Microbiome diversity in Haemaphysalis flava (life stage-host dependent) and Haemaphysalis longicornis ticks with zoonotic implications in Nantong, China.

Purpose: This study characterized the microbial communities of Haemaphysalis flava (H. flava) and Haemaphysalis longicornis (H. longicornis), in Nantong, China, and assessed the zoonotic implications.

Methods: We collected both on-host and off-host ticks and performed 16S rRNA amplicon sequencing. Subsequent bioinformatic analyses included taxonomic composition assessment, community diversity evaluation, differential abundance analysis, interspecies abundance correlation and functional inference.

Results: Rickettsia dominated in H. flava (77.31%), while H. longicornis exhibited higher abundances of Stenotrophomonas (10.78%), Coxiella (10.04%), and Psychrobacter (9.70%). Comparative analyses of life stages and host associations were only performed for H. flava due to limited sample sizes of H. longicornis across developmental stages. Rickettsia was enriched in on-host H. flava (90.41-90.51%) compared to off-host specimens (46.12%). α-diversity analysis showed higher microbial richness in off-host nymphs than in on-host adults. β-diversity revealed strong species-specific clustering. Network analysis demonstrated more complex microbial interactions in adult ticks. Pathogen screening detected Rickettsia japonica (R. japonica, host-specific to H. flava), Ehrlichia ewingii (E. ewingii), and Anaplasma bovis (A. bovis). Functional prediction highlighted elevated B vitamin biosynthesis pathways in nymphs, aligning with Coxiella-like endosymbionts (CLEs)'s putative nutritional role.

Conclusion: This study emphasizes the importance of enhanced tick surveillance and regular pathogen screening in domestic animals, particularly for spotted fever group (SFG) Rickettsia. CLEs may exhibit stage-specific abundance patterns aligned with the host's developmental nutritional requirements. These findings highlight the need for integrated One Health surveillance to mitigate tick-borne disease threats.