Scabies

Scabies is a contagious skin disease caused by mites. The female mites burrow into the upper layer of the skin and leave their eggs and excretions there. This causes an eczema reaction. Severe itching that becomes especially noticeable at night is typical for scabies.

The word scabies is derived from the Latin word scabere, meaning “to scrape”. Scabies can be treated effectively with drugs. Known as scabicides, they are usually applied to the skin as creams or ointments.

On average it takes 2-5 weeks after an initial infestation with scabies mites for the itchy eczema reaction to occur. However, an infected person can already infect others before the onset of symptoms. With repeated infection, the symptoms appear after just a few days since the body is sensitized – so it already knows the parasites – and therefore reacts more quickly with an immunological response.

Severe itching, which occasionally affects the entire body and increases during the night due to the warmth of a bed, is typical for scabies. The itching involves a rash that is characterized by small lumps and blisters. This itchy eczema is an immunological reaction to the mite infestation.

The mite burrows can initially be recognized on the skin as fine irregular papules (raised areas) on the skin that are up to a centimeter long and resemble a comma with their curved shape. They cannot be easily made out with the naked eye, and the mites themselves can only be seen with a microscope or certain magnifying glasses (dermatoscope).

The burrows are often located:

• between fingers and toes
• on ankles, wrists and elbows
• on the penis
• on armpits, nipples and the navel
• in the groin and buttocks

In rare cases, especially with babies and small children, the head (when it has grown hair), face, palms and soles can also be affected.

People with a weakened immune defense often have an especially virulent form of scabies in which extensive scaly areas of redness and thick scabs develop on the skin. This is more particularly known as crusted scabies (Scabies crustosa). The otherwise so typical itching is sometimes absent in this form of the disease. Due to the abundance of mites, even brief skin contact or contact with objects used by the infected person can be contagious.

Scabies is predominantly transmitted by direct skin contact. Because the scabies mites move very slowly however, a continuous and extensive contact over 5-10 minutes is needed, for example during playing, cuddling or sleeping in the same bed. A simple handshake or short hugs on the other hand do not cause infection as a rule.

An exception to this rule is crusted scabies (Scabies crustosa), in which patients’ skin is colonized by thousands or even millions of parasites. In this case, brief skin contact or contact with flakes of shed skin is sometimes enough to cause infection.

Along with the scabies mites that specialize in humans, there are other types of mites that infest pets. These mite diseases in animals are called mange.

While the animal mites occasionally migrate to humans, they die off quickly on human skin without multiplying there. The skin irritation that they sometimes cause (“pseudoscabies”) usually disappears by itself after a short time.

Scabies occurs in all age groups throughout the world. However, it is especially prevalent in children and sexually active people with changing partners. Elderly people or people who are taking drugs that weaken the immune system are prone to highly contagious crusted scabies.

Scabies outbreaks can also occur in community facilities such as kindergartens, rest homes, hospitals, homeless shelters or prisons.

However, there are no verified figures about how common overall this parasite infestation is in Germany, because there is no broad obligation to notify the authorities. However, scabies is one of the most widespread infectious diseases and may affect many thousands of people in this country every year. A 2016 study by the Robert Koch Institute about the morbidity rate, among others, implies this. At the same time, the morbidity rate may fluctuate from region to region over the course of many years.

Scabies mites are often transmitted to other people unseen before the outbreak of the disease. In such cases, it is hardly possible to prevent infection.

But if, on the other hand, the disease has already been discovered in a patient, close contacts should be examined and all of them treated, preferably at the same time. If physical contact with sick people cannot be avoided, for example when caring for relatives, long-sleeved clothing and disposable gloves provide protection.

To stop mites spreading via objects in a shared household, the clothes and towels of the infected person should be washed every day at a minimum temperature of 50 degrees, beds freshly covered and upholstery vacuumed with a powerful vacuum cleaner.

Contaminated objects should also be stored in plastic bags for 3 days at a minimum temperature of 21 degrees, for example close to a heater, or frozen for 2 hours at minus 25 degrees. In this way, the scabies mites die off.

People who have scabies or are suspected of having it should not visit community facilities like schools or kindergartens or work in them until the treatment has finished.

Experienced doctors or GPs can often already recognize scabies based on the typical symptoms and a physical examination, and confirm the diagnosis by detecting the mites in skin particle scrapings under a microscope or with a direct light microscope (dermatoscopy). Lab tests are not necessary for a scabies diagnosis.

As a general rule, scabies can be treated well with drugs that are applied externally to the skin. Permethrin is usually used as the active ingredient here. Alternatively, crotamiton for instance can also be used. Taking tablets with ivermectin as the active ingredient is possible in certain cases.

After a thorough one-time treatment with permethrin – for example by applying an ointment overnight – or alternatively 24 hours after taking ivermectin, a person with scabies is usually no longer contagious. However, ivermectin should not be used for pregnant women or small children.

After treatment, the itching subsides within 1-2 weeks.

With severe crusted scabies (Scabies crustosa) however, repeated treatment and an extended avoidance of unprotected contacts is required.