RESUMEN
Pediculus capitis or head-louse infestation has been a worldwide public-health problem, especially among school-aged children. To determine the intensity of infestation (abundance) among schoolchildren, children's sex and social factors were analyzed as modifiers of the general prevalence of parasitism. The study included 847 schoolchildren (407 girls, 440 boys) aged 6-12 years, from 12 public rural primary schools of Hamedan, Hamedan Province, Iran. Classic prevalence was obtained as the percentage of children with nits and/or lice. The general prevalence was 6.85% (girls: 13.5%; boys: 0.7%, p<0.001), head lice were much more common in girls than boys. The results showed significant variations in head lice infestation, and factors such as parents' literacy, type of hair, previous infestation, sharing of bed and comb, and care centers, while there was no significant variation between school grade, parents' job, members of family, and pediculosis in the studied areas (p>0.05). Sex and social factors are important modifiers of P. capitis general prevalence and degree of infestation. The classification of children by intensity of infestation allowed a more precise delimitation of this condition, which is especially important for disease surveillance and application of control measures.