# Impact factors and genetic characteristics of head lice infestation in schoolchildren: a cross-sectional study from 2018 to 2023 in central China

## TL;DR

A study in central China found that head lice infestation in schoolchildren is linked to poverty and poor hygiene, and developed a new test to distinguish two genetic types of lice.

## Contribution

The study introduces a novel mtDNA duplex PCR method for distinguishing head lice clades A and B with high accuracy.

## Key findings

- Head lice infestation was strongly associated with gender, school location, and socioeconomic factors.
- Clade B of head lice is now dominant in Hunan Province, central China.
- The new PCR test achieved 100% sensitivity and specificity in differentiating clades A and B.

## Abstract

Head lice (Pediculus humanus capitis) infestation is a worldwide public health concern, especially in school-aged children. However, its main impact factors and genetic characteristics remain poorly understood in China. Hence, the purpose of the study was to explore the precise association between multiple impact factors and head lice infestation, characterize the genetic variation of the head lice, and develop a sensitive and specific mitochondrial (mt) DNA duplex polymerase chain reaction (PCR) for accurately distinguishing clades A and B.

A cross-sectional study was conducted in Hunan Province, central China from January 2018 to July 2023. A total of 9254 schoolchildren from 48 primary schools in each administrative region were examined for head lice. Impact factors for infestation were analyzed using the data collected by a questionnaire. The mt cytb gene sequences of head lice collected in the current study were used for sequence analysis, then were added to the global pool to conduct the phylogenetic analyses. Primers designed on the basis of this gene sequence were used in duplex PCR to diagnose head lice clades A and B by amplicon size.

Head lice infestation was found in 93.8% (45/48) of the primary schools included in the study. Overall, 6.8% (630/9254) of the examined schoolchildren harbored head lice, with 94.6% (596/630) being girls. A total of 2132 adult head lice were collected from 630 infested cases. The impact factors for head lice infestation included gender, school location, family situation, per capita income, study mode, and hair washing per week (p < 0.01). However, season and age were not considered as impact factors for head lice prevalence (p > 0.05). Phylogenetic analysis based on mt cytb gene sequences showed that head lice are classified into two clades (A and B), with clade B being more dominant in Hunan Province, central China. The newly developed duplex PCR was able to differentiate clades A from B in China with 100% sensitivity and specificity.

Our findings revealed that head lice infestation is mostly associated with poverty and poor hygiene in Hunan Province, central China. It is crucial to consider the simultaneous surveillance of head lice infestation in schoolchildren in regions with low level of socioeconomic status; however, datasets from other provinces are warranted to confirm the findings. It further showed that clades A and B are common in central China and that the latter has emerged and become the dominant one.

The online version contains supplementary material available at 10.1186/s13071-025-06825-9.