Chlamydial infections
Chlamydophila psittaci : Clinical
signs in humans
In humans, C. psittaci infection may be
asymptomatic or may present as an atypical pneumonia or
pyrexia (fever) of unknown origin (PUO).
Many cases probably go undiagnosed while some may be picked up by finding the
presence of high antibodies to chlamydial antigen when screening for agents of
fever of unknown origin. However, the main serological test commonly used for
screening (the CFT) does not distinguish
C. psittaci infection from C. pneumoniae. In the USA, an outbreak of clinically mild psittacosis in humans occurred as a result of contact with a large shipment of infected birds that were distributed to a number of pet stores. Mild illness and asymptomatic infections in persons exposed to infected birds were unusual characteristics of this zoonosis
(Moroney et al., 1998).
Symptomatic
C. psittaci infection in humans may present as two forms:
a severe atypical pneumonia / pneumonitis or a systemic toxic/septic form without respiratory involvement. In both cases, fever, chills, muscular aches and pains, and severe headache are typical. There may be diarrhoea, nausea and vomiting. The incubation period of C. psittaci infection is highly variable, from 1-4 weeks
(Eugster, 1980). The onset of disease
may be acute or insidious. As the disease progresses, the patient’s temperature may rise to 100-103 °F. The severity of the disease usually increases with age. Severe systemic illness may involve
endocarditis,
myocarditis and possibly renal
[kidney] complications. In fatal cases, the respiration rate may increase by about
three-fold, leading to respiratory failure requiring mechanical ventilation
(Wainright
et al., 1987). In surviving cases, recovery may be prolonged and complications including
encephalitis, meningitis, myelitis
[inflammation of the spinal cord] and liver
involvement may arise (Vanrompay et al.,
1995). Recent cases of C. psittaci infection in humans include infection and reinfection in a veterinarian
(Gosebell et al., 1999) and a case of
severe, systemic psittacosis requiring artificial ventilation (Soni et al.,
1999).
Fortunately, fatalities are nowadays rare
because the disease usually responds to the tetracyclines. However, if antibiotic treatment is insufficient, relapse may occur
(Grimes, 1994).
NEXT: C. psittaci:
Laboratory diagnosis
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