Psittacosis (ornithosis, parrot fever)

Notification requirement for psittacosis (ornithosis, parrot fever)

Psittacosis is a ‘routine’ notifiable condition and must be notified by pathology services in writing within 5 days of diagnosis. Medical practitioners are not required to notify cases of psittacosis.

This is a Victorian statutory requirement.

Primary school and children’s services services exclusion for psittacosis

Exclusion is not applicable.

Infectious agent of psittacosis

Chlamydophila psittaci is a Gram-negative obligate intracellular bacterium.

Identification of psittacosis

Clinical features

The clinical presentation can be variable, but 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. The pulse may be slow relative to temperature; splenomegaly and rash may also occur. In association with pneumonia, these features are said to be suggestive of the diagnosis. Chest X-rays may show patchy or focal consolidation that can be more extensive than respiratory symptoms would suggest.

The illness usually lasts for 7–10 days and is mild or moderate in severity. It may be more 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.

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 Legionella infections.

Antibiotic treatment may delay or attenuate antibody formation, so convalescent sera should be taken at least 2 weeks after the acute specimen.

A polymerase chain reaction (PCR) test is also available at the Victorian Infectious Diseases Reference Laboratory and can be performed on respiratory specimens if rapid definitive diagnosis is required.

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.

Incubation period of psittacosis

Onset of illness follows an incubation period of 5–21 days, typically 10 days, but possibly up to 4 weeks. Immunity following infection is incomplete and transitory, so patients can be reinfected.

Public health significance and occurrence of psittacosis

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 of psittacosis

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. Illness in birds is known as avian chlamydiosis; symptoms range from mild to severe and may include anorexia, lethargy, oculonasal discharge and diarrhoea. Healthy birds may be carriers. Cats, dogs, goats and sheep may be infected but this is rare.

Mode of transmission of psittacosis

Infection is generally acquired by inhaling dust from dried faeces or fresh or dried ocular and nasal secretions from infected birds, which may remain infectious for months. Direct contact with birds is not required for infection. Rare person-to-person transmission has been reported.

Period of communicability of psittacosis

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 and resistance to psittacosis

C. psittaci is highly infectious. At-risk groups include bird owners, pet shop employees, veterinarians, poultry-processing workers, zoo workers and taxidermists. Lawn mowing without a grasscatcher and gardening have also been associated with disease transmission.

Older adults and pregnant women may have a more severe illness. Immunocompromised people do not appear to be at increased risk of contracting the disease. Immunity following infection may be incomplete, and reinfection occurs occasionally.

Control measures for psittacosis

Preventive measures

• Educate the public about the danger of household or occupational exposure to infected pet birds.
• Wear gloves and dust masks or P2 respirators when cleaning areas with which birds have frequent contact, such as cages and bird feeders.
• Do not allow birds to come near their owner’s mouth and nose.
• Owners should seek advice and treatment from a veterinarian as soon as pet birds develop signs of respiratory illness.
• Avoid feeding and handling wild birds.
• Institute appropriate surveillance of commercial flocks, pet shops and aviaries and manage infected birds and premises.
• Use a catcher on lawn mowers and wear a dust mask or P2 respirator while mowing.

Control of case

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

Control of contacts

A diagnosis of psittacosis should be considered in symptomatic contacts.

Control of environment

If suspected birds were purchased recently, their origin should be traced. This is the responsibility of the department in liaison with the Department of Environment, Land, Water and Planning.

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

C. psittaci is susceptible to most disinfectants and detergents as well as heat; however, it is resistant to acid and alkali. Appropriate disinfectants include quaternary ammonium disinfectants, 3 per cent hydrogen peroxide, benzalkonium chloride, alcoholic iodine solutions and 70 per cent ethanol. Hospital grade disinfectants based on sodium hypochlorite are also suitable. A 1:100 dilution should be prepared immediately before use and discarded at the end of each disinfection session. Many disinfectants are respiratory irritants and should be used in well-ventilated areas. Avoid mixing disinfectants with any other product.

Outbreak measures for psittacosis

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

Outbreaks should be reported to the department.