Information for clinicians on the characteristics, diagnosis and epidemiology of infections caused by Chlamydia psittaci.
Psittacosis is an infection of birds caused by the bacterium C. psittaci.
The disease has been described in many species of birds, particularly in parrots, parakeets, budgerigars and cockatiels. Other commonly affected birds include pigeons and doves. Ducks and turkeys may also be affected, but chickens less frequently.
Infections in birds are important as they represent a biological hazard to human health, as well as economic loss to the poultry industry and the pet bird retail trade. Birds can carry the organism without any signs of disease, or they can become mildly to severely ill.
Birds can transmit C. psittaci to humans; the resulting infection is also known as psittacosis or ornithosis.
Transmission of disease from birds to humans occurs mainly through inhalation of airborne particles from respiratory secretions, dried faeces or feather dust. Oral infection and handling of infected birds’ plumage and tissues are alternative routes.
Those at greatest risk of contracting the disease include bird fanciers and owners of pet birds. Pet shop employees and others whose occupation places them at risk of exposure (such as poultry slaughter-house workers, veterinarians, wildlife and zoo workers) are also at risk.
Because human infection can result from brief, passing exposure to infected birds or their dried contaminated droppings, people with no identified occupational or recreational risk can become infected.
Between 25 and 50 cases are laboratory confirmed in England & Wales each year.
The common animal-associated infections quarterly report: 2014 summarises confirmed cases of zoonoses reported in England and Wales.
Infection in humans
Psittacosis is an acute respiratory disease with an incubation period of between 1 and 4 weeks.
It typically causes flu-like symptoms (fever, headache, muscle aches) but can lead to severe pneumonia and non-respiratory health problems.
Although human disease may often be mild or moderate, it can be severe especially when untreated in elderly or immunocompromised individuals.
Diagnosis of the disease in humans can be confirmed by serological testing in which blood samples are tested for antibodies. Additionally, PCR testing is available from our respiratory and vaccine preventable bacteria reference unit (RVPBRU).
Clinicians should consider a diagnosis of psittacosis in patients with appropriate symptoms who have a history of exposure to birds and elevated or increasing antibody titres or who are PCR positive.