Scabies

Scabies is a skin disease that is triggered by parasites. Its main symptom is severe itching, which is what gave the disease its name. This occurs when itch mites have penetrated the horny layer of the skin, drill tunnels there, lay their eggs and secrete feces. However, it takes a while for the parasite infestation to become noticeable after the initial contact. The disease usually goes unnoticed for weeks after an initial infection.

The first signs (itching and skin changes) only appear after two to six weeks. This long period of time results from the life cycle of the mites: it usually takes about four weeks until the animals have reproduced so much that the immune system reacts to the intruders or their excretions with clear symptoms. In the early stages of an initial attack and therefore without symptoms, it is hardly possible to recognize scabies. In the event of a renewed infestation, however, the body is already sensitized and shows the typical itching after just a few days.

How contagious is scabies?

Anyone can become infected with scabies as long as they have sufficiently long skin contact with an infected person or textiles that are close to the body. Since the mites, they carry the scientific name Sarcoptes scabiei, only move slowly, this contact must be extensive and last longer than five to ten minutes. Handshakes, greeting kisses, hugs, a medical examination of the skin or the like are without risk in patients with common scabies (from the Latin scabere = scratch), the technical term for scabies.

Scabies from poor hygiene?

Poor hygiene is often thought to be the cause of scabies. However, like lice, the animals spread on every body they can reach, regardless of the state of care. Scabies can be transmitted in places where many people come together. For example in the family, the shared apartment, in the kindergarten, the school, in the nursing home or in collective accommodation.

Indirect transmission, such as through textiles, is possible, but unlikely. The longer the itch mites are out of direct skin contact, the less contagious they are. At the room temperatures customary in Germany (21 ° C) and a relative humidity of 40 to 80 percent, it is very likely that after 48 hours it will no longer be transferable via textiles and the like. Lower temperatures and higher relative humidity, on the other hand, extend the survival time. Below 16 degrees Celsius, itch mites can only move to a limited extent and can no longer penetrate the skin.

How dangerous is scabies?

The risk of contracting scabies increases with the number of mites on their skin. It is very high in scabies in the end stage, i.e. severe infestation, and scabies crustosa (crust or bark itch). Dandruff that has already been detached or contact with clothing that is close to the body can lead to infection.

The typical signs of scabies (itching and skin papules) usually appear around four weeks after the infection when they are first infected. As long as the disease remains unnoticed and can be passed on to other people.

The scabies infestation of a private person is not notifiable. Institutions such as care facilities, collective accommodation, schools or kindergartens (Kita), on the other hand, must immediately report (suspected) cases to the responsible health department (Infection Protection Act (IfSG) § 6 and 7).

Particularly contagious scabies

In addition to the common scabies, there are the crustaceans (Scabies crustosa), formerly also called bark scabies (Scabies norvegica). This occurs mainly in people with a weakened immune system. With them, the mites can multiply unchecked, so that up to several million occur on and in the skin. Crustacean scabies are highly contagious; even brief skin contact can lead to infection.

The skin changes caused by scabies crustosa differ significantly from those of common scabies. The skin reddens and thickens in the affected areas. Scales and crusts form. In addition, bacteria can cause inflammation and get into the bloodstream through the damaged skin. Then there is a risk of blood poisoning (sepsis). In Scabies crustosa, the scalp, face, neck and nails are also attacked by the mites.

Because of the weakened immune defense of those affected, scabies crustosa can proceed without the itching typical of common scabies. Since the skin ( eczema ) does not have the typical papules (nodules), the diagnosis is often delayed. Another, but rare, form of scabies is Scabies nodosa. It causes rounded, often reddish-brown lumps up to 20 millimeters in size and extreme itching.

Scabies infections are common in many countries in the southern hemisphere. The mites infest children particularly often. Common scabies should be treated promptly but is not a medical emergency.

 

Symptoms of scabies

A typical sign of an infestation with itch mites, tiny arachnids, is itching. This usually increases during the night. As a further sign, elongated swellings or pimples (medical: papules) form in the skin. The female itch mites are primarily responsible for the symptoms: They drill passages into the horny layer of the skin (stratum corneum) and lay their eggs there. The male mite stay on the surface of the skin. With a maximum size of 0.5 millimeters, the animals are difficult to see with the naked eye.

It is often the hands that are particularly affected by scabies at the beginning, especially the spaces between the fingers. In male patients also the genital area, more precisely: the penile shaft. The scabies is contagious. The itch mites and larvae are usually the first to reach a new host via the hand.

Affected parts of the body

The itch mites prefer warm areas of skin with a thin horny layer. In addition to the spaces between the fingers and toes, they prefer to colonize the elbows, armpits (axillary folds), areola, umbilical region, belt line, groin, buttocks and the genital area, especially the penis shaft and anal folds, as well as the ankle region and inner edges of the foot.

The head, face, neck, and fingertips of adults are usually not affected by scabies. In babies (infants) and toddlers, however, the scalp, face, palms of the hands and soles of the feet can also be attacked by scabies.

The skin changes in scabies are based on the comma-like, winding and up to one centimeter long corridors of the scabies mites. Sometimes a small blister (pimple / papule) forms at the end of the passage. In addition, eczema with reddened, partly crusted nodules and vesicles develops on affected areas of the skin.

Where does the itch come from?

The eczema also causes the severe itching characteristic of scabies. It is triggered by the body's defense reaction against the mite products (especially the faeces) that the animals leave behind in the upper layer of the skin.

The diagnosis: on the trail of the mites

Only a doctor can reliably make the diagnosis, but only visit the person concerned if they notice symptoms. In men, severe itching and papules on the penis shaft are almost proof of scabies. As a rule, the doctor confirms the diagnosis with further examinations. This can be evidence of mites, their eggs or excrement (skybala) under the microscope or the reflected light microscope.