Radiographic changes may include splenomegaly, hepatomegaly and soft tissue opacities in the air sacs and lungs, indicating possible air sacculitis and pneumonitis. On necropsy, gross lesions vary. Air sacculitis, hepatomegaly, splenomegaly, enteritis, peritonitis, pericarditis, bronchopneumonia and sinusitis may be present. Some infected birds may present with no gross lesions. It is important to obtain as detailed a history as possible to assist in rendering a diagnosis of chlamydiosis.
Young birds are generally more susceptible than adults.
Macaws and Amazon parrots appear to be more susceptible than other psittacine species. More important than species and age is the condition of the bird. Compare this to an Orange Wing Amazon parrot with its fourth owner in two years, living in a cramped filthy cage fed a seed-only diet. She showed only a slight rhinitis, noisy respiration and dull feathers but, subsequently, tested positive for chlamydiosis. Humans can acquire the disease from their pet bird, poultry or pigeons through inhalation of aerosolized fecal material or contact with nasal or ocular exudates that are then ingested.