Concomitant or Consecutive Infection with Coxiella burnetii and Tickborne Diseases

Background. Q fever is a worldwide zoonosis caused by Coxiella burnetii, which can be isolated from ticks. Reports of people with both Q fever and other tickborne diseases are rare. In this study, we describe 6 patients with Q fever who were infected with 1 of the following tickborne pathogens: Rickettsia conorii (2 patients),Rickettsia slovaca (2), Rickettsia africae (1), and Francisella tularensis (1). Methods. Diagnoses were made on the basis of results of microimmunofluorescence assays for detection of C. burnetii, R. conorii, R. slovaca, R. africae, and F. tularensis antigens. Cross-adsorption studies and Western blots were used to confirm dual infections. Results. Among the 6 cases presented, 3 were probably due to a concomitant infection after a tick bite, whereas the remaining 3 were more likely consecutive infections. Conclusions. Because acute Q fever is often asymptomatic, we recommend that patients infected with the tickborne pathogens mentioned above also undergo routine testing for concurrent infections with C. burnetii. Coxiella burnetii is a strictly intracellular bacterium that is the etiological agent of Q fever, a worldwide zoonosis that may present as acute or chronic disease. There are 3 major clinical presentations of acute Q fever: febril