Insights into the microbiota profile of Pediculus humanus capitis using metagenomic next-generation sequencing and molecular detection of unexpected pathogen DNA in Hunan Province, China

Abstract Background The head louse, Pediculus humanus capitis, remains a significant public health concern affecting millions of people worldwide and has been implicated as a potential vector for multiple human pathogens. Characterization of the microbiota of head lice could improve our understanding of their public health significance and potential role in pathogen transmission. Here, we characterize the microbiota of head lice and investigate microbiota differences among different clades of head lice. Methods Head lice were collected from Hunan Province, China, and classified into clade A and clade B (CACB) using polymerase chain reaction (PCR)-based genotyping. The microbiota of pooled CACB of head lice samples ( n = 46) was investigated by metagenomic shotgun sequencing and comparatively analysed at the phylum, genus, and species levels. In addition, the prevalence of potential pathogen DNA in head lice samples ( n = 204) was assessed using real-time PCR with stringent negative controls. Results We obtained non-redundant CACB microbial gene catalog comprising 79,232 genes, of which 4.70% (3,722 genes) were taxonomically assigned. The relative abundance of bacteria (2.52%) was higher than that of eukaryotes (2.04%), viruses (0.11%), and archaea (0.02%). Comparative analysis identified 655 and 750 unique genes in CACB, respectively. The dominant phyla in the CACB of head lice were Proteobacteria. At the genus level, DNA sequences corresponding to Anaplasma (25.98%; 53/204), Mycobacterium (24.02%; 49/204), Chlamydia (23.53%; 48/204), Ehrlichia (10.29%; 21/204), and Vibrio (0.49%; 1/204) were detected, suggesting the presence of bacterial DNA from these taxa. Conclusions Our results provide a preliminary characterization of the annotated fraction of the CACB microbiome in head lice. The high proportion of unannotated genes (>95%) underscores the limited representation of louse-associated microbial genomes in public databases and suggests substantial, yet unexplored, microbial diversity. The detection of pathogen DNA does not confirm organism viability or vector competence,however it may suggest prior exposure, mechanical carriage, or residual DNA from blood meals. These exploratory findings contribute new insights into the microbiota associated with human lice.