Chlamydia psittaci is the causative agent of psittacosis. It is classified as a bacteria and most species of free-ranging and domestic birds are considered to be susceptible. Chlamydiosis should be considered in any bird with clinical signs that suggest damage to the respiratory or digestive tracts. These include difficult breathing, depression, weight loss, loss of appetite, diarrhea, nasal discharge, swelling of the tissues around the eyes or discharge from the eyes. Yellowish or greenish discoloration of the urates and urine is a common symptom.
For more information, read Psittacosis.