DEFINITION: Infectious Coryza (IC) is an infectious contagious respiratory bacterial disease of several avian species. The disease is acute to subacute at onset but progresses to a chronic state as the disease works through the flock. Common names for the disease are roup, cold and Coryza. Coryza is characterized by nasal discharge, facial swelling, sneezing, labored breathing and fetid odor of the exudates. Coryza is a disease of the upper respiratory tract–trachea, sinuses and air passages of the head. Coryza occurs worldwide. In the United States, it is predominately found in small noncommercial, menagerie, or hobby type flocks. The causative agent is Hemophilus paragallinarum, a polar staining, pleomorphic, non-motile, gram negative rod that was first described in 1920. There are three antigenic types (A, B, and C) which all share certain antigens. H. paragallinarum requires “V” factor, a special growth factor in the media to grow. While chickens are the primary host of Coryza, pheasants, guinea fowl and turkeys are also susceptible. It is assumed that other gamebird species will become infected if commingle on a regular basis with chronically infected gamebirds or poultry flocks. Age-wise, Coryza is a disease of juvenile and mature birds or birds 14 weeks of age or older. The incubation period is 1 to 3 days and the course of the disease is 4 to 12 weeks.
TRANSMISSION AND CLINICAL SIGNS:
Chronically ill or inapparent healthy carrier birds are the reservoir of infection. The source of the disease is often the addition of carrier birds to the flock. Recovered birds remain carriers and shedders for life. Transmission occurs by direct bird to bird contact, inhalation of infectious aerosols coughed into the air, or through ingestion of contaminated feed and water. The organism can be transferred on contaminated clothing, equipment and fomites. Incubation is 1
to 3 days with duration of the disease 14 days in the infected individual bird. The slow spread extends the period of sick birds within the flock to several weeks. The presence of other respiratory infections as mycoplasma will increase the duration and severity of illness of sick birds and impact on flock growth and production. Once a flock has been infected, it is a constant threat to other clean flocks. The clinical signs are those of an upper respiratory disease–sneezing, lacrimation, swollen face, and nasal exudates. The nasal exudates are thick clear sticky in texture with a fetid or rotten odor. Sick birds become lethargic, will sit humped, have ruffled feathers, go off feed and water and have swollen faces. Some birds also have sinusitis. The facial swelling is primarily around the eye and not always involving the infra-orbital sinus. Mortality can be as high as 50 percent but usually no more than 20 percent. The course and mortality of the disease correlate with the virulence of the pathogen, treatment, and concomitant infections.
LESIONS AND DIAGNOSIS:
In the acute stage, the principal lesions are swollen face, watery eyes, rhinitis, nasal exudates that become crusty on the beak around nostrils and cheesy in nostrils and sinuses. Eyelids stick together by the exudate or an accumulation of cheesy exudate in the conjunctival sac. Early exudates are copious, grayish-yellowish, thick and sticky. Other lesions include tracheitis, bronchitis and on occasion air sacculitis. The exudates in the trachea produce raffling (rales). A presumptive diagnosis can be rendered on the flock history, progress of the disease and the lesions. When present, the fetid odors of nasal exudates are diagnostic. Confirmation requires laboratory diagnostic work up with isolation and identification of the organism. The pathogen has special growth media requirement; therefore, the bacteriology laboratory must be alerted to the diagnostic suspicion of infectious Coryza (H. paragallinarum). The organism can be demonstrated in a gram-stained smear of the nasal exudates. Cultures should be made from nostrils, eye, cleft and trachea plus lung or air sacs if lesions are present. Flock treatment should be started based on presumptive diagnosis.
TREATMENT AND CONTROL:
Flock medication with a sulfonamide or antibiotic is recommended. Various sulfonamides — sulfadimethoxine (SDM), sulfaqumnline (SQ), sulfamet hazine (sulmet) are all effective; however, sulfadimethoxine is the safest and the one prescribed as treatment of choice. SQ and Sulmet are more toxic and require intermittent administration. Therapy in the drinking water will give more immediate response and reduce the severity of the disease. Feed administration of the sulfa or antibiotic does extend the period of treatment for better control. A combination treatment approach is advisable. Administer medication in the drinking water until medicated feed can be provided. Antibiotics that are beneficial include tetracycline, erythromycin, spectihomycin and tylosin. All are safe and approved for use in poultry. Control cannot be accomplished with drugs alone. Management is equally important. A bacterin is available that can be used in a control or eradication program. The bacterin requires multiple injections to be effective which makes it costly and cumbersome for commercial flocks. Control requires attention to flock sanitation, biosecurity, preventive medication, clean and sanitary premises, and disease-free replacements.
Prevention requires eradication of the disease (depopulation if necessary), good husbandry, strict biosecurity, all in-all out program, raise own breeder replacement, and do not mix ages or species. Most outbreaks occur as a result of mixing flocks. If you have an outbreak, segregate birds by age, etc., properly dispose of dead birds, medicate to stop the spread of the disease and initiate eradication procedures. Do not save recovered birds for breeder replacements. Premises should be vacant for 30 to 60 days after cleaning and disinfecting before repopulating or onset of the new season. Breeders should be replaced from a Coryza-clean source.
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Thank-you so much for this excellent information.I have a question: my flock got infected with coryza last year from other birds. we had to cull a few that got really sick, the others get shaky heads and lethargic/low egg production (mild symptoms) whenever stressed (I use natural remedies to get them back to good health - but now I understand they are all carriers/shedders). One of the hens hatched some chicks now we're wondering if it is safe to eat the cockerels? (they are dual purpose) Sounds like we need to cull all birds - hard to do, but will someday.