Basics
Description
- Infestation by organisms that live in close association with host
- Bites are painless
- Signs and symptoms result from host response to saliva and anticoagulant injected during feeding
- Transmitted by direct contact and fomites (inanimate objects)
- Head lice are transmitted by head-to-head contact:
- Head lice are more common in children and females
- Pubic lice are transmitted by sexual contact
- Obligate human parasites cannot survive away from hosts >7 " 10 days
Etiology
Infestation by:
- Pediculus capitis (head louse):
- Most common
- All socioeconomic groups
- Pediculus corporis (body louse):
- Associated with poverty, poor hygiene, and overcrowding
- Live in clothing and transfer to human host for feeding
- Can live up to 30 days off of human
- Related to bed bugs
- Phthirus pubis (pubic or crab louse)
Pubic lice may also indicate sexual abuse in children
Diagnosis
Signs and Symptoms
History
- Head lice:
- Dandruff
- Pruritus
- Often asymptomatic
- Body lice:
- Pruritus
- Excoriation particularly at belt lines or seams of clothing
- Pubic lice:
- Intense pruritus, worse at night
Physical Exam
- Examine hair for adult lice and nits:
- Nits are cemented on hair shafts and are not easily removed
- Head lice and pubic lice infestation is confirmed by differentiating nits from scales, hair casts, and other easily brushed-off artifacts
- Empty nits are not diagnostic of active infection
- Scalp and posterior neck erythema, scaling, and excoriated papules:
- May lead to pyoderma, posterior cervical lymphadenopathy, and bacterial superinfection
- Body lice are observed only in very heavy infestation; infestation is confirmed by finding nits in clothing seams:
- Linear excoriations of neck and trunk
- Pus or serum stains on clothing
- Pubic lice:
- Occasional urticaria with typical flare/wheal formation
- May infest eyelashes and scalp in children
- Characteristic bluish macules (maculae ceruleae) appear infrequently on trunk and thighs
- Prefer the perineum and pubic areas
- Inguinal adenopathy
Essential Workup
- Careful history and physical exam
- Universal precautions
Diagnosis Tests & Interpretation
Lab
- Nits may be visualized under low-power microscopy along hair shafts. They are <1 mm long:
- Fluorescent under Wood lamp
- Mature lice are 3 " 4 mm long
- Pubic louse ¢ ¼1 mm long but wider body than head or body louse
Imaging
No imaging indicated
Differential Diagnosis
- Scabies
- Contact or allergic dermatitis
- Seborrheic dermatitis
- Bed bugs (Cimicidae)
Treatment
Pre-Hospital
Maintain universal precautions
Initial Stabilization/Therapy
Not applicable for routine cases
Ed Treatment/Procedures
- Oral antihistamines and topical steroids may help pruritic symptoms of all lice infestations
- Head lice:
- Topical pediculicidal agents:
- Permethrin 1% cream rinse (Nix) is a reasonable agent; it has low toxicity and cost and is ovicidal; however, resistance is becoming more common
- Pyrethrin (Rid) also has low toxicity but is less effective
- All agents require reapplication in 7 " 10 days if further adult lice or nits noted
- Remove nits with fine-toothed comb
- Examine all members of household; treat infested individuals
- Change clothing and machine wash and dry (using hot cycles) all clothing, towels, linens, and headgear:
- Vacuum floors and furniture
- Wash combs and brushes in hot water for 10 " 20 min or coat with pediculicide for 15 min and wash
- Temperature >131 °F (55 °C) for >5 min kills eggs, nymphs, and mature lice
- Body lice:
- Wash and dry bedding and clothing using hot cycles
- Apply topical pediculicide cream or lotions from chin to toes
- Pubic lice:
- Topical pediculicide applied to hairy areas of chest, axilla, and groin
- Remove nits with fine-toothed comb
- Treat sexual contacts simultaneously
- Wash and dry bedding and clothing using hot cycles
- Treat eyelash involvement with topical petrolatum twice daily for 9 days
Medication
First Line
- Antipruritics:
- Diphenhydramine: 25 " 50 mg PO (peds: 5 mg/kg/d) q6h
- Hydroxyzine: 25 mg PO q8h (peds: 12.5 mg/dose q6h)
- Pediculicides:
- Permethrin 1% cream rinse (Nix): Apply to scalp and hair, rinse after 10 min; reapply in 7 " 10 days if needed
- Pyrethrin/piperonyl butoxide (Rid): Apply to scalp and hair, wash after 10 min; repeat in 7 " 10 days; avoid in patients with ragweed allergies
- Benzyl alcohol lotion 5% (Ulesfia lotion): Apply to scalp and hair, wash off after 10 min; repeat in 7 days
- Mercuric oxide ophthalmic ointment 1%: Use for louse infestation of eyelids: Apply QID for 14 days
Second Line
- Pediculicides:
- Ivermectin 0.5% lotion (Sklice): Apply to dry hair and scalp and rinse after 10 min
- Spinosad 0.9% suspension (Natroba): Apply to dry hair and rinse after 10 min; repeat in 7 days if necessary
- Ivermectin tablets (Stromectol): 200 " 400 ¼g/kg PO once; repeat in 7 " 10 days later
- Use if 1st-line agents (Nix, Rid, Ulesfia) are not tolerated or effective
- Antihistamine:
- Cetirizine (Zyrtec): Age >12 yr, 5 " 10 mg PO (peds: 6 " 11 yr, 5 " 10 mg PO; 2 " 5 yr, 2.5 mg PO) daily
- Nix is Class B and probably safe in lactation
- Rid is Class C and probably safe in lactation
- Ulesfia is Class B but should read package insert; safety unknown in lactation
- Ivermectin is Class C with safety unknown in lactation
- Spinosad is Class B but should read package insert for specifics; safety unknown in pregnancy
- Nix can be used in children >2 mo
- Rid can be used in children >2 yr
- Ulesfia can be used in children
- Ivermectin can be used in children >6 mo
- Spinosad can be used in children >4 yr
Follow-Up
Disposition
Admission Criteria
Extensive bacterial superinfection; systemic hypersensitivity reaction with cardiorespiratory compromise
Discharge Criteria
- Mild-to-moderate infestation with absence of significant superinfection or hypersensitivity reaction
- Children may return to school after initial treatment if repeat therapy is administered in 7 " 10 days
- Pubic lice are often associated with sexually transmitted diseases; prudent screening is recommended
Follow-Up Recommendations
- Re-evaluation is necessary to observe if treatment has been successful
- Case management and/or social services may be required if concern for child well-being
Pearls and Pitfalls
- Diagnosed by direct visualization
- Most of the topical agents need to be reapplied in 7 " 10 days because unhatched eggs are not killed
- Clothing and bedding must be washed and dried at a high heat to eradicate the infestation
- Lindane is no longer recommended
- Resistance to Nix and Rid is increasingly more common
- 2nd-line agents are more expensive
Additional Reading
- Benzyl alcohol lotion for head lice. Med Lett Drugs Ther. 2009;51:57.
- Chosidow O, Giraudeau B. Topical ivermectin " a step toward making head lice dead lice? N Engl J Med. 2012;367:1750 " 1752.
- Frankowski BL, Bocchini JA Jr, et al. Head lice. Pediatrics. 2010;126:392 " 403.
- Gunning K, Pippitt K, Kiraly B, et al. Pediculosis and scabies: Treatment update. Am Fam Physician. 2012;86:535 " 541.
- Ivermectin (Sklice) topical lotion for head lice. Med Lett Drugs Ther. 2012;54:61 " 63.
Codes
ICD9
- 132.0 Pediculus capitis [head louse]
- 132.1 Pediculus corporis [body louse]
- 132.9 Pediculosis, unspecified
- 132.2 Phthirus pubis [pubic louse]
- 132.3 Mixed pediculosis infestation
- 132 Pediculosis and phthirus infestation
ICD10
- B85.0 Pediculosis due to Pediculus humanus capitis
- B85.1 Pediculosis due to Pediculus humanus corporis
- B85.2 Pediculosis, unspecified
- B85.3 Phthiriasis
- B85.4 Mixed pediculosis and phthiriasis
- B85 Pediculosis and phthiriasis
SNOMED
- 20848007 Infestation by Pediculus (disorder)
- 81000006 Pediculosis capitis (disorder)
- 25188002 Pediculosis corporis (disorder)
- 71011005 Infestation by Phthirus pubis (disorder)
- 91566005 Mixed pediculosis