Pediculosis: A Comprehensive Guide to Head Lice, Body Lice, and Crab Lice
Definition
Pediculosis is the infestation of humans by lice, which are small, wingless insects that feed on human blood. There are three main types of lice that affect humans: head lice, body lice, and crab lice.
Morphology
* Head lice (Pediculus humanus capitis): * Two varieties: head lice and body lice * Depressed dorsoventral body, 2-4 mm long * Whitish color (may vary depending on host’s skin or hair pigmentation) * Small head with short antennae and simple eyes * Complex oral apparatus * Small thorax with three pairs of powerful legs * Voluminous abdomen with thick plates * Females lay eggs (nits) in the hair shafts, which are attached with a sticky substance * Eggs measure 0.8 mm long and have an operculum with mammelons * Body lice (Pediculus humanus corporalis): * Reside in seams of clothing, where they also lay eggs * Leave clothing only to feed on host’s blood * Lay nits that remain viable for up to a month * Crab lice (Pthirus pubis): * Located in the pubic and abdominal hair surrounding the genital area * May also be found in the axillae, mustache, beard, eyelashes, and eyebrows * Measure 1 to 1.5 mm in length and width * Have strong legs (crab-like) * Are dorsoventrally flattened and almost transparent in color * Females lay up to 50 eggs with grayish opercula crowned by high mammelons * Also secrete a sticky substance that joins the eggs together
Evolutionary Cycle
* Head lice and body lice: * Females lay eggs (nits) within two days of fertilization * Nits hatch into nymphs within 5 to 10 days * Nymphs undergo three molts to reach adulthood within two weeks * Adults have a short lifespan and remain on the host for several hours or even days * When the host becomes inhospitable due to thermal variations, lice abandon it and spread to new hosts * Crab lice: * Eggs hatch into nymphs within 6 to 8 days * Nymphs undergo three molts to reach adulthood within two weeks * Adults live for approximately one month
Epidemiology
* Cosmopolitan distribution * Prevalence varies according to climate, with higher rates in warm, humid environments * More frequent during wars, overcrowding, or poor personal hygiene * Head lice infestations are more common in school-aged girls * Body lice infestations are more common in vagabonds and indigent individuals without sanitary habits * Crab lice infestations are most common between 15 and 40 years of age, particularly among sexually active individuals
Pathology
* Medical importance: * Lice can transmit diseases (body lice only) * Cause irritation and discomfort due to their bites * Skin manifestations: * Micro or macronodular dermatitis * Excoriations and secondary infections (pyoderma, impetigo) * Irritation from saliva inoculation * Biological vectors: * Body lice can transmit the following diseases: * Epidemic typhus * Relapsing fever * Trench fever
Symptoms
* Head lice: * Itching of the scalp, especially in the temporal, occipital, and auricular regions * Secondary excoriations and bacterial infections, resulting in crusts and secretions * Body lice: * Small, macular, erythematous, and pruritic papules and excoriations * Melanoderma pediculi * Crab lice: * Dermatitis and itching (pruritus, erythematous papules, excoriations, or secondary infection) * Maculae ceruleae * In severe infestations, hyperkeratosis and melanoderma * In children, toxic follicular conjunctivitis * In adults, papillary conjunctivitis
Diagnosis
* General: * Finding the parasite in different stages of its life cycle * Physical examination to determine the location of the parasite * Good lighting for examination * Patient history * Head lice: * Physical examination of the scalp, especially in the auricular region * Examination of reinforced seams and folds of clothing * Crab lice: * Examination of the genital area * Microscopic examination of hair clippings
Treatment
* General: * Contact tracing and treatment of all household members * Health education * Chemical: * Permethrin 1-3% * Lindane 1% * Decamethrin 0.2% * Deltramethrin 0.02% * Malathion * For pregnant women and infants: * Physical removal of lice and nits * Body lice: * Elimination of infested clothing * Application of insecticide directly to dry clothing * Personal hygiene * Crab lice: * Same chemical treatment as for head lice * Mechanical removal for children’s eyebrows and eyelashes
Prophylaxis
HEALTH EDUCATION
-PROPER TREATMENT
-Do not share combs, ETC AND CONTACT “HEAD-HEAD” INFESTED WITH ANY PERSON
-KEEP THE HAIR MOORING
-STERILIZING EQUIPMENT of infected people
Linnen-WASH WITH HOT WATER