What is a scabies mite, what are its symptoms, and how is it treated?

What is a scabies mite, what are its symptoms, and how is it treated? - briefly

The scabies mite (Sarcoptes scabiei) is a microscopic parasite that excavates tunnels in the epidermis, producing intense itching and a rash with tiny burrows or papules typically on the hands, wrists, and torso. Treatment involves a prescribed topical scabicide—commonly 5 % permethrin cream applied overnight and repeated after 7 days—or oral ivermectin for refractory infections.

What is a scabies mite, what are its symptoms, and how is it treated? - in detail

The scabies parasite, Sarcoptes scabiei var. hominis, is a microscopic arthropod measuring 0.2–0.4 mm. Female mites burrow into the epidermis to lay eggs, creating a tunnel that triggers an immune response. The life cycle lasts 10–14 days: egg → larva → nymph → adult, after which the mite exits the skin to seek a new host.

Clinical manifestations appear 2–6 weeks after initial infestation in naïve individuals; in previously exposed patients, symptoms may develop within days. Typical signs include:

• Intense pruritus, especially at night
• Linear or serpentine burrows visible on the skin surface
• Papules, vesicles, or nodules at burrow termini
• Eczematous patches from secondary irritation
• Crusted lesions (Norwegian scabies) in immunocompromised hosts or those with prolonged untreated disease

Commonly affected sites are interdigital spaces, flexor surfaces of wrists, elbows, axillae, waistline, genitalia, and buttocks. Diagnosis relies on clinical pattern and confirmation by microscopic examination of skin scrapings, revealing mites, eggs, or fecal pellets.

Therapeutic regimens aim to eradicate the mite and alleviate symptoms:

1. Topical scabicides

   • Permethrin 5 % cream applied from neck to toes, left for 8–14 hours, then washed off; repeat after 7 days.
   • Ivermectin 1 % lotion (alternative where permethrin is unavailable).

2. Oral ivermectin

   • Single dose of 200 µg/kg body weight; repeat after 7 days for typical cases, after 14 days for crusted scabies.
   • Dosage adjustments for children <15 kg, pregnant or lactating women are contraindicated; alternative topical agents preferred.

3. Adjunctive measures

   • Antihistamines or topical corticosteroids to control itching.
   • Washing bedding, clothing, and towels in hot water (≥50 °C) or sealing in plastic bags for 72 hours to kill offstage mites.
   • Treating close contacts simultaneously, regardless of symptom presence.

Monitoring includes reassessment of pruritus and skin lesions after treatment completion. Persistent burrows or renewed itching may indicate treatment failure, resistance, or reinfestation, necessitating repeat dosing or alternative agents such as benzyl benzoate or sulfur ointment.