Psittacosis (Chlamydia psittaci) (Ornithosis)

1996 Case Definition

Clinical description

An illness characterized by fever, chills, headache, photophobia, cough, and myalgia

Laboratory criteria for diagnosis

• Isolation of Chlamydia psittaci from respiratory secretions, or
• Fourfold or greater increase in antibody against C. psittaci by complement fixation or microimmunofluorescence (MIF) to a reciprocal titer of greater than or equal to 32 between paired acute- and convalescent-phase serum specimens, or
• Presence of immunoglobulin M antibody against C. psittaci by MIF to a reciprocal titer of greater than or equal to 16

Case classification

Probable: a clinically compatible case that is epidemiologically linked to a confirmed case or that has supportive serology (e.g., C. psittaci titer of greater than or equal to 32 in one or more serum specimens obtained after onset of symptoms)

Confirmed: a clinically compatible case that is laboratory confirmed

Comment

The serologic findings by CF also may occur as a result of infection with Chlamydia pneumoniae or Chlamydia trachomatis. The MIF might be more specific for infection with C. psittaci, but experience with and availability of this newer test are more limited.

See also:

• 1990 Case Definition

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