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Infectious coryza in chicken

Infectious coryza in chicken

Infectious coryza is an acute respiratory disease of chickens and causes a reduction in egg production. In chicks and pullets, it can cause a reduced growth rate. The disease occurs worldwide, although in some parts of the world prevalence is low. It is especially an important disease in poultry farming in countries with a tropical or subtropical climate.

The causative agent is a bacterium, named Avibacterium paragallinarum. This bacterium causes an inflammation of the upper respiratory tract. Facial swelling , nasal discharge and conjunctivitis are the main clinical symptoms. In layers, egg production can be markedly reduced. Clinical signs usually appear 24-48 hours after infection and the duration of the disease is 10 to 14 days. The disease is highly contagious and most birds in a flock become infected. Mortality is usually low. In case of concurrent infections with other bacteria or viruses, the course of the disease can be longer and mortality can be higher.

Chickens of all ages are susceptible, but adult birds are usually more severely affected than younger birds. In younger birds, the disease can be limited to a decreased feed intake and a reduced growth.

After recovery, birds remain carriers of the bacterium. Placement of latent carriers into a flock is an important source of disease. The bacterium is spread by direct contact between infected and susceptible birds, through inhalation of infectious aerosols or through ingestion of contaminated feed or drinking water. The bacterium is not transmitted through the egg. 

Clinical signs

  • Nasal discharge
  • Facial swelling
  • Watery eyes
  • Closed eyes
  • Swollen wattles
  • Rales
  • Difficult breathing
  • Strong odour
  • Decreased food and water consumption
  • Weight loss or reduced growth rate
  • Severe reduction in egg production (10-40%)
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Post-mortem findings

  • Catarrhal to purulent inflammation of the upper respiratory tract, sinuses and conjunctivae.
  • The lower part of the respiratory tract may also be affected in case of concurrent infections with other bacteria or viruses.

Diagnosis

  • History and clinical signs are suggestive for infectious coryza.
  • For confirmation of the diagnosis, Avibacterium paragallinarum should be demonstrated (ask your veterinarian if needed):
    • Swab samples from affected sinuses should be taken for culture. Culture of this bacterium requires special growth media.
    • In case of specific colony growth, the bacterium should be further identified by biochemical tests or a PCR test.
    • A PCR test can also be performed directly on a sinus swab.
  • Serologic tests include haemagglutination-inhibition and a blocking ELISA test.
  • Diagnosis should be differentiated from Mycoplasma gallisepticum, Pasteurella multocida, Mycoplasma synoviae, Newcastle disease, low pathogenic avian influenza, avian metapneumovirus, infectious laryngotracheitis, and infectious bronchitis.


Treatment

Antibiotic treatment will reduce the severity of the course of the disease. This contributes to a reduction of egg production losses. Be aware that antibiotics do not eliminate the bacteria, birds remain carriers of the bacterium. Also be aware that some antibiotics are not suitable for layers producing eggs for human consumption.

Chicks and pullets may be treated with doxycycline (Doxyvet 200 wsp), oxytetracycline (Oxy 200 wsp), trimethoprim/sulphonamides (T.M.P.S. Oral), amoxicillin or enrofloxacin.
Do not use doxycycline, oxytetracycline or trimethoprim/sulphonamides in layers producing eggs for human consumption.

Laying hens may be treated with oxytetracycline (Oxy Plus Formula wsp), tylosin or enrofloxacin.

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