PSITTACOSIS

Last updated: 06 September 2004

1. Reason for surveillance

• Identify sources of infection (eg pet shop, poultry processing plant) and control them

• To monitor the epidemiology of psittacosis and so inform better prevention strategies.

2. Case definition

Probable case
A probable case requires:

• Laboratory suggestive evidence, and

• Clinical evidence, and

• Epidemiological evidence.

Laboratory suggestive evidence

• A single high total antibody level or detection of IgM antibody to Chlamydia psittaci by microimmunofluorescence (MIF), or

• A single high total antibody titre to Chlamydia species demonstrated by CF test in at least one sample obtained at least 2 weeks after onset of symptoms, or

• A fourfold rise in antibody titre against Chlamydia species as demonstrated by CF test.

Clinical evidence
As with confirmed case.

Epidemiological evidence
As with confirmed case.

Confirmed case
A confirmed case requires:

• Laboratory definitive evidence, and

• Clinical evidence, and

• Epidemiological evidence.

Laboratory definitive evidence

• A fourfold rise in antibody titre against C. psittaci as demonstrated by MIF on acute and convalescent sera (collected at least 2 weeks later) tested in parallel, or

• Detection of C. psittaci by nucleic acid testing (NAT) or culture in clinical samples.

Clinical evidence

• Pneumonia, or

• AT LEAST TWO of the following: fever, headache, myalgia, rigors, dry cough or dyspnoea.

Epidemiological evidence
Exposure to birds or bird products, or proximity to an outbreak of psittacosis.

Factors to be considered in case identification
Most diagnoses are established using serologic methods in which paired sera are tested for chlamydial antibodies by CF test. However because chlamydial CF antibody is not species-specific, high CF titres can also result from C. pneumoniae or C. trachomatis infections.

Acute-phase serum specimens should be obtained as soon as possible after onset of symptoms, and convalescent-phase serum specimens should be obtained at least 2 weeks after onset of symptoms. Because antibiotic treatment can delay or diminish the antibody response, a third serum sample at 8 weeks may be required to confirm the diagnosis. All sera should be tested simultaneously at the same laboratory.

If the patient's epidemiologic and clinical history indicate a possible diagnosis of psittacosis, MIF and polymerase chain reaction (PCR) assays can be used to distinguish C. psittaci infection from infection with other chlamydial species.

Whilst it is possible to isolate the infectious agent from the patient's sputum, pleural fluid, or clotted blood during acute illness and before treatment with antimicrobial agents, culture of C. psittaci is not routinely performed in NSW because of safety concerns and technical difficulty.

3. Notification criteria and procedure

Psittacosis is to be notified by:

• Laboratories on diagnosis (ideal reporting by routine mail or telephone).

Probable and confirmed cases should be entered onto NDD.

4. The disease

Infectious agents
Chlamydophila psittaci, a bacterium. In 1999, the taxonomy of the family Chlamydiacae was revised; the organism was formerly known as Chlamydia psittaci.

Mode of transmission
Infection with C. psittaci usually occurs when a person inhales the organism, which has been aerosolised from dried faeces or respiratory secretions (ie sneezed droplets) of infected birds. Other means of exposure include mouth-to-beak contact and possibly the handling of infected birds' plumage and tissues. Even brief exposures can lead to symptomatic infection; therefore, some patients with psittacosis might not recall or report having any contact with birds. Person-to-person transmission has been suggested but never proven. Standard infection control procedures are sufficient for cases.

In birds, disease caused by infection with C. psittaci is called avian chlamydiosis (AC). The disease severity varies from mild, with some birds acting as asymptomatic carriers that shed the bacterium intermittently, to a severe and fatal disease. An infected bird may show signs of lethargy, anorexia, ruffled feathers, ocular/nasal discharge and diarrhoea. Antibiotic treatment is available for infected birds but is prolonged (minimum 7 weeks of weekly injections) and may be ineffective if the organism is in a dormant phase. In addition birds do not develop protective immunity and so may become reinfected. AC is widespread in cage and aviary birds and racing pigeons in NSW.

Although all birds are susceptible, pet birds (eg parakeets, parrots, and cockatiels) and poultry (turkeys and ducks) are most frequently involved in transmission to humans. Accordingly, groups at risk include bird owners, pet shop employees, pigeon fanciers and persons whose occupation places them at risk for exposure (e.g., employees in poultry slaughtering and processing plants, veterinarians, veterinary technicians, laboratory workers, workers in avian quarantine stations, farmers, wildlife rehabilitators, and zoo workers).

Timeline
Onset of illness follows an incubation period of 4 - 15 days, typically 10 days. Immunity following infection is incomplete and transitory. Therefore patients can be reinfected.

Clinical manifestations
The severity of this disease ranges from inapparent illness through mild flu-like illness to systemic illness with severe pneumonia.

Persons with symptomatic infection typically have abrupt onset of fever, chills, headache, malaise, and myalgia. They usually develop a non-productive cough that can be accompanied by breathing difficulty and chest tightness. A pulse-temperature dissociation (fever without elevated pulse), enlarged spleen, and rash are sometimes observed and are suggestive of psittacosis in-patients with community-acquired pneumonia. C. psittaci can affect other organ systems and result in endocarditis, myocarditis, hepatitis, arthritis, keratoconjunctivitis, and encephalitis. Severe illness with respiratory failure, thrombocytopenia, hepatitis, and foetal death has been reported among pregnant women.

5. Managing single notifications

Response times
Investigation
Within 3 working days of laboratory notification determine whether case is probable or confirmed and begin follow-up investigation.

Data entry
Within 5 working days of notification enter confirmed and probable cases onto NDD.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness

• Confirm results of relevant pathology tests, or recommend the tests be done

• Find out if the case or relevant care-giver has been told what the diagnosis is before interviewing them

• Seek the doctor's permission to contact the case or relevant care-giver

• Review case management, and

• Identify likely source of infection.

Case management
Investigation and treatment
Tetracyclines are the drug of choice (eg doxycycline 100 mg bd). Where tetracyclines are contraindicated (pregnancy, children <9 years), erythromycin or roxithromycin are alternatives. Remission of symptoms usually occurs within 48-72 hours. However relapse can occur, so antibiotics should be continued for 14 days.

Education
The case or relevant caregiver should be informed about the nature of the infection and the mode of transmission.

Exposure investigation
A history of exposure to birds should be sought, especially in the 4-15 days before onset of symptoms. Pay particular attention to pet bird contact/ownership, occupations that would bring the case into contact with wild or domestic fowl or their droppings, or vocational pursuits that would result in these exposures.

Isolation and restriction
None.

Environmental evaluation
Birds that are suspected sources of human infection should be referred to a veterinarian for evaluation, testing and treatment. All birds with confirmed or probable avian chlamydiosis should be isolated and treated. To prevent reinfection, contaminated aviaries should be thoroughly cleaned and sanitised (see below). If the source of infection is a pet bird, obtain the history of ownership, date and place of acquisition, and bird's health history. Sampling environmental surfaces in the home setting is rarely warranted.

Further advice can be obtained through the Department of Agriculture, which can provide contact details for local avian veterinary expertise.

Environmental disinfection
Where infected birds are identified the following guidelines should be followed by bird keepers.

• Take care to always handle healthy birds before handling isolated or sick birds. Wash hands thoroughly after handling sick birds. Wearing gloves and dust masks are recommended when cleaning areas where bird nests are found

• Rooms and cages where infected birds were housed should be cleaned immediately and disinfected thoroughly. When the cage is being cleaned, transfer the bird to a clean cage. Thoroughly wash and scour the soiled cage with a detergent to remove all faecal debris, rinse the cage, disinfect it (allowing at least 5 minutes of contact with the disinfectant), and re-rinse the cage to remove the disinfectant. Discard all items that cannot be adequately disinfected (e.g., wooden perches, ropes, nest material, and litter)

• Minimise the circulation of feathers and dust by wet-mopping the floor frequently with disinfectants and preventing air currents and drafts within the area. Reduce contamination from dust by spraying the floor with a disinfectant or water before sweeping it. Do not use a vacuum cleaner, as it can aerosolise infectious particles. Frequently remove waste material from the cage (after moistening the material), and burn or double-bag the waste for disposal

• Use disinfection measures. C. psittaci is susceptible to most disinfectants and detergents as well as heat; however, it is resistant to acid and alkali. Appropriate disinfectant include quaternary ammonium disinfectants, household bleach and 70% isopropyl alcohol. Many disinfectants are respiratory irritants and should be used in a wellventilated area. Avoid mixing disinfectants with any other product.

Contact management
Identification of contacts
Where a likely source is identified, identify other people who potentially had the same exposure (eg family, coworkers). Persons with recent symptoms/signs compatible with psittacosis should be evaluated by a doctor.

Education
Education about psittacosis and its treatment and prevention should be provided.

Birds should be housed in clean cages of ample size. Cages should be lined with newspaper that is changed frequently. Birds should only be obtained from a licensed pet store or aviary.

6. Managing special situations

Pet shop associated disease
Where a bird with probable or confirmed AC linked to a human case has been acquired from a pet store, dealer or breeder within 60 days of the onset of signs of illness, an investigation should be undertaken to ensure that there is no ongoing risk associated with the source of the bird.

Special control measures may be necessary at pet stores that have been linked to cases of human psittacosis, or where there has been a recognised avian outbreak. These measures typically include the isolation, treatment, or (if the owner's preference) destruction of sick birds. (There is no technical reason to kill affected birds. If the species involved is threatened or rare, then zoos or aviculturists would accept the birds, treat them and manage them appropriately). Cleaning/disinfection of cages and other surfaces is also required. These measures should be undertaken on advice from and under supervision of an avian veterinarian. Contact the Communicable Diseases Branch who will liaise with the Department of Agriculture for advice. Store inspection may involve officers from the Department of Agriculture and Local Government and PHU officers.

Where a pet store has been linked to human disease, the suppliers should be notified by telephone and in writing of the situation.