contact with infected or carrier birds.
- Direct bird-to-bird contact: Bacteria are shed in nasal discharge, eye secretions, and respiratory droplets.
- Carrier birds: Birds that recover may look healthy but can still spread infection, especially during stress or flock mixing.
- Contaminated equipment and environments: Shared tools, feeders, waterers, bedding, boots, or clothing can move bacteria between birds or flocks.
- Close housing or mixed-age flocks: Spread is more likely when birds of different ages are kept together or housed closely.
How Do You Prevent Infectious Coryza?
Practice biosecurity
- Limit contact with birds from other flocks to prevent disease spread.
- Wear coop-dedicated shoes to keep out germs.
- Wash hands and keep coop/equipment clean.
Limit Visitors + Shared Tools
- Limit visitors. Require boot covers.
- Don’t share or borrow tools or equipment
Limit Spread from Carriers
- Do not mix recovered or carrier birds with new or healthy flocks.
- Keep age groups separate to reduce risk of spread
Buy from Clean Sources
- Get new birds or hatching eggs only from healthy, disease-free flocks.
- Do not buy birds from swaps, auctions, or unknown sellers.
What Do You Do if Infectious Coryza is Found in Your Flock?
Contact your veterinarian
- Your veterinarian can help confirm the disease and guide next steps.
- Laboratory testing is often needed to confirm infectious coryza and rule out other respiratory diseases.
Isolate Sick Birds
- Separate sick birds from the flock to reduce the spread of bacteria.
- Birds that recover may still carry infection.
Clean + Disinfect the Coop Area
- Remove feathers, dust, manure, and bedding.
- Wash and disinfect equipment, boots, and solid surfaces.
- Let the area dry completely before birds return.
Don’t Spread Disease
- Do not buy or sell birds during or after an outbreak.
- Birds that recover may look healthy but remain carriers and can spread the bacteria to new flocks.
Plan for the future
- If infection continues, consider depopulating and restocking with clean birds.
- Vaccination may be recommended in some situations. Work with your veterinarian to decide what is right for your flock.