Identification of Risk Factors for Chronic Q Fever, the Netherlands - Vol. 18 No. 4 - April 2012 - Emerging Infectious Disease journal - CDC
Table of Contents
Volume 18, Number 4–April 2012
Volume 18, Number 4—April 2012
Identification of Risk Factors for Chronic Q Fever, the Netherlands
Q fever, a zoonosis caused by the intracellular gram-negative bacterium Coxiella burnetii, is prevalent worldwide (1,2) and has various acute and chronic clinical manifestations. Acute Q fever is mostly a self-limiting, mild, influenza-like disease, sometimes complicated by severe pneumonia or hepatitis. Asymptomatic acute infection occurs in 50%–60% of patients (3–5). Among patients infected by C. burnetii, infection progresses to chronic Q fever in 1%–5%, months to years after primary infection (2,4,6). Previous data, mainly from France, show that endocarditis is the most common clinical manifestation (±75%), followed by infections of aortic aneurysms and vascular prostheses (±10%) (5,7–9). In the Netherlands, however, an equal distribution of endocarditis and vascular infections has been seen (10).
AbstractSince 2007, the Netherlands has experienced a large Q fever outbreak. To identify and quantify risk factors for development of chronic Q fever after Coxiella burnetii infection, we performed a case–control study. Comorbidity, cardiovascular risk factors, medications, and demographic characteristics from 105 patients with proven (n = 44), probable (n = 28), or possible (n = 33) chronic Q fever were compared with 201 patients who had acute Q fever in 2009 but in whom chronic Q fever did not develop (controls). Independent risk factors for development of proven chronic Q fever were valvular surgery, vascular prosthesis, aneurysm, renal insufficiency, and older age.
Chronic Q fever leads to high illness and death rates if untreated, which makes early case finding and preventive measures critical for patients at high risk. Treatment for Q fever consists of long-term antimicrobial drug therapy, preferably a combination of doxycycline and hydroxychloroquine for 18–24 months. Previously identified risk factors for chronic Q fever are preexisting cardiac valvulopathy, vascular grafts and aneurysms, immunosuppression, and pregnancy; however, most published studies have been descriptive, lacked statistical quantification, or included specific high-risk groups only (6–9,11,12).
Since 2007, a large Q fever outbreak has been ongoing in the Netherlands, with >4,000 acute Q fever cases reported (13). Because of asymptomatic disease and overlap with other febrile diseases, however, the actual number of Q fever infections is probably much higher. Although the acute Q fever epidemic in the Netherlands has subsided, the number of patients with chronic Q fever is rising (10,14). In this unique population, we conducted a case–control study to identify and quantify risk factors for development of chronic Q fever after C. burnetii infection.