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Scabies is a skin disease caused by parasitizing the scabies mite (Acarus scabiei) in the surface of the skin.
Scabies has been known for a long time. It is mentioned in Egyptian parchments. In ancient China and Babylon, this disease was also well known. The ancient Greek Aristotle even gives in his writings a description of the "smallest animals" in the vesicles of rashes on the skin of sick people.
At the present stage, the greatest prevalence of this disease is observed in socially unadapted groups of the population. Its outbreaks are observed in disadvantaged regions of the world, where there is a massive migration of the population under the influence of natural disasters and military operations.
In regions that are prosperous in this sense, no one is immune from this disease either. So, the appearance of one infected person in a group of people united for some time (from a trip on a bus to a long stay in the same room - a kindergarten, school, boarding school) already suggests the presence of a potential focus of the disease. The greatest risk of getting sick in the age ratio is for adolescents (25-35%). This is explained by the greatest contact activity in collectives both during training (school, technical school, institute) and after it (informal connections, courtyard, boarding school, dormitory).
The active migration processes of socially unprotected groups of the population in the context of globalization of the surrounding world contribute to an increase in the risk of contracting scabies. Mass tourism, especially extreme tourism, to exotic countries of the world, where this disease is quite common, also carries some risk.
Features of the life cycle of an itch mite
The clinical manifestations of the disease are due to the manifestation of the life cycle of scabies mites, so it is worth dwelling on it in detail.
An adult female scabies mite is about 1/3 mm in size. Their photo is shown on the right. Males are about 1.5 times smaller and have no significance in the clinical picture of the manifestation of the disease.
Like all insects, scabies mites pass through the larval and adult stages in their development. After fertilization, the female is introduced into the superficial section of the skin (epidermis). Feeding on the epidermis, it moves, making passages in it, where, in addition to the products of its vital activity, it leaves eggs. In one intra-epidermal course, 3-4 fertilized eggs can be detected at different stages of development. Above the place of laying, the females make holes to facilitate the release of the offspring to the surface of the skin. On the skin, the larvae, spreading around, penetrate the hair follicles (hair roots), under the keratinized scales of the skin, into various elements of the rash (especially the vesicles). There they undergo transformation, bypassing intermediate stages, immediately into adult sexually mature ticks. Mating occurs on the human skin, after which the females are introduced into the epidermis, and the males are brushed off, separated with micro-flakes of the skin and perished. The average lifespan of a female is 6-8 weeks, during which she lays about 60 eggs. It is estimated that the potential hatching of adult ticks from one female in three months can be up to 150 million individuals.
Removed from the skin, in the environment at room temperature, scabies mites can remain viable for about a week. Under less favorable conditions, females live for about three days, and larvae for about two.
Infection of a healthy person is carried out by close contact with a sick person or indirectly through his things (combs, washcloths, towels, etc.).
Symptoms of scabies
Scabies is of the following types:
Typical, classic.
No scabies.
Norwegian scabies.
Scabies "clean", or scabies "incognito".
Complicated scabies.
Scabious lymphoplasia of the skin.
Pseudosarcoptosis.
Typical (classic) form of scabies
From the moment of infection, to the first clinical manifestations, it can take from 8 days to 6 weeks. It all depends on the state of the immune status and the number of ticks that have invaded.
Itching
The main symptom that attracts attention is a strong, obsessive itching. Itching is the body's reaction to irritation by the waste products of the tick. It is the response of the immune system, one of the parts of the external manifestation of which is the sensation of itching, that restrains the unrestrained reproduction of the parasite, the outcome of which could be death. With special force, sometimes even depriving sleep, itching manifests itself in the evening and at night. This is due to the highest activity of the female tick at this time. Its main occupation during this period is the laying of intraepithelial passages.
Scabies
Scabies are the most common symptom of scabies. From each move, the female gnaws one or two branches, making several exit holes in them. Fertilized eggs are laid in each of the knees. Then she continues to move in the main course. With the onset of the morning and until the middle of the day, the activity of the female drops sharply, and at the same time in all individuals.
When the skin is exfoliated, the old passages are gradually revealed as whitish lines, like superficial scratches left when a needle is passed over the skin. Drawings have their own frequency and repetition, which can be used to judge the daily movement of the course.
The length of the daily stroke rarely exceeds 5 mm, and in her entire life the female travels about 3-6 cm. It is theoretically possible to identify scabies on any part of the body, but their most likely location is in areas with a thickened superficial epithelium. These areas are the skin of the hands and feet. The thickness of the epidermis layer present here allows the larvae to hatch from the eggs long before the stratum corneum is rejected. In addition, too high a temperature of the skin is not required to maintain the life cycle.
Rash
The body's reaction to the introduction of a tick is also the appearance of a rash in the form of small red bumps (papules) rising above the rest of the skin surface, 1-2 mm in diameter, sometimes having bubbles (pustules) filled with liquid at their apex. The first rashes of this type can be found over the place where the mite enters the skin. You can see a photo of a rash with scabies on the right.
The number of papules, as a rule, depends on the number of invading ticks. Rashes can be initially multiple and "pour" after the appearance of new mature individuals.
A scabby rash, along with scabby passages, can most often be found in the interdigital folds of the hands and feet. They can also be detected on the flexor surfaces of the wrist joint, along the lateral surfaces of the fingers, in the armpits in front, in the peri-umbilical region, on the inner surfaces of the thighs, buttocks. Alternatively, the location of the itch passages in men is found on the skin of the penis, in women - around the nipples.
For children, due to the peculiarities of the structure of the skin, the most characteristic localization of the rash and moves on the palms and soles.
With severe itching and subsequent scratching, the rash, due to the addition of an infection, takes on a pustular appearance, with yellow crusts. It is possible to add inflammatory skin diseases, up to boils and carbuncles. The addition of erysipelas and dermatitis is possible.
Other symptoms of typical scabies
In addition, a long history of observations of scabies has made it possible to identify a number of characteristic symptoms according to the authors, which make it possible to differentiate this disease from skin appearances of other diseases:
symptom of I.A.
Michaelis symptom (the appearance of bloody crusts in the intergluteal region against the background of enlightened skin areas);
Cesari's symptom (probing the parasite and scabby passages in the form of slightly perceptible elevations on palpation of the alleged location of the tick, determined in the presence of single skin elements of the rash).
Regional lymph nodes may also be enlarged.
Scabies without intraepithelial scabies
It is extremely rare. In these cases, infection is not carried out by a sexually mature individual, but at the stage of tick development in the larval stage. The rarity of this form of scabies is explained by the fact that in order to keep the parasite on the surface of the skin and introduce the parasite, it is necessary to have a developed gnawing mouth apparatus, which the larvae do not yet have. Individuals that were able to resist and penetrate the hair follicles cause a pronounced immune response to the stimulus. Severe itching and an allergic rash occurs not only in those places where the larva has penetrated, but also throughout the body. Accordingly, until the larva matures into a mature female (and this sometimes takes up to two weeks) and penetrates into the epidermis, it is not possible to detect itch burrows in the rash.
Norwegian scabies
It is so named because it was first described in Norway in patients with leprosy (leprosy) in the middle of the 19th century. This is the most contagious and malignant form of scabies in its course. It occurs in individuals with persistent background suppression of the immune system for various reasons. For example, after undergoing chemotherapy for cancer, with hormone therapy, some of the severe diseases with corticosteroids. Patients with Down syndrome and HIV-infected people are at risk of developing a severe form. Skin sensitivity disorders observed in paralysis of various etiologies, some other diseases, congenital features of keratinization of the skin can also contribute to the transition of the classic form of scabies to Norwegian.
Typical signs:
A variety of elements of the rash, which have a draining character, from spots to blisters, the presence of ulcerated cracks in the skin.
The appearance of crusts of various shades of yellow and brown. Increasing in thickness and merging, they can form a kind of "armor" over parts of the body.
In the crusts, during their study, a huge number of mites are revealed at different stages of their life cycle. Sometimes, their number reaches 200 per cm².
It is also possible to identify the parasite on the nail plates, which, under the influence of the fungal flora, also thicken and become loose, convenient for the tick to inhabit and the development of its offspring.
Accession to the described picture of extensive pustular skin lesions, furunculosis, due to the addition of a secondary infection.
There is a prolonged rise in temperature.
Scabies "clean", or scabies "incognito"
This form is characterized by the smoothness of the classical clinical picture due to professional (doctor, pastry chef, cook, etc.) and due to personal characteristics - cleanliness.
New passages are practically not formed, the manifestations of itching are minimal, and single elements of the rash are explained by an allergy to detergents.
The spread of the disease to other parts of the body due to the constant mechanical removal of mature individuals and larvae during washing does not occur.
Scabies are rare.
The danger of patients with this kind of scabies is that, due to their obvious cleanliness from the outside, no one considers them as the primary source of outbreaks of the disease. And the infected person himself does not consider himself sick with any disease.
However, complete self-healing in such cases does not occur, since the maximum release of ticks on the skin occurs at night, when the unsuspecting patient is asleep and does not perform his usual ablution.
Complicated scabies
With this form of the disease, there will be a clinic of complications in the form of dermatitis, furunculosis of the skin, erysipelas, abscesses and phlegmon of soft tissues. Occasionally, the disease can occur in the form of mild urticaria, as a complex response of the body to a foreign antigen. This will be the main focus of the treatment.
Accordingly, the disease will continue for a long time, and the patient will retain his danger to others, as a constant source of scabies.
Scabious lymphoplasia
It is manifested by the appearance of a rash in the form of nodules (papules) of a blue-purple color elongated into small lines. They appear in the projection of the itch passages and are most often observed on the inner thighs, on the scrotum, buttocks, elbows, and on the mammary glands in women. These rising redness over the passages are explained by an allergic reaction and the proximity of the lymph nodes in these zones. This is confirmed by the appearance of this type of rash in the same places with repeated infection with scabies.
Pseudosarcoptosis
This is an infection with scabies mites that parasitize exclusively on animals. The difference is that the infection is carried out by larvae, not adult ticks, and the disease manifests itself immediately. The introduction is carried out in open areas of the skin, which is explained by the penetration of the larva into the hair follicle. Due to the inability to stay on the surface, the parasite does not reach the hidden areas of the skin. When it reaches puberty, the mite either dies or is peeled off the surface of the skin. Thus, after a short itching and rash, self-healing occurs.
Diagnosis of the disease
In addition to the classic clinical picture, it is necessary to confirm the presence of the parasite at different stages of its development. This is accomplished by pulling it out with a needle.
In addition, under a microscope, the surface sections of the skin (epidermis) obtained by the layer-by-layer method and the thin-section method are examined using express diagnostics using a 40% aqueous solution of lactic acid.
Scabies treatment
It is carried out with the help of anti-scab agents, the choice of which has recently been quite large.
The difference from the previous generation of such funds was the high speed of the onset of the therapeutic effect in the absence of any side effects.
The most commonly used are spregal, benzyl benzoate.
The preparations are applied to the whole body in the evening, rubbing thoroughly, especially paying attention to the characteristic habitats of the parasite. The drug remains on the skin all night, and in the morning the patient is thoroughly washed. To improve the effect, it is recommended to repeat this procedure after 2-3 days.
In complicated cases, antibiotics, antihistamines and hormonal ointments are connected to the described therapy. In these cases, treatment should be under the guidance and supervision of a physician.
