Pediculosis (lice)

Pediculosis is a parasitic anthroponosis with a contact mechanism of pathogen transmission, the main symptom of which is skin itching. A synonym for the disease is lice infestation.

ICD-10 codes

• B85. Pediculosis and phthiriasis.
• B85.0. Pediculosis caused by Pediculus humanus capitis.
• B85.1. Pediculosis caused by Pediculus humanus corporis.
• B85.2. Pediculosis, unspecified.
• B85.3. Phthiriasis.
• B85.4. Pediculosis combined with phthiriasis.

Epidemiology of pediculosis (lice)

The source of the parasite is infected people. The transmission route is contact. The migration of lice increases with a decrease (if the source of the pathogen is a corpse) or an increase in body temperature (the source of the pathogen is a feverish person). Infection occurs during contacts in transport, groups (children's institutions), families living in unsanitary conditions, using common things (bed and underwear). Infection with phthiriasis almost always occurs during sexual contact: this is one of the most common diseases transmitted in this way.

Susceptibility is high: higher in whites than in blacks. Pediculosis is widespread, while body lice are common in countries with low levels of sanitary culture.

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What causes pediculosis (lice)?

The causative agents of pediculosis belong to the genus Anoplura, family Pediculidae. Lice are obligate blood-sucking ectoparasites. The head louse, Pediculus (humanis) capitis, lives on the scalp; the body louse, Pediculus (humanus) corporis (vestimenti), lives on underwear and clothing; the pubic louse, Phthirus pubis, lives on the hair of the pubis, armpits, beard, moustache, body, and eyebrows. Lice live and reproduce at an ambient temperature of 28-30 °C; below 15 °C, egg laying stops. Head and pubic lice lay eggs (nits) on the hair at a distance of 1-3 mm from the skin surface; the body louse attaches eggs to the fabric fibers near the seams. After 5-12 days, a blood-sucking larva (nymph) emerges from the eggs, which after three molts turns into a sexually mature individual. The life cycle of the pathogen is 16 days. The life span of an adult is 30-40 days (maximum 60 days).

Head lice (Pediculi capitis) are mobile, dark-gray parasites, ranging in size from 2-3 mm (male) to 3.5 mm (female). When settling on the scalp, females lay whitish eggs (nits) 0.7-0.8 mm in size, firmly gluing them to the surface of the hair. Nits are most visible on dark hair.

Body lice (Pediculi vestimenti) are mobile, whitish-gray insects ranging in size from 3-4 mm (male) to 3-5 mm (female); they lay eggs (nits) in the folds of clothing, gluing them to the fabric fibers.

Pubic lice (Pediculi pubis), or crabs, are slow-moving small (1-2 mm) insects, yellowish-brown in color, resembling a crab in shape. The intensity of the color depends on the content of the host's blood in the louse's intestines (after a bite, the insect becomes darker). Nits stick to the hair on the pubis, thighs, and abdomen. In advanced cases - in the armpits, chest, eyebrows, and eyelashes. In people with pronounced hair, insects and nits can be found in any hairy area (except for the scalp).

Infection with all types of lice occurs through direct physical contact with a sick person (household and sexual contact), as well as through indirect contact (through household items, bedding, linen, clothing, sports equipment, etc.).

Lice belong to the order of false-proboscideans, they feed on the blood of the host. The most optimal temperature for the development and fertilization of insects is 25-37 °C (air and body). The full development cycle is 16 days, the lifespan of insects varies within 20-40 days. A body louse lays from 6 to 14 eggs-nits per day, a head louse no more than 4. The nit is covered with a chitinous shell, which has pronounced protective properties.

Pathogenesis of pediculosis (lice)

The head louse, body louse, pubic louse, or crab louse pose an epidemic danger to humans.

With a piercing proboscis, insects plunge into the thickness of the skin and suck blood. At the same time, a secretion with a pronounced irritating property gets into the thickness of the skin. At the site of the bite, foci of a dense inflammatory infiltrate of polynucleotides, lymphocytes and, to a lesser extent, eosinophils appear in the dermis. The course of the inflammatory process is characterized by the expansion of blood vessels and the development of skin edema.

As a result of intense itching, pinpoint and local scratching appears, which is subsequently often complicated by pyoderma and eczematization.

Risk factors for head lice include crowding and failure to comply with sanitary and hygienic rules.

When biting, the louse injects substances into the wound that cause itching. Scratching the bite sites leads to eczematization of the skin and the addition of a secondary infection. Itching disrupts sleep and causes neurotic conditions, especially in children.

Symptoms of pediculosis (lice infestation)

The incubation period for pediculosis (lice) when infected by a mature individual is 6-12 days.

There are pediculosis of the trunk, head and pubic pediculosis (phthiriasis).

The symptoms of pediculosis (lice infestation) depend on the intensity of the infestation. With a small number of parasites and low skin sensitivity, the infected may not complain for a long time. The main subjective symptom of pediculosis is itching in the head, body or pubic area, depending on the type of parasite. In case of head pediculosis, during the examination, impetiginous lesions covered with a yellow ("honey") crust, folliculitis, areas of skin eczematization, especially in the area of the back of the head, temples, and behind-the-ear folds are detected. Lymphadenitis is often detected. In advanced cases, the formation of a mat is observed - tangled and glued together hair with purulent exudate. In case of body lice, the affected areas of the skin are those that are in close contact with clothing (these include the shoulders, upper back, axillary cavities, neck, and less commonly the abdomen, lower back, and femoral-inguinal region). Urticarial-papular rashes with subsequent cyanosis, hyperpigmentation of the skin, and often secondary pyoderma (ecthyma) occur at the sites of body lice bites. In case of chronic pediculosis, the skin thickens, becomes brown (melasma), and flakes. Whitish scars are visible after pustular lesions that complicate scratching. These skin changes are called "vagabond disease." In case of phthiriasis, itching is insignificant. At the site of the pubic louse bite, persistent grayish-bluish round or oval spots up to 1 cm in diameter (blue spots, maculae coeruleae) appear.

The head louse (Pediculosis capitis) parasitizes on the scalp and is grayish in color. The size of males is 2 mm, females - 3 mm. The clinical picture and diagnostics of pediculosis of the scalp do not present any particular difficulties. Itching, scratching, impetiginous crusts in the occipital region behind the ears give grounds to suspect pediculosis of the scalp.

Head lice settle on the scalp, mainly in the occipital and temporal zones. Being blood-sucking insects, they cause typical manifestations of bites - inflammatory papules of a hemispherical shape. Bites cause severe itching, the patient excoriates the papules, which are often complicated by a pyogenic infection in the form of vulgar impetigo. Purulent crusts glue the hair into one solid conglomerate, the occipital and cervical lymph nodes may enlarge. Therefore, if persistent itching of the scalp occurs and pyoderma is detected in the patient in the temporo-occipital zone, pediculosis should be excluded. Upon careful examination, small whitish nits can be found on the hair, mobile head lice are not always detected. The detection of nits and especially lice confirms the diagnosis.

Upon careful examination of the skin and hair, one can detect insects and nits of a grayish-white color, glued to the hair with a chitinous substance.

Pediculosis corporis is caused by the body louse, which lives in the folds of clothing. The favorite places for skin lesions are the shoulders, upper back, abdomen, lower back, and groin-femoral region. Symptoms of pediculosis (lice infestation) are characterized by intense itching, multiple linear scratches. The development of the process is accompanied by the formation of distinct brownish pigmentation and fine bran-like peeling.

By contact with a sick person, body lice get onto the clothes and skin of people around them. Settling in the folds of clothing, lice bite the skin of the host adjacent to the clothing. The skin's reaction to the bites can be in the form of inflammatory spots and edematous gray papules. The localization of the bites coincides with the zones where the underwear comes into maximum contact with the skin (lower back, interscapular and axillary zones, skin of the neck, shins). The bites cause intense itching, which can result in scratching and pyogenic complications in the form of streptococcal pyoderma. With prolonged existence of lice and chronic scratching, the skin becomes pigmented and lichenified. Body lice infestation poses a great epidemiological danger, since these insects are carriers of the causative agent of typhus.

Pubic lice (Pediculosis pubis) are caused by crabs that live on the skin of the pubis and the adjacent area of the thighs and abdomen. Sometimes the insects spread to the skin of the chest, armpits, eyebrows and eyelashes. At the site of the insect bites, round pale blue or pale gray spots form that do not disappear when pressed. Pubic lice are usually transmitted sexually, and often accompany venereal diseases.

Infection most often occurs during sexual contact. Pubic lice (crabs) settle in areas of body hair, mainly in the pubic area and perineum, less often in the armpits and on the chest. In advanced cases, lice are found on the eyebrows and eyelashes, where they stick their nits. In people with pronounced skin hair, pubic lice can be on the entire skin.

Crabs are not very mobile, they are attached to the skin and hair roots, sometimes an inflammatory reaction develops in these places in the form of small (up to 1 cm) bluish spots with a hemorrhagic tint (so-called louse spots, or maculae coeruleae), which do not disappear during diascopy. In case of damage to the eyelashes, swelling and inflammation of the eyelids (parasitic blepharitis) occurs.

Diagnosis of pediculosis (lice infestation)

Clinical diagnostics of pediculosis (lice infestation) is based on collecting anamnesis (patient complaints of itching) and a thorough examination of the patient. Head lice are found when combing hair (preferably over a sheet of white paper), nits are found at the roots, their shells - along the hair. Pathogens are easy to detect in the folds of underwear or clothing that comes into contact with the skin. Crabs are visible as grayish-brown dots at the roots of the hair, where small whitish dense nits are also located.

People with phthiriasis should be examined to detect sexually transmitted diseases (found in 30% of patients).

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Differential diagnostics of pediculosis (lice infestation)

Pediculosis (pediculosis) must be differentiated from scabies and vulgar impetigo. Scabies is characterized by itching of the skin in the evening and at night, and there are scabies passages with multiple papules and vesicles. Vulgar impetigo of the scalp is characterized by follicularly located pustules surrounded by a narrow hyperemic crown; the rashes are mostly multiple, not accompanied by itching of the skin.

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Treatment of pediculosis (lice)

Treatment of lice (pediculosis) includes measures aimed at destroying adult insects and nits (the biological characteristics of their habitat on human skin are taken into account).

Most antiparasitic agents are derivatives of permethrin. Nittifor (permethrin) is available as a 0.5% aqueous-alcoholic solution. When applied externally, it destroys nits, larvae and adult head and pubic lice.

To mechanically remove dead insects and nits, the hair on the head is carefully combed with a fine-toothed comb. When treating pubic lice, to destroy nits, the hair in the pubic area, thighs, abdomen, and armpits is shaved.

In case of pronounced hairiness, it is necessary to shave the hair on the body and limbs completely. In case of eyebrow and eyelash lesions, nittifor is gently rubbed into the skin and 40 minutes after washing off the preparation, lice and nits are carefully removed from the eyebrows and eyelashes with flat tweezers.

PARA PLUS - aerosol for external use, contains permethrin, malathion, piperonyl butoxide. It is used to treat head and pubic lice (destroys adult insects and nits). The preparation is applied similarly to nittifor, but the exposure time is shorter - 10 minutes. After washing off the preparation, the same measures are taken as when treating with nittifor. After 7 days, it is recommended to repeat the antiparasitic treatment to kill the lice larvae that can hatch from the remaining viable nits.

When fighting against lice infestation, it is necessary to take into account the fact that lice parasitize in clothes, where nits are also found. Therefore, the main measures should be aimed at heat treatment of clothes, bedding (boiling, washing in hot water, ironing, autoclaving, etc.).

Treatment of pediculosis (lice infestation) is outpatient. For head lice, malathion (1% shampoo or 0.5% lotion) and permethrin are used, for pubic lice - permethrin (medifox - 5% concentrate for the preparation of emulsion and medifox - 20% emulsion).

Head lice. The head is treated with a 20% water-soap emulsion of benzyl benzoate for 15 minutes, then washed with hot water and soap.

Body lice. Wash the patient with soap, disinfect clothing and bedding.

Pubic lice. Hair is shaved, skin is lubricated with 20% benzyl benzoate emulsion. After 4-5 hours - bath with linen change. A good remedy for single skin treatment is loncid solution.

Working capacity is not impaired.

Clinical examination

They don't.

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How to prevent pediculosis (lice)?

Pediculosis (lice infestation) can be prevented by following general rules of personal hygiene, changing underwear and bed linen at least once a week, systematically washing and combing hair, and maintaining hygiene of the genitals. In case of pediculosis of the body, measures are taken to combat lice: linen and clothing are boiled or subjected to chamber disinfection.

Anti-epidemic measures should include:

• antiparasitic treatment of the sick person's hair and skin in the affected areas;
• medical examination and mandatory antiparasitic treatment of contacts (sexual and domestic contacts);
• sanitary treatment of clothing, headwear, bedding, upholstery of upholstered furniture, towels, washcloths, soft children's toys (washing at a temperature above 80 C, ironing with steam, treatment with chemical acaricidal agents).