Prevalence of Coxiella-infections in ticks - review and meta-analysis

Abstract

Q fever is a global zoonotic infection caused by the intracellular Gram-negative bacterium Coxiella burnetii. Historically, it is considered a vector-borne disease, but the role of ticks in transmission has not fully been elucidated yet. Excretion of C. burnetii in tick feces and saliva is well documented but the role of these findings or the epidemiological context is discussed controversially. Thus, the aim of this study was to determine the prevalence of C. burnetii DNA in ticks to clarify the potential role of tick species for maintenance of C. burnetii infection. A literature review was performed using Google scholar, Agora, Science Direct, PubMed and Scopus to identify original studies on C. burnetii DNA presence in ticks. The search was limited to literature published from 2009 to 2020 in English and French and focused on data obtained by molecular detection of C. burnetii DNA in ticks. Overall, the prevalence of C. burnetii in ticks collected in Africa varied from 2.91% to 13.97%, in Europe from 2.46% to 10.52% and the Middle East from 4.76% to 12.53%. Ticks collected from animals showed a prevalence of 8% (95% CI: 6%–10%), followed by ticks collected from the environment and animals of 7% (95% CI: 5%–10%). C. burnetii DNA has been found in samples of many tick species with the highest prevalence in Rhipicephalus evertsi and Amblyomma variegatum. However, most of these studies did not include a differentiation between C. burnetii and Coxiella-like endosymbionts making it finally difficult to estimate the potential role that ticks play in the epidemiology of Q fever. Therefore, it is necessary to analyze the vector competence of different tick species to transmit C. burnetii. Knowledge of the vector and reservoir competence of ticks is important for taking adequate preventive measures to limit infection risks.