Dr. Latif Ahmad (DVM-PhD), Assistant Professor, HOD Infectious Coryza Dr. Latif Ahmad (DVM-PhD), Assistant Professor, HOD

Infectious coryza (IC) is an acute respiratory disease of chickens caused by the bacterium Avibacterium paragallinarum, once known as Haemophilus paragallinarum

Etiology Three Avibacterium paragallinarum serotypes designated A, B and C are recognized. The dis. is potentially encountered in any poultry-raising area but freq. occurs in sp. regions or countries as a chronic or seasonal problem. Coryza results in dec. egg prod. in com. multiage laying & breeder operations.

Host Range The chicken is the natural host for Av. paragallinarum. There are several reports that the village chickens of Asia are as susceptible to infectious coryza as normal commercial breeds Outbreaks of dis associated with this species have also been reported in guinea fowl in Africa & turkeys in Europe. A single isolate has been reported from a healthy duck & a goose of unspecified health status. Turkey, pigeon, sparrow, duck, crow, rabbit, guinea pig, and mouse are refractory to experimental inf.

Transmission Inf. may follow: Direct (from bird to bird and flock to flock) contact with cl. affected/asymptomatic carriers and airborne infected dust particles and via the drinking water. Indirect contact with contaminated equipment or personnel. The pathogen does not remain viable outside the host for periods exceeding 24 hours. The incubation period varies from 1 to 3 days.

Clinical Signs Flock morbidity varies from 1 to 20%. Feed and water intake is reduced, leading to loss of weight. Mortality is negligible in uncomplicated cases of coryza. Egg prod. in young com. or breeder flocks is reduced following inf. Clinically affected birds show unilateral or bilateral ocular discharge progressing to facial cellulitis & chronic sinusitis

Ocular discharge and swelling of nasal sinus associated with coryza Ocular discharge and swelling of nasal sinus associated with coryza.  Differential diagnosis includes Mycoplasmosis or Laryngotracheitis.  The main signs of the disease are inflammation of eyes and nose with foul-smelling discharges, conjunctivitis, sneezing & facial swellings; similar signs to chronic respiratory dis, Dx is difficult to establish.

Pathology Acute cases show severe conjunctivitis and inflammation of the periorbital fascia. Chronic cases show serous to caseous sinusitis. Other gross lesions associated with Av. gallinarum inf. are diverse & include airsacculitis, pericarditis & perihepatitis

Pathology Microscopically Essential changes in the nasal cavity, infraorbital sinuses & trachea consisted of: Sloughing, disintegration, & hyperplasia of mucosal & glandular epithelia, and Edema & hyperemia with heterophil infiltration in tunica propria of the mucous membranes. In severe cases, severe subacute to chronic pyogranulomatous pneumonia, airsacculitis, pericarditis, perihepatitis, synovitis, and myositis. There may be severe lymphoid depeletion of the bursa of Fabricius

Diagnosis Haemophilus paragallinarum can be isolated from sinus swabs in acutely affected birds. Since the organism is susceptible to desiccation it is recommended that acutely infected live birds should be submitted to a diagnostic laboratory whenever possible. Alternatively, severed heads packed on ice can be forwarded to a laboratory. Isolation involves semiaerobic culture on a blood agar medium streaked with Staphylococcus sp. incubated in a candle jar. The condition should be differentiated from pasteurellosis and viral infections including LPAI, and other respiratory agents.

Treatment Immature birds can be treated with water-soluble sulfonamides. Rx with antibiotics can be given to subdue clinical inf. Only. Combinations of tetracyclines are frequently used to treat coryza by administration in water or injected directly by the intramuscular route. Sulfonamides should not be administered to mature flocks due to residues in eggs and the deleterious effect of sulfonamides on production and shell quality. Compulsory or recommended withdrawal periods before marketing eggs should be followed after treatment of commercial flocks.

Prevention Appropriate biosecurity measures will limit the possibility of introducing inf. on to breeding and com. egg prod. farms. Immature flocks can be partly protected by administration of inactivated multivalent or homologous bacterins in aq. suspension or oil emulsion. Two doses of inactivated vaccine should be administered by the S/C or I/M route at 4-wk intervals during rearing period, as recommended by manufacturer. In case of dis, eradication & prevention are most desirable means of control of coryza. Vaccines have been developed, but are only used in areas where the disease is endemic & cannot be eradicated.