Molecular detection of Coxiella-like endosymbionts in Rhipicephalus microplus from north India

Apart from the tick-borne pathogens affecting human and animal health, ticks also harbor various non-pathogenic endosymbionts with dynamic ecological interactions. These endosymbionts are unexplored from the Indian ticks; hence this pilot study was conducted. Seventy-nine ticks were collected from Nainital district of Uttarakhand state of north India and were identified as Rhipicephalus microplus morphologically and by molecular analysis. PCR and sequence analysis were carried out to detect the presence of Rickettsia-like, Coxiella-like and Francisella-like endosymbionts in these ticks. Based on the partial 16S rRNA gene sequence, Coxiella-like endosymbiont (CLE) was detected in the adult and other life-cycle stages of ticks with 96.6-97.7% nucleotide sequence identity with the published CLE sequences from GenBank. The phylogenetic analysis revealed that the CLE from R. microplus were clustered with the CLE from other Rhipicephalus species. All these CLE formed distinct clades from the pathogenic Coxiella burnetii. None of the tick samples was found positive for Rickettsia-like and Francisella-like endosymbionts in the present study. We also demonstrated the vertical transmission of CLE from surface sterilized and laboratory reared fully engorged adult females to the eggs and the larvae. However, large scale studies are to be conducted to detect various endosymbionts and endosymbiont-tick associations in the Indian tick species and to explore these associations for tick and tick-borne disease control.