Infections Coryza is usually acute and sometimes chronic, highly infectious disease of chickens, occasionally pheasants and guinea-fowl. Infectious Coryza is 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 the disease over a 2-3 day period with the whole flock affected within 10 days. This results 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.
Infectious coryza, which is also referred to as a cold or roup, is caused by the bacterium Haemophilus paragallinarum. This disease primarily affects chickens, but quail and pheasants may also be affected.
Coryza is primarily transmitted by direct bird-to-bird contact. In addition, birds can also catch the disease by breathing airborne bacteria and consuming contaminated feed and/or water. The disease can also be introduced when infected birds are brought into the flock. Birds that have recovered from the disease remain carriers of the organism and may occasionally shed the bacteria during their lives. Birds risk exposure at poultry shows, bird swaps, and live-bird sales. Outbreaks commonly result when infected birds that are not showing any signs of the illness are brought into a healthy flock.
Purulent ocular and nasal discharge.
Loss in condition.
Drop in egg production of 10-40%.
Inappetance. Typical signs of coryza include the following:
Swelling around the face
Foul-smelling, thick and sticky discharge from the nostrils and eyes
In addition, the eyelids of an infected bird can become irritated and might stick together. Diarrhea may occur. Growing birds may become stunted. Infection can decrease egg production and increase the incidence and/or severity of secondary infections.
Mortality can be as high as 50%, but 20% is more common. The disease can last as little as a few days or as long as a few months, particularly when secondary infections occur.
Catarrhal inflammation of nasal passages and sinuses.
Caseous material in conjunctiva/sinus.
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.
Because coryza is caused by bacteria, antibiotics can be used to treat a flock. It is important to follow the labels on any medication. Although antibiotics can be effective in reducing clinical signs of the disease, they do not eliminate the bacteria from carriers.
Prevention and Control
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.
Good management, rigorous sanitation, and a comprehensive biosecurity plan are the best ways to avoid infectious coryza. Most outbreaks occur as a result of mixing flocks. Vaccines are available, but multiple vaccinations are required to be effective. When bringing in replacement birds on a farm that has had infectious coryza, it is recommended that all the birds be vaccinated.