Skabies B86

Author: Prof. Dr. med. Peter Altmeyer

Co-Autors: Dr. med. Eva Kämmerer, Aleksandra Kulberg, Jeton Luzha, Dr. med. Antje Polensky, Hadrian Tran

All authors of this article

Last updated on: 06.04.2021

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Synonym(s)

Acariasis; Acarodermatitis; Scabies

History
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Renucci 1835

Definition
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Frequent, globally spread, highly itchy parasitic skin infection caused by Sarcoptes scabiei hominis. The reactive dermatitis induced by the infection is to be interpreted as an immunological reaction of the organism to the mite components. The skin symptoms vary considerably depending on the age of the disease, individual reaction situation and intensity of body care.

Pathogen
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Acarus siro var. Hominis o. Sarcoptes scabiei hominis. S.u. mites. Female scabies mites grow to a size of 0.3-0.5 mm (male 0.21-0.29 mm) and are just visible as a black spot. The mating takes place on the surface of the skin. Male mites then die. Female mites dig tunnel-shaped passages into the stratum corneum and remain viable for about 30-60 days. They lay 2-3 eggs per day, from which larvae hatch after 2-3 days. Scabies mites cannot survive outside the body for more than 48 hours. In immunocompetent patients the number of mites found is low (10-12/patient). In immunocompetent patients, the number can rise to > 1 million mites (picture of Scabies norvegica).

Occurrence/Epidemiology
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Frequent, 200-400 million diseases/year worldwide. The prevalence is mainly based on socio-economic conditions, population density and hygienic circumstances. It fluctuates between < 1% and 30-40% and occurs epidemically.

Etiopathogenesis
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The transmission of the mated female by close physical contact (sexual contact, warmth of bed, living together in a small space, between children), less often via linen, textiles or fleeting contact (exception: Scabies norvegica). The risk of getting infected through bed linen in which a scabies patient had been lying is < 1: 200.

According to the classification of Coombs and Gell, post-scabial eczema is an allergic reaction of type IV (late type allergic reaction). The female scabies mite lays 4-6 eggs a day in so-called mite ducts, which are located in the stratum corneum and can reach the stratum granulosum. The mite eggs are recognized by the body as antigens and are internalized by Langerhans cells to be presented as T-helper cells which then release pro-inflammatory cytokines and chemokines to eliminate the target cells.

Efflorescence(s)
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Redness, linear (comma-shaped) papules, scales, blisters, itching.

Localization
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Especially interdigital wrinkles of hands and feet, elbows, anterior axillary fold, areola, navel, girdle region, penis, ankle region, contact surfaces of the glutaeen. The back is less frequently affected, head and neck as well as palmae and plantae are always free, (exception in old people with atrophic palmae and plantae; in neglected patients the palms of the hands and soles of the feet may also be affected).

With long-term (unkempt) scabies, the emphasis on the typical "scabies regions" is lost. A generalised eczema picture then appears (picture of microbial eczema).

In infants and toddlers: basically ubiquitous, also Palmae and Plantae affected; back of fingers and feet, face.

Clinical features
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Clinically symptomatic is a scabies in the first disease only 3-6 weeks after infection. In case of reinfection the clinical symptoms develop after 24 hours. This means that the mite is literally scratched out of the skin.

The leading symptom of the scabies is a strong itching, especially at night. In addition, there are tortuous, millimetre-long, clearly palpable mite ducts with the mite recognisable as a dark dot at the end of the duct (mite mound). Scratching effects, eczematisation and secondary bacterial infections usually characterise the clinical picture.

The maculopapular, partly urticarial and papulovesicular skin changes are mostly an expression of an allergic reaction of the organism to the mite infection (so-called Id reaction, Scabid).

S.a.

Other special forms:

  • Cultivated scabies: Clinically only isolated papules; diagnostically important is the detection of mite ducts, which must be searched for. The strong nocturnal itching is a signpost.
  • Neglected scabies: Clinical picture of an extensive "microbial eczema". Gang structures must be searched for, they are not in the foreground of the clinical picture. It is not uncommon for plaques to form over the entire surface. Also weeping or pustular areas.
  • Persistent scabies granuloma: In infants and adults, even after sufficient antiscabial therapy, severely itching, 2-4 mm large, mostly scratched papules may persist, probably as a hyperergic reaction to the persistent scabies allergen (late type reaction).
  • Post-scabial itching: Itching persists for several days or even weeks after sufficient scabies treatment.
  • Scabies incognita: Glucocorticoids, applied systemically or locally, can completely hide the clinical symptoms.
  • Localised scabies: A therapy-resistant nipple eczema may be an example of a localised scabies.
  • Scabies in infants and toddlers: The face, head, neck and often (sometimes exclusively) Palmae and Plantae are affected. Efflorescences in children are often very succulent. Excruciating itching persists. Blisters and pustules may occur. These may be clinically formative.
  • Scabies in seniors: especially in patients with dementia, the scabies is often clinically atypical, e.g. without the typical pruritus (in a larger study in 61% of cases), only recognizable by treatment-resistant eczematous lesions (Cassell JA et al. 2018).

Detection method:

  • Native detection of mites: opening of the mite duct by means of a fine cannula, application of the contents on a microscope slide, native examination under the microscope.
  • It is also possible to visualise the mite duct by dabbing a dye (felt pen) and applying an alcohol drop (dye is sucked into the duct by capillary forces).
  • Microscopic mite detection by means of reflected-light microscopy (high sensitivity) (brownish triangular contour, formed by the front part of the mite!)
  • Histological detection of mites (especially in Scabies norwegica easily possible; otherwise mite detection is only possible in step sections, if at all).

Histology
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Acanthosis, also focal spongiosis, orthokeratosis interspersed with parakeratosis mounds. Differing degrees of dermal oedema; dense, diffuse and perivascular lymphohistiocytic infiltrate penetrating the upper and middle (and often deep) dermis. Often more or less clearly pronounced histoeosinophilia. Not infrequently, mite excrement in the form of round or oval globules (skybala) can be detected in the str. corneum. In most cases, mites cannot be detected even in cut series.

Differential diagnosis
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  • Histological: Allergic contact dermatitis; atopic eczema; other arthropod reactions.
  • Clinical signs: contact dermatitis; atopic eczema; microbial eczema; contagious impetigo; Paget's disease (for nipple eczema), dermatitis herpetiformis, diseases with erythroderma, pseudo-scratches.

Complication(s)
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Development of post-scabial pruritus, persistent post-scabial papules or post-scabial eczema is possible. Occasional provocation of other dermatoses such as psoriasis, lichen planus or perforating, reactive collagenosis.

General therapy
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In older children and adults, the entire body is treated with the antiscabiosum without any gaps from the lower jaw downwards. In the case of skabies norwegica, the head must also be treated (recess of the periocular and perioral region). After rinsing or washing the product, new underwear should be applied! Beds are to be changed!

External therapy
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  • Adults and adolescents:
    • Permethrin 5% in a cream base (e.g. InfectoScab) is the first choice therapy. Apply once for 8-12 hours, repeat after 14 days if necessary. In case of severe infestation with stationary treatment indication we recommend a 3-day local treatment.
    • Alternative: Crotamiton (e.g. CROTAMITEX®) (see below).
    • Alternative: Benzyl benzoate (see below), in case of itching at the capillitium, co-treatment of the hairy scalp with Antiscabiosum 25% is possible, as this can be washed out of the hair as an emulsion.
    • Alternative: Allethrin I (e.g. Jacutin N, Spregal Spray (+ piperonyl butoxide).
    • Alternative: 0.5% aqueous malathion lotion.
    • Alternative: 1% ivermectin lotion .
    • Remark! Additional daily change of outer clothing and bed linen. Bed linen should be washed at > 60 °C. Alternative: Store in a plastic bag for 3-5 days. The mites will then die.

    • Alternative (rarely used): 5% tea tree oil.
    • Alternative (rarely used): 10% precipitated sulphur in vaseline or hydrophilic base(sulphur cream 2.5-10%): apply 2 times/day for 3-7 days each time after a soap bath.
  • Pregnancy (see below Pregnancy, Prescriptions):
    • Remark. None of the above-mentioned agents is approved, therefore in pregnant women these therapy modalities are applicable in off-label use! Permethrin is listed in the Red List as a Group 4 drug, i.e. there is insufficient experience of its use in humans; in animal studies there is no evidence of embryotoxic/teratogenic effects.

    • Permethrin 5% in a cream base (e.g. InfectoScab) is therapy of first choice. Apply once for 8-12 hours, repeat after 14 days if necessary.
    • Benzyl benzoate (e.g. Antiscabiosum Mago 25%; alterative NRF formulation: benzyl benzoate emulsion 10 or 25 %: apply once/day, use for 3 days, then shower off.
    • Alternatively: 10% Crotamiton ointment (e.g. Crotamitex® gel/lotion/ointment)apply for 3-5 consecutive days. Cure rates vary between 50-70%.
  • Nursing mothers: Therapy as for pregnant women.
    • Primarily apply permethrin and benzyl benzoate, see above. (Pyrethroids pass into breast milk; nothing is known about benzyl benzoate). According to the S1 guideline of the German Dermatological Society (as of 2016), a breastfeeding break of 5 days should be observed after treatment with permethrin and benzyl benzoates.
  • Newborns and infants:
    • Permethrin 2.5% ( R194 ), applied once over 8-12 hours. Treatment of the entire integument including the head (excluding the mouth and eye area).
    • Alternative: Apply crotamiton ointment for 3-5 consecutive days.
    • Benzyl benzoate is not recommended; it is banned in the USA because of the so-called Gasping syndrome (severe progressive encephalopathy with metabolic acidosis and other symptoms). This syndrome occurred in infants whose catheters and infusion systems were flushed with benzyl alcohol.
  • Infants or older children:
    • Permethrin: Up to 2 years of age 2.5% ( R194 ), from 2 years of age 5% (e.g. Infectoscab 5.0% cream, not on the capillitium as it cannot be washed out of hair) applied once over 8-12 hrs.
    • Alternatively: Benzyl benzoate 10% (e.g. Antiscabiosum Mago 10% for children, if necessary treatment of the capillitium is possible, as the emulsion can be washed out of the hair; or apply benzyl benzoate emulsion 10 or 25 % ( R027 ) once a day, apply for 3 days, then shower off.

      Reminder. Use of benzoyl benzoate is prohibited in neonates in the USA (deaths when using infusion systems purified with benzyl alcohol [so-called Gasping syndrome = progressive encephalopathy, metabolic acidosis, bone marrow depression])!

    • Alternative: 2,5% precipitated sulphur in vaseline or hydrophilic base ( R232 ): apply 2 times/day for 3-7 days each time after a soap bath (Cave: odour nuisance).
  • Immunosuppressed patients:
    • Permethrin 5% as recommended for adults. Repeat after 14 days.
    • In case of recurrence, in addition to local therapy, peroral application of ivermectin.
  • Severely eczematized patients:
    • Pretreatment with a glucocorticoid externum (e.g. 1% hydrocortisone cream) for 2-3 days; followed by classical antiscabi therapy.

Internal therapy
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In case of therapy resistance (frequent in patients with HIV infection), systemic therapy with ivermectin (e.g. Driponin or Scabioral) is recommended. Dosage: 200 µg/kg bw p.o. (max. up to 400 μg/kg bw) as a single dose, always round up to whole 3-mg tablets in cases of doubt. There is no maximum limit to the number of tablets to be taken. Calculated number of tablets to be taken all at once (with water) and 2 hours apart with a meal (empty stomach). This is usually a one-time treatment. Treatment may need to be repeated after 2-4 weeks. A return to communal facilities can take place after 24 hours according to the RKI recommendations (see source 1) if ivermectin is taken correctly.

Naturopathy
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Some smaller studies have been published about the alternative use of 5% tea tree oil, which prove the anti-cabiotic effect of this treatment. For further details see below. Tea Tree Oil.

Aftercare
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Pre- and post-treatment: For post-treatment and in the case of very weeping, irritated skin before therapy, glucocorticoid-containing topicals are used, such as 0.25% prednicarbate (e.g. Dermatop cream). As killed mites continue to act as allergens in the skin for weeks, the itching often remains for a while after the treatment. In the case of open, weeping spots, moist compresses with antiseptic additives such as potassium permanganate, s.a. eczema, post-scabious.

Notice!

Persistent itchy eczema in treated scabies is often caused by sensitization to dead mites, but occasionally by resistance to antiscabiosa or reinfection! scabies granulomas should be treated with topical glucorticoids (if necessary under occlusion). In some cases local injections with glucocorticoid crystal suspensions are necessary. For contact persons: examination, co-treatment if disease is suspected.

Note(s)
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  • If left untreated, the scabies is chronic, but can heal spontaneously even after several years.
  • Resistance has been described for permethrin, crotamiton, lindane and benzoyl benzoate.
  • Notice! Studies on the evidence and efficiency of topical antiscabial agents show the best results with permethrin.

  • School attendance is possible again after a single application of permethrin!

Literature
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  1. Agathos M (1994) Skabies. dermatologist 45: 889-903
  2. American Academy of Pediatrics (Scabies). In: Peter, G. (eds.) 2000 Red Book: Report of the Committee on Infectious Diseases, 25th ed. Elk Grove Village, IL pp. 506-508.
  3. Aristotle (340 BC) (1960) Animalium historia. In: Aristotle's opera, Volume I. De Gruyter Publishers
  4. Bezold G et al (2001) Hidden scabies: diagnosis by polymerase chain reaction. Br J Dermatol 144: 614-618
  5. Cassell JA et al (2018) Scabies outbreaks in ten care homes for elderly people: a prospective study ofclinical
    features, epidemiology, and treatment outcomes.Lancet Infect Dis 18:894-902.
  6. Chosidow O (2000) Scabies and pediculosis. Lancet 355: 819-826
  7. Chouela E et al (2002) Diagnosis and treatment of scabies: a practical guide. At J Clin Dermatol 3: 9-18
  8. Dupuy A et al (2006) Accuracy of standard dermoscopy for diagnosing scabies. J Am Acad Dermatol 56: 53-62
  9. Folster-Holst R et al (2000) Treatment of scabies with special consideration of the approach in infancy, pregnancy and while nursing. dermatologist 51: 7-13
  10. Haas N (1987) A simple vital-microscopic aid for the detection of the scabies mite. Z Hautkr 62: 1395-1398
  11. Hu S et al (2008) Treating scabies results. Arch Dermatol 144: 1638-1641
  12. Karre S et al (1997) Steroid-induced Scabies norvegica. dermatologist 48: 343-346
  13. Madan V et al (2001) Oral ivermectin in scabies patients: a comparison with 1% topical lindane lotion. J Dermatol 28: 481-484
  14. Müllegger RR et al (2010) Skin infections during pregnancy. dermatologist 61: 1034-1039
  15. Paasch U, Haustein UF (2001) Treatment of endemic scabies with allethrin, permethrin and ivermectin. Evaluation of a treatment strategy. dermatologist 52: 31-37
  16. Tzenow et al (1997) Oral treatment of scabies with ivermectin. Dermatologist 48: 2-4
  17. Walton S et al (2004) Acaricidal activity of melaleuca aternifolia (tea tree) oil. Arch Dermatol 140: 563-566

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