Understanding Scabies: A Comprehensive Overview of Management and Treatment

Scabies is a widespread and extremely contagious skin infestation that is brought on by Sarcoptes scabiei var. hominis, a human itch mite. This minute parasite burrows into the epidermis' topmost layer, where it lays its eggs and thrives. It causes an immunological reaction that results in a rash and severe itching. The body reacts allergicly to the mites, their eggs, and their excrement, which causes itching that is frequently worst at night. People of all ages, races, and socioeconomic backgrounds are susceptible to scabies, although it is more common in places with congested housing, inadequate sanitation, and little access to medical care. Direct, persistent skin-to-skin contact with an infected individual is how it is spread. Although less frequent, it can occasionally also be transmitted by contaminated clothing, furniture, or bedding. In settings including schools, jails, nursing homes, and refugee camps, outbreaks are common. Small red papules, burrows (thin, wavy lines on the skin), and severe itching are all part of the clinical presentation. The wrists, elbows, fingers, waist, and genital area are frequently infested. Scabies can manifest more severely as crusted (Norwegian) scabies in babies and immunocompromised people, which is characterized by thick skin crusts that are home to a high number of mites. Although skin scrapings and dermoscopy can help confirm the diagnosis, clinical symptoms are frequently used to make the diagnosis. Topical drugs like permethrin cream or oral meds like ivermectin can be used to treat scabies. To contain outbreaks and stop reinfestation, prompt diagnosis and treatment are essential, as are close contact management and personal item disinfection.

Mechanism of scabies

Sarcoptes scabiei var. hominis, a mite, infests the skin as part of the scabies process. After coming into touch with human skin, the female mite burrows into the stratum corneum, which is the epidermis' outermost layer, creating slender, wavy tunnels. The female deposits eggs inside these burrows, and the eggs hatch into larvae in three to four days. In roughly 10–14 days, the larvae develop into adult mites, completing the cycle. The body's immune reaction to mite antigens, such as their saliva, eggs, and feces (scybala), is what causes the main symptoms of scabies, such as the extreme itching, rather than the mites themselves. Four to six weeks following the initial infestation, this hypersensitive reaction usually manifests. Due to earlier sensitization, symptoms may manifest in previously infected persons within 1-4 days. At night, the itching is at its worst, and a rash with tiny red papules, vesicles, and burrows is also present. These immune-mediated responses may result in scratching, which may develop to impetigo and other secondary bacterial infections. A more severe type of scabies called crusted (Norwegian) scabies can develop in immunocompromised people. Thousands to millions of mites may be present on the skin in this form, causing thick scaling and hyperkeratotic crusts that are often widespread without much itching because of a weakened immune system.  In general, the pathogenic mechanism of scabies consists of both host immunological responses to mite-derived components and direct mite activity (reproduction and burrowing). In order to stop the mite's life cycle and reduce symptoms, prompt identification and treatment are essential.

The actual presence of the mites and the body's immune reaction to them both contribute to the variety of distinctive signs and symptoms that characterize scabies. Severe itching is the most prevalent and early symptom, and it usually gets worse at night. The body's allergic response to the mites, their eggs, and their waste products is what causes this itching. Burrows, which are thin, wavy, grayish-white, or skin-colored lines on the skin's surface, are one of the telltale symptoms of scabies. The vaginal area, armpits, waist, buttocks, wrists, elbows, and crevices between fingers are among the warm, damp parts of the body where these burrows are usually discovered. The scalp, face, neck, and palms of newborns and young children may also be impacted. Additional symptoms include tiny red zits or blisters that can resemble pimples or insect bites and may show up in clusters. These lesions may become crusted, excoriated, or secondary infected as a result of frequent scratching, which can result in problems such as impetigo.

Transmission of Scabies:

Mostly, scabies is spread by direct skin-to-skin contact with an infected individual over an extended period of time. This means that the infection is typically not transferred by casual contact, such a quick hug or handshake. In contrast, transmission usually happens through close contact, such as between members of the same household, sexual partners, or those residing in crowded settings like prisons, nursing homes, dorms, and refugee camps.  Additionally, shared personal objects including clothing, towels, and bedding can spread scabies, particularly in cases of crusted (Norwegian) scabies, when the mite burden is rather high. Because skin crusts containing live mites shed in these situations, indirect transmission becomes more likely. It's crucial to remember that mites can live for 24 to 36 hours outside of the human body, and in cases of crusted scabies, they may live for even longer. In order to control outbreaks, it is crucial to practice good hygiene and disinfect infected goods. Since scabies symptoms may not show up for weeks after the first infection, an infected individual may unintentionally transmit the mites during this time. Therefore, even if they do not exhibit symptoms, close contacts of an infected individual should also receive treatment concurrently to stop reinfestation and further dissemination. In conclusion, scabies is transmitted by direct contact and, less frequently, by contaminated objects. In order to disrupt the cycle of transmission, prompt identification, treatment, and hygiene measures are essential.

Diagnosis of Scabies

Scabies is mostly diagnosed clinically based on the physical examination results and typical symptoms. Important symptoms include severe itching, particularly at night, and a common rash with vesicles, papules, or burrows that are frequently found in particular places including the buttocks, waist, genital area, wrists, elbows, and fingers. The scalp, face, palms, and soles may also be affected in newborns and young children. A thorough medical history is crucial, especially if the patient has recently had direct contact with someone who is exhibiting symptoms or has lived in a busy area. A crucial diagnostic hint may come from family members or close acquaintances who exhibit same symptoms. Several diagnostic methods can assist confirm the presence of scabies mites, eggs, or fecal pellets (scybala), even though clinical indications are frequently sufficient.

1. Skin Scraping: The most popular technique is scraping the skin in the afflicted areas and looking at the particles under a microscope. The diagnosis is confirmed if mites, eggs, or excrement are found to be present.
2. Dermoscopy: The distinctive "delta wing jet" indication, a triangular structure that symbolizes the mite at the end of a burrow, can be seen using a handheld dermoscope. This non-invasive method works well for finding mites and burrows.
3. Adhesive Tape Test: To find mites or eggs, clear adhesive tape is applied to the skin and then viewed under a microscope.
4. Ink Test: Ink is put to the skin and then removed using an earlier technique, leaving a black path in the burrows.
5. Due to the quantity of mites, diagnosing crusted scabies may be simpler; but, without thorough examination, the illness may be mistaken for psoriasis or eczema.
   Finally, to stop scabies from spreading and to start treatment for the patient and their close contacts as soon as possible, an early and precise diagnosis is essential.

Management and Treatment of Scabies

Eliminating the mites, reducing symptoms, treating close contacts, and avoiding reinfestation are the main goals of scabies management and treatment. In order to prevent transmission and lower the risk of consequences such secondary infections, prompt and adequate treatment is crucial.

1. Topical Treatments:

• Permethrin 5% cream is the most often recommended and successful topical medication. Before being washed off, it is applied from the neck down, including between the fingers and toes and under the nails. It is then kept on for 8 to 14 hours. Treatment for the face and scalp may also be necessary for immunocompromised people, the elderly, and babies.

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Figure 3 Permethrin 5% cream

• Alternative topical agents include benzyl benzoate, sulfur ointment (5–10%), crotamiton, and malathion, especially in cases where permethrin is contraindicated or not available.

2. Oral Medications:

• Ivermectin is an effective oral antiparasitic used especially in crusted (Norwegian) scabies, in institutional outbreaks, or when topical therapy fails. The typical dosage is 200 µg/kg, taken as a single dose and repeated after 7–14 days.
• Ivermectin is not routinely recommended for pregnant women or children weighing less than 15 kg, unless the benefits outweigh the risks.