# The Microbiome and Coxiella Diversity Found in Amblyomma hebraeum and Dermacentor rhinocerinus Ticks Sampled from White Rhinoceros

## TL;DR

This study explores the bacterial communities in two tick species found on white rhinoceroses and finds that both ticks host diverse bacteria, including the pathogen Coxiella burnetii.

## Contribution

The study identifies distinct microbiome profiles and Coxiella diversity in two tick species associated with white rhinoceroses.

## Key findings

- Proteobacteria dominated both tick microbiomes, with Coxiella most abundant in Amblyomma hebraeum and Rickettsia in Dermacentor rhinocerinus.
- Dermacentor rhinocerinus harbored significantly greater Coxiella diversity than Amblyomma hebraeum.
- Coxiella burnetii prevalence was detected at 66.1% in Dermacentor rhinocerinus and 55.8% in Amblyomma hebraeum.

## Abstract

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, South Africa. Specific emphasis was also given to further investigate the prevalence of the pathogenic C. burnetti in these tick species. At the phylum level, Proteobacteria dominated both tick microbiomes, followed by Actinobacteria and Firmicutes; 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 species-specific 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 a correlation to tick species identity with D. rhinocerinus harboring significantly greater Coxiella diversity than A. hebraeum—potentially indicative of different coevolutionary pathways between the bacteria and their respective hosts. 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 composition and that both A. hebraeum and D. rhinocerinus may act as reservoirs and potential vectors of C. burnetii to white rhinoceros.

The online version contains supplementary material available at 10.1007/s00248-025-02549-6.