Scabies is a highly contagious parasitic infestation of the skin caused by the mite Sarcoptes scabiei var. hominis. It is characterized by intense itching and skin rash, primarily affecting areas with thin skin, such as the interdigital spaces of the fingers, wrists, elbows, axillae, waistline, buttocks, and genitalia. Scabies infestation occurs worldwide and can affect individuals of all ages, socioeconomic backgrounds, and hygiene levels.
Etiopathogenesis of Scabies
The pathogenesis of scabies involves several stages of mite infestation and immune response:
1. Transmission: Scabies mites are primarily transmitted through direct skin-to-skin contact with an infested individual. The mites can also spread indirectly through contaminated clothing, bedding, or furniture.
2. Burrowing and Feeding: Female scabies mites burrow into the upper layers of the skin (stratum corneum) to lay eggs and feed on host tissue fluids, triggering an inflammatory response.
3. Immune Response: Sensitization to mite antigens induces a delayed hypersensitivity reaction, leading to intense itching, erythema, and papular rash. Secondary bacterial infections may occur due to scratching and skin breakdown.
Clinical Manifestations:
The clinical presentation of scabies can vary depending on the individual’s immune response, duration of infestation, and previous exposure:
1. Pruritus (Itching): The hallmark symptom of scabies is severe itching, which is typically worse at night and may interfere with sleep. Itching is often more intense in areas with higher mite burden or where the skin is warmer.
2. Skin Rash: Scabies rash manifests as erythematous papules, vesicles, pustules, and excoriation marks, distributed in characteristic patterns:
Burrows: Linear or serpiginous, grayish-white, thread-like tracks representing the mite’s burrowing tunnels, commonly found on fingers, wrists, elbows, and genitalia.
Papules and Vesicles: Small, red papules or vesicles may develop in interdigital spaces, flexural areas, and other sites of mite infestation.
Secondary Lesions: Scratching can lead to excoriation, crusting, and secondary bacterial infections, resulting in impetigo, cellulitis, or eczematization.
3. Distribution: Scabies lesions tend to spare the face and scalp in adults but may involve these areas in infants and young children. In immunocompromised individuals, lesions may be widespread and atypical, resembling eczema or psoriasis.
Non-pharmacological Management of Scabies
Non-pharmacological interventions are important components of scabies management and focus on eradicating mites from the environment and preventing reinfestation:
1. Hygiene Measures: Thorough washing of clothes, bedding, and personal items in hot water (>50°C) followed by drying in a hot dryer or ironing can help kill mites and prevent transmission.
2. Isolation and Quarantine: Infested individuals should avoid close contact with others, particularly during the initial phase of treatment, to prevent spread of the infestation.
3. Environmental Decontamination: Vacuuming carpets and upholstered furniture, sealing non-washable items in plastic bags for several days, and disinfecting surfaces with acaricidal agents can help eliminate mites from the environment.
4. Avoiding Shared Spaces: Individuals with scabies should avoid sharing beds, towels, and clothing with others to prevent transmission.
5. Treatment of Close Contacts: Close contacts of infested individuals should be examined and treated if necessary to prevent reinfestation.
Pharmacological Management of Scabies
Pharmacological treatment of scabies aims to eliminate mites and relieve symptoms of itching and skin inflammation:
1. Topical Scabicides: Permethrin cream (5%) is the first-line treatment for scabies infestation. It is applied to the entire body from the neck down and washed off after 8-14 hours. Other topical scabicides include benzyl benzoate, sulfur ointment, and crotamiton cream.
2. Oral Medications: In cases of crusted (Norwegian) scabies or when topical therapy is impractical, oral ivermectin may be used as an alternative. It is administered as a single dose, with a repeat dose after 7-14 days if necessary.
3. Symptomatic Treatment: Antihistamines such as diphenhydramine or cetirizine can help relieve itching and improve sleep quality. Topical corticosteroids may be prescribed to reduce inflammation and skin irritation.
4. Treatment of Complications: Secondary bacterial infections should be treated with appropriate antibiotics, such as topical or systemic antibiotics for impetigo or cellulitis.
5. Follow-Up and Retreatment: Close follow-up is essential to monitor treatment response and ensure eradication of mites. Retreatment may be necessary if symptoms persist or if there is evidence of treatment failure.
Conclusion:
Scabies is a common and highly contagious parasitic infestation of the skin caused by the mite Sarcoptes scabiei. It is characterized by intense itching, skin rash, and burrows, primarily affecting areas with thin skin. Management of scabies involves a combination of pharmacological and non-pharmacological interventions aimed at eradicating mites from the skin and environment, relieving symptoms, and preventing reinfestation. Close coordination between healthcare providers, patients, and close contacts is essential for successful treatment and control of scabies infestation.
