Scabies is a highly contagious parasitic skin infestation caused by the mite Sarcoptes scabiei var. hominis. This microscopic ectoparasite burrows into the epidermis, causing intense pruritus and characteristic skin lesions. This comprehensive review provides medical professionals with current evidence-based information on the diagnosis, management, and prevention of scabies infestations.
Epidemiology
- Global prevalence: affects >200 million people worldwide
- Risk factors:
- Crowded living conditions
- Poor hygiene
- Immunocompromised status
- Institutional settings (nursing homes, prisons)
- Close physical contact with infected individuals
- Transmission:
- Direct skin-to-skin contact (15-20 minutes)
- Sharing contaminated bedding or clothing
- Higher risk in sexual contact
Pathophysiology
- Life Cycle
- Female mites burrow into epidermis
- Lay 2-3 eggs daily
- Eggs hatch in 3-4 days
- Larvae mature in 10-14 days
- Total life cycle: 30 days
- Host Response
- Delayed type IV hypersensitivity reaction
- Development of specific IgE antibodies
- Inflammatory response to mites and their products
Clinical Manifestations
Classic Scabies
- Primary symptoms:
- Intense pruritus (worse at night)
- Burrows (pathognomonic)
- Papular eruptions
- Excoriations
- Distribution:
- Interdigital web spaces
- Flexor surfaces of wrists
- Periumbilical area
- Axillae
- Genitalia
- Periareolar region
Crusted (Norwegian) Scabies
- Severe form in immunocompromised patients
- Characteristics:
- Hyperkeratotic plaques
- Thick crusts
- Millions of mites present
- Minimal pruritus may occur
Diagnostic Approach
Clinical Diagnosis
- History:
- Characteristic symptoms
- Contact history
- Timeline of symptoms
- Physical examination:
- Burrows identification
- Distribution pattern
- Secondary changes
Laboratory Confirmation
- Microscopic examination
- Mineral oil scraping
- Dermoscopy
- Adhesive tape test
- Skin biopsy (rarely needed)
Treatment Strategies
Topical Treatments
- First-line agents:
- Permethrin 5% cream (preferred)
- Application technique
- Repeat in 7 days
- Alternative options:
- Benzyl benzoate
- Malathion
- Sulfur preparations
- Crotamiton
Oral Therapy
- Ivermectin
- Dosing: 200 μg/kg
- Repeat in 7-14 days
- Preferred in crusted scabies
Management of Complications
- Secondary bacterial infections
- Post-scabetic itch
- Eczematization
- Psychological impact
Prevention and Control
Contact Management
- Identification of contacts
- Simultaneous treatment
- Environmental measures
- Washing bedding and clothing (60°C)
- Isolation of items for 72 hours
- Vacuum cleaning
Institutional Outbreak Control
- Mass treatment protocols
- Isolation procedures
- Environmental cleaning
- Staff education
- Surveillance measures
Special Populations
- Infants and children
- Modified treatment protocols
- Safety considerations
- Pregnant women
- Immunocompromised patients
- Elderly in care facilities
Follow-up and Monitoring
- Assessment of treatment response
- Management of persistent symptoms
- Prevention of reinfestation
- Documentation and reporting
Public Health Implications
- Surveillance systems
- Community education
- Prevention strategies
- Resource allocation
Conclusion
Scabies remains a significant global health challenge requiring prompt recognition and appropriate management. Success in treatment depends on correct diagnosis, appropriate medication choice, and comprehensive contact management. Healthcare providers must remain vigilant in identifying and treating this common but often misdiagnosed condition.
Date of last update: December 2024
Disclaimer: This article is intended for medical professionals and students. Clinical judgment should be exercised in the application of this information to patient care.