question about coryza


5 Years
Nov 17, 2014
South Carolina
If you don't give antibiotics, and thereby create healthy carriers of the disease in your flock that can get other chickens sick, is it possible to have coryza in your flock and not know it and only have the occasional death or sick chicken? Or is coryza virulent enough that if it's present then it's most likely making a lot of your chickens sick and most likely killing many of your chickens and there is no mistaking that your flock has it.

I get the occasional sick chicken with a swollen eye and appears sick. I'm pretty quick to cull sick chickens. I would say within the past year I've had 2 like that. Locally there is somebody that had coryza and had to destroy their flock and I've gotten some chickens from them. Just makes me paranoid I could possibly have it in my flock and not know it.


Premium Feather Member
11 Years
Apr 3, 2011
southern Ohio
Mycoplasma gallisepticum is more common in backyard flocks than coryza. Coryza tends to cause a very bad odor, and the symptoms are much worse with swelling on one or both eyes with pus drainage, coughing, wheezing, and gurling, and a thick yellow nasal draiange. Mycoplasma MG) can cause eye bubbles or foam in one eye, sometimes swelling around the eye, and sometimes it doesn't cause much at all besides a little runny eyes or nose. Testing a recently dead chicken by having your vet do a necropsy can get some answers. Without testing by a poultry lab on live chick ns or the necropsy, it is difficult to know for sure.

Glenda Heywoodo

Dec 19, 2016
Cassville Missouri
Excellent answer by Eggcessive.
Here is some information I found on Coryza:
Infectious coryza is a specific respiratory disease in chickens that occurs most often in semi-mature or adult birds. Infection may result in a slow-spreading, chronic disease that affects only a small number of birds at one time, or in a rapid spreading disease with a higher percentage of birds being affected.

Glenda Heywoodo

Dec 19, 2016
Cassville Missouri
Infectious Coryza
Detailed Information on the Poultry disease Infectious Coryza
Extracted From:
A Pocket Guide to
Poultry Health

By Paul McMullin
© 2004
A usually acute, sometimes chronic, highly infectious disease of chickens, occasionally pheasants and guinea-fowl, characterised by catarrhal inflammation of the upper respiratory tract, especially nasal and sinus mucosae.

Infectious Coryza is caused by the bacterium Haemophilus paragallinarum and is seen in many countries especially in multi-age farms that are never depopulated. Morbidity is high but mortality low if uncomplicated although it may be up to 20%.

The route of infection is conjunctival or nasal with an incubation period of 1-3 days followed by rapid onset of disease over a 2-3 day period with the whole flock affected within 10 days, resulting in increased culling. Carriers are important with transmission via exudates and by direct contact. It is not egg transmitted.

The bacterium survives 2-3 days outside the bird but is easily killed by heat, drying and disinfectants. Intercurrent respiratory viral and bacterial infections are predisposing factors.
  • Facial swelling.
  • Purulent ocular and nasal discharge.
  • Swollen wattles.
  • Sneezing.
  • Dyspnoea.
  • Loss in condition.
  • Drop in egg production of 10-40%.
  • Inappetance.
Post-mortem lesions
  • Catarrhal inflammation of nasal passages and sinuses.
  • Conjunctivitis.
  • Eye-lid adherence.
  • Caseous material in conjunctiva/sinus.
  • Tracheitis.
A presumptive diagnosis may be made on signs, lesions, identification of the bacteria in a Gram-stained smear from sinus. Confirmation is by isolation and identification - requires X (Haematin) and V (NAD) factors, preferably in raised CO2 such as a candle jar. Serology: HI, DID, agglutination and IF have all been used but are not routine.

Differentiate from Mycoplasmosis, respiratory viruses, chronic or localised pasteurellosis and vitamin A deficiency.
Streptomycin, Dihydrostreptomycin, sulphonamides, tylosin, erythromycin. Flouroquinolones are bactericidal and might prevent carriers.
Stock coryza-free birds on an all-in/all-out production policy. Bacterin at intervals if history justifies or if multi-age; at least two doses are required. Commercial bacterins may not fully protect against all field strains but reduce the severity of reactions. Live attenutated strains have been used but are more risky. Controlled exposure has also been practised.

Vaccines are used in areas of high incidence. Birds recovered from challenge of one sero-type are resistant to others, while bacterins only protect against homologous strains.

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