LECTURE No. 2. Parasitic dermatoses

Infectious parasitic diseases of the skin include scabies and lice.

1. Scabies

Scabies is a very common and contagious parasitic skin disease caused by an external parasite, the scabies mite.

Etiology and pathogenesis. The causative agent of the disease is the scabies mite or, as it is also called, itching. The tick is an obligate parasite of humans (humans are the only host of the tick in nature). The pathogen has a size of about 100 microns.

After individuals or larvae enter human skin, females burrow through the epidermis for 0,5-1 hour, forming scabies burrows in which they lay eggs. After 3-4 days, larvae emerge from the laid eggs and accumulate in the area of ​​the stratum corneum. After 2-3 days, they have their first molt with the formation of nymphs from the larvae, which emerge to the surface of the skin, then after 3-4 days ticks appear from the nymphs. The walls of scabies ducts are covered with excreta of parasites, which can cause an allergic reaction, causing clinical manifestations of scabies.

In the external environment, the tick is unstable: at negative temperatures, as well as at a temperature of +55 ° C, it dies within 10 minutes, at a temperature of +80 ° C and above, the tick dies instantly.

Transmission routes. The source of infection is a person with scabies. Scabies is transmitted by contact. Infection can occur directly through contact with a sick person, as well as indirectly, i.e. through contact with infected household items (bed linen, used clothing, soft toys, upholstered furniture). An epidemic focus is created due to the fact that a sick person infects people with scabies who are in household, professional or sexual contact with him. Animals cannot be carriers of the scabies mite, since the mite can only parasitize human skin.

Clinic. Immediately after infection, an incubation period for the pathogen begins, the duration of which varies. When females begin to lay eggs, morphological changes appear on the skin, which are the result of a proliferative inflammatory response. As the number of parasites living in the skin increases, a person begins to feel itching. The average incubation period is from 3 to 14 days.

The main complaint presented by patients with scabies is skin itching, which bothers them mainly in the evening and at night.

The clinical picture of scabies is due to several factors: the vital activity of the mite and the formation of scabies by it, the degree of allergization of the body to the pathogen and the appearance of allergic rashes on the skin. There are several clinical forms of the disease.

Typical form of scabies. The rashes are localized in the most typical places: on the abdomen, especially around the navel, on the anterior inner thigh, on the buttocks, mammary glands, lateral surfaces of the fingers and toes, in men on the skin of the penis and scrotum. Rashes on the face and scalp are very rare; only isolated rashes may appear on the skin of the palms and soles. Scabies burrows look like a slightly raised whitish or grayish straight or curved line, 5-7 mm long.

More often, it is difficult to visually detect the course, and its endings are visible in the form of miliary papules and vesicles, in which a scabies mite can be detected in a laboratory study. These small papulovesicular elements (0,5 - 0,7 mm) are located at one of the ends of the course and are partially covered with dotted bloody crusts due to scratching.

In addition to paired papulovesicles and scabies, pinpoint and linear excoriations (indicating itching) are found on the patient's skin, as well as various pyococcal complications, which often begin in the extensor zone of the elbows. Ardi's symptom - detection of purulent or purulent-bloody crusts on the elbows.

К atypical forms of scabies include: clean scabies, nodular scabies and crusted (Norwegian) scabies. Differences in the clinical picture are due to the patient's altered reactivity (increased or decreased), which leads to a different reaction of the body to tick infestation.

Cleanliness scabies is an erased, abortive form of the disease that develops in people who carefully follow the rules of personal hygiene and have normal immunoreactivity. Clinical manifestations in this case will be minimal and represent separate small follicular papules or vesicles, single small hemorrhagic crusts located mainly on the front surface of the body (around the navel and on the chest). Single rashes are accompanied by severe itching at night.

Nodular scabies (nodular scabious lymphoplasia) occurs as a result of a delayed-type hyperergic reaction that develops on the waste products of the mite. Papules can form with untreated scabies (typical form or erased), mainly in patients who have been ill for a long time or had scabies as a result of misdiagnosis, reinvasion or relapse.

Itchy, lenticular, reddish-brown nodules occur under the burrows and are always located in areas characteristic of typical scabies. Papules are located mainly on closed areas of the skin. The nodules are resistant to a variety of antiscabiosis therapy.

The most rare atypical form of scabies is crusted or Norwegian scabies. This type of scabies occurs in patients who have a sharply weakened immunoreactivity. Crusted scabies is manifested by the formation of crusts on the surface of the skin and is the most contagious form of scabies. Most often, Norwegian scabies develops in patients who suffer from immunodeficiency conditions (AIDS, long-term treatment with cytostatic and glucocorticoid drugs for systemic diseases, alcoholism, exhaustion).

The manifestation can be limited and widespread, up to the development of erythroderma. This form of scabies is characterized by grayish-dirty crusts, which tend to layer on top of each other, having a different area and thickness. The crusts are tightly soldered to the underlying tissues, they are removed with difficulty and painfully. After removing the crusts, yellow erosions are exposed under them.

The extensor surfaces of the limbs (rear of the hands, fingers, elbows, knees), buttocks, scalp, face, ears are affected mainly. When the palms and soles are affected, thick hyperkeratosis develops, which limits movement and simulates flexion contractures. In addition, nail plates can also be affected: they are deformed, thickened, their color changes, they easily crumble and resemble onychomycosis.

Complications. Clinical manifestations of scabies can be masked by its complications, leading to errors in diagnosis. Dermatitis (simple or allergic), pyoderma, less common - microbial eczema and nodular lymphoplasia are more common.

Diagnostics. The diagnosis of scabies can be made taking into account the following criteria:

1) clinical data (evening-night itching, characteristic rashes in typical places, as well as the symptom of Ardi and Gorchakov, the presence of papules on the glans penis, foreskin or skin of the mammary glands);

2) epidemiological information (examination of contact persons and detection of clinical signs of scabies in them, information about the patient's stay in the epidemiological site);

3) laboratory diagnostics (detection of a tick and its eggs in scrapings of rash elements).

Treatment. To treat patients with scabies, it is necessary to use agents that have a detrimental effect on scabies mites and their larvae parasitizing in the stratum corneum. Regardless of the drug chosen and the method of its use, for successful treatment, a patient with scabies must follow the following rules:

1) treat the entire skin with a proto-scab preparation, and not just the areas affected by the scabies mite, the only exception is the scalp;

2) strictly observe the method of treatment recommended by the doctor;

3) wash only immediately before treatment and after its final completion;

4) carry out a change of underwear and bed linen before and after treatment.

In recent years, due to high efficiency and low toxicity, benzyl benzoate (benzyl ester of benzoic acid) has become widespread.

This drug is made in the form of an official emulsion ointment (20% ointment), which is carefully rubbed into the skin. In children, a 10% ointment is used. First, it is necessary to treat the upper limbs (2 minutes each), the trunk (excluding the scalp, face and neck), and then the lower limbs (also 2 minutes each). Particular attention should be paid to the interdigital spaces, free nail edge, large skin folds, perianal and genital areas.

The sequence of protoparasitic treatment of the skin is the same for all methods of treatment. After each treatment of the surface of the body, the patient needs to change underwear and bedding; dirty bed linen and underwear must be subjected to heat treatment after washing. Re-treatment of the skin is carried out on the second (or fourth) day. This method of processing is due to the fact that the larvae of scabies that hatched within 2 days are more accessible to the effects of anti-scabies therapy. 3 days after the end of treatment, the patient should be advised to re-change underwear and bed linen, as well as thorough washing. It is necessary to disinfect outerwear and upholstered furniture.

The use of drugs containing sulfur for scabies is common; sulfur ointment is more often used (20%, for children 6-10%), and the method of M. P. Demyanovich is also used. Sulfur ointment is rubbed daily at night for 5 days onto the entire skin (except for the scalp, face and neck). A day after completion of treatment, the patient washes in the shower with soap and changes his underwear and bed linen, and thermally treats outer clothing (iron).

Modern treatments for scabies such as spregal (aerosol of esdepalletrin in combination with piperonyl butoxide in a balloon, produced in France) and lindane are highly effective and safe. In the evening, without prior washing, the patient sprays the entire skin (except the head and face) with spregal from a distance of 20-30 cm from the surface of the skin, leaving no area of ​​the body untreated. After 12 hours, you need to wash yourself thoroughly with soap; usually, a single use of the drug is sufficient. If the disease lasts for a long time, the skin is treated twice (once a day).

Undesirable effects such as tingling of the skin and irritation of the larynx are rare. Usually one cylinder is enough to treat 2-3 people. Spregal can be used to treat children.

Lindane is an organochlorine insecticide (hexachlorocyclohexane). It is highly effective, colorless and odorless. Rub 1% cream (emulsion) in the evening for 3 days in a row over the entire skin (from the neck to the tips of the toes). Before treatment and every day 12-24 hours after treatment, you should take a warm shower or bath. Lindane treatment is not recommended for pregnant women and children.

Features of the treatment of crusted scabies. After the removal of massive crusts (as a result of the use of keratolytic ointments and general baths), courses of treatment of scabies with conventional anti-scabiosis drugs are carried out until a complete cure. It is important to express the pathogenesis of the immunodeficiency state, i.e., to establish the disease (condition) that led to a sharp weakening of the patient's reactivity, and, if possible, to correct it.

Prevention. For prevention, active early identification of patients with scabies and their timely treatment are important. It is necessary to identify foci of scabies and organize work to eliminate them (examination and treatment of family members, people living in the same room with the patient, members of organized groups). It is very important to carry out simultaneous treatment of all patients identified in one outbreak (to prevent reinvasion).

2. Nice

Lice is a parasitic lesion of the skin by obligate human parasites - lice.

Etiology. Three types of lice can infest human skin: head, body and pubic lice.

head lice - mobile parasites of dark gray color, size from 2-3 mm (male) to 3,5 mm (female). After the female settles on the scalp, she lays whitish eggs (nits) 0,7 - 0,8 mm long, tightly gluing them to the surface of the hair. Nits are most noticeable on dark hair.

body lice - mobile insects of whitish-gray color, ranging in size from 3-4 mm (male) to 3-5 mm (female) - lay eggs (nits) in the folds of the skin, gluing them to the fibers of the fabric.

Pubic lice, or flatheads, - sedentary small (1-2 mm) insects, yellowish-brown in color, reminiscent of a crab in shape. The intensity of the color depends on the content of the host’s blood in the lice’s intestines (after the insect bites, the insect becomes darker). Nits stick to the hair on the pubic area, thighs, and abdomen. In advanced cases, nits can be found on the hair in the armpits, chest, eyebrows, and eyelashes. In persons with pronounced hair growth, insects and nits can be located in any area of ​​hair growth (except for the scalp).

Infection with all types of lice is carried out through direct bodily contact with a sick person (household and sexual contact), as well as through indirect contact (through household items, bedding, underwear, clothes, sports equipment).

Clinic.

Head lice. Head lice settle on the scalp mainly in the occipital and temporal regions. Head lice are blood-sucking insects, so inflammatory spherical papules form at the site of their bites. Bites cause unbearable itching, as a result of which the patient excoriates papules, which are complicated by a pyogenic infection in the form of impetigo vulgaris. Purulent crusts glue the hair into a single continuous glomerate, and cervical and occipital lymph nodes can also increase. Upon careful examination of the patient, whitish nits can be found on the hair, mobile head lice are not always visible. Detection of nits and especially lice confirms the diagnosis.

Clothes lice. By contact with a sick person, body lice get on the clothes and skin of people around them. Body lice settle in the folds of clothing and bite the skin adjacent to them. The reaction of the skin to bites can be in the form of inflammatory spots and edematous serous papules. The localization of the bites coincides with the areas where the clothing is as close as possible to the surface of the skin (these are the lower back, interscapular and axillary zones, the skin of the neck, legs). Bites cause intense itching, which can result in scratching and pyogenic complications in the form of streptostaphylococcal pyodermatitis. With prolonged existence of lice and chronic scratching, the skin becomes pigmented and lichenified. Body lice is a great epidemiological danger, since these insects are carriers of the causative agent of typhus.

Pubic lice. Infection occurs mainly through sexual contact. Pubic lice (ploshchitsy) settle in areas of body hair (mainly in the pubic region and perineum, less often in the armpits, on the chest). In advanced cases, lice are found on the eyebrows and eyelashes, where they stick their nits. Ploshchitsy are inactive, attached to the skin and hair bases; sometimes in these places an inflammatory reaction develops in the form of small (up to 1 cm) cyanotic spots with a hemorrhagic tint (the so-called lousy spots) that do not disappear during diascopy. If the eyelashes are damaged, swelling occurs and the eyelids become inflamed.

Diagnostics. It is the same for all types of lice and is based on the detection of parasites, nits and traces of their bites. However, with the development of extensive purulent complications on the scalp and skin of the body, the clinical picture of lice can be masked. In such cases, you should pay attention to the patient’s complaints (itching of the skin in the appropriate locations), as well as information about itching from family members and other contact persons.

Anti-epidemic measures should include:

1) antiparasitic treatment in a sick person of hair and skin in the affected areas;

2) medical examination and mandatory antiparasitic treatment of contact persons (sexual and household contacts);

3) sanitization of clothes, hats, bedding, upholstery of upholstered furniture, towels, washcloths, soft toys for children (washing at temperatures above 80 ° C, ironing with steam, treatment with chemical acaricidal agents).

Treatment. Therapeutic measures are aimed primarily at the destruction of adult insects and nits (the biological characteristics of their habitat on human skin are taken into account).

Most antiparasitic agents are derivatives of permethrin. Permethrin (nittifor) is available in the form of a 0,5% aqueous-alcoholic solution. When applied externally, nits, larvae and mature individuals of head and pubic lice are destroyed. Para-plus - an aerosol for external use - contains permethrin, malathion, piperonyl butoxide. It is used for the treatment of pubic and head lice, destroys adult insects and nits, the required exposure time is 10 minutes. After 7 days, it is recommended to repeat the antiparasitic treatment in order to destroy the lice larvae that may hatch from the remaining viable nits.

When dealing with body lice, one should take into account the fact that lice parasitize in clothes where nits are also located. Therefore, the main activities should be aimed at thermal processing of clothing, bedding (including boiling, washing in hot water, ironing, autoclaving).

Author: Sitkalieva E.V.

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