Head lice is caused due to the infestation by the blood-feeding insects Pediculosis capitis.
There is little information on the countrywide prevalence of the head lice. It is commonly seen in boys more than in girls and those in urban areas compared to rural areas (1).
The major symptom is pruritus (but might not indicate active disease) (1), especially over the occiput.
- direct contact is the route of transmission for head lice. Commonly head-to-head contact with a person who already has head lice (2)
- transmission from pets do not occur (1)
- usual infestations contain around 30 lice per head (1)
- head lice are 1-4 mm long (about the size of a sesame seed) and cling to the hair shaft with hook-like claws found on the legs. They cannot hop or fly. They move about by crawling
- during the life cycle of lice, the female louse lays eggs (oval and yellow white), called nits which can be found attached to the hair shaft (1)
- careful examination may show adult lice on the scalp or nits firmly cemented to the hair
- nits attach to the hair shaft close to the scalp or body - nits, which resemble dandruff, are attached with a water-insoluble, glue-like substance that makes them difficult to remove
- after 6-10 days, the nits hatch as nymphs (immature lice) - nymphs become adults in 10 days (1)
- adult lice live for approximately 30 days on their human hosts
- structured detection combing is helpful in diagnosis. It is more reliable than simple visual confirmation of the presence of active infestation
- live lice should be present to confirm the diagnosis (1)
- if the diagnosis is in doubt, place a plucked hair with attached nit on a glass slide with a drop of oil, and examine under a microscope
- head lice die if they are away from a human's head or body for more than 2 days
Reference:
- 1. American Academy of Paediatrics, Nolt D, Moore S, et al. Head Lice. Paediatrics. 2022 Oct 1;150(4):e2022059282.
- 2. Burgess I. Human lice and their control. Ann Rev Entomol. 2004;49:457-81.