Handling the Microbial Complexity Associated to Ticks

Abstract

Ticks and the pathogens they transmit constitute a growing burden for human and animal health worldwide. In the last years, high-throughput detection and sequencing technologies (HTT) have revealed that individual ticks carry a high diversity of microorganisms, including pathogenic and non-pathogenic bacteria. Despite several studies have contributed to the availability of a catalog of microorganisms associated to different tick species, major limitations and challenges remain ahead HTT studies to acquire further insights on the microbial complexity associated to ticks. Currently, using next generation sequencing (NGS), bacteria genera (or higher taxonomic levels) can be recorded; however, species identification remains problematic which in turn affects pathogen detection using NGS. Microfluidic PCR, a high-throughput detection technology, can detect up to 96 different pathogen species, and its combination with NGS might render interesting insights into pathogenmicrobiota co-occurrence patterns. Microfluidic PCR, however, is also limited because detection of pathogen strains has not been implemented, and therefore, putative associations among bacterial genotypes are currently unknown. Combining NGS and microfluidic PCR data may prove challenging. Here, we review the impact of some HTT applied to tick microbiology research and propose network analysis as an integrative data analysis benchmark to unravel the structure and significance of microbial communities associated to ticks in different ecosystems.

Resistance of Tick Gut Microbiome to Anti-Tick Vaccines, Pathogen Infection and Antimicrobial Peptides

“…The complex community of microbes living in the tick guts [2] plays an important role in pathogen colonization [3,4] and potentially on tick fitness. However, despite its presumed importance, the distinction between 'constitutive' and 'transient' tick microbiota has remained an elusive task.…”

“…However, both bacteria are maintained in a mammal-tick infectious cycle that involves intimate interactions with ticks during the colonization of its gut, and subsequent migration to the salivary gland, before transmission to the vertebrate host [1]. Ixodes scapularis harbors a diverse group of native microbes, ranging from viruses to bacteria [2]. These microbial communities influence the ability of B. burgdorferi and A. phagocytophilum to colonize and persist within the vector [3][4][5].…”

The scale affects our view on the identification and distribution of microbial communities in ticks

“…Several contrasting findings can however be observed according to the tick scale we are looking at. With sensitive detection tools, tick co-infections are usually observed in tick-borne pathogen analyses [8,29,39].…”

“…In addition, it is now well established that TBPs coexist with many other microorganisms (microbiota) in ticks constituting a tick microbial complex recently named pathobiome [32]. The microbial communities of several tick species of the genera Ixodes, Dermacentor, Hyalomma, Haemaphysalis, Rhipicephalus and Amblyomma have been studied [33][34][35][36][37][38][39] improving our knowledge on the diversity and composition of the tick microbiome. Microbiome often consists of endosymbionts, which can have multiple detrimental, neutral, or beneficial effects to their tick hosts [40,41], and therefore might play various roles in fitness, nutritional adaptation, development, reproduction, defence against environmental stress, and immunity [42].…”

“…In this context, the identification and characterization of tick microbiota has become crucial to better understand tick-microbe interactions. With the development of high throughput sequencing technologies, the number of studies dealing with the tick pathobiome considerably increased in the past ten years revealing new pathogens and an unexpected microbial diversity in ticks [5,39,[44][45][46]. It is of great interest to identify members of the microbial community which strongly affect the risk of TBPs transmission, either by affecting the fitness of ticks, their survival, or the transmission capacity of pathogens.…”