Q Fever Endocarditis: A Review of Local and all Reported Cases in the Literature

Background: Q fever endocarditis by Coxiella burnetii is rare and presents a diagnostic challenge. With limited data available, the aim of this study was to review all reported cases together with unpublished local cases to understand risk factor profiles, diagnostic methods, clinical features, treatments and outcomes. Methods: A search of the PubMed database using the term ‘Q fever endocarditis’ identified cases between 1950–2019. Included cases had positive polymerase chain reaction testing, valve culture or serology. Separately, to identify local cases meeting our criteria we queried the Western Australian Health Open Patient Administration System at two local hospitals for the ICD-10-AM diagnosis code A78 between 2013–2019. Results: We identified 181 cases from 31 publications and four local cases to create a combined series of 185 cases. The majority 141 (76%) were male and only 11% had normal cardiac valves. Most (72%) of patients had a history of contact with animals or travel. Nearly all (98%) cases had positive serology and over half (56%) had surgery performed. Overall mortality was 17%, and mortality for native valve endocarditis and prosthetic valve endocarditis was 12% and 3% respectively. No patients treated with doxycycline and hydroxychloroquine died. Mortality prior to 1999 was 28%, compared with 5% for more recent cases. Conclusion: Serological diagnosis is key in Q fever endocarditis and possible risk factors exist such as male gender, pre-existing valvular conditions and contact with animals or travel. Native valve endocarditis and treatment with drugs other than doxycycline and hydroxychloroquine increase the risk of death.