Scabies

Scabies: A Highly Contagious Skin Infestation

Scabies is a common parasitic skin infestation caused by the Sarcoptes scabiei mite, which burrows into the skin, triggering intense itching and a rash. Scabies is highly contagious and spreads quickly through direct skin-to-skin contact, making timely diagnosis and treatment essential. As healthcare professionals, understanding scabies’ clinical presentation, treatment, and preventive measures is critical in managing outbreaks and minimizing transmission.

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Definition

Scabies is an infestation of the skin by the microscopic mite Sarcoptes scabiei var. hominis, leading to intense itching and a rash due to the body’s allergic reaction to the mites, their eggs, and their waste.

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Etiology

Scabies is caused by:

• Sarcoptes scabiei var. hominis, a parasitic mite that burrows into the outer layer of the skin (stratum corneum) to lay eggs. These mites are not visible to the naked eye.
• The infestation spreads primarily through direct, prolonged skin-to-skin contact with an infested person.
• Less commonly, scabies can spread via contact with contaminated clothing, bedding, or furniture, although the mites cannot survive for long off the human body.

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Pathophysiology

1. Mite Infestation: Female mites burrow into the skin, creating tunnels where they lay eggs.
2. Allergic Reaction: The immune system reacts to the mites and their waste products, causing inflammation and intense itching.
3. Life Cycle: Mite eggs hatch within 3-4 days, and the larvae mature within a week, perpetuating the infestation.
4. Chronic Inflammation: The intense itching leads to scratching, causing secondary bacterial infections and further skin damage.

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Clinical Manifestations

1. Intense Itching: Especially at night, due to the increased activity of mites.
2. Burrow Tracks: Thin, grayish-white or skin-colored lines where the mites have burrowed, commonly found in areas like:
   • Between the fingers
   • Wrists
   • Elbows
   • Genitals
   • Buttocks
3. Rash: Small, red, raised bumps or blisters, often in a linear arrangement, resembling pimples or insect bites.
4. Crusted (Norwegian) Scabies: A severe form of scabies with thick, crusty skin lesions containing a large number of mites, seen in immunocompromised individuals.
5. Secondary Bacterial Infections: Resulting from excessive scratching, leading to complications like impetigo.

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Diagnosis

1. Clinical Examination: Based on the characteristic symptoms of intense itching, burrows, and rash distribution.
2. Microscopic Examination: Skin scrapings viewed under a microscope can confirm the presence of mites, eggs, or fecal matter.
3. Dermoscopy: A non-invasive tool used to visualize the mite burrows more clearly.

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Treatment

Pharmacological Treatment

1. Topical Scabicides:
   • Permethrin 5% Cream: First-line treatment applied from neck to toe and left on for 8-14 hours before washing off. It’s effective in killing both mites and eggs.
   • Benzyl Benzoate: An alternative scabicide, although it can cause skin irritation.
   • Sulfur Ointment: Used in individuals who cannot tolerate other treatments (e.g., pregnant women or infants).
   • Crotamiton: Another option with antipruritic properties.
2. Oral Treatment:
   • Ivermectin: An oral antiparasitic used in severe cases, such as crusted scabies or where topical treatments have failed. It is taken as a single dose and may require a repeat dose after 1-2 weeks.
3. Antihistamines: To help alleviate itching, particularly at night.
4. Antibiotics: If secondary bacterial infections (e.g., impetigo) occur, appropriate antibiotics may be prescribed.

Non-Pharmacological Measures

1. Environmental Decontamination: Wash clothing, bedding, and towels in hot water and dry them on a hot cycle to kill mites. Items that cannot be washed should be sealed in plastic bags for at least 72 hours.
2. Treat Household Members: As scabies spreads quickly, treating all close contacts at the same time is essential to prevent reinfestation.
3. Avoid Close Contact: With others during the treatment period to minimize transmission risk.

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Prevention

1. Prompt Treatment: Early diagnosis and treatment of scabies are critical to preventing its spread.
2. Hygiene Measures: Regular handwashing and avoiding sharing clothing, towels, or bedding with others can help reduce transmission.
3. Close Contact Monitoring: In institutional settings (e.g., nursing homes, daycare centers), frequent screening and treatment of affected individuals are necessary.

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FAQs about Scabies

1. How long does it take for scabies symptoms to appear? Symptoms typically appear 2-6 weeks after the initial infestation, but in individuals previously infected, symptoms can appear within 1-4 days.

2. Can scabies spread through casual contact? Scabies requires prolonged skin-to-skin contact to spread. Brief handshakes or hugs are unlikely to transmit the infestation.

3. How long do scabies mites live on the skin? The mites can live for 1-2 months on a human host but die within 72 hours when off the body.

4. Can pets spread scabies to humans? No, human scabies is caused by a different mite species than that affecting animals. However, animal mites can cause a temporary, self-limited rash in humans (e.g., mange from dogs).