ABSTRACT
INTRODUCTION Coxiella burnetii, a gram-negative, pleomorphic coccobacillus, is characterized by its obligate intracellular localization and close association with arthropod and mammalian hosts. An infection with this organism causes Q (query) fever in humans and animals, first described by Derrick (1) in 1937 during an outbreak of a febrile illness among abattoir workers in Australia. Q fever, a zoonosis with a worldwide distribution, normally appears in humans as an acute, flu-like, and self-limiting illness, with fever and severe headaches. The less common chronic form can be life-threatening and manifests primarily as endocarditis or hepatitis (2). Impressive is the extremely broad host range of C. burnetii, including domestic animals, such as sheep, goats, and cattle, but also wild animals (3). This wide spectrum of reservoirs and the unique resistance of C. burnetii to environmental factors make tracing the source of infection difficult. Furthermore, the low infective dose, aerosolic transmission, and the capacity to disable a large group of humans led to the classification of C. burnetii as potential biological weapon in 1942 (4) and recently as a category B Select Agent by the Centers for Disease Control and Prevention. This renewed concern has led to new efforts to investigate the epidemiology, pathogenesis, and genomic aspects of this organism and to develop new vaccine and treatment strategies.
