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.