Global variations and implications of microbiome communities in Ixodidae ticks: a systematic review and quality assessment

Ticks are blood-feeding arthropods that infest a wide range of terrestrial vertebrates and serve as important vectors of disease. While primary pathogens have received substantial attention, the broader microbial communities harbored by ticks remain comparatively understudied. This systematic review synthesizes global literature on bacterial communities associated with Ixodidae tick species, focusing on studies utilizing Illumina-based sequencing of the 16S rRNA V3-V4 hypervariable region. A systematic literature search was conducted using Google Scholar, PubMed, Science Direct, Scopus and Web of Science Core Collection databases for articles published between January 2011 to July 2024, yielding 68 eligible selected articles. The included studies covered tick genera Amblyomma, Bothriocroton, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus across 23 countries. Overall, Ixodidae ticks exhibited a limited core microbiota dominated by Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria independent of tick species, sex, host, geographic region and tissue type. Taxonomic composition varied across studies, with Coxiella and Rickettsia consistently reported as dominant endosymbionts. Microbial diversity differed according to tick species, sex, developmental stage, feeding status and tick organ, whereas the effects of geographic location and pathogen infection status were inconsistent across studies. Interpretation of temporal changes remains limited due to the paucity of longitudinal studies. We herein integrated global findings of Ixodidae microbial composition and the key factors influencing bacterial richness and diversity.

Ticks are blood-feeding obligate ectoparasites of a wide range of vertebrates, which include livestock, wildlife, and humans (Che Lah et al., 2023). The Ixodida are classified into three extant families, Ixodidae (~700 species), the Argasidae (~200 species) and the monospecific Nuttalliellidae (Charrier et al., 2019). Larval, nymphal and adult developmental stages can feed on different vertebrate hosts, facilitating the transmission of a wide range of pathogens which include bacteria, helminths, protozoa and viruses.

Aside from pathogens, ticks also harbor a wide range of symbiotic and commensal microorganisms (Alreshidi et al., 2020). The tick microbiome, which is the community of microorganisms residing within ticks, consists of bacteria, eukaryotes and viruses, with bacteria as the dominant and most functionally important group contributing to tick survival, reproduction and vectorial competence (Greay et al., 2018). Primary pathogens which include pathogenic species of Anaplasma, Borrelia, Coxiella, Ehrlichia, Rickettsia, Babesia and Theileria have received great attention, but the overall microbial communities harbored by ticks remain understudied (Egan et al., 2021).

Several studies have reported on the structure and microbial composition of field-collected and laboratory-maintained ixodid tick populations (Andreotti et al., 2011; Menchaca et al., 2013; Rojas-Jaimes et al., 2022), with the most extensively studied bacterial communities associated with tick genera Amblyomma, Dermacentor, Ixodes and Rhipicephalus. The primary focus of tick microbiome research has been the microbial profiling of field-collected ticks to baseline the bacterial communities present. However, the tick microbiome is a dynamic community, and investigation remains a continuous effort (Adegoke et al., 2022). The ability of Next Generation Sequencing (NGS) technologies to identify a wide range of microbes simultaneously has eliminated the need for individually designed bacterial specific primers and thus expanded our knowledge on tick-associated bacterial communities.

This systematic review synthesizes global microbiome research from field-collected and laboratory-reared Ixodidae ticks, with a focus on studies targeting the 16S rRNA V3 – V4 hypervariable region. The review focuses on (i) the structure and composition of the bacterial communities and (ii) the ecological and biological factors that influence microbiota diversity and community dynamics and (iii) the synergistic and antagonistic interactions between bacterial community members that influence tick survival and reproduction which could be beneficial in the development of tick control strategies and interruption of pathogen transmission.

Search strategy

A systematic literature search was conducted using five electronic databases: Google Scholar, PubMed, Science Direct, Scopus, and the Web of Science Core Collection, restricted to peer-reviewed articles published in English between January 2011 and July 2024 (13 years). Boolean Operators (AND, OR) were used in combination with the following keywords: Ixodidae OR Ixodid OR hard ticks AND 16S rRNA AND microbiome AND Next Generation Sequencing. To ensure comprehensive coverage, the reference lists of retrieved articles were also screened for any relevant articles (snowballing). Preferred Reporting Items for Systematic reviews and Meta- Analyses (PRISMA) guidelines for systematic reviews were followed during the conduction and reporting of this systematic review (Figure 1).

Inclusion and exclusion criteria

Articles included in the review were those published between January 2011 and July 2024 in peer-reviewed journals and explicitly reported on (i) microbiome studies of any of the Ixodidae tick life stages (egg, larva, nymph, adult) using field collected (questing), host collected or laboratory-reared ticks, and (ii) the bacterial 16S rRNA V3 – V4 hypervariable region was amplified and sequenced via Illumina NGS. Illumina sequencing of the 16S rRNA V3–V4 region was selected to maximize comparability across studies, as this approach is the most consistently applied method in tick microbiome research. Restricting inclusion to a single sequencing platform helped reduce methodological heterogeneity and facilitated more reliable cross study synthesis (Bentley et al., 2008; Klindworth et al., 2013).

The review excluded (i) microbiome studies of soft ticks from the family Argasidae and the monotypic Nuttalliellidae (ii) studies which applied NGS methods which were not Illumina sequencing of the 16S rRNA V3-V4 region (iii) studies where NGS was used for specific pathogen identification (iv) studies where the natural tick microbiota was directly altered/manipulated (v) studies which focused on evaluation of methods (vi) bioinformatics studies that used previously published data (vii) conference abstracts, dissertations, duplicate studies, reviews, short communication papers and unpublished reports (viii) non-English studies and studies outside the specified period range.

Data extraction and synthesis

All retrieved articles were screened by title and abstract, and duplicate records and studies that did not meet the inclusion criteria were removed and the remaining studies were retrieved. Full-text articles were then assessed independently for eligibility, and articles that were deemed ineligible were removed. Once consensus had been reached by authors on which articles to include in the study, data was extracted into a pre-designed data sheet in Microsoft Excel. The data extracted included year of publication, geographic location, sampling year, tick metadata (questing/host collected, vertebrate host, tick species, sample size, tick sex, tick instar, whole tick/organ analysis, sample grouping), aims and outcomes of the study and author reference. The compiled microbiome data was reviewed for consistency and accuracy before synthesis.

Quality assessment

To ensure methodological transparency and adherence to the expected standards of conducting and reporting systematic reviews, we applied A Measurement Tool to Assess Systematic Reviews, version 2 (AMSTAR2) checklist (Shea et al., 2017) (Additional File 2). The methodological quality of included studies was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklists appropriate to study design (cross-sectional checklist for cross sectional studies and the cohort checklist for longitudinal studies) adapted for tick microbiome studies (Joanna Briggs Institute, 2023). To ensure transparency and completeness in reporting of laboratory and bioinformatics methods of the reviewed studies, the Strengthening the Organization and Reporting of Microbiome Studies (STORMS) checklist was used in parallel for evaluation. The STORMS checklist, developed for reporting on the quality of human microbiome studies comprises a structured 17-item checklist for standardized reporting of key quality and methodology parameters (Mirzayi et al., 2021).

Data analysis and visualization

The number of studies conducted per country and tick genera studied were displayed as pie charts on a map created in QGIS software (version 3.34.8) (Figure 2). Country central coordinates (centroids) were used as plotting points for the pie charts (Additional File 1. Dataset S3). The reported proportions and their corresponding 95% confidence intervals were calculated in RStudio (version 4.5.0) using the Clopper-Pearson method.

The top ten most abundant bacterial genera reported per tick genus were retrieved from each study. Bacterial genera were recorded as present (1) or absent (0), based on their occurrence in each tick genera studied. To highlight shared bacterial taxa across studied tick genera, a presence/absence heatmap (Figure 3) was constructed in RStudio (version 4.5.0) using the ComplexHeatmap package with default hierarchical clustering based on the Euclidean distance method and complete linkage. The binary presence–absence matrix was used without transformation, and bacterial genera were categorized into “Core”, “Moderate”, and “Rare” groups based on reported occurrence across reviewed tick genera (≥0.8, ≥0.3 and <0.3 respectively). The number of shared bacterial taxa across tick genera were highlighted in UpSet plots (Figure 4) constructed in RStudio (version 4.5.0) using the ComplexUpset package. A bipartite network showing tick-microbial co-occurrence was created in RStudio (version 4.5.0) with the igraph and ggraph packages using the Fruchterman–Reingold layout to highlight core microbial taxa reported across tick genera (Figure 5). The node size for bacterial taxa was weighted by the number of tick genera in which they occurred, while tick nodes were assigned uniform size. The putative core microbiota was determined as the genera present in 6–7 tick genera from the reviewed studies based on criteria adapted from Chicana et al. (2019) and Shade and Handelsman (2012). As analyses were restricted to the most frequently reported bacterial genera per study, inferred associations were interpreted as patterns of co-occurrence rather than direct ecological interactions.

Search results

The literature search yielded a total of 930 studies. After removing 278 duplicates, the remaining 652 records were screened by title and abstract, resulting in the exclusion of 439 articles. The full texts of the remaining 213 articles were retrieved and assessed for eligibility, of which 145 were deemed ineligible, leaving 68 articles for inclusion in the systematic review (Figure 1).

Quality assessment

According to the JBI cross-sectional checklists, all cross-sectional studies (58/58, 95% CI: 93.8 – 100%) selected for the study described the study area, study participants, and the study selection criteria (Additional File 1. Dataset S4). When assessed using the JBI checklist for cohort studies, all longitudinal studies accurately reported on locality and study participants details (10/10, 95% CI: 69.2 – 100%). For eight studies, a tick cohort from the same population was followed through successive developmental stages to monitor changes in the microbiome composition and diversity (Kwan et al., 2017; Couper et al., 2019; Brinkerhoff et al., 2020; Li et al., 2020; Adegoke et al., 2022; Kumar et al., 2022b). Follow up procedures were adequately reported and no loss to follow up was reported for all the studies (10/10, 95% CI: 69.2 – 100%). (Additional File 1. Dataset S5).

The reviewed studies did not meet all the key criteria outlined in the STORMS checklist. None of the studies that investigated ticks collected from humans or domestic livestock, reported information on host exposure to acaricides. Majority of studies (58/68, 95% CI: 74.1 – 92.7%) described how samples were stored between collection and processing. Among the collection and storage methods described, ticks were mostly transported from the field alive, under controlled temperature and humidity, or in 70% - 100% ethanol with subsequent storage at temperatures ranging from room temperature and -80 °C before DNA extraction. Overall heterogeneity in storage conditions across studies was observed, however storage of DNA extracts prior to amplification and sequencing was universally at -20 °C or -80 °C across studies.

A subset of the studies incorporated experimental controls to assess contamination and sequencing accuracy. Negative controls including DNA extraction blanks and PCR no-template controls were processed with samples to detect potential contamination in 37 of the 68 studies (95% CI: 41.9 – 66.6%). Taxa predominantly detected in negative controls were filtered from the dataset during analysis. Positive controls such as commercially available mock community standards were included in 15 studies (15/68, 95% CI: 12.9 – 33.8%) for validation of DNA extraction, sequencing and bioinformatic analysis protocols.

In terms of data transparency, 45 studies submitted raw data in publicly available databases such as the National Center for Biotechnology Information (NCBI) and the European Molecular Biology Laboratory-European Bioinformatics Institute (EMBL-EBI) and provided project accession numbers. Full results of all conducted analyses in computer readable formats such as Tab-delimited text (.tsv) and Comma-Separated Values (.csv) were available for 48.5% of the reviewed studies (33/68, 95% CI: 36.2 – 61.0%). Majority of studies (51/68, 95% CI: 63.1 – 84.4%) discussed limitations and accounted for potential sources of bias and imprecision (Additional File 1. Dataset S6).

Geographic distribution of tick microbiome research

Of the 68 studies reviewed, the majority were conducted in Asia (30/68; 44.1%, 95% CI: 32.1 – 56.7%), followed by North America (17/68; 25.0%, CI:15.3– 37.0%), and Europe (10/68; 14.7%, 95% CI: 7.28 – 25.4%). Few studies were conducted in Africa (5/68; 7.35%,95% CI: 2.43 – 16.3%), South America (4.41%; 3/68, 95% CI: 0.92 – 12.4%), and Australasia (4.41%; 3/68, 95% CI: 0.92 – 12.4%) as illustrated in Figure 2. When stratified by country, the People’s Republic of China contributed the largest number of studies (17/68; 25.0%, 95% CI: 15.3 – 37.0%), followed by the United States of America (15/68; 22.1%, 95% CI: 12.9 – 33.8%). Australia, Colombia and the United Arab Emirates accounted for three studies (4.41%; 3/68, 95% CI: 0.92 – 12.4%), while France, Germany, Japan, Malaysia, Mexico, Netherlands, Saudi Arabia, South Africa, and Thailand each had two studies (2/68; 2.94%, 95% CI: 0.36 – 10.2%).

Tick metadata and sample grouping for analysis

The reviewed studies collectively represented seven genera of hard ticks: Amblyomma (13/68, 95% CI: 10.6% – 30.5%), Bothriocroton (1/68, 95% CI: 0.04% – 7.92%), Dermacentor (15/68, 95% CI: 12.9% – 33.8%), Haemaphysalis (22/68, 95% CI: 21.5% – 44.8%), Hyalomma (9/68, 95% CI: 6.23% – 23.6%), Ixodes (26/68, 95% CI: 26.7% – 50.8%) and Rhipicephalus (13/68, 95% CI: 10.6% – 30.5%). Collection approaches varied and included dragging and carbon dioxide traps for collection of questing ticks and direct removal from hosts with tools such as fine-tipped forceps. Domestic livestock including camels, cattle, goats and sheep were the most common vertebrate hosts sampled. Other studies investigated ticks collected from humans and diverse wildlife hosts (Additional File 1. Dataset S1). Ticks were examined across multiple developmental stages, including eggs, larvae, nymphs, and adult ticks. Majority of studies conducted whole tick analysis of both male and female ticks, while a small subset of studies targeted specific tissues such as the midgut, malpighian tubes, reproductive organs (ovaries, uterus) and salivary glands (10.3%, 95% CI: 4.24 – 20.1%).

Symbionts, potential pathogens and bacterial co-occurrence

The heatmap depicting presence or absence of bacterial genera across studied tick genera showed clustering by tick genera, with Ixodes, Dermacentor and Haemaphysalis displaying the highest counts of bacteria genera, respectively (Figure 3). Corynebacterium, Coxiella, Rickettsia and Staphylococcus were commonly detected across tick genera. Presence of genera Escherichia-Shigella, Enterobacter, Borrelia, Citrobacter, Pseudomonas and Rickettsia which harbor potential human pathogenic species were identified across reviewed studies. Transient bacterial genera such as Pseudomonas, Sphingomonas, Acinetobacter, Bacillus, and Staphylococcus, linked to host bloodmeal and environmental exposure were mostly present in the generalist tick genera (Figure 3).

Ixodes and Haemaphysalis displayed the highest number of shared bacterial genera with other tick genera in the UpSet plot, indicating broader co-occurrence across studies (Figure 4). Limited overlap was observed in specialist tick genus Bothriocroton from Australia, highlighting ecological restriction. Only one study looked at this tick genera, which also contributed to the limited overlap (Beard et al., 2021).

Bipartite network analysis summarized co-occurrence of bacterial genera across Ixodidae tick genera, with Acinetobacter, Bacillus, Corynebacterium, Coxiella, Rickettsia, identified as some of the putative core genera associated with Ixodidae ticks. It is important to note that classification as core, moderate or rare reflects detection frequency of the top 10 reported genera from the reviewed studies and does not exclude the possibility that additional genera may be more broadly distributed than presented in this network. Environmentally acquired bacteria such as soil-borne Sphingobium and Ralstonia, were positioned at network peripheries, whereas known symbionts such as Coxiella and Rickettsia were much more centrally positioned in the network reflecting their common detection across tick genera in the reviewed literature (Figure 5).

Ecophysiological factors shaping Ixodidae microbiomes

The reviewed studies showed that variation in bacterial diversity in ticks is determined by both ecological and physiological factors which include tick species, sex, ontogenic stage, host blood meal, pathogen infection status as well as spatial and temporal factors. Tick species exhibited a distinct core microbiota, regardless of developmental stage or environment (Turnbaugh et al., 2007; Shade and Handelsman, 2012). Across studies, the phyla Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria dominated regardless of tick species, sex, host, geographic region and tissue/organ of the specimens analyzed.

Males typically showed greater microbial richness than female ticks, however some studies reported no significant differences between sexes where male and female ticks harbored similar composition of bacterial communities and only differed in symbiont abundance (Yu et al., 2017). Overall, findings suggest that sex-related differences in microbiome composition are species dependent and likely influenced by physiological factors and the presence of specific endosymbionts.

Despite compositional shifts among stages, dominant bacteria Francisella, Candidatus Midichloria mitochondrii, and Rickettsia were maintained throughout development (Zolnik et al., 2016; Chicana et al., 2019; Brinkerhoff et al., 2020; Li et al., 2020; Adegoke et al., 2022). Community richness and evenness declined from larva to adult, likely due to blood-meal feeding and physiological filtering. Overall, findings highlighted that developmental stage influences tick microbiome structure, mostly through vertical transmission and feeding-related shifts with persistence of dominant endosymbionts across life stages. Bacterial richness and diversity in ticks varied depending on host and feeding status, with significant overlap of bacteria between engorged ticks and the host blood, with an increase in bacterial diversity in host-collected ticks (He and Cheng, 2018; Liu et al., 2024). Field-collected ticks displayed more diverse and distinct communities, while laboratory-reared ticks appeared more depauperate and dominated by endosymbionts (Kwan et al., 2017; Couper et al., 2019; Kumar et al., 2022b).

Tick organs such as the midgut, salivary glands, and ovaries presented niches that harbored distinct microbial assemblages, with reproductive tissue and Malpighian tubules displaying the lowest bacterial diversity and richness (Wang et al., 2018; Grandi et al., 2023). Midgut tissue exhibited the highest diversity across studies and displayed a dynamic microbiota profile.

Overall, studies reported heterogenous effect of pathogen infection on tick microbiome composition or diversity (Trout Fryxell and DeBruyn, 2016; Kwan et al., 2017; Kisten et al., 2021).

Geographic location had limited influence on tick microbiome composition, with similar bacterial communities reported across regions in Haemaphysalis, Ixodes and Rhipicephalus ticks sampled from Japan, Peninsular Malaysia, Southwest China, France, Germany (Alafaci et al., 2021; Hoffmann et al., 2021; Becker et al., 2023; Che Lah et al., 2023; Xiang et al., 2023). Contrastingly, some studies reported significant geographic variation in tick microbiome communities in other parts of Asia, Europe, and North America. These findings suggest that while some tick-associated bacterial communities may be conserved across broad geographical regions, local environmental factors such as soil type, vegetation and available hosts can drive microbiome divergence among geographically distinct populations.

Only three studies investigated the temporal fluctuations of microbial communities providing inconclusive results on the temporal fluctuations of microbial communities in Ixodidae ticks.

Tick microbiome interactions are increasingly attributed as a key player in vector-pathogen dynamics, with non-pathogenic members exerting variable effects on pathogens within the tick (Steiner et al., 2008; Bonnet et al., 2017). Visualization of bacterial community assemblages through heatmaps, UpSet plots, and bipartite networks offer complementary perspectives on the structure and ecological functioning of tick‐associated microbiomes. Generalist, three-host genera such as Ixodes (Lejal et al., 2021; Krawczyk et al., 2022a, Krawczyk et al., 2022b; Kumar et al., 2022a), Haemaphysalis (Li et al., 2022, Li et al., 2024; Moustafa et al., 2024), and Dermacentor showed the highest bacterial diversity (Galaviz-Silva et al., 2022; Qiu et al., 2022; Holguin-Rocha et al., 2023). These species have broad host ranges and feed on diverse mammals and have prolonged off-host environmental stages. This diverse ecological exposure allows for the acquisition of transient environmental and host derived microbes. In contrast, Bothriocroton, a highly host-specific tick of wombats (Vombatus ursinus), which is restricted to Australasia, lacks this varied exposure, resulting in the depauperate microbiome seen in the UpSet plot (Beard et al., 2021).

Despite this variation in overall richness, a consistently dominant core microbiota specifically of Acinetobacter, Bacillus, Corynebacterium, Coxiella and Rickettsia was observed across the studied tick genera, suggesting possible long‐term phylosymbiotic relationships. Within this framework, these taxa may serve as keystone symbionts contributing to network stability and tick resilience, while peripheral communities might allow for adaptation across variable environmental contexts (Vayssier-Taussat et al., 2015; Bonnet et al., 2017; de la Fuente et al., 2017; Fountain-Jones et al., 2023). Independent of geographic location, studies across Asia and North America consistently showed that internal tick organs act as filters like in the midgut of Dermacentor and Amblyomma, which consistently harbored higher diversity, whereas reproductive tissues maintained restricted, specialized assemblages to ensure vertical transmission (Wang et al., 2018; Grandi et al., 2023).

The capacity of vertebrate host immunoglobulins to remain functional within tick hemolymph has been pivotal in shaping the development of anti-microbiota vaccines, enabling modulation of the tick microbiome and providing critical insights into its mechanistic and functional dynamics (Mateos-Hernández et al., 2021; Wu-Chuang et al., 2021; Maldonado-Ruiz, 2024; Boulanger, 2025). Obregón et al. (2019) and Estrada-Peña et al. (2020a) demonstrated functional redundancy in the tick microbiome, where a high number of bacterial genera contributed to a single pathway. Such functional redundancy suggests that ticks have evolved mechanisms to modulate their microbiome, selecting for multiple bacterial genera that contribute to a functional profile which confers ecological advantages (Obregón et al., 2019; Estrada-Peña et al., 2020a; b).

Understanding how bacterial dominance and functional redundancy are distributed across host-associated microbiomes has become increasingly significant in translational research (Amabebe et al., 2022; Canowitz et al., 2026). The ecological dynamics observed within the tick microbiome, including competitive exclusion among bacterial taxa and the disproportionate influence of keystone species on community stability, reflect organizational principles documented across a broad range of host-associated microbiome systems (Hajishengallis et al., 2012). In Ixodes ricinus, Wolbachia, a widespread endosymbiont of arthropod vectors, limited the presence and transmission of Anaplasma, Borrelia, Neoehrlichia and Rickettsia genera in field-collected tick populations (Boulanger et al., 2023). While paratransgenesis via Wolbachia has been successfully demonstrated in mosquito vectors to induce pathogen refractoriness, its application in Ixodidae remains limited due to biological differences between the two groups of arthropods (Alam et al., 2011; Bian et al., 2013; Caragata et al., 2021; Minwuyelet et al., 2023; Wang et al., 2023).

A trend identified across the 68 reviewed studies is the disparity in microbial richness between laboratory-reared and field collected ticks (Kwan et al., 2017; Couper et al., 2019; Kumar et al., 2022b). Field-collected Ixodes and Amblyomma ticks consistently displayed higher bacterial diversity, likely due to continuous environmental exposure to soil and vertebrate host skin flora, whereas laboratory-maintained colonies exhibited depauperate communities. While tick associated microbial communities have been extensively researched, their interaction with vertebrate skin microbiomes remains understudied (Boulanger et al., 2023). Modification of the host skin microbiota to repel ticks presents an alternative avenue for pathogen transmission control. Manipulation of skin bacterial commensals to repel mosquitoes has been explored in the context of malaria transmission (Lucas-Barbosa et al., 2022). In human medicine, studies on skin microbiota modulation have significantly progressed, with therapies based on commensal bacteria Staphylococcus epidermidis and Staphylococcus hominis (ShA9) currently in use for various skin inflammation conditions (O’Neill et al., 2020; Callewaert et al., 2021; Nakatsuji et al., 2021).

While current literature points to encouraging possibilities in microbiota-based interventions for tick-borne diseases, the strength and utility of findings depend on the methodological quality of the studies from which they are drawn. The studies we reviewed varied in methodological rigor as assessed using the STORMS checklist, with differences in surface decontamination protocols, application of controls, as well as data availability and deposition practices. Although no formal analysis was conducted, this observed heterogeneity has direct implications on the confidence with which reported dominant or core taxa can be interpreted (McLaren et al., 2019; Prodan et al., 2020). Accordingly, the classification of genera as core, moderate or rare presented in this review should be interpreted with this consideration. These limitations highlight the necessity of standardized protocols and reporting frameworks for broader generalizability of tick microbiome research findings.

Microbiome studies are often prone to significant bias when confounding variables are not adequately identified and accounted or mitigated for, and tick microbiome studies are no exception (McGuinness et al., 2024). Host-related variables such as nutrition, health condition and prior exposure to acaricides or antibiotics, were rarely reported despite their expected influence on tick microbiome composition. For field studies, contamination risks are compounded by environmental DNA from the collection environment, underscoring the importance of inclusion of environmental swabs and equipment as controls (Salter et al., 2014; Fierer et al., 2025). While standardized surface sterilization protocols for tick microbiome studies remain to be established, full reporting of sterilization methods, processing of surface wash water as a negative control, and tissue dissection where internal microbiome resolution is required represent minimum recommended practice (Binetruy et al., 2019; Fernández-Ruiz et al., 2023). Complementing these measures with well-designed mock microbial communities suited for arthropod vector systems will enable identification of laboratory-introduced bias, allowing for the amendment of protocols (Shetty et al., 2023; Wiesinger et al., 2023; McGuinness et al., 2024).

Owing to the inherent heterogeneity of microbiomes, as well as the variability in field, laboratory, and bioinformatic protocols, thorough reporting of experimental design and bioinformatics analyses is essential. Research infrastructure initiatives such as INFRAVEC2 have been instrumental in advancing arthropod research by providing access to standardized guidelines and protocols for vector studies, bioinformatic resources and multidisciplinary collaboration (Vernick, 2017; Pondeville et al., 2023). The use of data hosting and sharing platforms, for raw data and analysis codes allows for transparency and replicability of findings (McGuinness et al., 2024). For these purposes, the Minimum Information about any (x) Sequence (MixS) metadata standards were developed and are adopted by several databases which include NCBI and EMBL. The MixS standards cover the most critical parts of microbiome data production and processing, therefore their application is recommended. The Minimum Information about a Marker gene Sequence (MIMARKS) checklist which provides detailed guidance on the technical aspects of data reporting of sequencing studies is also recommended (Yilmaz et al., 2011). Future tick microbiome studies can additionally apply the Standards for Technical Reporting in Environmental and Host-Associated Microbiome Studies (STREAMS) guidelines developed for non-human host-associated microbiome studies, which provide actionable recommendations for the reporting of host-associated microbiome data (Kelliher et al., 2025). These guidelines complement the broader STORMS checklist which was applied in this review (Mirzayi et al., 2021).

A major limitation of this review was the disproportionate geographical distribution of reviewed studies, with paucity of studies in Africa and Australasia, which may hamper the broad generalizability of findings. Temporal microbiome changes in ticks would be most aptly addressed through longitudinal studies; however, we only found three temporal investigations of tick microbiomes, which is another limitation of the current literature reviewed.

In summing up our findings, tick microbial communities vary due to factors which include tick species, tick developmental stage, sampling location, tick feeding status and host species, but findings are inconsistent across studies due to biological, environmental and technical factors. Future work should prioritize standardizing methods, improving reporting of host/sex/stage metadata, and functional studies to clarify how tick microbiomes influence tick biology and pathogen transmission. Beyond the fundamental understanding of tick microbiome community interactions, CRISPR/Cas technologies which enable targeted genetic engineering promise to unravel interesting possibilities for tick biology research (Nuss et al., 2021; Sharma et al., 2022).