LOUSES

From Big Medical Encyclopedia

LOUSES — blood-sicking insects of Anoplura group; parasites of mammals and person. More than 150 types of V. Vydelyayut 3 families are known: Haematopinidae (blind louses) — parasites of land mammals (except primacies); Echinophthiridae (prickly louses) — parasites of marine mammals; Pediculidae (pedikulida) — parasites of monkeys and the person. Century — strictly specialized parasites, to-rye live on certain animal species. So, Haematopinus macrocephalus lives on horses, H. eurysternus — on cattle, H. suis — on pigs, Linognathus piliferus — on dogs.

Louses (length of a body of 1-5 mm): 1 — head; 2 — clothes; 3 — pubic. On the right — nits.

On the person parasitize head V. — Pediculus humanus capitis, clothes V. — R. of humanus vestimenti and pubic V., or a crab-louse — Phthirus pubis (fig). The structure of a body of V. is adapted for a parasitic way of life: it is flattened in the dorsoventral direction and covered with a chitinous cuticle. Length of a body is 1 — 5 mm. Males more small than females. On the head two simple peepholes. Many types are blind. The oral device of the kolyushche-sucking type (at suction of blood the front department of a gullet extends, working as the pump). The chest department is not dismembered and bears three pairs of strong tenacious legs. The pad of a leg uniarticulate, comes to an end with a claw. A claw, connecting to a ledge of a shin, forms «claw», with the help V.'s cut strong keeps on hair. The abdomen is large, consists of 10 joints, at a female on the end is doubled; at a male the rear edge of an abdomen equal. All life cycle of V. occurs on the owner.

Out of the owner V. happen and live not for long. V. often, eat small portions (cannot long starve). If V. eats one - twice a day, then at once she can drink 0,7 — 1,1 ml of blood. Males drink slightly less, than females.

Treat insects with hemimetaboly century. The cycle of their development develops of egg, the larva passing three age, and an imago (a puberal individual). Complete life cycle of V. of the sort Pediculus develops of the periods: a) germinal — from 4 days to 6 weeks; b) larvae of three stages of development — from 3 to 5 weeks for each stage; c) puberal form; a maximum of life for clothes V.'s female — 46 days, for a male — 32 days, for head V.'s female — up to 38 days, for a male — up to 27 days. Eggs (nits — fig.) an elongated and oval form, white-yellow color, are pasted by a female by means of a secret of glue glands to hair or fibers of fabric.

During life the female postpones until 300 eggs (from 5 to 14 pieces a day). Temperature, optimum for an otkladka, 28 — 30 °. Terms of hatching of eggs and further development also depend on temperature. Larvae differ from adult V. in the smaller sizes and lack of the outside sexual device. Already in half an hour after hatching they begin to suck blood. After the third molt the larva turns in adult Century. A complete life cycle of V. (from the moment of an otkladka of egg prior to the beginning of a laying of eggs the female who developed from this egg) lasts not less than 15 days.

V.'s stings cause the severe itch conducting to raschesa and irritation of skin. The sting of a crab-louse is followed by emergence on skin of livors.

Century of the sort Pediculus, hl. obr. clothes, infect the person with an epidemic sapropyra (see. Sapropyra epidemic ) and the Volynsk (five-day) fever (see. Trench fever ), and also a vshiny typhinia (see. Typhinia , epidemic).

Catch rickettsiae of a sapropyra (Rickettsia prowazeki) B. at a krovososaniye on the patient. Rickettsiae breed in an epithelium of a stomach of V., the epithelium at the same time collapses, and the activator, being released, gets to a gleam of intestines of V. and together with excrement is removed outside. In excrement B. of a rickettsia appear on 5 — the 9th day after infecting krovososaniya. Perish at intensive reproduction of rickettsiae in their body century. Life expectancy of the infected V. (3 — 31 day) depends on temperature and the infecting dose. Transovarial transfer of rickettsiae for V. it is not established. V.'s sting is not infectious since do not get into sialadens of a rickettsia. The person catches when excrements of the infected V. get on his injured skin (raschesa), and also on mucous membranes.

Infection with a sapropyra can occur at crush by the infected V., at inhalation of dust, the infected material since rickettsiae in excrements of the infected V. well transfer drying contains edges.

Activators of a typhinia — a spirochete (Spirochaeta recurrentis) get with blood into V.'s stomach, then quickly from there disappear, but to 6 — to the 7th day appear in a perigastrium of an insect in a large number and collect in band liquid. Are infectious since 6th day after a krovososaniye on the patient century.

The person catches at crush of insects and rubbing in of band liquid B. with spirochetes in wounds, raschesa, mucous membranes.

Clothes V. is also a carrier of rickettsiae of the Volynsk fever (R. quintana). Rickettsiae of the Volynsk fever breed vnekletochno in V.'s intestines and are allocated with its excrements. Infection of the person occurs at rubbing in in grazes, raschesa of the infected V.'s excrements or at crush of insects.

Distribution of pediculosis is observed at adverse a dignity. - a gigabyte. conditions, low material level, especially during the periods of wars and other disasters. Stings of louses cause the skin rashes which are followed by an itch and raschesa.

Distinguish pediculosis of a pilar part of the head, skin of a trunk and skin of a pubis.

Pediculosis of a pilar part of the head (pediculosis capitis) head louses cause. Are surprised preferential occipital and temporal areas, especially in the presence of long hair (is more often at women and children). Head louses paste the testicles (nits) to a core of a hair by means of a special chitinous skeleton near an exit of a hair. On places of stings of louses owing to having combed vulgar impetigo, impetiginous eczema develop; at the same time increase in cervical, occipital and zaushny lymph nodes is quite often observed.

In the started cases the plentiful serous and purulent discharge sticks together hair; at the same time the so-called plica poconica (plica polonica, trichoma) — pasting of hair like felt can be formed. The diagnosis is defined by finding of louses and nits.

Apply one of the next ways to treatment of uncomplicated pediculosis of the head: 1) rub in head skin (better after a hairstyle) kerosene (pure or in half with sunflower-seed or any other vegetable oil), cover the head with compresseal paper and tie a scarf; after 1 — 2 such procedures wash the head with warm water with soap; 2) three days in a row plentifully moisten hair with sabadillovy vinegar then wash the head; 3) rub in skin and hair of 50% soap solventovuyu paste or an emulsion, then tie the head a kerchief for 15 — 20 min. then wash the head. After use of all means frequent washing of the head, is necessary for final removal of nits — frequent moistening of hair the warm vinegar dissolving chitin, and combing of hair a fine-tooth comb. At a complication of impetigo after removal of louses and nits appoint 2 — 5% white mercury ointment.

Pediculosis of skin of a trunk (pediculosis corporis) clothes louses cause, to-rye live and lay eggs mainly pleated of linen from where they pass to skin only for suction of blood therefore preferential lumbar area and a neck where the clothes adjoin to a body most densely are surprised. At pediculosis of a trunk raschesa and quite often a pyoderma are observed (see); on these sites usually there is a hyperpegmentation.

At the pediculosis existing for years change of skin develops, a cut English and fr. doctors suggested to call «a disease of tramps»; skin becomes thick, rough, hyper pigmented, especially in a waist and shovels, shoulders, an inner surface of hips.

Frequent soap bathtubs are necessary for treatment; linen before washing is exposed to disinsection; at a complication a pyoderma apply the corresponding therapy.

Pediculosis of skin of a pubis (pediculosis pubis; synonym ftiriaz) pubic louses (crab-louses) who parasitize preferential on skin of a pubis and the bottom of a stomach, hips from where they can pass also to other parts of a body covered with hair cause (a breast, extremities, axillary hollows, moustaches, a beard, eyelashes, eyebrows, and in children and on a pilar part of the head). Crab-louses are strong attached by a proboscis to the mouth of hair follicles, and front spoons — to hair. On places of their stings remain peculiar round, a spot up to 1 cm from pale blue till pale gray color — so-called blue spots (maculae caeruleae) reminding the going-out syphilitic or typhus roseola. These spots are caused by impact of saliva of a parasite on hemoglobin of blood of the owner. Raschesa, pustules and crusts happen very seldom. Infection, as a rule, occurs at the sexual intercourse, but sometimes and through bed linen.

Treatment

is Shaved off by hair and wash skin hot water with soap that eliminates the majority of crab-louses; for final destruction of crab-louses and nits rub sublimate vinegar (1: 300); sometimes 5 — 10% use white mercury ointment (to watch a condition of a mucous membrane of an oral cavity!). Rubbing in of gray mercury ointment can cause heavy dermatitis and therefore it is not recommended.

Prevention

In fight against V. and its distribution is of great importance personal hygiene: regular washing of a body and head, frequent change of linen, at least once in 7 days, if necessary — disinsection of linen, clothes and bedding (see. Cleansing ). For public prevention it is necessary to perform inspections for identification nitty in places of public accommodation or the greatest accumulation of people. At sanitary cleaning of people or nitty linen the medical staff should put on special long clothes from the rubberized matter or a dense canvas.


Bibliography: Blagoveshchensk D. I. Methods of a research of louses (Siphuneulata), L., 19 72; The Multivolume guide to a dermatovenereology, under the editorship of S. T. Pavlov, t. 2, page 426, L., 1961; Pavlov-with to and y E. H. Guide to parasitology of the person, t. 2, page 62 5, M. — L., 1948; Sh t of e y A. K N. Dermatitis from zooparasites, in book: Bases wedge., Eksperim, and sots. veins. and dermas., under the editorship of. A. P. Iordana, t. 1, page 462, 476, etc., M. — L., 1931, bibliogr.; Degos R. Dermatologie, t. 2, p. 9 56, P., 19 53; S a 1 a m o n T. u. L a z o-v i with - T e p a v a with O. Herdformige Alopezie dure h Kopflause, Derm. Mschr., Bd 156, S. 676, 1970.

L. H. Mashkilleyson, H. M. Grokhovskaya.

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