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Infectious Coryza

Other Names: Roup, Catarrh, Cold, Hemophilus Infection, Infectious Catarrh

Infectious coryza (IC) is an acute upper respiratory disease of chickens caused by Avibacterium paragallinarum (previously referred to as Haemophilus paragallinarum). IC occurs worldwide. Within the United States, it is most prevalent in California and the Southeastern states.

IC usually begins abruptly, with all susceptible chickens showing signs of disease within 24-72 hours after exposure to infection. The typical symptoms are facial swelling and sinuses with a clear discharge progressively becoming foul smelling and purulent. Roosters may have swollen wattles. There is marked conjunctivitis and lacrimation (tearing or watery eyes). Infected birds may have their eyes partially or completely closed due to the excessive eye discharge, making it difficult for them to see to eat and drink. The disease course in uncomplicated cases of IC is usually 7-11 days. If the disease is complicated by concurrent infections it can persist for a month and longer.

Diagnosis of Infectious Coryza

Diagnosis of IC is based on history, clinical signs, and bacteriological examinations of the suspected causal agent leading to isolation, and identification of the causative agent. There are many diagnostic laboratory tests available for detection of A. paragallinarum, which include:
  • Direct isolation: For direct isolation, the pathogen can be isolated from sterile cotton swabs obtained from the infraorbital sinus, trachea, and air sac. To be an effective form of diagnosis, the pathogen must be isolated during the acute stage of infection (1 to 7 days of the incubation period).
  • Hemagglutination inhibition (HI) test: There are three main forms of HI tests available, which are widely used for detecting changes in antibody titers, in cases of field infection or vaccination, and for evaluating the prevalence of IC within flocks.
  • PCR testing: PCR tests are available which provide rapid (often within 6 hours) results.
Diagnosis of infectious coryza can be more complicated when it occurs alongside other pathogens.

Infectious Coryza Transmission

The main reservoirs of infection for A. paragallinarum are chronic or apparently healthy carrier birds. Once introduced into a flock, A. paragallinarum is spread rapidly via direct or indirect contact with infected birds, through ingestion of contaminated feed or water, and by aerosols. Susceptible birds exposed to infected birds may show signs of the disease within 24-72 hours. Chickens who have recovered can become carriers, shedding the bactera when stressed.

Clinical Signs

Facial swelling
Nasal discharge
Eye discharge
Watery eyes
Abnormal breathing sounds
Change in voice
Open-mouth breathing
Increased respiratory rate
Swollen wattles
Head shaking
Gurgling sounds
Reduced appetite
Weight loss
Decreased egg production
Ruffled feathers


  • History
  • Clinical signs
  • Physical exam
  • Necropsy
  • Lab tests

Reported Cases

  • Case 1: Infectious coryza in a Chickens Six 16-week-old male chickens from a flock of 500 birds were presented for necropsy at the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) in Gonzales. History noted one-week of swollen sinuses with minimal abnormal respiratory sounds and negligible mortality.  The incidence was relatively low. Upon necropsy examination, each of the six birds had one of the sinuses swollen while the other sinus appeared relatively normal. A thick honey-like exudate was extracted from the sinuses of three birds. Two of the six birds also had a small abscess in the left wattle. No other lesions of note were observed. Bacterial cultures taken from the swollen sinus of each bird were plated on sheep blood agar and MacConkey plates. A Staphylococcus aureus nurse colony was provided on the blood agar plate for supplementation. Plates were aerobically incubated at 37o C with 5% CO2 for 24 hours. From each bird, small bacterial colonies were isolated along the S. aureus nurse colony which were identified as Avibacterium paragallinarum. Following testing, bacterial sinusitis (infectious coryza) caused by A. paragallinarum was determined as a diagnosis. Ref

  • Case 2: Otitis and meningoencephalitis in a Chickens In March 2017, the Turlock branch of the California Animal Health and Food Safety laboratory system encountered an unusual clinical and pathologic presentation of infectious coryza in 6 live, 29-d-old, commercial broiler chickens that were submitted for diagnostic investigation. Antemortem evaluation revealed severe neurologic signs, including disorientation, torticollis, and opisthotonos. Swollen head–like syndrome and sinusitis were also present. Histologically, severe sinusitis, cranial osteomyelitis, otitis media and interna, and meningoencephalitis were noted, explaining the clinical signs described. A. paragallinarum was readily isolated from the upper and lower respiratory tract, brain, and cranial bones. Infectious bronchitis virus (IBV) was also detected by PCR, and IBV was isolated in embryonated chicken eggs. Based on sequencing analysis, the IBV appeared 99% homologous to strain CA1737. A synergistic effect between A. paragallinarum and IBV, resulting in exacerbation of clinical signs and increased mortality, may have occurred in this case. A. paragallinarum should be considered among the possible causes of neurologic signs in chickens. Ref

  • Case 3: Infectious coryza and fowl adenovirus in a Commercial laying hens The diagnosis of a concurrent infection of Avibacterium paragallinarum and fowl adenovirus (FAdV) in an infectious coryza–like outbreak in the outskirt of Beijing was reported. The primary signs of the infection were acute respiratory signs, a drop in egg production, and the presence of hydropericardium–hepatitis syndrome–like gross lesions. Laboratory examination confirmed the presence of A. paragallinarum by bacterial isolation and a species-specific PCR test. In addition, conventional serotyping identified the isolates as Page serovar A. Fowl adenovirus was isolated from chicken liver specimen and identified by hexon gene amplification. In addition, histopathologic analysis and transmission electron microscopy examination further confirmed the presence of the virus. Both hexon gene sequencing and phylogenetic analysis defined the viral isolate as FAdV-4. The pathogenic role of A. paragallinarum and FAdV was evaluated by experimental infection of specific-pathogen-free chickens. The challenge trial showed that combined A. paragallinarum and FAdV infection resulted in more severe clinical signs than that by FAdV infection alone. The concurrent infection caused 50% mortality compared with 40% mortality by FAdV infection alone and zero mortality by A. paragallinarum infection alone. Ref

  • Case 4: Infectious coryza complicated by Ornithobacterium rhinotracheale in a Chickens The coinfection of Avibacterium paragallinarum and Ornithobacterium rhinotracheale in two outbreaks of infectious coryza from Peru was reported. The diagnosis was confirmed by bacteriologic isolation, PCR testing, and sequencing of the 16S rRNA gene. The susceptibility of the isolates to 12 antimicrobial agents was tested by a disk diffusion method. The isolates were susceptible to amoxicillin/clavulanic acid and florfenicol and were resistant to oxacillin and sulfamethoxazole/trimethoprim. The coinfection of Av. paragallinarum and O. rhinotracheale and the severity of clinical signs were evaluated by experimental infection of specific-pathogen-free chickens. The group inoculated with O. rhinotracheale alone presented minimal clinical signs in 3 of 10 chickens. However, the groups inoculated with both Av. paragallinarum and O. rhinotracheale induced the most-severe clinical signs compared with the group inoculated with Av. paragallinarum alone. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Danofloxacin mesylate5 mg/kg PO, IM, IVB Speer
Enrofloxacin (Baytril)Administered in drinking water (50 mg/L) or PO, SC, IM (10-15 mg/kg)B Speer
NorfloxacinAdministered orally (8-10 mg/kg q24h), or in drinking water (100 mg/L x 5 days)B Speer
Sulfadimethoxine oral solution and powderAdministered in drinking water (330-400 mg/L initially, then reduced to 200-265 mg/L x 4 days) or orally (25-55 mg/kg q24h x 3-7 days)B Speer
Tylosin (Tylan)Administered IM (15-30 mg/kg q6-12h) or in drinking water (250-1000 mg/L)B Speer



  • Vaccine : Given by intramuscular injection twice a year
  • Provide warm, draft-free housing in the winter
  • Quarantine any new birds before adding to your flock.

Scientific References

Good Overviews

Age Range

Chickens 14 weeks of age and older are most susceptible.

Risk Factors

  • Bringing birds to or purchasing birds from poultry auctions, swap meets, shows, county fairs, or other large poultry-associated events.