Treatment of Coxiella burnetii endocarditis with hydroxychloroquine. Is it evidence-based?

Treatment of persistent focalized Q fever: time has come for an international randomized controlled trial

Q fever is a worldwide zoonosis due to Coxiella burnetii, responsible for endocarditis and endovascular infections. Since the 1990s, the combination hydroxychloroquine + doxycycline has constituted the curative and prophylactic treatment in persistent focalized Q fever. This combination appears to have significantly reduced the treatment's duration (from 60 to 26 months), yet substantial evidence of effectiveness remains lacking. Data are mostly based on in vitro and observational studies. We conducted a literature review to assess the effectiveness of this therapy, along with potential alternatives. The proposed in vitro mechanism of action describes the inhibition of Coxiella replication by doxycycline through the restoration of its bactericidal activity (inhibited in acidic environment) by alkalinization of phagolysosome-like vacuoles with hydroxychloroquine. So far, the rarity and heterogeneous presentation of cases have made it challenging to design prospective studies with statistical power. The main studies supporting this treatment are retrospective cohorts, dating back to the 1990s-2000s. Retrospective studies from the large Dutch outbreak of Q fever (>4000 cases between 2007 and 2010) did not corroborate a clear benefit of this combination, notably in comparison with other regimens. Thus, there is still no consensus among the medical community on this issue. However insufficient the evidence, today the doxycycline + hydroxychloroquine combination remains the regimen with the largest clinical experience in the treatment of 'chronic' Q fever. Reinforcing the guidelines' level of evidence is critical. We herein propose the creation of an extensive international registry, followed by a prospective cohort or ideally a randomized controlled trial.

Acute Q fever revealed by an anti-phospholipid syndrome: A case report

INTRODUCTION

Q fever is a zoonosis caused by Coxiella burnetii. Acute infection is mainly asymptomatic. In other cases it mainly causes a flu-like illness, a pneumonia, or an hepatitis. We present an atypical case of an acute Q fever revealed by a massive pleural effusion.

CASE REPORT

We report the case of a 43-year-old man referred to our hospital for an acute respiratory distress. Further analyses showed an exudative eosinophilic pleural effusion, associated with a pulmonary embolism and a deep femoral vein thrombosis. Aetiologic explorations revealed an acute Q fever (IgM and IgG against C. burnetii phase II antigens) associated with anti-phospholipids. The outcome was favorable with vitamin K antagonists, doxycycline, and hydroxychloroquine, till the negativation of the anti-phospholipid antibodies.

DISCUSSION AND CONCLUSION

During acute C. burnetii infections, anti-phospholipid antibodies are highly prevalent but thrombotic complications are rare. The 2023 ACR/EULAR APS criteria restricts the diagnosis of APS, as in our case of acute severe infection. In front of an atypical pneumonia and/or thrombotic events, screening of C. burnetii and anti-phospholipid antibodies could be useful. Given its low level of evidence, prolongated treatment by doxycycline, hydroxychloroquine ± anticoagulant for C. burnetii's associated anti-phospholipid syndrome is discussed, but succeeded in our case.

Overview of Q fever in Brazil: an underestimated zoonosis

This review aims to provide current information about Q fever, elucidating the etiological, epidemiological, pathogenic, clinical, diagnostic, therapeutic, and prophylactic aspects of the disease for the medical community. We discuss the main forms of presentation of the agent, its ability to persist in the body, the infinite possibilities of susceptible hosts, the main known forms of transmission, its importance in populations at occupational risk, and the role of arthropods in the natural history of the disease. Focusing on Brazil, we present the cases already described and studies developed since its first report, and how there is still much to unravel. We are aware of the possibilities of the persistence of the agent and the development of severe clinical pictures and the specific treatments currently instituted. We also wish to raise awareness about the future, the new genotypes that are emerging, the need to study the effects of vaccines, and the impact of Q fever on the population. Q fever is a poorly understood disease in Latin America, and recent studies, especially in Brazil, have revealed the importance of developing new studies.