Sarcoptes scabiei (itch mite)

Sarcoptes scabiei

What is the itch mite?

Sarcoptes scabiei var. hominis, the itch mite, is a parasite that specialises in humans. The skin infestation is medically referred to as scabies. The parasites belong to the arachnids and reach a size of 0.2 – 0.5 millimetres. This means they are barely visible to the naked eye. The females dig into the upper skin layer and lay their eggs there. People with a weakened immune system are particularly susceptible. Skabicides are used for treatment. These are administered in the form of creams, sprays or ointments, and infrequently, also as tablets. The disease is no longer contagious 24 hours after the application or dose of medication.

How is the itch mite transmitted?

The transmission takes place mainly from person to person via skin contact. Even before the first symptoms appear, the mites may have been transmitted. Symptoms appear after two to five weeks. Brief skin contact, such as shaking hands, is usually not sufficient for the disease to spread. Typical modes of transmission are playing with children, sleeping together in a bed, bodily care of small children by parents or of sick children by care-givers.

With scabies crustosa, on the other hand, short skin contact can be sufficient. This highly contagious form of itch mite is accompanied by strong crust formation and a very high number of mites on the skin. Because the transmission takes place mainly by skin, particularly high-risk places include kindergartens, facilities for the handicapped, homeless shelters, prisons, care homes for the elderly and hospitals.

Infestation via clothing or bed linen is also possible. However, this type of transmission is unlikely in the common form of scabies, as the mites can only survive one to two days outside the host.

What are the symptoms of the disease?

Burning and itchy skin, which is particularly intense at night in a warm bed, is typical. Mainly the spaces between fingers and toes, wrists, ankles, armpits, elbows, nipples and genitals become infested. Even regions that are not directly affected can show symptoms. In infants, the head, face, palms of the feet and hands may also be affected. Fine, dark and irregular lines are typically visible on the skin, but are difficult to see with the naked eye. After some time, blisters, reddened raised nodules or pustules form on the skin. Scratched skin can also become purulent and inflamed. Allergic skin rash can also develop.

Significance for infections in hospitals and in the outpatient sector

If individual cases occur, people who have been in close contact with the infected person should be identified, so they can also receive adequate treatment. Medical personnel who have close professional contact with a person who is suspected or confirmed to have scabies, or who has an increased risk of being colonised by scabies mites, must wear disposable gloves and long-sleeved protective clothing to avoid skin contact. In the case of inpatients, isolation of the infected persons is recommended until the treatment has taken effect. The usual basic hygiene measures to avoid other infection risks, for example, hand disinfection after taking off disposable gloves, continue to apply.

The international Alliance for the Control of Scabies recommends notes that "an important aspect of control and elimination programs is the integration of these programs into existing clinical and public health programs and systems".

Survival time of pathogens on inanimate surfaces

2 to 3 days; at 12 °C and in humid conditions up to 14 days

Disinfectant effectiveness for prevention

Hand disinfectants are not effective. In case of an infestation, textiles can be thermally disinfected by washing them at 50°C or by storing them in a dry place for at least seven days at a constant 21°C.

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