The pet bird owner may be increasingly aware of the prevalence of psittacosis, but that is believed due to be improved diagnostic methods rather than actual increase in disease incidence. Transmission Transmission of psittacosis is primarily by inhalation of infected dust from droppings or feathers, and is enhanced by close contact with sick birds that are shedding the organism. For this reason, the disease is most often seen in birds that have been recently imported, housed in pet shops or boarded with other birds.
Birds tend to shed the organism under conditions of stress.
Birds do not have to show symptoms of disease in order to transmit chlamydia. There are no specific signs that are characteristic of psittacosis. Of course, these signs may be related to diseases other than psittacosis. Many birds carry the chlamydial organism but do not show any signs of disease under stable conditions. These birds may become sick after some stressful occurrence, or breeding birds may pass the organism on to their offspring, which may die in the nest or at weaning.