Acarias

Damage to the skin by arachnid arthropods - acariform mites, as well as resulting dermatological ectoparasitic diseases are defined as acariasis (akari - mite).

[1], [2]

Causes of the acariasis

Common causes of acariasis are bites of ticks. And people are bitten not by adult arthropods, but by their deytonymphs (larval stage of the life cycle of mites, its main parasitic phase).

The main causative agents of acarias identified today are representatives of two nomenclature groups of very small (in the tenth of a millimeter) acariform mites: thrombidiformes (Trombidiformes) and sarcopptiformes (Sarcoptiformes).

Some of them are ectoparasites of insects, birds or mammals; a part lives in symbiosis with its owners or refers to commensals, many and freely inhabiting varieties. And although the ways of infection - opening bite free access to skin tissue, acariform mites do not need ferritin, which is contained in red blood cells and which is fed by blood-sucking parasitiform ticks. Food for most of the acariforms is the decomposition products of organic substances, that is, they are detritophages.

It is noteworthy that a special tube (stylostoma) is formed in the larvae of most acariform mites for attachment to the host's skin and unhindered "food intake" between the chelicerae (oral appendages).

This is what distinguishes them from hematophagous-ticks (Ixodes, gamazovyh, argasids), which bites into the human bloodstream pathogens fall tick-borne encephalitis, borreliosis, rickettsialpox, koksielleza, anaplasmosis or babesiosis.

The most famous of damaging human skin acariformes - sarkopter or  itch mite  (Sarcoptes scabiei), parasitic on humans and many families of mammals and Demodex - trombidiformes Demodex folliculorum (subfamily Demodicidae), which bypassed called ugritsey or subcutaneous mite. 

Because of sarcopter damage, scabies develop, which, in fact, is a sarcoptic acariasis. A disease, provoked by the tick D. Folliculorum, dermatologists usually call  demodicosis of the skin  and extremely rarely - demodectic acariasis.

Thrombiformiform mites Pyemotes ventricosus (parasites on woodworm insects), Pyemotes herfsi (feeding on hemolymph of larvae of leafless midges in oak galls) and triticite mites (Pyemotes tritici), usually reproducing during storage of hay, straw, dried legumes and cereals, are the causes of acariasis , defined as hay or cereal scabies.

Two species of Psoroptidia and Suidasia pontifica, related to the sarcoptiform group, cause acariasis of the ear.

Acariasis dermatitis is caused by the sarcoptiform tick of Glycyphagus domesticus or parasitizing on birds and rodents by the reddish mite Trombidium ferox. The defeat of the skin with barnyard (mites) Tyroglyphus farinae or Glycyphagidae destructor can be called a scabby scab or tyroglyphosis.

As experts of European Association of Acarologists, perhaps the most numerous population piroglifidnyh Dermatophagoideses - Dermatophagoides farinae, D. Microceras and D. Pteronyssinus, called  dust mites, dwells in every dwelling, feeding due to the decomposition of dead and exfoliated cells of the horny layer of human skin. They lead to the development of acariasis dermatitis, called dermatophagoidosis.

When the route of infection is inhalational, there may be an acarias allergy. Immunologists have proved the involvement of these mites in the sensitization of the human body and their high cross-allergic reactivity with the mold tick Tyrophagus putreseltiae and the seeds of Glycyphagidae, which live on seeds and grain products.

Of blood-sucking parasitiform ticks involved in the emergence of this type of acarias in humans, like dermanissiosis, consider the Dermanyssus gallinae - mites of poultry and pigeons.

[3], [4], [5], [6], [7],

Risk factors

Among the risk factors for the development of acariasis, physicians, in the first place, note a decrease in the general resistance of the organism.

You can get acariasis: when keeping poultry or working in poultry farming; during work in granaries and warehouses (where flour and cereals are stored and packaged); on haymaking or harvesting of grain crops.

It should be borne in mind that any domestic pet in a typical city apartment is a potential carrier of acariform ticks, not to mention the rats running around in garbage dumps.

And even when there are no animals or birds in the house, there is such a huge reservoir of pathogens of allergic and dermatological acariases, like dust.

[8], [9], [10], [11],

Pathogenesis

If, with transmissible parasitic diseases, blood-sucking parasitiform mites transfer infections from an infected warm-blooded organism to a healthy one (including a human), the pathogenesis of acariasis is completely different.

With the bite of the acariform tick, an enzyme is released that performs two functions at once: it paralyzes the victim (another insect or small vertebral) and splits the substances of its tissues at the site of the bite to a state that allows the tick to suck it and thus satisfy its nutritional needs.

The peculiarity is caused by scabies Sarcoptes scabiei: getting on the skin, the tick female secretes an enzymatic liquid (presumably saliva), which softens the stratum corneum and facilitates the penetration of the tick deeper into the skin. Further penetration leads to the formation of a tunnel hole in the stratum corneum. Here S. Scabiei feeds on tissue fluids and lays eggs, filling the hole to the very bottom.

Regardless of the type of tick (trombidiform or sarcoptiform) that enters the human skin, the mechanism of dermatitis development is one - the activation of innate local immunity in response to penetration of foreign proteins (antigens) through the epidermal barrier.

Such antigens expressing PRR and PAR-2 receptors of the epidermis are the actinidin collagen protein (a component of the chitin sheath of mites), the enzymes they release (anion or cysteine proteases), as well as the products of their vital activity.

In response to infection, keratinocytes of the stratum corneum (which are pro-inflammatory effector cells) produce more protective peptides (β-defensins, cathelicidins and RNases) and pro-inflammatory cytokines and chemokines. All immune cells present in the dermis are mobilized: mononuclear phagocytes (dendritic cells of Langerhans), mast cells and macrophages, B and T cells and plasmacytoid, fibroblasts and natural killers.

Almost the same principle develops sensitization and acariasis when dust mites get on the respiratory mucosa.

[12], [13]

Symptoms of the acariasis

The first signs of bites of acariform mites and the subsequent acariasis dermatitis manifest within 24 hours almost the same: hyperemic areas causing intense pruritis (itching sensation). The area of the skin swells, it can be hot to the touch, sometimes there is burning, numbness or tingling.

After some time on the skin, the following symptoms of acarias are visualized: on the background of reddening, often acquiring the character of erythema, small transparent vesicles (vesicles) are formed, filled with exudate (serous fluid); vesicles can be transformed into pustules - a rounded cavity with purulent contents that protrude above the surface of the epidermis.

Because of combing, the elements of the eruption are subjected to destruction, exudate, pouring onto the skin, causes additional irritation and expansion of the inflamed zone. Crusts appear, wetlands are possible.

Symptomatic of sarcoptic acariasis is described in detail in the publication -  Scabies.

The bites of Pyemotes ventricosus or Pyemotes tritici, the causative agents of cereal scabies, appear for 10-24 hours with an itchy hyperemic area (including the neck, arms, shoulders and upper torso) protruding above the surface of the skin with dense papules, topped with a vesicle, for the formation of purulent exudate. The rash is resolved after five to seven days, in some cases in two weeks. Approximately 20% of patients have comorbid symptoms in the form of fever, runny nose and wheezing with breathing.

About the symptoms that occur when air dust mites get into the respiratory tract, in detail in the article -  Allergy to dust mites.

[14], [15], [16], [17]

Complications and consequences

The most common complications of skin lesions with acariform mites are secondary bacterial infections (staphylo- and streptococcal), which develop on the site of scratching and lead to purulent inflammation - pyoderma.

And pyoderma can be complicated by the formation of local abscesses, which involve deep layers of the dermis and subcutaneous tissues.

Acariasis, associated with dust mites, complicates the work of the respiratory system, causing chronic  pulmonary eosinophilia.

[18], [19], [20]

Diagnostics of the acariasis

The only tests performed with suspicion of tick-borne dermatitis or sensitization are an analysis of the level of IgE, that is, the  immunoglobulin E in the blood

Molecular methods of identification of mites of dermatologists are not available. In addition, many acariform ticks, for example the Pyemotes subfamily (0.1 - 0.2 mm long) can not be seen with the naked eye, and the chances of finding them at the bite site are minimal; besides they leave long before the onset of an inflammatory reaction.

Therefore, for diagnosis it is important to identify the presence of ticks on animals, even if they are not found in the affected person.

Instrumental diagnostics of acariasis caused by some varieties of ticks is possible: scrapings from the skin are studied under a microscope. And most often parasites are found on the edges of lesions, in the zone of peeling and crusts. Ear mites can be seen with the help of an otoscope.

The dermatologist conducts the  examination of the skin, and the pulmonologist  studies the lungs and bronchi .

[21], [22], [23]

Differential diagnosis

The most difficult is differential diagnosis, as it is necessary to distinguish acarias from hives and a number of allergic dermatoses, as well as from herpes or erythema multiforme. And to identify  allergies to ticks, you need special tests, which are conducted by an allergist.

Treatment of the acariasis

The main goal pursued by the treatment of acariasis is the relief of itching and the removal of inflammation, as well as the prevention of secondary bacterial infections.

Reduction of itching and redness of the skin is facilitated by washing the affected area with soap and water, applying packets of ice (for 5-10 minutes every 45-60 minutes).

The main drugs used in the therapy of acariasis dermatitis are symptomatic. Possible intake of antihistamines, which, read -  Tablets from the itching of the skin.

To lubricate the rash, use salicylic or menthol alcohol, emulsion with benzyl benzoate, cream or lotion Crotamiton. The external agents are: sulfuric and zinc ointments, Dermadrin, Dexpanthenol, various ointments with corticosteroids. More in the publications:

• Ointments for dermatitis for adults
• Non-hormonal ointments from dermatitis
• How to treat a rash on the skin

Alternative treatment

Alternative means include: compresses from a raw leaf of white cabbage, raw grated potatoes, aloe juice, plantain, propolis dissolved in water.

It is suggested to lubricate the rash with tinctures of marigold or propolis, concentrated soda solution, mummy solution, lemon juice.

Herbal treatment involves lotions with a decoction of calendula flowers, creeper roots creeping or elecampane - with the addition of a few drops of camomile oil, lavender, tea tree.

See also -  Rapid and effective treatment of scabies at home

[24], [25], [26], [27]

Prevention

The very high reproductive potential of acariform ticks, microscopic size and high wind dispersion make it difficult to control their populations and prevent acariasis.

Prevention recommended by the World Health Organization for people: avoid contaminated areas and places, potential habitat for these arthropods, and also use repellents and insecticides based on diethyltoluamide.

[28], [29], [30], [31], [32]

Forecast

Timely therapy leads to a complete cure of cutaneous manifestations of acariasis, the prognosis is favorable. With weakened immunity acaciasis sensitization takes a chronic form.