Nanopore sequencing reveals a diversity of microorganisms in ticks from Ethiopia

Ethiopia is home to a diverse group of ixodid ticks that are known to transmit disease to both animals and humans. Recent advances in metagenome sequencing show there is more microorganism diversity found in ticks than previously known. Compared to amplicon-based gene identification methods, agnostic metagenomic sequencing provides broader insights into the diversity of microorganisms in ticks, providing knowledge that will better enable public health measures in preventing the spread of zoonotic disease. In the present study, metagenomic sequencing was used to look at the microbial diversity of ticks collected from livestock in Ethiopia. This study identified six bacterial genera (Coxiella, Francisella, spotted-fever group (SFG) Rickettsia, Spiroplasma, Ehrlichia, and Borrelia), one genus of eukaryotic parasite (Babesia sp.), and one virus species (Parapoxvirus bovinestomatitis) from 154 tick pools representing 22 species of ticks among four genera (Amblyomma, Haemaphysalis, Hyalomma, and Rhipicephalus). We were able to differentiate between pathogenic and nonpathogenic microorganisms, highlighting concerns among traditional gene-targeted screening methods. Among all pooled samples, the predominant microorganisms included Coxiella-like endosymbionts (55.2%), SFG Rickettsia (38.3%), and nonpathogenic Francisella spp. (26.0%). Rickettsia africae was the predominant pathogenic agent detected, and phylogenetic analysis of two samples from A. gemma and A. variegatum confirmed the presence of R. africae. This study highlights the power of metagenomics applied to potential vectors of zoonotic disease, and it expands the knowledge on tick-pathogen associations in Ethiopia.