Definition And Etiology
- Represents infestation by obligate human ectoparasites.
- Pathogenesis involves salivary juice injection during blood feeding.
- Pruritus develops secondary to host allergic sensitization.
| Louse Species | Common Name | Anatomical Target | Disease Vector Status |
|---|
| Pediculus humanus capitis | Head louse | Scalp hair. | None. |
| Pediculus humanus corporis | Body louse | Clothing seams, body skin. | Transmits typhus, trench fever, relapsing fever. |
| Phthirus pubis | Pubic louse | Pubic hair, eyelashes. | None. |
Clinical Manifestations By Subtype
Pediculosis Capitis
- Peak incidence in children aged 3 to 12 years.
- Transmitted via head-to-head contact or fomites including combs and towels.
- Features intense scalp pruritus.
- Ova (nits) firmly cemented to proximal hair shafts.
- Favors occipital region and above ears.
- Complications include secondary pyoderma, hair matting, and occipital lymphadenopathy.
Pediculosis Corporis
- Associated with poor hygiene and cold climates.
- Primary lesion features pruritic red macule with central hemorrhagic punctum.
- Predilection for shoulders, trunk, and buttocks.
- Chronic infestation produces vagabond’s skin (lichenified, hyperpigmented plaques).
Pediculosis Pubis
- Transmitted via sexual contact or skin-to-skin exposure.
- Manifests in children occasionally as eyelash or eyebrow infestation.
- Exhibits maculae ceruleae (steel-gray spots) on trunk or thighs.
Management Protocol
Environmental Control
- Treat all household members and close contacts simultaneously.
- Launder clothing and bedding in hot water exceeding 65 degrees Celsius.
- Seal unwashable items in plastic bags for minimum 48 hours to 2 weeks.
Pharmacotherapy
| Pharmacologic Agent | Administration Specifics | Clinical Notes |
|---|
| Permethrin 1% Lotion | Apply to wet hair for 10 minutes, rinse. Repeat in 7 days. | First-line therapy. Safe for infants older than 2 months. |
| Malathion 0.5% Lotion | Apply to dry hair for 8-12 hours. | Flammable. Contraindicated in infants younger than 24 months. |
| Ivermectin | Administer 0.5% topical lotion or 200 micrograms/kg oral dose. | Oral administration reserved for difficult cases (weight exceeding 15 kg). |
| Lindane 1% Shampoo | Apply overnight or for 10 minutes. | Alternative therapy only. High systemic neurotoxicity risk. |
| Spinosad 0.9% | Single 10-minute application. | Safe for infants older than 6 months. |
