Sexually Transmitted Diseases - I. I. Mavrov 2005

Pubic lice

A parasitic Skin disease caused by pubic lice was first described in 1668 by F. Redi.

Etiology. The CAUSATIVE AGENT OF the disease is the pubic louse (Phthirus pubis). Unlike HEAD and body lice, the pubic louse clings to the Hair using only three legs on one side of its body, moving along the hair in the same manner. It faces the hair sideways, whereas the common louse faces it with its abdomen; this difference in orientation is also characteristic of embryos within nits.

The abdomen of the parasite consists of nine segments with barely visible divisions between them, bearing four lateral tubercles studded with setae. The female is larger (body length 1.5 mm), featuring a concavity at the end of the abdomen and a slightly greater number of setae. The male is smaller (up to 1 mm), with a rounded end of the abdomen and 5–6 setae on it. The coloration of the pubic louse is gray, though it may be darker. The female lays up to 10 eggs, as the oviducts contain only one embryo at a time. Egg development takes 6–8 days. Larvae molt three times over 15–17 days, become fertile after the third molt, and lay their first egg 2–3 days later.

Pubic lice prefer the genital region (pubis, Scrotum, Perineum), hair around the anus, and the axillary regions, because these areas contain a high concentration of apocrine glands, toward which the SENSE OF SMELL of pubic lice is specifically oriented. The mustache, eyebrows, eyelashes, and scalp hair in children are rarely affected.

Epidemiology. Currently, Western Europe and the United States are experiencing a sharp increase in the incidence of pediculosis. A growing trend in the number of pediculosis cases is also noted in Ukraine.

Pubic pediculosis is increasingly encountered in patients at venereal clinics, particularly among individuals practicing promiscuous Sexual Behavior. Nearly a third of patients with pediculosis also present with other Sexually Transmitted Infections (Gonorrhea, chlamydia, mycoplasmosis, Trichomoniasis). The presence of pubic lice is frequently noted alongside condyloma acuminatum in the genital area. Pubic pediculosis occurs predominantly in women aged 15–19 years; after the age of 20, its frequency equalizes between men and women (M. Orkin, H. Maibach, 1982).

Routes of transmission. Infection almost always occurs sexually, and possibly during bed-sharing, in crowded conditions (barracks, dormitories), or from unwashed bed linen in hotels, trains, and the like. If children Sleep with adults who have pubic pediculosis, they can become infected, often presenting with an unusual localization of lice (eyelashes, scalp hair).

Clinical manifestations. The pubic louse, which resembles a tiny grayish-white speck, is located at the Base of the hair, holding onto it firmly. It is completely immobile and, if few lice are present, unnoticeable. When an attempt is made to pull off a louse, it shows Signs of Life and grips the hair even more tightly, making it very difficult to detach. To remove a louse, it is necessary to pull it with tweezers along the entire length of the hair. It is easier to pluck the respective hair, along with which the louse is generally removed.

Attaching to the hair using claws located on its legs, the louse inserts its mouthparts into the skin and sucks Blood from capillaries at brief intervals. The itching caused by pubic lice is mild and is driven more by immunological than mechanical factors (W. McCormack, 1982). The incubation period from the moment of infection to the onset of itching is about 30 days.

The intensity of the itching caused by pubic lice varies and depends on the patient's individual sensitivity. As a result of scratching, excoriations appear with their usual consequences (excoriation, secondary infection, eczematization, skin irritation).

The condition is primarily confined to the pubic area, though the thighs and trunk may be involved, especially in individuals with excessive hair growth, as well as the mustache and beard. Involvement of the eyelashes and scalp is more commonly observed in children infected by their mothers. Infestation of the eyebrows and eyelashes also occurs in adults; in such cases, chronic blepharitis may develop.

Following pubic louse bites, bluish or shadow-like spots up to 1 cm in diameter appear and quickly fade. They are particularly distinct on the abdomen, chest, lateral trunk, and thighs. Such spots arise either as a result of minute hemorrhages during blood feeding by the lice or due to the deposition of their salivary gland secretion.

Upon detecting any pruritic rashes on hairy areas, pediculosis should be ruled out. The axillary vaults and other body regions must be examined, as the patient may have attempted self-Treatment and eliminated parasites from the pubic area while leaving other body sites untreated. Diagnosing pubic pediculosis is particularly challenging when eyelashes are affected, as the infestation can mimic seborrheic, infectious, or eczematous blepharitis, and the parasite can only be found through a careful examination using a magnifying Glass.

Diagnosis. Pubic pediculosis is diagnosed through visual inspection. Adult lice can be seen with the naked eye using a magnifying glass or lens. Parasites are easier to spot after they have fed on blood and acquired a "rusty" hue. Occasionally, rusty-colored particles—louse excrement—are observed in the affected areas.

However, nits attached by a cementing substance to the pubic hair near the base, close to the skin surface, are more commonly detected. As the hair grows, the nits move away from the skin surface, making it possible to roughly estimate the duration of the infestation by their height. Nits are sometimes mistaken for twisted hair, hair casts, or scales in seborrheic dermatitis. Therefore, to confirm the diagnosis, such hair must be examined under a Microscope.

Pubic pediculosis is differentiated from impetigo, Pyoderma, microbial eczema, neurodermatitis, seborrheic dermatitis, psoriasis, and contact dermatitis.

Treatment and Prevention. Therapeutic agents are applied to the affected hair and surrounding areas. Special attention is paid to the pubic and perianal regions. If hair is present, the skin of the thighs, trunk, and axillae is treated, as these areas may also be infected. Sexual partners are treated simultaneously to prevent reinfection. Other healthy family members do not require treatment. Clothing and personal linen must be disinfected.

Treatments utilized include 3–10% sulfur ointment, 5–10% white mercurial ointment, and solutions of mercuric chloride in 3% acetic acid (1:300). Ointments and solutions of mercuric dichloride soil linen and irritate the skin (mercurial dermatitis). Therefore, xylene is best applied, as it is effective even with a single use. It is prescribed as a solution (xylene — 50 mL, ethanol, and ether — 25 mL each) or a cream (xylene — 3 mL, petroleum jelly — 100 g). The cream or solution is applied in a thin layer to the affected hair and adjacent areas, left for 2 days, and then thoroughly washed off. One application is usually sufficient. If necessary, the Procedure is repeated a week later.

In cases of pubic lice parasitizing the eyebrows and eyelashes, epilation of the affected hair and application of yellow mercuric oxide ointment on a petrolatum base (0.1 g of mercury compound per 10 g of white petrolatum) to the affected areas are effective.

Sometimes, 33% sulfur ointment, hellebore tincture, or a 15–20% aqueous-soap emulsion of benzyl benzoate are preferred in the treatment of pubic pediculosis.

Early Diagnosis and treatment of patients and their sexual partners constitute the primary method for preventing pubic pediculosis. All patients with pediculosis must be screened for Syphilis, gonorrhea, chlamydia, and other sexually transmitted infections.