Scabies

SCABIES (scabies), a contagious skin disease caused by the animal parasite—the scabies mite (Acarus siro var. hominis, s. Sarcoptes scabiei) (fig. 1). This mite is an animal of a barely visible, turtle-like shape to the naked eye. The female is larger than the male (length 300-490 μm, width 250-380 μm), the head, thorax, and abdomen are fused into one oval formation (a fused-body animal) (fig. 2). The upper surface of the body is convex, covered with transverse grooves and triangular spines pointing backward with their apices; the lower, flatter abdominal surface has no spines. The head part has a proboscis (mouth), at the upper part of which are the chelicerae and pedipalps, and below them—the hypostome (lower jaws). On the sides of the head part are two pairs of front legs, consisting of a coxa, trochanter, femur, tibia, and tarsi ending in stalks with cup-shaped suckers at their ends. The two hind pairs of legs are on the abdominal part of the body and end in long bristles in females, while in males one pair of legs (hind inner) ends in suckers (fig. 3). The anal opening is at the posterior edge of the body along the midline. In front of the anal opening at the level of the posterior body spines in females there is a ring-shaped opening surrounded by a yellowish chitinous ring—a copulatory organ. On the abdominal surface between the 4th pair of legs in the female there is a transverse slit-shaped opening intended for laying eggs, while in the male there is a sexual organ having a horseshoe shape, ending in a thin emission spike.

The main cause of the development of scabies in humans is the fertilized female, which, upon getting on the skin, immediately begins to burrow a tunnel in the skin and lay eggs; a male that gets on the skin soon dies and cannot cause the development of scabies; when larvae and nymphs get on the skin, the possibility of infection is debatable. Thus, for infection with scabies, suitable conditions are required: close contact with patients (sleeping together, coitus) or using the bedding, towels, clothing, etc., of patients. The incubation period for the development of scabies varies depending on various conditions (when sleeping together, it is possible for a large number of scabies mites to get on the skin of a healthy person, and in such cases, the development of scabies manifestations can be rapid and abundant). In the experimental transfer of scabies mites to the skin, the appearance of the first blisters is noted after 9-10 days, and the manifestations of widespread scabies - after 12 weeks. The clinical manifestations of scabies come down to the presence of scabies burrows and small blisters with transparent contents. The scabies burrow appears as a whitish or grayish line, winding or broken, with dark dots (contaminated openings of the burrow cover), 1-5-8 mm in length. One end of the burrow is open (beginning of the burrow), and the other is blind, and at this point a whitish elevated dot is often noted, and with a magnifying glass, the smallest brown dots can be seen - the chitinous parts of the female. The scabies blisters are located deeper than the burrow, which is in the cover of the blister, and sometimes the female can be seen here, although more often she has moved beyond the cover of the blister. Scabies burrows can be noted in the following places: in the interdigital folds of the hands, in the area of the flexor surfaces of the wrist joints, on the palms (and in children also on the soles), on the skin of the penis, and in women in the area of the nipples; on other parts of the body, burrows are rarely seen and usually nodules with an excoriated surface, scratches, pustules (as a result of secondary infection by pyogenic bacteria), crusts, scales, and manifestations of skin eczematization are noted in these places. The favorite localization of scabies is: the interdigital spaces of the hands, the flexor surfaces of the wrist joints, the flexor surfaces of the upper extremities (especially the elbow bends), the skin in front of the axillary fossae (the fossae themselves are free); the area of the belt and navel, the lower half of the abdomen, the area of the mammary glands (mainly in women), the skin of the penis, the gluteal area, and the lower extremities (in children often the soles, and sometimes the face). In adults, the neck and face are free from manifestations, and the upper part of the back is also usually free (in so-called Norwegian scabies, manifestations can spread to the entire surface of the body, including the hairy part of the head). Sometimes, due to the patient's profession, features in localization are noted (predominant involvement of the gluteal area in tailors, cobblers, laundresses - hands; in people dealing with lubricants, the hands are often free from scabies manifestations, etc.). In some cases, almost exclusive localization is noted. The female (after fertilization by the male) burrows into the horny layer of the epidermis and lays eggs there, while she burrows herself a tunnel in a horizontal direction, advancing about 1 mm per day, and then stops for 4 days, drills an opening in the cover of the tunnel and lays 4 eggs, and then moves forward again and repeats the stop for 4 days with drilling of the cover of the tunnel and laying of 4 eggs, and so on. On average, a fertilized female manages to lay about 50 eggs during her life (6-8 weeks). After fertilizing the female, the male dies; he lives on the skin under scales or in shallow tunnels made by him, but he does not dig real tunnels. From the eggs laid by the female, larvae hatch after 2-7 days, having only 6 legs (one pair of hind legs is missing), which then turn into the first stage nymph, which already has 8 legs, which after changing its shell turns into the second stage nymph (for males, development ends at this point); the latter after a new shell change turns into a sexually mature female. The entire life of the scabies mite passes in human skin, and outside it the mites die in 2-3 days (skin and surface mites of animals can live outside skin conditions for 40-60 days; these mites give so-called surface and skin localization in the genital area (infection during sexual intercourse). Skin itching is an essential sign of scabies. The itching usually sharply increases at night, which depends on the biological properties of the mite (burrowing of tunnels at night). In its pure form, scabies is relatively rare; more often one has to observe scabies complicated by pyodermic elements from secondary infection of the skin by pyogenic bacteria or the presence of eczematous manifestations (redness, blisters, weeping, etc.). Among other clinical symptoms in scabies, albuminuria and blood eosinophilia are sometimes noted. Pathoanatomical changes in the skin in pure scabies are negligible: in the horny layer, burrows, eggs, and mites are noted; there are no noticeable inflammatory phenomena in the papillary and subpapillary layers of the skin. In complicated scabies, inflammatory phenomena are clearly manifested with a characteristic picture of a pyodermic or eczematous process. Diagnosis of pure cases presents no difficulties (presence of scabies burrows and blisters, characteristic localization of manifestations and finding mites at the blind end of the burrow). In complicated cases, one has to take into account the localization of the process, and also try to find scabies burrows. Norwegian scabies represents a special clinical form of scabies, caused by the same mite that causes ordinary scabies. In Norwegian scabies, the itching of patients bothers little or is completely absent. The main symptom is the abundant deposition of scales and crusts on the skin (why this form of scabies is called crusty scabies), in which a large number of scabies mites (in different stages of development) and scabies burrows, located in several layers, are noted. The crusts are difficult to remove, and under them a red, moist surface is exposed, covered with a mass of moving whitish dots (live mites). This form of scabies was named Norwegian in honor of the Norwegian authors who first described it (Danielssen). Norwegian scabies usually develops as a result of long-lasting ordinary scabies, when patients perhaps get used to the itching and stop scratching their bodies. The mite is identical in both Norwegian and ordinary scabies. Animal scabies as such does not pass to humans, because the scabies mites of animals (in its mange form, depending on the mange mite) do not find suitable conditions for life on human skin, do not burrow tunnels, and do not lay eggs. Experimental attempts to infect human skin with mites of animal scabies, as well as attempts to infect animals with mites of human scabies, remain unsuccessful. Even more so, there is no basis for the assumption of the possibility of human infection with other forms of animal scabies, caused by surface or skin mites. However, in people dealing with scabies animals (horses, cats, etc., including wild animals), itchy skin lesions have been noted, which depended on the transfer of animal scabies mites to human skin, and all manifestations passed without any treatment only if the patient was isolated from the scabies animal. In terms of frequency, scabies occupies one of the first places among skin diseases in various countries of the world. In some places, it is extremely widespread (for example, in China, scabies was noted in 1/3 of the entire population, in Shanghai - 44%, in Iceland - 46%, among children in Queensland, 90% were found to be affected by scabies). During wars, especially prolonged ones, a constant increase in the number of scabies diseases was noted. During the imperialist war of 1914-18, an increase in scabies morbidity was noted in all countries participating in the war, and scabies among other dermatoses came to constitute 15.6-22.3%. Before the October Revolution in former Russia, according to far from complete official data, an increase in scabies morbidity was noted, and in 1895, for every 10,000 inhabitants, 122.7 scabies patients were noted, in 1900 - 237.7, in 1905 - 249.4, in 1910 - 270.7, and in 1913 - 336.8, and in absolute figures for that year, 5,475,594 scabies patients were noted, of which 521,540 (i.e., 10%) were urban and 4,954,054 (90%) were non-urban scabies patients. From 1914, more or less accurate statistical data on the spread of scabies were not available, but according to some data, it must be concluded that during wartime, the increase in scabies morbidity rose (for example, in the Saratov province in 1914, 83,757, and in 1917, 236,359 scabies patients were registered; in the Simbir province in 1914 - 90,834, and in 1915 - 134,543, etc.). The main reason for the mass spread of scabies is the lack of hygienic living conditions, which depends mainly on poverty, unculturedness, and backwardness of the population, as well as on the insufficiency of medical care for scabies patients. All these conditions existed in pre-revolutionary Russia, especially on the outskirts, in areas of national minorities, where medical posts were often located many tens of versts away from populated areas.

It is quite understandable that from year to year in pre-revolutionary Russia, an increase in the number of scabies cases was noted, especially sharp during wartime. After the October Revolution^ and the end of the civil war, with the rapid improvement of cultural-domestic and material living conditions of the population, with the wide development of a network of medical institutions and measures of a sanitary-hygiene nature, the incidence of Scabies began to sharply decrease. In Odessa in 1919, the ratio of Scabies to other skin diseases was 26.6%, while in 1928 it was 3.2%. In Leningrad in 1930, the ratio of Scabies to other skin diseases became only 1.3%. It is interesting to note that in the conditions of the new construction of Magnitogorsk for 1931, only 27.6 cases per 10,000 population were registered, i.e., the prevalence of Scabies was significantly lower than those that existed in pre-revolutionary times in major centers (in Moscow in 1913 there were 92.3 per 10,000 population, in Odessa - 113.6, in Nikolaev - 134.4, etc.). Treatment of Scabies is usually carried out by rubbing in various ointments containing sulfur or other preparations for several days in a row (without changing bedding). For example: Rp. Sulf. pp., 0.1 Rusci Шл 30.0, Sap. virid., Vaselini an 60.0, Cret. alb. 20.0, MDS ointment. Rp. Styracis liquidi 15.0, Sap. virid., Spiriti Vini aa 5.0, Axung. Porci 30.0, MDS ointment. Rp. Bals. peruv., Alkoholi aa 50.0, MDS. Further, various means were proposed, partly so-called 'patented' (mitigal, ristin, catamin, ecrasol, etc.), Flemings's liquid, Moor's liquid, fumigation with sulfur gas, etc. It should be borne in mind the possibility of side effects (for example, irritation of the kidneys) from tar and naphthol preparations when applied to large areas of the body, especially in persons with diseased kidneys and in small children, who showed severe symptoms of poisoning even from sulfur preparations. In addition to the methodical treatment of Scabies, so-called accelerated treatment methods for Scabies were proposed; the oldest, but still applied until recently, is the Hardy-Bazin method (using a bristle brush, green soap is rubbed into the body for 30 minutes, then a warm bath is taken for an hour and the rubbing of soap continues, then with the same brush, Helmerich's ointment is rubbed in for 20-30 minutes: Rp. Flor. Sulf. 20.0, Kali carbon. 10.0, Axung. Porci 120.0, MDS; the patient is wrapped in a sheet and remains lying in a warm room for 2-4 hours or even up to 12 hours; then the ointment is washed off under the shower and to prevent dermatitis, the body is covered with a paste or lotion or a starch bath is given followed by dusting the body with talc). All these methods can be carried out in a special institution equipped with water installations (baths, showers)-scabiosories; these methods are cumbersome, sometimes give dermatitis, sometimes turn out to be ineffective. The method of rapid cure of Scabies, first proposed by Demyanovich in 1922 and subsequently developed by him, provides a cure for Scabies in 1^st _1/2-2 hours. The method is simple to apply in any conditions of the city, new construction, collective farms, villages and even in the conditions of campaign and front-line life of Red Army men; it is safe as it does not give side effects. The method consists of repeated rubbings of the body with solutions of hyposulfite and hydrochloric acid (the entire skin of the body is rubbed with brushes soaked in the solution with a 40% solution of hyposulfite for 15 minutes, then a pause of 10 minutes is made for drying, then over the hyposulfite crystallized on the surface of the body, a 15-minute rubbing with a 5% solution of hydrochloric acid is performed, again a pause of 10 minutes is made for drying and another such cycle of rubbing with hyposulfite and hydrochloric acid is carried out; after the last one dries, clean underwear is put on, and after 3 days a bath is allowed). The method is based on the chemical decomposition of hyposulfite by hydrochloric acid, with the following chemical reaction occurring: Na₂S₂O₃+2HCl = 2NaCl+H₂S₂O₃=2NaCl + H₂SO₃ + S=2NaCl + H₂O+SO₂ +S. The last two products (sulfur dioxide and sulfur) act killingly on the scabies mite especially energetically at the moment of their secretion (in statu nascendi). On the spread and measures of public prevention against scabies, see Contagious diseases. Lit.: Demyanovich M., Scabies, M.-L., 1934; Kiess, Scabies crustosa, Lpz., 1928; PiciW., Tierische Parasiten der Haut Skabies (Hndb. d. Haut. u. Geschlechtskrankheiten, hrsg. v. J. Jadassohn, B. IX, H. 1, p. 170, B., 1929, lit.).