Prevalence and associated factors of head lice (Pediculus humanus capitis) among schoolchildren in Mérida (Yucatán) and Monterrey (Nuevo León), Mexico.

Pediculosis capitis is a common parasitic infestation in school settings and can disrupt wellbeing and school attendance. Despite its public-health relevance, epidemiological data describing Pediculosis capitis prevalence and associated factors in Mexico remain limited at the city level. This study aimed to estimate the prevalence of Pediculosis capitis and identify associated factors among schoolchildren from Monterrey and Mérida, Mexico. Aggregated data from a school-based cross-sectional survey were analyzed. Infestation status was determined through standardized individual scalp inspection performed by the research team. Prevalence and unadjusted odds ratio were calculated for sociodemographic, household, and hygiene-related variables. A total of 6372 schoolchildren were examined (3743 in Monterrey; 2629 in Mérida) with 590 positive cases overall. Prevalence was 16.40% in Monterrey and 6.57% in Mérida, with marked variation among schools. The strongest and most consistent associations were observed for sex and hair length, with higher infestation rates among girls and children with long hair. Associations with household and hygiene factors such as sharing of personal items, bathing frequency, room density, parental education, and employment were heterogeneous across cities and did not follow a uniform pattern. These findings highlight the need for school-home collaboration and continuous surveillance, promoting early detection, hygiene education, and preventive practices adapted to local school environments.