Lice/Scabies

Pediculosis Pubis and Scabies Infestation

Medical content reviewed and approved by Dr. GP Yadav, MD, Dermatology Specialist; STI/STD Expert

Definition

Lice (Pediculosis pubis) and Scabies (Sarcoptes scabiei infestation) are common parasitic infections affecting the anogenital and cutaneous regions. Pubic lice are ectoparasites that infest coarse body hair, while scabies mites burrow into the epidermis causing intense pruritus and discomfort.

Symptoms of Lice/Scabies

Pubic lice cause intense itching in the genital area, often worse at night. Visible lice and nits (eggs) can be seen attached to pubic hair shafts. Secondary excoriation and bacterial infection are common. Scabies presents with intense generalized pruritus, particularly at night, caused by allergic sensitization to the mite and its products. Characteristic burrows appear as thin, serpiginous, grayish lines in interdigital spaces, wrists, elbows, axillae, and genital region. In immunocompromised patients, crusted (Norwegian) scabies with profuse mite burden can develop.

Common Symptoms:

Intense pruritus in the anogenital region (worse at night)
Visible lice or nits attached to pubic hair shafts
Excoriations and secondary bacterial infections from scratching
Burrows visible as thin, wavy lines on skin (scabies)
Erythematous papules and vesicles in intertriginous areas

Clinical Images

Pubic lice infestation showing adult Phthirus pubis crab louse attached to pubic hair with visible nits eggs on hair shafts diagnosed at STD Nepal — Pubic lice (Phthirus pubis) infestation showing an adult louse attached to a pubic hair shaft with visible nits (eggs) cemented along the hair shaft.
Image provided by Dr. GP Yadav

Scabies burrows on interdigital web space showing characteristic thin wavy grayish lines caused by Sarcoptes scabiei mite infestation — Scabies burrows in the interdigital web space demonstrating the characteristic thin, serpiginous, grayish lines that represent the mite burrowing in the epidermis.
Image provided by Dr. GP Yadav

Scabies infestation on wrist showing erythematous papules and burrows with excoriations from intense pruritus typical of Sarcoptes scabiei infection — Scabies presenting on the wrist with erythematous papules, characteristic burrows, and excoriations from the intense pruritus associated with mite sensitization.
Image provided by Dr. GP Yadav

Generalized scabies rash on trunk showing widespread erythematous papules and excoriated lesions from Sarcoptes scabiei mite infestation — Disseminated scabies infection with widespread erythematous papules and excoriated lesions on the trunk, demonstrating the diffuse nature of the infestation.
Image provided by Dr. GP Yadav

Crusted Norwegian scabies showing hyperkeratotic plaques with thick crusts containing thousands of mites in immunocompromised patient — Crusted (Norwegian) scabies demonstrating thick hyperkeratotic plaques and crusts containing thousands to millions of mites, typically seen in immunocompromised patients.
Image provided by Dr. GP Yadav

Scabies nodules on male genitalia showing persistent erythematous nodular lesions in scrotal region as hypersensitivity reaction to mite antigens — Scabies nodules on the male genitalia showing characteristic persistent erythematous nodular lesions on the scrotum, a common post-scabetic hypersensitivity reaction.
Image provided by Dr. GP Yadav

Transmission of Lice/Scabies

Both lice and scabies are transmitted through prolonged direct skin-to-skin contact, including sexual contact. Pubic lice are primarily sexually transmitted in adults, while scabies can spread through non-sexual close contact, especially in overcrowded living conditions. Fomite transmission via shared clothing, towels, and bedding can occur, particularly for lice, as adult lice can survive 24-48 hours away from the host. Scabies mites survive only 24-36 hours off the host at room temperature.

Transmission Methods:

Direct skin-to-skin contact with infested individual
Sexual contact and close personal contact
Sharing of infested clothing, towels, or bedding
Fomite transmission (less common for scabies)

Incubation Period

Typical period: 2-6 weeks

The incubation period for primary infestation of both lice and scabies is 2-6 weeks, during which time the individual may be asymptomatic. In subsequent infestations, symptoms develop within 1-4 days due to pre-existing hypersensitivity. This prolonged incubation period in primary cases contributes to unrecognized transmission within close contacts and sexual networks.

Complications of Lice/Scabies

The most common complication is secondary bacterial infection from scratching, typically with Staphylococcus aureus or Streptococcus pyogenes, causing impetigo, folliculitis, or cellulitis. Post-streptococcal glomerulonephritis is a rare but serious complication of secondary infection. Crusted scabies in immunocompromised, elderly, or disabled patients involves thousands to millions of mites with widespread hyperkeratotic lesions. Chronic pruritus causes sleep disturbance and significantly impacts quality of life.

Possible Complications:

Secondary bacterial infections (impetigo, cellulitis)
Post-streptococcal glomerulonephritis (rare)
Crusted (Norwegian) scabies in immunocompromised patients
Sleep disturbance due to nocturnal pruritus
Psychosocial distress and stigmatization

Treatment Options for Lice/Scabies

Treatment of lice and scabies requires application of scabicides/pediculicides to all affected areas. Sexual partners and close household contacts should be treated simultaneously to prevent reinfection. Clothing, towels, and bedding should be washed in hot water or sealed in plastic bags for 72 hours. Pruritus may persist for 2-4 weeks after successful treatment due to residual hypersensitivity. Patients should be counseled that the itching does not necessarily indicate treatment failure. Institutional outbreaks require coordinated mass treatment strategies.

Permethrin 5% cream (scabies) or 1% lotion (lice)

Permethrin 5% cream applied from neck to toes for 8-14 hours for scabies. Permethrin 1% lotion applied to affected hair for 10 minutes for pubic lice. Repeat after 7 days.

Ivermectin 200mcg/kg oral single dose

Oral ivermectin is highly effective for both scabies and lice. Two doses 7-14 days apart for scabies. Particularly useful for crusted scabies and institutional outbreaks.

Benzyl benzoate 25% lotion

Benzyl benzoate 25% lotion applied for 24 hours is a cost-effective alternative, particularly in resource-limited settings. Requires 2-3 applications over 24 hours.

Prevention of Lice/Scabies

Prevention focuses on avoiding direct contact with infested individuals and their personal items. Sexual partners and household contacts should be examined and treated. Items that cannot be washed can be sealed in plastic bags for 72 hours. Institutional settings such as nursing homes and prisons require surveillance and prompt outbreak management. Health education about recognition of symptoms and proper treatment is essential for community control.

Prevention Measures:

Avoiding direct skin-to-skin contact with infested individuals
Not sharing clothing, towels, or bedding
Washing infested items in hot water (50°C/122°F)
Treating all sexual partners and close contacts simultaneously
Regular inspection of children and close contacts

Important Disclaimer

⚠️This information is for educational purposes only and should not be used for self-diagnosis.
⚠️For accurate diagnosis and treatment, please consult with a qualified healthcare professional at an accredited medical facility.
⚠️Medical procedures and treatments should only be administered by licensed healthcare providers.
⚠️If you suspect you have an STI, visit STD Nepal clinic for confidential testing and treatment.

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