Chlamydia psittaci in Birds: Signs, Transmission and Human Health Risks
Chlamydia psittaci is an important bacterial infection of birds because it can cause disease in birds and can also be transmitted to people.
The infection is commonly called avian chlamydiosis in birds and psittacosis when it causes disease in humans. You may also hear it referred to as "parrot disease", although parrots are certainly not the only birds that can carry it.
Because infected birds can sometimes appear completely healthy, C. psittaci is an important consideration for bird owners, veterinarians, breeders and wildlife rehabilitators.
Which Birds Can Carry Chlamydia psittaci?
C. psittaci has been identified in many bird species.
It is particularly associated with psittacine birds such as:
- Cockatiels
- Budgerigars
- Parrots
However, infection can also occur in pigeons, doves, poultry, ducks, canaries, finches and many wild bird species.
Some infected birds develop obvious disease, while others may carry and shed the organism without showing significant clinical signs.
How Does Chlamydia psittaci Spread?
The bacteria can be shed in respiratory secretions, ocular discharge and droppings.
Transmission commonly occurs when contaminated material dries and microscopic particles become airborne and are inhaled.
Potential routes of exposure include:
- Inhaling contaminated dust from dried droppings or secretions
- Cleaning cages and aviaries
- Handling infected birds
- Contact with respiratory or ocular secretions
- Handling contaminated feathers, equipment or surfaces
Stress can increase shedding in infected birds. Transport, breeding, overcrowding, illness and other stressful events may therefore increase the risk of transmission.
What Are the Signs in Birds?
Avian chlamydiosis can be frustrating because there is no single set of signs that confirms infection.
Some birds remain apparently healthy, while others become severely unwell.
Clinical signs can include:
- Lethargy
- Reduced appetite
- Weight loss
- Fluffed or ruffled feathers
- Conjunctivitis
- Discharge from the eyes or nostrils
- Sneezing or other respiratory signs
- Abnormal droppings
- Green or yellow discolouration of the urates
- Diarrhoea
- Sudden deterioration or death in severe cases
These signs can occur with many other avian diseases, so laboratory testing is important.
How Is Chlamydia psittaci Diagnosed?
PCR testing is commonly used to detect C. psittaci.
Depending on the bird and circumstances, samples may include conjunctival, choanal or cloacal swabs, faecal material or other appropriate clinical samples.
One challenge is that infected birds may not shed the organism continuously. A negative result therefore needs to be interpreted alongside the bird's clinical signs, history and exposure risk.
Additional testing may be recommended when suspicion remains high.
How Is It Treated?
C. psittaci can be treated with appropriate antibiotics, but treatment protocols can be relatively prolonged because the organism lives inside the host's cells.
Treatment should be managed by a veterinarian, particularly because the bird's species, clinical condition, flock circumstances and potential human exposure all need to be considered.
Supportive care may also be required for birds that are significantly unwell.
Why Does Chlamydia psittaci Matter to People?
Psittacosis is a zoonotic disease, meaning infection can pass from birds to humans.
People with frequent or close bird contact may have greater exposure, including:
- Bird owners and breeders
- Wildlife rehabilitators
- Veterinarians and veterinary staff
- Poultry workers
- Pet shop and aviary workers
Human infection can range from relatively mild illness to significant systemic disease and pneumonia.
Anyone who develops compatible illness following exposure to a bird suspected or confirmed to have C. psittaci should tell their doctor about the bird exposure. That information can be important when determining which diseases should be investigated.
Biosecurity Around a Suspected Bird
Good infection control is particularly important while C. psittaci is being investigated or treated.
Isolate the Bird
Keep suspected or confirmed birds separated from other birds, ideally within a separate airspace where practical.
New birds should also be quarantined before being introduced into an established flock or aviary.
Reduce Dust and Aerosols
Avoid dry sweeping or other cleaning methods that send contaminated dust into the air.
Moisten contaminated material before cleaning and remove organic material carefully.
Wear Appropriate PPE
When caring for a suspected or confirmed case, appropriate protective equipment may include:
- Gloves
- Protective clothing
- Eye protection
- A well-fitting respirator such as an N95 or equivalent
Hand hygiene is essential after handling the bird or its environment.
Clean Before You Disinfect
Disinfectants work poorly when surfaces remain covered in droppings, food, feathers and other organic material.
Physically remove contamination first, then use an appropriate disinfectant at the correct concentration and contact time.
Chlamydia psittaci in Bird Rehabilitation
This disease deserves particular attention in rehabilitation facilities.
Birds often arrive with unknown histories and may be stressed, sick or shedding pathogens. Housing multiple birds within the same airspace creates an opportunity for organisms such as C. psittaci to spread.
Good quarantine, ventilation, PPE, cleaning protocols and appropriate diagnostic testing help protect other patients as well as the people caring for them.
The Takeaway
Chlamydia psittaci is important because an infected bird may pose a risk even when it doesn't appear particularly sick.
Respiratory disease, conjunctivitis, abnormal droppings and green or yellow urates can raise suspicion, but testing is required because these signs are not specific to chlamydiosis.
For bird owners and rehabilitators, the most important principles are early recognition, appropriate testing, good quarantine and careful infection control.
And if a person becomes unwell after exposure to a suspected or confirmed bird, make sure their healthcare provider knows about the bird contact.
Written by Dr Sam Hurley, BSc, BVSc, MAHM
Photo above from www.melbournebirdvet.com