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Scabies

Overview

Scabies is an itchy skin condition that is caused by a mite infestation. The mites bury your skin’s outer layers and lay eggs to increase their number. They can be present in any part of the skin, although they are more commonly observed on the skin between fingers, wrists, and waist. It is not an infection of the skin, rather an infestation that triggers an allergic response by your immune system. It is a contagious disease that can spread from one person to another by direct skin contact and sharing bedding or clothes. 

Causes

The mite responsible for causing scabies is known as Sarcoptes scabiei. The mites are tiny and often not visible to the naked eye. The female mites infest the outermost layer of skin and lay eggs that hatch in three to ten days. These mites form tiny burrows or tunnels in the outer layer of skin, and their movement triggers your immune response. Infestation with scabies mites may take over three to six weeks before the symptoms develop. 

Even in the absence of symptoms, an affected person can still transfer the mites to another by direct skin contact. Skin contact needs to be prolonged (at least 10 minutes) to transfer mites from one person to another. This is why sexual intercourse is one of the most common modes of transfer, even though mites are not transmitted from genital organs, unlike STDs. Other modes of transmission include sharing clothes, towels, bedding, etc., with a person who has already been infested with scabies mites. 

Risk Factors And Epidemiology

Scabies can affect all individuals, but individuals with compromised immunity are at the highest risk. Scabies mites persist longer and lay millions of eggs in an immunocompromised patient. The resulting condition is much more severe and is known as crusted scabies. People with HIV/AIDS, leukemia, diabetes mellitus, etc., are at the highest risk of developing crusted scabies. Lack of personal hygiene can be another factor. Since scabies is highly contagious, living in crowded areas such as children’s care, nursing homes, prisons, etc., can increase the risk if even one person gets infested with these mites. It is also found more frequently in tropical and subtropical areas. 

Scabies occurs in people of all ages, but young children and older adults are more commonly affected due to their lower immunities. It is prevalent in both males and females. Tropical and developing countries have more cases of scabies than other parts of the world. 

Signs And Symptoms

Signs and symptoms of scabies may take three to six weeks to develop after mites infest your skin layer. Typical case of scabies presents with excessive itching of the affected areas that gets worse at night. Upon close examination, small tunnels or burrows may be noticed on the affected skin region. These may be present on any part of the skin, but they are more commonly observed on wrists, between fingers, waist, elbows, armpits, nipples, or buttocks. In children, skin infestation with scabies may also appear on the scalp, palms, and soles. Itching is often accompanied by rashes. Severe itching can break open the skin, increasing the chance of bacterial infections. People with immunocompromised systems develop crusted scabies with itching, thick crusts or skin scales, and much deeper burrows. 

Diagnosis

Diagnosis of scabies is usually made based on the history of contact and presenting symptoms. Clinical examination of the affected skin regions is done to locate tunnels or burrowing tracks characteristic of scabies. These tunnels can also be highlighted by using fountain pen ink or a tetracycline solution. The tunnels absorb the liquid and can be seen in a zig-zag pattern on the skin. Conformational diagnosis of scabies is made by taking a swab from an affected region and observing it under a microscope to visualize scabies mites. 

Differential Diagnosis

Signs and symptoms of scabies may be confused with other skin diseases that cause itchiness or rashes. These diseases include eczema, measles, atopic dermatitis, insect bites, psoriasis, tinea corporis, bullous pemphigoid, systemic lupus erythematosus, seborrheic dermatitis, etc.  

Treatment

Scabies can be effectively treated with prescribed ointments or creams on the affected skin areas. Oral medication may be prescribed as well in a few cases. The symptoms may persist for a few days, even after applying topical agents. During this period, it is suggested to avoid sharing bedding, clothes, or towels with another person. Used clothes or other items such as pillow covers, towels, bed covers, etc., should be washed once with detergent and water. Most doctors prefer treatment of people in close contact even if they have not developed any symptoms. 

Medication

Topical antibiotics are the preferred mode of treatment for scabies. These include permethrin, ivermectin, lindane, etc. These are available in the form of ointments, creams, or lotions and to be used as prescribed by your doctor. An oral dose of antibiotics may be required in severe or persistent cases of scabies. 

Prognosis

The overall prognosis is good in patients with a healthy immune system. It can be cured completely after the use of topical medications as prescribed. A severe form of scabies (crusted scabies) or other complications may develop only in patients with a compromised immune system. Such a condition may require a longer and more aggressive form of treatment because the number of mites present among such individuals is in the millions. They are present in much deeper burrows than regular scabies. 

Prevention

Primary modes of prevention of scabies are by avoiding prolonged contact with a person infected with scabies mites. Sharing clothing items, pillows, bedding or towels, etc., should also be avoided. If you have come in contact with a person who was not diagnosed, it is better to consult a doctor and apply topical medication in advance, even if you have not developed any symptoms. Maintenance of personal hygiene is necessary to avoid infestation of these mites.