Q Fever

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Q fever is a worldwide zoonosis caused by the pathogen Coxiella burnetii causing acute and chronic clinical manifestations. The name “Q fever” derives from “Query fever” and was given in 1935 following an outbreak of febrile illness in an abattoir in Queensland, Australia. C burnetii is considered a potential agent of bioterrorism (class B by the Centers for Disease Control).

Section snippets

Microbiology

C burnetii is a short (0.3 to 1.0 μm) gram-negative bacterium stained by the Gimenez method. Previously classified in the order Rickettsiales, C burnetii has been placed with Legionella and Francisella into the gamma subdivision of the Proteobacteria on the basis of sequences of the 16S rDNA encoding gene [3]. Coxiella burnetii is a strict intracellular bacterium and can be cultivated in embryonated eggs, laboratory animals, and cell cultures from clinical or animal specimens [1]. C burnetii

Epidemiology

Q fever is a worldwide zoonosis. Humans are incidental hosts in the zoonotic infection caused by C burnetii. The reservoir is large and includes mammals, birds, and arthropods, mainly ticks [1]. The most commonly identified sources of human infection are cattle, goats, and sheep; however, pets, including cats, rabbits, pigeons [7], and dogs, can serve as sources of infection [1]. Infected mammals shed C burnetii in urine, feces, milk, and birth products. High concentrations of C burnetii (up to

Clinical features

Primary infection with C burnetii is commonly asymptomatic. During an outbreak of 415 cases of Q fever in Switzerland, 224 patients (54%) were asymptomatic and only 2% were hospitalized [23]. The factors that determine whether symptoms will develop are unknown. Symptomatic infection is more likely in adults when compared with children and in men when compared with women [25]. The genotype of the organism also may be important [26]. Symptomatic illness can be divided into acute and chronic

Diagnosis

The laboratory findings during acute Q fever are nonspecific, and the diagnosis is usually made by serology. The leukocyte count is generally normal but may be elevated or decreased [21]. The erythrocyte sedimentation rate might also be high. Thrombocytopenia is noted in 25% of cases. Liver enzymes are commonly moderately elevated. Autoantibodies are commonly found, including antimitochondrial antibodies, anti–smooth muscle antibodies, and antibodies to phospholipids [1]. Anticardiolipin

Treatment

Acute Q fever is usually a mild disease that resolves spontaneously within 2 weeks. Therapy is warranted only in symptomatic patients. Tetracycline reduces fever duration significantly more than placebo [46]. Doxycycline is now recommended [46]. In children, doxycycline is recommended when the disease is established. Fluoroquinolones such as ofloxacin (200 mg three times a day) and pefloxacin (400 mg twice a day) have been used successfully. The efficacy of erythromycin is disputed, but newer

Prevention

An effective whole-cell vaccine for Q fever has been developed in Australia and has protected humans in occupational settings [1]. To prevent and control Q fever, it is useful for persons at high risk (eg, those who have cardiac valvular disease, those with vascular grafts, pregnant women) to avoid high-risk situations unless they are immune [25].

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      Citation Excerpt :

      Q fever infection can manifest as acute (primary) or chronic (localized) infections. While up to 50% of primary infections are thought to be asymptomatic, symptomatic acute infections typically present as a nondescript febrile illness following a 2- to 3-week incubation period [45]. Acute infections may present as a severe headache that is often retro-orbital and includes photophobia [46].

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