Skin lesions caused by arthropods

Crustaceans (sea shallow-water crustaceans Cymothoidea) cause painful bites by attaching to a person's hands or feet. At the sites of their attachment, pinpoint bleeding appears, and later the clinical picture of dermatitis develops, which regresses within a week.

When scorpions bite a person, they cause acute pain, swelling and hyperemia of the skin, up to hemorrhage and necrosis. Their venom causes an acute toxic reaction, which (especially in children) can lead to collapse and even death.

Spiders. After a black widow bite, acute pain and burning, erythema, swelling, and then papulovesicular elements and skin thickening quickly appear. After 10-30 minutes, a general toxic reaction, convulsions, disseminated maculopapular and vesiculopustular rash develop. A fatal outcome is observed in 3-5% of cases.

Tarantula bites are not dangerous; only a local reaction (erythema, swelling) is observed at the site of their attack.

The bellied mite causes grain scabies. It lives in straw, on cereals, in old stacks, mattresses. After the mite attacks a person, itchy, reddish, small papules or papulovesicles appear, prone to pustulization. Autosanitation usually occurs within 2 weeks. Epidemic outbreaks are possible.

The larvae of the red mite (live on beans, ivy, red currant bushes, gooseberries, cereals) get on a person while in a field, in a vegetable garden, in a forest and penetrate into the mouths of hair follicles. After a few hours, a small edematous erythema appears at the site of suction, then a papule or vesicle, sometimes small-point petechiae, lymphadenitis is possible. Usually exposed areas of the body are affected. After the ticks fall off (are extracted), the elements of the rash regress within a short time. The parasite is easily detected with a magnifying glass: it looks like a red grain, tightly sitting in the mouth of the hair follicle.

Argas ticks (up to 2 cm long) parasitize wild and domestic animals, birds. After a tick bite (usually Ornithodorus), pain and radiating erythema and edema appear on the second day. A pinpoint hemorrhage or papule (vesiculopustule) is often visible in the center of the element. Over the next 2-3 days, the inflammation increases, the general condition is disturbed, and a widespread urticarial and bullous rash appears. Regression of the rash is slow (4-5 weeks).

Gamasid mites parasitize on birds and rodents. At the bite sites (trunk and limbs) there is acute pain, burning, itching and a hemorrhagic spot, around which erythematous spots, papulovesicles and urticaria appear. In the presence of increased sensitivity, the rash becomes widespread, accompanied by itching, pyoderma elements. Usually the rash regresses within 3-4 days (in the absence of complications).

Ixodid ticks (usually "dog tick", longhorn beetle) are blood-sucking parasites of humans and animals. After a few hours, a painless erythematous spot appears at the site of the bite, which gradually increases in size, then takes the form of an eccentrically growing erythema (up to 15-20 cm in diameter) of a bright red color, edematous, itchy. Recovery occurs in 2-3 weeks. With the help of a biting apparatus, ticks penetrate into the folds of the skin, the area of the external genitalia, joints, abdomen, buttocks.

Demodex mites parasitize in hair follicles and sebaceous glands of the face, auricles, auditory canal, eyelashes, mammary glands, and genitals. Two varieties of these mites are found in humans: Demodex folliculorum and Demodex brevis (0.2-0.3 mm long). They have a spindle-shaped body, short limbs, and a piercing mouth organ. Demodex mites cause demodicosis in animals, and in humans they are a common cause of rosacea-like and perioral dermatitis (more often in women), blepharitis, and external otitis. Many people are asymptomatic carriers of Demodex.

Bed bugs - often cause damage to human skin. At the site of their bite (arms, neck, chest, external genitalia, buttocks) a red itchy spot, papule or blister with perifocal erythema appears. The formation of rash groups consisting of 2-3 elements arranged linearly is characteristic. In sensitized individuals, a widespread skin reaction such as papular urticaria and the formation of blisters, blisters is possible. In uncomplicated cases, the elements resolve within a few days.

"Kissing" bugs bite a person at the junction of the skin and mucous membranes on the face (lips, nose). At the sites of attack, papular rashes with a dot in the center, herpetiform vesicles, diffuse brownish urticaria, as well as hemorrhagic and bullous elements can be found.

Lice (head, body, pubic) are blood-sucking parasites of humans. Lice infestation is evidence of poor sanitary and hygienic conditions in humans. In the USA, 6-10 million children are infected with pediculosis every year; it is widespread in Africa and other hot countries.

Caterpillars of some butterflies cause dermatitis when they come into contact with human skin. After 10-20 minutes, a burning sensation, itching, and a linear edematous-erythematous strip appear at the site of contact between the caterpillar and the skin. By scratching the itchy area, a person transfers caterpillar hairs to other places, where new spotted and urticarial elements appear. Dermatitis usually regresses within 1-2 weeks. With repeated contact with caterpillars and the presence of sensitization, a maculobullous rash develops; the disease takes on a more prolonged course. Treatment is symptomatic.

Skin lesions caused by some beetles occur when they are crushed and the toxic liquid contained in the beetle's body is rubbed into the skin. Within 24 hours, a contact skin reaction develops in the form of erythema, edema, and blisters of varying size and shape, which tend to grow peripherally. Itching is insignificant. The rash resolves within two weeks.

At the site of flea bites (they parasitize mammals and birds), a burning sensation appears, then a spot, papule, blister or vesicle (blister) with a hemorrhagic point in the center. With severe allergy of the body, papules, urticaria, multiple elements of the type of erythema multiforme with severe itching appear. The rash is most often detected on the thighs, buttocks, and arms. In America, Africa, and Asia, tungiasis (sarcosylosis) is often encountered - a disease caused by the sand (earth) flea, in which spots appear on the genitals, perianal area, thighs and arms, then itchy nodules with a pustule in the center, nodes, necrotic ulcers, abscesses, lymphangitis, lymphadenitis; septicemia may develop, sometimes tetanus, gas gangrene, self-amputation of fingers.

Among the centipedes, the herbivorous millipedes and carnivorous centipedes are important for humans. The former secrete a protective foul-smelling liquid that causes various eye and skin lesions (burning, pain, redness, swelling, blisters). Centipedes secrete a poison that causes pain, swelling, and purpura, most often on the lower extremities.

Treatment: removal of the parasite, prevention of secondary infection; in case of massive invasion - thiabendazole 25 mg/kg/day, or albendazole 400 mg/day for 3 days.

Bee, wasp, hornet and ant stings are common and are usually accompanied by burning pain, erythema and local swelling of the skin. If the bee sting is not removed, a long-term granulomatous node (up to the size of a nut) may develop at the site of the sting. With high reactivity to stings, angioedema, urticaria and even systemic disorders develop within half an hour. Repeated stings can cause very severe reactions with hemorrhagic rash.

When bitten by dipterans (mosquitoes, sandflies, midges, horseflies, blood-sucking flies), mild pain, erythema, blisters appear and within 24 hours an itchy papule forms. Sensitized patients may have widespread urticarial reactions, papular and vesiculobullous rashes.

After bites from mosquitoes of the genus Phlebotomus dermia, phlebotoderma and harara appear (see their description below).

Myiasis is a disease caused by worm-like larvae of non-bloodsucking dipterans (some flies, gadflies). There are superficial and deep, obligate and facultative myiasis. Superficial myiasis is caused by flies that lay eggs in open festering abrasions and wounds. The developing larvae feed on the exudate of the wounds. Deep myiasis is caused by tungsten fly larvae that affect the skin, subcutaneous tissue and mucous membranes. The larvae feed on necrotic and healthy tissue, forming ulcers and deep passages. In cordylobiasis (African myiasis), more often in children, nodes, ulcers and abscesses are formed. Dermatobiasis (South American myiasis) is characterized by tumor-like inflammation and subcutaneous abscesses with fistulous openings on the surface. The larvae of gadflies cause "linear migratory myiasis" by penetrating the skin and making tortuous passages in it.

Treatment: immobilization and removal of larvae. When furuncle-like formations are lubricated with Vaseline, the larvae leave their ecological niche; in case of dipteran bites - symptomatic treatment.

Prevention: public and personal hygiene measures, use of repellents.

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