The microbiome and Coxiella diversity in Amblyomma hebraeum and Dermacentor rhinocerinus ticks found on white rhinoceros

The microbiome and the prevalence of the pathogenic bacterium Coxiella burnetii in ticks associated with white rhinoceros, Ceratotherium simum , is unknown. Targeted Illumina 16S rRNA amplicon sequencing was used to characterize the bacterial microbiome diversity found within 40 Amblyomma hebraeum and 40 Dermacentor rhinocerinus ticks collected from 40 white rhinoceros individuals in the Kruger National Park (KNP), South Africa. At the phylum level Proteobacteria dominated the both tick microbiomes, followed by Actinobacteria and Firmicutes; however, Coxiella was the most abundant genus within A. hebraeum and Rickettsia within D. rhinocerinus . While alpha diversity did not differ significantly between the two tick species, beta diversity revealed significant differences in bacterial community composition. Additionally, there was no correlation between sampling region and microbiome diversity or composition for either tick species. Twenty-five Coxiella amplicon sequence variants (ASVs) were identified, forming three distinct monophyletic Coxiella clades and a fourth single ASV lineage. The Coxiella clades showed correlation to tick species identity with D. rhinocerinus harbouring significantly greater Coxiella diversity than A. hebraeum . PCR of the IS1111 transposase gene for 238 ticks detected a 66.1% (56.7–74.4%) prevalence for C. burnetii in D. rhinocerinus compared to 55.8% in A. hebraeum (46.5–64.8%). These findings support a notion that each tick species is characterized by its own microbiome community and that both A. hebraeum and D. rhinocerinus may act as reservoirs and potential vectors of C. burnetii to white rhinoceros.