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Avian Chlamydiosis

Chlamydiosis, Parrot Fever, Psittacosis, Chlamydia, Ornithosis

Avian chlamydiosis (AC) is a zoonotic bacterial disease caused by infection with Chlamydia psittaci, C. avium, or C. gallinacea. Infection can result in a number of different disease manifestations, including conjunctivitis, enteritis, pneumonia, and hepatitis. Some birds may be infected but show no clinical signs.


Birds are the primary hosts of Chlamydia spp., and a wide range of avian species are susceptible to infection. Numerous wild birds have been reported to be infected with Chlamydia spp. worldwide. Generally, these wild birds are asymptomatic (showing no evidence of illness despite being infected), however they will may intermittently shed the bacteria in nasal secretions and feces, especially when stressed. Chickens become infected with Chlamydia spp. by inhaling aerosolized respiratory or nasal secretions or contaminated dust, soil, and bedding particles, or through ingestion of contaminated feeders, waterers, or pasture forage.

Clinical Signs

Greenish-yellow diarrhea
Open mouth breathing
Ruffled feathers
Nasal discharge
Weight loss


  • History
  • Clinical signs
  • PCR
  • Radiographs
  • Endoscopy
  • Cytology
  • Sinus flush and culture


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.
DoxycyclineVibravenos 50-100 mg/kg IM q 7 d for 6 injections; Vibramycin 25 mg/kg PO q 12 h for 45 days.
OxytetracyclineLA-200 50 mg/kg IM q 24 h x 5-7 days, if doxycycline is unavailable.



  • Minimize exposure to wild birds
  • Do not hang wild bird feeders, as you don't want to attract wild birds.
  • Do not expose chickens to exotic wild birds, as they are common carriers.
  • Thoroughly wash your hands and/or change clothes before handling your flock after visiting pet stores and zoos.

Scientific References

Good Overviews

Risk Factors

  • Wild birds on the premises
  • Exposure to exotic pet birds
  • Hanging wild bird feeders on your property
  • Stress