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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, a Gram-negative, obligate intracellular bacteria found in wild and domestic birds, mammals, and humans worldwide. Chickens are most commonly infected with C. psittaci or C. gallinacea, and less commonly, C. abortus and C. avium. C. psittaci is the most widespread, and found in over 450 different bird species worldwide--including domestic pet birds such as parakeets, cockatiels, and other Psittaciformes. Often times, infected birds remain asymptomatic and may only intermittently shed the bacteria in nasal secretions and in their droppings during stressful events. C. psittaci and C. abortus are able to infect humans, with outbreaks of the disease reported in people who had direct contact with infected birds.

Clinical signs

Infection can result in a number of different disease manifestations, including conjunctivitis, enteritis, pneumonia, and hepatitis. Most clinical signs observed in chickens are non-specific, and can include nasal discharge, diarrhea with greenish-yellow feces, ruffled feathers, loss of appetite, and watery eyes.


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.


Avian chlamydiosis is treated with antibiotics, usually tetracyclines (chlortetracycline or doxycycline).

Clinical Signs

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


  • 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