Beyond the usual suspects: Uncovering less-recognized pathogenic bacteria in Ghanaian blood-feeding Amblyomma variegatum ticks using 16S rRNA amplicon sequencing.

Abstract

Ticks are important vectors of bacterial pathogens affecting both human and animal health. In Ghana, Amblyomma variegatum is the predominant cattle-infesting tick, yet most studies have focused on a limited range of well-characterized pathogens, potentially overlooking a broader diversity of less-recognized, emerging, or opportunistic bacteria. In this study, we used 16S rRNA amplicon sequencing to characterize the bacteriome of partially blood-fed Am. variegatum ticks, with emphasis on underexplored taxa. As ticks were blood-fed at the time of collection, some detected microorganisms may represent transient, host-derived bacteria rather than endogenous tick microbiota; therefore, findings should also be interpreted within the context of xenosurveillance. Partially-fed ticks were collected from cattle across three ecological zones within Ghana's Greater Accra Region. 11 Am. variegatum ticks, confirmed through both morphological and molecular analyses, were subjected to high-throughput sequencing, and bacterial diversity and composition were analysed using established bioinformatics tools. Sequencing generated over 1.75 million high-quality reads and 3172 amplicon sequence variants. Five dominant bacterial phyla were detected, with Actinomycetota and Bacillota being the most abundant. While Rickettsia spp. were prevalent in some samples, Anaplasma and Coxiella, two commonly studied tick-borne bacteria, were not detected. Several less-recognized or opportunistic species, including multidrug-resistant Corynebacterium resistens and bovine-associated Porphyromonas levii, were identified at high relative abundance. These findings suggest that Am. variegatum may harbor a broader range of bacterial taxa than previously recognized. Incorporating such neglected microorganisms into a One Health tick-surveillance framework may improve disease risk assessment and guide public and animal health interventions in the region.