Infectious coryza is a contagious bacterial respiratory infection of chickens. While there are reports of a similar disease in other birds such as pheasants and guinea fowl, there is considerable doubt if these non-chicken cases are associated with the same aetiological agent. The disease 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. Symptoms include swelling around the face and wattles, watery or pus-like discharge from the eyes and nostrils, difficulty breathing, sneezing, loss of appetite and weight and a drop in egg production.
Infectious coryza is caused by a bacterium now known as Avibacterium paragallinarum. Earlier names for this organism such as Haemophilus paragallinarum and Haemophilus gallinarum should no longer be used. The bacterium is spread through contact with infected birds or exudates. Recovered birds may appear normal but remain carriers of the bacteria for long periods. Once a flock is infected, all birds must be considered as carriers. The bacterium survives 2-3 days outside the bird but is easily killed by heat, drying and disinfectants. Birds can be more susceptible if already infected with other respiratory viral or bacterial infections.
Infectious coryza can be treated with a number of antibiotics and vaccines are used in high incidence areas, however control of the disease requires good husbandry practices. Prevention is best achieved using biosecurity principles based on an all-in/all-out replacement policy and ensuring replacement birds are not infected. If infection occurs, complete depopulation followed by thorough cleaning/disinfecting is the only means for eliminating the disease.
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