Fever of unknown origin and Q-fever: a case series in a Bulgarian hospital

Background: Fever of unknown origin (FUO) is a perplexing medical problem. The causes for FUO are more than 200 diseases. The aim of the study was to present human clinical cases of Coxiella burnetii infection debuting as FUO. Methods: The following methods were conducted in the study: literature search, laboratory, imaging, and statistical methods. Criteria of Durack and Street were applied for FUO definition. For the etiological diagnosis indirect immunoenzyme assay (ELISA) for antibodies detection against Coxiella burnetii was used (cut-off = 0.481–0.519). Results: From 2008 until 2015, nine patients with FUO caused by C. burnetii were hospitalized at the Military Medical Academy of Sofia. Male gender was predominant (male/female – 77.8% /22.2%), mean age was 48.78±14.52 years (range: 26–67), hospital stay was 9.78±2.95 days (range: 5–15), fever duration was 54.33±56.23 days (range: 21–180). Laboratory investigations estimated the elevation of erythrocyte sedimentation rate 49.11±31.74mm/h (95%CI = 13.09–111.31), C-reactive protein 37.68±37.62mg/L (95% CI = 36.07–111.42) and fibrinogen 5.69±1.59g/L (95% CI=2.57–8.81). The mean values of liver enzymes were in reference range. Among imaging tests, abdominal ultrasound and X-ray demonstrated 33.3% contribution to the final diagnosis. Transthoracic echocardiography found 22.2% contribution. Serological methods presented 100% contribution. Conclusion: C. burnetii infection was accepted as a final diagnosis among 9 patients with FUO based on the integrated information from the applied methods. Active search and establishment of this pathogen among FUO should lead to avoiding potential complications and consequences in case of untreated patients infected with C. burnetii.