How is scabies transmitted? Mention the complications of scabies. Discuss the clinical features of crusted scabies and its management.

Transmission of Scabies

Scabies is primarily transmitted through direct, prolonged skin-to-skin contact with a person who has scabies. This contact typically needs to last at least 15-20 minutes to allow for the transfer of mites. Less commonly, it can be spread through shared items such as bedding, clothing, and towels, although this requires a higher mite load and is less efficient. Transmission is facilitated by:

• Direct Contact: The most common mode, especially in families, childcare settings, and nursing homes.
• Indirect Contact: Through contaminated items, though less frequent.
• Sexual Contact: Scabies can be transmitted through sexual contact, particularly Norwegian scabies.

Complications of Scabies

While scabies itself is not life-threatening, it can lead to several complications:

• Secondary Bacterial Infections: Intense scratching can break the skin, allowing bacteria (often *Staphylococcus aureus* or *Streptococcus pyogenes*) to enter, leading to impetigo, cellulitis, or even more serious infections like sepsis.
• Post-Streptococcal Glomerulonephritis: A rare but serious complication following streptococcal skin infections secondary to scabies.
• Eczematization: Chronic scratching can lead to thickened, leathery skin and eczema-like changes.
• Allergic Reactions: Some individuals may develop allergic reactions to the mites or the treatment medications.
• Psychological Distress: Chronic itching and skin lesions can cause significant anxiety, depression, and sleep disturbances.

Clinical Features of Crusted Scabies (Norwegian Scabies)

Crusted scabies is a severe form of scabies that occurs in individuals with impaired cell-mediated immunity (e.g., HIV/AIDS, leukemia, organ transplant recipients, those on immunosuppressants). It is characterized by:

• Extensive Crusting: Thick, hyperkeratotic, and crusted skin lesions, often affecting the hands, feet, elbows, and genitals.
• Minimal Inflammation: Surprisingly, there may be relatively little itching or inflammation compared to typical scabies, due to the overwhelming number of mites.
• High Mite Load: Crusted scabies lesions contain an extraordinarily high number of mites, making it highly contagious.
• Nail Involvement: Subungual hyperkeratosis (thickening under the nails) is common.
• Erythroderma: Widespread redness and scaling of the skin can occur.

Diagnosis is confirmed by microscopic examination of skin scrapings, revealing a large number of mites, eggs, and fecal pellets. A skin biopsy can also be helpful, showing mites within the hyperkeratotic crusts.

Management of Crusted Scabies

Managing crusted scabies requires a more aggressive approach than typical scabies:

• Topical Treatment: Permethrin 5% cream is often used, but may be less effective due to the thick crusts. Application needs to be repeated frequently (e.g., twice weekly for several weeks).
• Systemic Treatment: Ivermectin is often preferred, given orally, typically repeated at 7-14 day intervals for several doses.
• Keratolytic Agents: Salicylic acid or urea creams can help to remove the crusts, improving the penetration of topical medications.
• Debridement: Careful debridement of the crusts may be necessary, but should be performed cautiously to avoid trauma and secondary infection.
• Treatment of Underlying Immunodeficiency: Addressing the underlying immune compromise is crucial for long-term management.
• Public Health Measures: All close contacts should be treated simultaneously, even if asymptomatic, to prevent re-infestation. Environmental decontamination (washing bedding and clothing in hot water) is also important.

Hospitalization may be necessary for severely affected individuals, particularly those with secondary infections or significant systemic illness.