Tick-Borne Pathogens Shape the Native Microbiome Within Tick Vectors

Ticks are blood-feeding arthropods and transmit a variety of medically important viral, bacterial, protozoan pathogens to animals and humans. Ticks also harbor a diverse community of microbes linked to their biological processes, such as hematophagy, and hence affect vector competence. The interactions between bacterial and/or protozoan pathogens and the tick microbiome is a black-box, and therefore we tested the hypothesis that the presence of a protozoan or bacterial pathogen will alter the microbial composition within a tick. Hence, this study was designed to define the microbial composition of two tick species,Hyalomma (H.) anatolicumandRhipicephalus (R.) microplus. We used a combination of PCR based pathogen (Anaplasma marginaleandTheileriaspecies) and symbiont (Wolbachiaspecies) identification followed by metagenomic sequencing and comparison of the microbial communities in PCR positive and negative ticks. A total of 1786 operational taxonomic units was identified representing 25 phyla, 50 classes, and 342 genera. The phylum Proteobacteria, Firmicutes, Actinobacteriota, and Bacteroidota were the most represented bacteria group. Alpha and beta diversity were not significantly affected in the presence or absence ofTheileriasp. andA. marginaleas see withH. anatolicumticks. Interestingly, bacterial communities were significantly reduced inTheileriasp. infectedR. microplusticks, while also exhibiting a significant reduction in microbial richness and evenness. Putting these observations together, we referred to the effect the presence ofTheileriasp. has onR. microplusa "pathogen-induced dysbiosis". We also identify the presence ofPlasmodium falciparum, the causative agent of human malaria from the microbiome of bothH. anatolicumandR. microplusticks. These findings support the presence of a "pathogen-induced dysbiosis" within the tick and further validation experiments are required to investigate how they are important in the vector competence of ticks. Understanding the mechanism of "pathogen-induced dysbiosis" on tick microbial composition may aid the discovery of intervention strategies for the control of emerging tick-borne infections.