Psittacosis
Information for clinicians on the characteristics, diagnosis and epidemiology of infections caused by Chlamydia psittaci.
Characteristics
Psittacosis is a bacterial infection caused by Chlamydia psittaci (C.psittaci), which usually infects birds.
The disease can be transmitted from birds to humans leading to a respiratory illness. The disease is commonly associated with pet birds such as parrots, parakeets, budgerigars and cockatiels, but many other bird species can be infected. Not all birds will have symptoms when infected with C.psittaci, however they are still able to transmit infection.
Epidemiology
Transmission of disease from birds to humans occurs mainly through inhalation of infected respiratory particles, or dust contaminated with faeces or respiratory secretions. Direct oral contact with an infected bird 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.
Usually less than 10 PCR confirmed cases are reported each year in England. The Common animal-associated infections (England): first quarter 2024 report summarises confirmed cases of zoonoses reported in England from samples received in the UKHSA reference laboratory and those reported by local laboratories through SGSS (Second Generation Surveillance System).
Infection in humans
Psittacosis is an acute respiratory disease with an incubation period of between 1 and 4 weeks.
Individuals with infection typically present with non-specific flu-like symptoms such as fever, headache, muscle aches and cough. Whilst human infection may often be mild, it can lead to severe pneumonia and respiratory failure especially when untreated in elderly or immunocompromised individuals. Very rarely it may lead to severe complications including inflammation of other organs such as the heart, liver or brain. Cases can be treated with appropriate antibiotics.
Diagnosis
Clinicians should consider a diagnosis of psittacosis in patients with appropriate symptoms who have a history of exposure to birds or environments contaminated with bird excreta. Testing should also be considered in patients with severe undiagnosed pneumonia, even in the absence of known bird exposure.
Diagnosis of the disease in humans can be confirmed by molecular (PCR) testing of respiratory samples, which is available from the UKHSA respiratory and vaccine preventable bacteria reference unit (RVPBRU).
Some NHS trusts may also have their own in-house PCR testing. Where primary testing is undertaken locally, all positive samples should be referred to RVPBRU for confirmatory testing.
Current PCR testing does not distinguish between C.psittaci and Chlamydia abortus (C.abortus). However, human infection with C. abortus is rare and follows exposure to infected sheep.
Serological testing in which acute and convalescent blood samples are tested for antibodies has historically been used for psittacosis diagnosis but is no longer considered best practice.
Trusts should refer to the RVPBRU user manual when making requests to the reference laboratory.
Samples should be submitted using the appropriate respiratory and systematic bacteria request form.
Prevention and control
Prevention of transmission of infection from birds to humans relies on:
- reducing the accumulation of infected droppings, feathers and other secretions, to prevent the generation of infected dust
- ensuring good ventilation to minimise the risk of breathing in infected material in areas where birds congregate.
The Health and Safety Executive (HSE) provide guidance on managing the risk of psittacosis in the workplace.
It is good practice to ensure that bird feeding stations for wild birds are well maintained, to minimise the risk of transmitting a variety of infections to other birds and humans. Further information is available from Garden Wildlife Health (GWH).
Updates to this page
Last updated 28 November 2024 + show all updates
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Updated to reflect changes in testing.
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Updated diagnosis section to include PCR detection of infection and services offered and a link to the RVPBRU webpage.
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First published.