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Psittacosis (ornithosis)

Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | Additional sources of information

Victorian statutory requirement

Psittacosis (Group B disease) must be notified in writing within five days of diagnosis.

School exclusion is not applicable.

Infectious agent

Chlamydia psittaci is an obligate intracellular bacterium.

Identification

Clinical features
The onset of psittacosis is usually abrupt with fever, prominent headache, photophobia, myalgia, and upper or lower respiratory tract symptoms. Dry cough is a common feature. Pulse-temperature dissociation, splenomegaly and rash may occur. In association with pneumonia these are said to be suggestive of the diagnosis. Chest X-rays may show patchy or focal consolidation.

The illness usually lasts for seven to ten days and is mild or moderate. It may be severe in pregnant or older, untreated patients. Asymptomatic infection or mild flu-like illness may also occur.

Complications include encephalitis, endocarditis, myocarditis and thrombophlebitis. Relapses may occur, especially when there has been inadequate treatment.

Method of diagnosis
Humans
Infection is generally diagnosed by seroconversion on paired acute and convalescent phase sera, although a single high acute phase titre in the setting of clinically-compatible illness is significant. Low positive titres are common in high risk groups. False positives may occur in C. pneumoniae, C trachomatis and occasionally in Legionella infections.

Antibiotic treatment may delay or attenuate antibody formation so convalescent sera should be taken at least two weeks after the acute specimen.

Culture of the organism is generally not performed because of danger to laboratory workers.

Birds
Birds suspected of being infected should be referred to a veterinarian for diagnosis and treatment as required. The Avian Medicine Section at Primary Industries Research Victoria, Attwood (03) 9217 4200 has further details of specimen collection and transport requirements.

Incubation period

The incubation period is four days to four weeks, commonly ten days.

Public health significance & occurrence

Most cases are sporadic but outbreaks of infection may occur rarely within individual households or through contact with affected pet shops or poultry processing plants.

Reservoir

Birds of all types act as a reservoir. This is especially common for psittacine birds (parrots, lorikeets, cockatiels, budgerigars) but also pigeons, turkeys, ducks and occasionally chickens. Healthy birds may be carriers. Cats, dogs, goats or sheep may be infected but this is rare.

Mode of transmission

Infection is generally acquired by inhaling dust from dried faeces or fresh or dried ocular and nasal secretions from infected birds. Direct contact with birds is not required for infection. Rare person to person transmission has occurred.

Period of communicability

Infected birds may shed the agent intermittently for a prolonged period. Shedding may be precipitated by stress on the birds such as cold, crowding or shipping. Dried secretions may remain infectious for many months.

Susceptibility & resistance

Chlamydia psittaci is highly infectious. At risk groups include bird owners, pet shop employees, veterinarians, poultry-processing workers, zoo workers and taxidermists.

Older adults and pregnant women may have a more severe illness. Immunity following infection may be incomplete and reinfection occurs occasionally.

Control measures

Preventive measures
Educate the public about the danger of household or occupational exposure to infected pet birds.

Wearing gloves and dust masks is recommended when cleaning areas with which birds have frequent contact such as cages and bird feeders.

Prevent or eliminate infections of birds by quarantine and antibiotic treatment.
Appropriate surveillance of commercial flocks, pet shops and aviaries should be instituted.

Destroy or treat infected birds and disinfect premises.

Control of case
Isolation is not necessary, but instruct the patient to cough into disposable tissues. Treatment with tetracyclines should be continued for 10–14 days after fever settles. If tetracyclines are contraindicated erythromycin can be used. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited).

Control of contacts
A diagnosis of psittacosis should be considered in symptomatic contacts.

Control of environment
If birds were recently purchased the origin of suspected birds should be traced. This is the responsibility of the Department of Health in liaison with the Department of Primary Industries.

Prophylactic use of tetracyclines can suppress, but not eliminate, infection in flocks and may complicate investigations.

For disinfection of floors and cages use a 1:100 dilution of household bleach in water or 70% isopropyl alcohol.

Outbreak measures

All cases should be thoroughly investigated in order to identify more extensive outbreaks.

Outbreaks should be reported to the Department of Health, Victoria.

Additional sources of information

Centers for Disease Control and Prevention 2000, ‘Compendium of measures to control Chlamydia psittaci infection among humans and pet birds’, Morbidity and Mortality Weekly Report, vol. 49, RR08, pp. 3–17
www.cdc.gov/mmwr

 


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