What is scabies?
Scabies - from the Latin scabere = to scratch - is an infectious and particularly contagious dermatological disease.
Supported by the mite Sarcoptes scabiei hominis, it causes an intense itching and the appearance of raised red spots (papules), often associated with vesicles and secondary infections.
Vital Cycle of the Mite of Scabies
The adult female, in particular, penetrates into the most superficial layer of the epidermis, digging a kind of tunnel ( scabies tunnel ) at the bottom of which it deposits two or three eggs every day.
After 2-4 days from their deposition, the eggs hatch, allowing the larvae to escape, which - by digging small secondary outlets towards the skin surface - reach maturity and mate at a distance of 15-17 days.
The female, more long-lived than the male, lives for 4-6 weeks and can lay up to 50 eggs; measures approximately 0.35 - 0.45 mm long x 0.20-0.30 wide; it is ovoid in shape, greyish in color, and has four pairs of short and stumpy legs: the front ones are equipped with suction cups and the hind ones have long bristles.
The male, smaller, dies immediately after copulation, while the female can survive in objects for up to 4 or 5 days, before dying of hunger.
In people with scabies the number of parasites is limited to 5-10 adults and generally does not exceed 30 - 40 units.
Symptoms and complications
itch
The most typical symptom of scabies is intense itching, especially at night.To dig their burrows in the stratum corneum, the scabies mite secretes keratolytic substances from the buccal apparatus; these substances - together with the faecal particles excreted in the burrows - determine a small inflammatory reaction mediated by the release of epidermal cytokines; this explains the subsequent appearance of an intense itching, especially at night, and of the typical erythematous-papular eruption.
Skin lesions
As anticipated, scabies manifests itself with fine, greyish streaks, some millimeters long and known as tunnels or scabies . However, these tunnels are not always visible, as scratching can create lesions that mask or destroy the tunnels.
Through scratching and / or the immune reaction, the tunnels can then evolve into papules, nodules, ulcers and crusts, on an underlying redness (rash).
Scabies photo
Photo: tunnel of the scabies
Photo: Typical lesions of Scabies due to hypersensitivity to mites.
See other Scabies Photos
Incubation Period
The signs and symptoms of scabies appear after about one month from the infection, a time necessary for the development of dermal sensitization.
The incubation period for scabies is about three weeks; in case of reinfestation the symptoms can appear more quickly, on average within 1-4 days, since the individual is already sensitized.
Complications
The irresistible need to scratch is often associated with scratching lesions, which can become complicated as a result of bacterial superinfections leaving space for pimples, folliculitis and impetigino.
In some cases the symptoms of scabies can extend to the entire body surface, apparently due to an exaggerated allergic reaction.
Location of injuries
The typical body regions in which this symptomatology becomes evident are the interdigital spaces, the anterior aspect of the wrist, the anterior pillar of the axilla, the navel, the intergluteal and subgluteal furrows, and the external genitalia; these are areas where the skin, thinner and more delicate, favors the penetration of the parasite.
In children the eruption can also affect the palms of the hands, the soles of the feet, the face and the scalp; in the adult woman the localization to the mammary areola is typical, while in the man the skin of the penis is often involved.
Deepening: Scabies symptoms
Norwegian Scabies
A particularly serious clinical form is the Norwegian scab or scab scab .
Common in immunocompromised or debilitated patients, it is characterized by a high degree of infectiousness and a very high number of parasites, which live in a body heavily marked by severe ulcerated or crusted skin lesions, with frequent involvement of nails and alopecia.
Photo: Scab scabies in a person with AIDS
In scabies with scabs, the infection can be carried out more easily directly, through contact with clothes, towels, bedding such as sheets / blankets used by the patient (due to the presence of the parasite in the scabs). The possibility of indirect contagion is however limited.
Contagion
The scabies parasite is transmitted by direct, close and prolonged human contact, for example during sexual intercourse.
The limited possibilities of indirect transmission, through the promiscuous use of clothes, towels and sheets, become more concrete in the form of scabies with scabs.
Can scabies be taken from an animal?
As for animal scabies, the parasites that support it are incapable of multiplying on human skin, where they can still reside for a few days and cause the onset of a symptomatology similar to that described, but with the absence of the scabious burrows.
The period of infectiousness lasts for as long as the patient has not been adequately treated.
Scabies and Personal Hygiene
The spread of scabies, like that of lice, is favored by overcrowding and lacking hygienic conditions; however - not necessarily linked to these factors - it can affect people from all walks of life, regardless of personal hygiene and without distinction of age or sex. This observation is confirmed by the recent increase in episodes of scabies in the most industrialized countries; all this can be explained on the basis of the numerous immigration waves from developing countries, of promiscuity, of frequent international trips and of the long stay in crowded places (even if of excellent hygienic level).
Curiosity: Scabies: why are children particularly susceptible?
Curiosity: Scabbia: who is at risk?
Diagnosis
The diagnostic assessment of scabies is carried out by searching for its four pathognomic elements:
- presence of mites, eggs, excrement and above all the burrows;
- appearance of more or less specific lesions in typical sites by sex and age;
- intense itching that shows a recrudescence when going to sleep (the heat retained by the blankets increases the activity of the mites);
- finding of the same symptomatology in people in close contact with the patient, reflecting the great contagiousness of scabies.
The burrow is a small filiform lesion, typically white or gray, with a more or less rectilinear or tortuous course, from a few mm up to 10-15 mm long. Observing it with a lens it is possible to appreciate the entrance orifice and, at the opposite end, the mite, which appears as a grayish and shining dot. If the tunnel is not clearly manifested, it is possible to highlight it by dropping a drop of water-soluble dye into the lesion, and then cleanse the skin with water or alcohol; the dye penetrated into the tunnel by capillarity, is not removed by cleaning, making its path very evident. At this point, it is possible to remove the scabious tunnel with a cutting edge or insert a very thin needle to pick up the mite.
Curiosity: Scabbia: how do you recognize it?
Care
Disinfection of Environments and Clothing
To eliminate scabies, the disinfestation of domestic environments and personal effects plays a fundamental role; it is therefore necessary to carefully sanitize clothing in contact with the skin, linen and bed linen (pillowcases and sheets) by boiling or washing in hot water (at least 60 ° C, better 90 ° C) and soap. Even the brushes and combs must be treated at high temperatures.
Anything that cannot be washed at high temperatures should be exposed to air for at least 2 or 3 days. In fact, the mite does not survive long away from human skin.
Alternatively, the effects can be stored in sealed plastic bags and left inside for about a week and then exposed to air.
Sofas and cushions can be washed with a high temperature steam jet and then wrapped in waterproof bags for a few days. Alternatively, they can be sealed in a waterproof plastic bag in which an insecticide spray based on pyrethrum is sprayed and is left closed for at least 24 hours and then the effects are exposed to the air.
Those who lend themselves to the disinfection or assistance of patients with scabies must be equipped with appropriate protective clothing (in particular disposable gloves and gowns).
Deepening: What to do in case of Scabies? Practical indications
Isolation of the patient
Scabies is a disease subject to mandatory notification by the doctor that diagnoses it.
The Public Hygiene Service that receives this report undertakes to carry out an epidemiological investigation to trace the alleged methods of infection and extend the investigations to people with whom the patient has had close contact.
The patient with scabies must be treated with appropriate therapy and isolated for at least 24 hours after starting treatment. Isolation requires that the patient remain separated from all other persons, with the exception of those who assist him
drugs
Local treatment is generally performed with lotions or creams based on benzyl benzoate, crotamitone or permethrin . Often recourse is made to galenic preparations prepared by the pharmacist on the advice of the dermatologist.
It is very important to apply these products all over the body, from the neck down, after a hot and prolonged bath followed by an energetic friction of the skin (scrub), especially in the sites where the cunicular lesions are present; this care has the purpose of exposing the mites and the eggs contained in the tunnels to the active ingredient. After 8-12 hours from application, the anti-fogging products must be removed with water.
Oral antihistamines and topical emollients help relieve itching, which often, sustained by irritative phenomena (even the psychic component should not be underestimated), persists for several days; antibiotics can be used in the event of bacterial infections.
Prophylactic monitoring and treatment should be extended to all cohabitants and subjects in close contact with the scabious, such as sexual partners and cohabitants; to curb the spread of infestation, the sick person must abstain from work in public establishments, colleges or other communities as long as the disinfestation work is not completed.
Deepening: Scabbia - Drugs for the treatment of Scabies
Natural Care
Natural remedies include peruvian balm ointments, naturally rich in benzyl benzoate.Prevention
The prevention of scabies is carried out respecting the common hygienic rules, avoiding as much as possible the overcrowding and the use of towels or shared linen, especially in schools, colleges and communities. Complaint is mandatory.
In the case of animal scabies, the eradication of the parasitosis in the four-legged friend (generally dogs or cats) leads to a speedy recovery also in humans.
