Human scabies

Human scabies is a highly contagious skin infestation caused by the microscopic mite Sarcoptes scabiei var. hominis. This condition is characterized by intense itching, especially at night, and a pimple-like rash. Scabies is a global issue, affecting people of all ages, races, and socioeconomic statuses. It is spread through direct skin-to-skin contact with an infected person or, less commonly, by sharing clothing, bedding, or towels.

Causes and Transmission

The sole cause of human scabies is the infestation by the female mite Sarcoptes scabiei var. hominis. After mating, the female mite burrows into the epidermis, where she lays eggs. The larvae that hatch from these eggs migrate to the skin surface and mature into adults, continuing the cycle. Transmission primarily occurs through prolonged direct skin contact with an infected individual. Indirect transmission through contaminated items is less common but possible.

Symptoms

The primary symptom of scabies is severe itching (pruritus), which tends to worsen at night. The allergic reaction to the mites, their eggs, and waste products causes the itching. Other symptoms include:

• Rash, often appearing as small blisters or pimples
• Thin, irregular burrow tracks made up of tiny blisters or bumps on the skin
• Sores resulting from scratching, which may lead to secondary infections

Common sites of infestation include the webbing between fingers, wrists, elbows, armpits, waist, buttocks, genital area, and under the breasts in women.

Diagnosis

Diagnosis of scabies is primarily based on the presence of typical symptoms and signs. A definitive diagnosis can be made by identifying the mite, its eggs, or fecal matter in skin scrapings examined under a microscope. Dermoscopy can also aid in visualizing burrows.

Treatment

Treatment involves the application of prescribed scabicidal agents, such as permethrin cream, lindane lotion, or ivermectin. All household members and close contacts should be treated simultaneously to prevent re-infestation. It is also recommended to wash all clothing, bedding, and towels in hot water and to vacuum furniture and carpets.

Prevention

Preventive measures include avoiding direct skin-to-skin contact with an infected person and not sharing personal items. In the case of an outbreak, prompt treatment of all affected individuals is crucial to prevent the spread of the disease.

Complications

If left untreated, scabies can lead to severe skin conditions like crusted scabies, also known as Norwegian scabies, which is characterized by thick crusts of skin that contain large numbers of scabies mites and eggs. Secondary skin infections, such as impetigo, can also occur due to bacterial infection of the open sores.

Epidemiology

Scabies is a common condition worldwide, with outbreaks occurring in various settings, including homes, hospitals, long-term care facilities, and other crowded environments. It is estimated that about 200 million people are affected by scabies at any given time.