Infectious Coryza

Cause
This is a bacterial disease caused by Avibacterium paragallinarum, (in the past known as Haemophilus paragallinarum). There are 3 common serotypes, representing different immunotypes: A, B, C.

Transmission
The disease spreads from bird to bird and flock to flock by contact and airborne infected dust particles and via the drinking water. Spread by equipment and personnel have also been reported. The incubation period varies from 1 to 3 days.
Species affected
The chicken is the natural host for Avibacterium paragallinarum. All ages are susceptible, but the disease is usually less severe in juvenile birds.

Clinical signs
The main clinical signs are due to an acute inflammation around the eyes and upper respiratory tract. Signs include a serous to mucoid discharge in the nasal passage and sinuses, facial edema and conjunctivitis. Feed and water consumption will be decreased resulting in loss of weight gain and loss of egg production (10-40%) in laying birds. In affected breeders, the hatchability and day-old chick quality might decline. Mortality will vary with the virulence of the infection, but is generally low. Complicating infections with eg IB (Infectious bronchitis), ILT (Infectious laryngotracheitis) and ND (Newcastle disease) can make it worse.

Diagnosis
A field infection produces similar symptoms to chronic respiratory disease, therefore a diagnosis based only on clinical signs is difficult to establish. The most certain diagnosis may be obtained by the isolation of the organism from the sinus or airsac exudate from affected birds. This procedure must be carried out in the laboratory. There is no practical serological test.

Eradication
Eradication is not economically feasible.

Treatment
Treatment with various antibiotics (erythromycin and tetracycline are commonly used) will alleviate the severity and course of the disease.
Relapse often occurs after treatment is discontinued and recovered birds will remain carriers. Because of noted drug resistance of Avibacterium paragallinarum, an antimicrobial sensitivity test is recommended.

Prevention
Vaccination is the preferred control method and is standard in most endemic Coryza areas.
Vaccination with multi-serotype inactivated vaccines during the rearing period will reduce clinical signs/control Infectious Coryza.