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Arachnoentomoses of humans and animals

 
, medical expert
Last reviewed: 12.08.2022
 
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A myriad of species of insects and arthropods (arthropods), which make up more than 80% of all known representatives of the planet's fauna, lives next to us. Some of them can cause invasive parasitic diseases of humans and animals - arachnoentomosis.

Epidemiology

In general, the statistics of arachnoentomoses is unknown, although some data are available for their individual types.

Thus, according to WHO information, at least 200 million people suffer from scabies on a global scale, and up to 10% of them are children. This disease is most common in hot countries and in areas with high population density, these are South and Southeast Asia, the tropics of Latin America, the Caribbean, Africa (below the Sahara).[1]

Head lice infestation is estimated at 0.62% of the total population. At the same time, in Asian countries, the incidence rate varies in the range of 0.7-60%, in South America - 3.6-61%, in Europe - 1-20%.

Causes of the arachnoentomoses

In the etiology of human arachnoentomosis, the main place is occupied by parasitiform mites (arachnopods), wingless arthropods (lice, bugs of the family Cimicidae, fleas Pulex irritans, etc.) and insects of the Diptera order - gadflies and flies.

Thus, the causes of the development of human or animal arachnoentomosis in most cases are associated with inoculative skin lesions, that is, with the bites of ticks, flies or lice as a result of their infestation (attack) and parasitic infection (invasion).

Read more:

Bed bugs (Cimex lectularius) and some other representatives of the order Hemiptera, insects of the genus Pediculus - lice, as well as fleas (arthropods of the family Aphaniptera) - parasitic hematophagous insects (feeding on the blood of warm-blooded mammals), cause superficial arachnoentomosis.

Head lice (Pediculus humanus capitus) cause  pediculosis  (diagnosis code B85 in the section of infectious and parasitic diseases of the ICD-10), [2]and infestation with pubic lice (Phthirus pubis) causes  phthiriasis .[3]

But when bitten by a sand flea living in the tropics (Tunga penetrans), which penetrates the skin, sucks blood and lays eggs, tungiasis develops  (  code B88.1 according to ICD-10).[4]

The defeat of Demodex folliculorum mite, which belong to histophages (eating tissues) is the cause of another type of arachnoentomosis, and this is  demodicosis of the skin , head, eyes and eyelids (according to ICD-10 code B88.0).[5]

In case of damage to the skin by the scabies mite (Sarcoptes scabei), a type of acariasis such as  scabies  develops (the disease has the B86 code according to the ICD-10).[6], [7]

Tyroglyphosis (flour scabies) is caused by infestation of the acariform flour mites Tyroglyphus farinae, and grain scabies (called pyemotous dermatitis) is provoked by the bites of mites of the Pyemotes subfamily. Acariasis caused by red mites of the Trombiculidae family (more precisely, their larvae) is called thrombidiosis.[8]

In addition, allergic arachnoentomoses are observed: getting into the body with inhaled air, barn and flour mites - Glycyphagus destructor, Aleuroglyphus ovatus, Gohieria fusca, Acarus siro, etc. - and their excretion can lead to the development of an  allergy to ticks  in the form of respiratory allergosis.[9]

House dust also contains mites (including those of the Dermatophagoides family) that can cause  dust mite allergy .[10]

Entomoses include  myiasis  (skin or intestinal) associated with infection by larvae of detritus flies or gadflies that enter wounds, on intact skin, in the nasal cavity, ear canals, and when swallowed with food, in the gastrointestinal tract. At the same time, the larvae, feeding on the tissues of the host, continue to grow.[11]

The causative agents of myiasis are larvae of gadflies (Dermatobia hominis, Hypoderma tarandi, etc.), blue and green meat (carrion) flies - Calliphora uralensis, Lucilia sericata, etc., flies of the genus Wohlfahrtia and the family Drosophilidae.

Risk factors

The potential threat of being bitten by insects or arachnid arthropods that cause arachnoentomoses is exposed to everyone in their habitat: these are forests and parks, pastures and household plots, premises of granaries and livestock enterprises, as well as contact with agricultural products affected by ticks. And experts associate additional risk factors for the development of an allergic form of arachnoentomosis with sensitization of the human body (a tendency to allergic reactions).

Myiasis may be more common in people with open wounds.

As for pediculosis, phthiriasis, scabies and the same myiasis, here the risk of infection with their pathogens increases if sanitary and hygienic standards are not observed in everyday life and / or poor living conditions.

Pathogenesis

The pathogenesis of arachnoentomosis is caused by the saliva of blood-sucking arthropods, which contains antihemostatic protein substances that prevent platelet aggregation and blood clotting when bitten, and immunogenic compounds of various protein enzymes (proteases) and excrement.

The result of damage to the epidermis and dermis and the ingress of foreign proteins into the skin is the immediate onset of acute inflammation and the formation of a local immune response: activation of leukocytes, mast cells, neutrophils and other protective cells; release of pro-inflammatory cytokines and chemotactic factors (histamine, leukotrienes, macrophage inflammatory protein MIP-1α, etc.); production of antibodies by dendritic cells and T-lymphocytes.

The mechanism of development of allergic respiratory arachnoentomosis is also identical. And with myiasis, tissue damage by larvae occurs, which leads to inflammation and focal necrosis.

Symptoms of the arachnoentomoses

Most often, the symptoms are manifested by acrodermatitis: erythema, local edema and tissue induration, hyperemic spots, urticaria, hemorrhagic papules and vesicles (bubble rashes), skin itching and local pain of varying intensity.

More information:

With pyemotic dermatitis (grain scabies) - in addition to papular-pustular rashes, flushing and itching of the skin - general malaise, fever, headaches and joint pains, asthmatic attacks can be observed.

Symptoms of myiasis are interrelated with its form: cutaneous (superficial or deep), linear migratory, furuncular, ophthalmic, ear or intestinal.

Read more:

Intestinal myiasis is usually asymptomatic, and accidentally swallowed larvae or eggs of flies present in water or food are excreted in the feces. But in some cases, there may be discomfort and pain in the abdominal region, nausea, intestinal disorders, etc.

Complications and consequences

The usual complications of arachnoentomoses are damage to the skin and their local inflammation during scratching, as well as the addition of a secondary (bacterial) infection - often with the formation of skin ulcers and the development of pyoderma or abscess.

Respiratory tick allergy can be complicated by bronchial asthma and angioedema.

The consequences of ophthalmomyiasis can be inflammation of the choroid of the eyes (uveitis) and retinal detachment. And in cases of myiasis that affects the nasal cavity and auditory canals, the penetration of larvae into the base of the brain can lead to inflammation of its membranes (meningitis).

Diagnostics of the arachnoentomoses

Only at first glance, the diagnosis of arachnoentomoses does not present any particular difficulties. In fact, it is quite difficult to diagnose an insect bite correctly, since different people - due to the individual characteristics of immune reactions - the symptoms may vary.

Therefore, specialists determine the cause of the onset of symptoms not only by their appearance - by conducting a thorough examination of the patient, but also find out the circumstances of the alleged bite.

Help in the diagnosis of blood tests for eosinophils, for immunoglobulin E (IgE), etc., skin scraping at the site of the bite. See also:

Instrumental diagnostics may be limited to dermatoscopy, but other hardware studies are carried out if necessary.

But differential diagnosis in many cases can really be a difficult task, since it is not always possible to identify a particular tick or fly that has bitten a patient.

Treatment of the arachnoentomoses

Treatment of diseases caused by inoculation of the skin by insects and arachnid arthropods typically involves cleaning the affected area and using topical agents (particularly glucocorticoids and NSAIDs). Systemic antihistamines or  itch ointment are used to reduce itching and prevent excoriation of the skin at the sites of bites .

Antibiotics are used in cases of secondary infections.

More information in the materials:

Arachnoentomoses of animals and birds

No less numerous and diverse are arachnoentomoses of animals, which are caused by the bites of ticks and gadflies or the ingestion of larvae of gadflies and flies inside, and are manifested by both skin and gastrointestinal symptoms.

Acariasis of livestock, domestic animals and birds is the result of bites of parasitic argas mites (Alveonasus lahorensis, Alveonasus сanestrini, Otobius megnini, etc.), as well as gamasid mites of the families Phytoseiidae, Laelapidae, etc. In rabbits, scabies with inflammation of the skin and hair loss is caused by parasitic on them ticks of the genus Psoroptes.

Bites from the bovine gadfly Hypoderma bovis lead to the development of cutaneous myiasis in cattle. Intestinal myiasis of horses, mules and donkeys is caused by the horse gadfly Gasterophilus intestinalis, sheep and goats by flies of the genus Oestrus. In the nostrils and ear canals of livestock, gadflies of the Oestrinae and Hypodermatinae families can lay eggs (from which larvae hatch that penetrate the skin).

Avian arachnoentomoses include skin-eating scabies, an epidermoptosis of poultry caused by Epidermoptes bilobatus mites parasitizing the skin (at the base of feathers); knemidokoptosis (caused by acariform mites of the genus Knemidokoptes) - with damage not only to the skin, but also to the joints of the extremities.

Bites of the gamasid mite Dermanyssus gallinae lead to dermanissiosis in chickens. And ticks Ornithonyssus spp. Macronyssidae families infect wild birds, but some subspecies are also common in poultry farms.

Ticks of the subfamilies Rhinonyssidae, Ptilonyssus, Mesonyssus can penetrate the respiratory organs of birds, which leads to inflammation of the lungs and mucous membrane of the air sac (aerocystitis) in birds.

In most cases, dog arachnoentomosis is caused by the bites of the Ixodes dog tick Ixodes ricinus and ticks of the Cheyletiella and Trombiculidae families. And the mite Demodex folliculorum, like in humans, is the cause of demodicosis in dogs.

In addition, dogs can be bothered by dog fleas (Ctenocephalides canis), and cats by Ctenocephalides felis, the bites of which cause focal inflammation of the skin, accompanied by severe itching and scratching - flea dermatitis.

Also, dogs have trichodectosis, a skin disease associated with the defeat of the lice Trichodectes canis of the suborder Mallophaga (which are called withers); infection is manifested by itching of the skin and its thickening, the formation of wounds due to scratching and hair loss in the affected areas.

The main method of combating parasitiform mites and parasitic insects is the veterinary treatment of animals against arachnoentomoses, which consists in the external application of acaricidal agents (with permethrin or amitrazine) and appropriate insecticides.

More details in the publications:

Prevention

A preventive measure against arachnoentomoses is the prevention of bites from ticks, flies and other insects. Repellents are used to scare them away: going out into nature with their help, you can protect exposed skin. And for destruction, pest control is carried out.

Read:

Forecast

Cutaneous arachnoentomoses in the form of scabies and other acarodermatitis are cured and have a good health prognosis.

But we must not forget that it is in the inoculative way - through the bites of insects and arthropods - that many transmissible diseases are transferred: bacterial, viral, protozoal.

So, lice can be carriers of typhoid, and  the consequences after a tick bite  include tick-borne borreliosis (Lyme disease), tick-borne encephalitis, babesiosis.

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