Generality
The bites of mites can cause intense itching and discomfort, but what most worries are the pathologies that can derive from it.
In fact, in some cases mite infestations can give rise to real diseases (eg scabies, demodicosis); while in other cases the mites can act as vectors for pathogenic microorganisms capable of triggering infectious pathologies in the hosts (eg leprosy, tropical typhus).
Contrary to what many think, mites are not insects, but arachnids belonging to the phylum of arthropods and belonging to the large group of ectoparasites .
There are really many species of mites capable of attacking man, some of which live perennially on the surface of the human body (permanent ectoparasites); while others normally live in other places, but can occasionally attack mammals such as humans or other animals.
Acari stings: a bit of clarity
The term "mite bites" is often used to indicate all the lesions caused by these ectoparasites. In many cases, however, this use is improperly carried out.
In fact - with the exception of some hematophagous species - usually, the mites do not sting and do not bite, but live on the body surface because they feed on sebum and cellular debris.
Therefore, except for the species that feed on the blood of humans and animals, in most cases, it would be more correct to speak of " lesions caused by mites " and not "mite bites".
Types of Mites
Mites are arthropods belonging to the order Acarina, class Arachnida (arachnids), subphylum Chelicerata and phylum Arthropoda (arthropods).
The species of greatest health interest for humans are those belonging to the following genera:
- Genus Sarcoptes (Sarcoptidae family): the main exponent of health interest for both men and animals is Sarcoptes scabiei, mite responsible for scabies .
- Genus Demodex (family Demodecidae): among the mites belonging to this genus we remember the species D. folliculorum and D. brevis that usually live as commensals in the hair follicles and in the sebaceous glands of man. However, their excessive proliferation can cause real infestations and assume pathological characters.
- Genus Dermatophagoides (Pyroglyphidae family): the mites belonging to this genus usually do not live on humans, but are found in furniture and home accessories, in household linen and in dust (dust mites ). These arthropods are however of health relevance due to allergies (inflammation of the respiratory tract, eye diseases and dermatitis) which can trigger the glycoprotein allergens contained in their excrement.
Other Mites
The bites of mites - or rather the lesions caused by mites on humans - can also be caused by arachnids belonging to different genres from those listed above. These are usually mites that live on other mammals, or on plants or foodstuffs, but which can occasionally attack humans, giving rise to skin lesions.
However, for some of these ectoparasites, talking about mite bites is not improper, since, in the larval stage, they are hematophagous and can bite humans or animals to feed on their blood. Among the mites of this type, we recall:
- Trombicula autumnalis : it is a species of mite that normally lives in the vegetation but that can attack the man localizing especially in the lower limbs.
- Trombicula akamushi : this species of mite also normally lives in the vegetation, but it can attack humans to feed themselves. It is a species particularly widespread in India and in the regions bordering the Western Pacific.
Symptoms
What are the symptoms and characteristics of mite bites?
The characteristics and symptoms of mite bites can vary depending on the species that caused the lesions.
Sarcoptes scabiei
The stings of S. scabiei mites are not real punctures, but they are injuries caused by the "excavation operations" carried out by the female specimens to lay the eggs and by the larvae that are born after the hatching.
The females of S. scabiei, in fact, dig real burrows in the skin, at the level of which they lay their eggs and then die. When the eggs hatch, larvae emerge with an appearance similar to that of an adult that pierce the burrow up to the skin surface, where they will turn into nymphs and, later, into adult individuals.
S. scabiei infestation is the cause of skin disease known as scabies . The lesions that characterize this disease cause the guest an intense itching, especially at night, which causes the victim to scratch himself vigorously, favoring the appearance of blisters and scratching lesions that can then be complicated by bacterial superinfections .
Did you know that ...
There are many varieties of S. scabiei existing, each of which is host-specific, or species-specific if you prefer. This means that each variety infests a certain type of guest (man, dog, cat, rabbit, etc.). Therefore, there is a mite capable of causing scabies in men, one capable of causing it in dogs and so on for other animals. The scabies mite that affects humans is S. scabiei var. hominis .
However, it is important to point out that the S. scabiei mites responsible for animal scabies can still attack humans, causing symptoms similar - but not the same - to those caused by the man's scabies mite.
Demodex spp.
Also with regard to the species of the genus Demodex, to speak of bites of mites would be improper.
In fact, these arachnids do not usually bite the host but live on the skin surface as diners feeding on sebum and cellular debris. Under normal conditions, injuries caused by Demodex spp. they are not obvious, or only minimally, and manifest themselves as itchy acne- like lesions .
Among the mites belonging to this genus of particular interest for humans we find D. brevis and D. folliculorum . The latter species normally lives within the hair follicles of many individuals without creating problems. However, under certain conditions, it can proliferate excessively giving rise to the so-called demodicosis of man .
Moreover, it seems that the presence of these mites can somehow facilitate and favor the appearance of pimples, folliculitis and rosacea.
Curiosity
Demodex canis - mite that infests the hair follicles of the dog - is responsible for the demodicosis of the dog, also known as red mange.
Trombicula spp.
As mentioned, the mites belonging to the genus Trombicula are generally found in the vegetation, but they can attack man - especially in the larval phase - to feed on his blood.
The mite bites of the genus Trombicula species autumnalis are generally located at the level of the lower limbs and are of the erythematous type . Not surprisingly, these arachnids give rise to the so-called " autumnal erythema ".
The bites of mites of the genus Trombicula species akamushi, on the other hand, give rise to erythematous- bullous lesions .
Transmitted pathogens
What pathogens can be transmitted through mite bites?
Some species of mites can act as vectors for microorganisms capable of triggering infectious diseases in the unfortunate host.
Among the pathogens that can potentially be transmitted through mite bites, we recall:
- Mycobacterium leprae : also known as Hansen's bacillus, is the beat responsible for leprosy. In areas where this disease is endemic, it can be transmitted by mites belonging to the Demodex genus.
- Orientia tsutsugamushi : sometimes also called Rickettsia tsutsugamushi, it is the beat responsible for Japan's river fever, otherwise known as bush typhus, typhoid tsutsugamushi, tropical typhus or mite typhus. The microorganism that causes this disease is transmitted through the bites of Trombicula akamushi mites.
Cure and Prevention
Are there treatments against infestations and mite stings?
The treatments currently available against mite bites provide for the elimination of the same ectoparasites from the skin surface of the host.
Usually, to counter S. scabiei, use is made of drugs for topical use based on permethrin (Scabiacid®, Scabianil®).
Demodex spp. Infestations, on the other hand, are treated only when they take on pathological (demodicosis) characteristics. In this regard, drugs for topical use based on ivermectin (Efacti®) have proved particularly useful in killing mites of this type.
As for the larvae of the mites belonging to the genus Trombicula, usually, after a blood meal, they tend to fall to the ground to return to live in the surrounding environment and complete the development phases up to the adult stage.
Finally, diseases caused by infectious agents transmitted by mite bites, such as leprosy and tropical typhus, must be treated by the use of specific antibiotic drugs .
Of course, the aforementioned drug therapies must be prescribed by the doctor. However, the best cure for mite bites remains prevention .
How can mite bites be prevented?
The only way to prevent mite bites is to avoid contact and subsequent infestation by these ectoparasites. To do this it is necessary:
- Avoid, as far as possible, direct contact with mite-infested patients ( S. scabiei, in fact, is transmitted by direct contact from person to person);
- Avoid contact and / or use of clothing, household linen and towels used by mite-infested patients ( S. scabiei, in fact, can also be transmitted through contact with clothing and linen; while Demodex spp. Is transmitted above all through the mixed use of towels used by infested people);
- Wash clothes, towels, underwear and household linen at high temperatures (at least 60 ° C);
- Avoid going to or staying in places known to be mites;
- Properly protect their pets by using special pesticides, especially if they live both outside and at home.
If in spite of the aforementioned precautions, however, mite bites occur, it is necessary to go to the doctor and possibly to companies specialized in disinfestation, in order to eliminate these unwelcome guests from their own home.
