Q fever, caused by Coxiella burnetii, may cause vascular complications, but the role that this infection may play in the development of atherosclerotic cardiovascular disease remains unknown. This study examined the association between Q fever serology and cardiovascular disease in a region where Q fever is endemic. A case-control study was conducted in the Hospital Universitario de Burgos (Spain) between February 2011 and June 2012. A total of 513 samples were tested, from 454 hospitalized patients ≥65 years old, of whom 164 were cases (patients with prevalent or incident coronary heart, cerebrovascular or peripheral artery, disease) and 290 controls (patients without cardiovascular disease). Serum IgG antibody phase II titres against Q fever were determined by immunofluorescence assay. Seropositivity (titres ≥1:256) was detected in 84/164 (51.2%) cases and in 109/290 (37.6%) controls (p = 0.005; OR, 1.7; 95% CI, 1.1-2.5). This ratio increases when adjusted for sex, hypertension, dyslipidaemia, smoking, diabetes and atrial fibrillation (OR, 2.6; 95% CI, 1.5-4.7). The geometric mean titre (GMT) for C. burnetii phase II assay was higher in cases than in controls (p = 0.004). We found no significant relationship between cardiovascular disease and C. pneumoniae, and Cytomegalovirus seropositivity (both determined by the IgG ELISA method). In conclusion, serological evidence of past Q fever is associated with atherosclerotic cardiovascular disease in elderly patients in an endemic region.

Whether persistent or chronic Q fever may act as a risk factor for stroke is unknown. A case-control study was conducted in the Hospital Universitario de Burgos (Spain) between February 2011 and December 2012. A total of 803 samples from 634 consecutive hospitalized patients ≥65 years old were tested, of whom 111 were cases (patients with prevalent or incident ischaemic stroke and/or transient ischaemic attack) and 523 were controls (patients without ischaemic stroke and/or transient ischaemic attack). Immunoglobulin G (IgG) antibody titres phase I and II against Q fever, and IgG antibodies levels against Chlamydia pneumoniae and cytomegalovirus (CMV), were determined using immunofluorescence assay and ELISA methods, respectively. Phase I IgG titres against Coxiella burnetii ≥1:256 (compatible with chronic or persistent Q fever) were detected in 16 of 110 (14.5%) cases and in 32 of 524 (6.1%) controls; P = .004, odds ratio (OR) 2.6, 95% confidence interval (CI) 1.3 to 4.9. This ratio was maintained after adjusting for age, sex, hypertension, dyslipidaemia, cardioembolic focus, smoking, diabetes, other cardiovascular diseases, C-reactive protein, and leukocyte count (OR 2.6, 95% CI 1.3 to 5.3). High-titre IgG antibodies (top quartile) against CMV (OR 2.1, 95% CI 1.3 to 3.5), but not against C. pneumoniae (OR 0.9, 95% CI 0.5 to 1.6), also were associated with ischaemic stroke after adjustment for risk factors. In conclusion, serology compatible with persistent or chronic Q fever is associated with ischaemic stroke in elderly patients. High levels of IgG antibodies against CMV, but not against C. pneumoniae, also are associated with ischaemic stroke in these patients.

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