Coxiella endosymbionts of ticks
As in recent studies by Mwamuye et al. (2017) and Oundo et al. (2020), we also obtained Coxiella endosymbiont sequences from Rickettsia 16S rRNA primer amplicons. Previous studies have shown that these endosymbionts, which are closely related to the pathogen responsible for Q fever, C. burnetii, provide additional essential nutrients and reproductive fitness to ticks. Their elimination with antibiotic treatment was shown to negatively impact the fitness of the lone star tick Amblyomma americanum (Zhong et al., 2007). The phylogenetic co-divergence between the different tick species and their Coxiella endosymbionts shows the high specificity of these endosymbionts to their tick hosts. Four phylogenetic clades (A-D) have been described for tick-associated Coxiella endosymbionts. The sequences of endosymbionts from this study fell into groups B and C. Group B consists of Coxiella-endosymbionts of Amblyomma and Ornithodoros, while group C consists of rhipicephaline endosymbionts (Duron et al., 2015). These endosymbionts are non-pathogenic. However, it is important to note that there is evidence that Coxiella burnetii evolved recently from a maternally-inherited symbiont of ticks (Duron et al., 2015).