Scabies

This page is about clinical aspects of the disease.  For microbiologic aspects of the causative organism(s), see Sarcoptes scabiei.

For patient information click here

WikiDoc Resources for Scabies
Articles
Most recent articles on Scabies Most cited articles on Scabies Review articles on Scabies Articles on Scabies in N Eng J Med, Lancet, BMJ
Media
Powerpoint slides on Scabies Images of Scabies Photos of Scabies Podcasts & MP3s on Scabies Videos on Scabies
Evidence Based Medicine
Cochrane Collaboration on Scabies Bandolier on Scabies TRIP on Scabies
Clinical Trials
Ongoing Trials on Scabies at Clinical Trials.gov Trial results on Scabies Clinical Trials on Scabies at Google
Guidelines / Policies / Govt
US National Guidelines Clearinghouse on Scabies NICE Guidance on Scabies NHS PRODIGY Guidance FDA on Scabies CDC on Scabies
Books
Books on Scabies
News
Scabies in the news Be alerted to news on Scabies News trends on Scabies
Commentary
Blogs on Scabies
Definitions
Definitions of Scabies
Patient Resources / Community
Patient resources on Scabies Discussion groups on Scabies Patient Handouts on Scabies Directions to Hospitals Treating Scabies Risk calculators and risk factors for Scabies
Healthcare Provider Resources
Symptoms of Scabies Causes & Risk Factors for Scabies Diagnostic studies for Scabies Treatment of Scabies
Continuing Medical Education (CME)
CME Programs on Scabies
International
Scabies en Espanol Scabies en Francais
Business
Scabies in the Marketplace Patents on Scabies
Experimental / Informatics
List of terms related to Scabies

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2], Dima Nimri, M.D. [3]

Synonyms and keywords: Norwegian scabies

Overview

Scabies is a skin infection caused by Sarcoptes scabiei and the mite is transmitted mostly by direct skin-to-skin contact. Scabies can be classified into 2 major types depending on the resultant skin lesions into typical scabies infestation and crusted (or Norwegian scabies). Crusted scabies is usually associated with an immunocompromised status. The characteristic symptoms of scabies is that of intense itching, which is worse at night and erythema of the skin. Examination reveals skin lesions of various sizes in certain areas of predilection, which include the webs of fingers and toes and wrists. With appropriate antimicrobial therapy, scabies has an excellent prognosis. Treatment must be initiated for patients and individuals with close contact with the patient, even if they are asymptomatic.

Historical Perspective

• In 1687, Giovan Cosimo Bonomo, an Italian physician, described the relationship between mites infestation and the resultant skin lesions.
• Cases of scabies have been described in literature as early as 1853.
• In the early days, the use of sulfur-containing products, whether in the form of baths, vapors or ointments was believed to be the treatment of choice for scabies.

Classification

Scabies can be divided into 2 major types depending on the resultant skin lesions:

Type of Scabies	Number of mites	Age Group	Associated Conditions	Characteristic Lesion	Areas of Predilection	Itching	Complications
Typical Infestation	Usually less than 100	Mostly children and adolescents	Patients are usually healthy	Papules, which can progress to vesicles and bullae	Webs of fingers and toes Wrists	Intense	Secondary bacterial infection of the skin and soft tissues
Crusted Scabies (Scabies Crustosa, Norwegian Scabies, Keratotic Scabies)	Typically thousands	Mostly elderly	Underlying immunosuppression: DM, HIV, HTLV-1, leukemia Patients with Down syndrome	Exfoliating scales and crusts, which can become warty	Scalp Hands and feet	Minimal or absent	Sepsis

Pathophysiology

Pathogenesis

Mode of Transmission

The most common mode of transmission of scabies is through direct skin-to-skin contact. However other methods of transmission include:

• Sexual transmission, especially among men who have sex with men
• Fomites and shared clothing are a rare source of transmission of scabies; however, cases are more likely to occur with crusted scabies, due to the higher burden of mites
• Cross infectivity from other mammals: this is a rare mode of transmission, however, cases of cross infectivity of humans from companion dogs were reported.

Mite Lifecycle and Pathogenesis

The following summarizes the lifecycle of the mite and the pathophysiology behind scabies infection:

• Away from the host, mites are viable for a period of 24-36 hours at a temperature of 21 C.
• Once the female mite comes in contact with human skin, it digs a small tunnel (i.e.: burrow) at a rate of 0.5-5.0 mm per day through the layers of the epidermis.
• A male mite searches for an unfertilized female, which lays 2-4 eggs per day and larvae hatches 2-4 days later. Larvae develop into adult mites 10-14 days later.
• The clinical presentation of intense itching, redness of the skin and the multiple skin lesions are due to a delayed type hypersensitivity reaction by the host immune system.

Microscopic Pathology

The histopathology of scabies consists of mites being surrounded by an inflammatory infiltrate of eosinophils, lymphocytes and histiocytes.

Associated Conditions

Crusted scabies may be associated with the following medical conditions:

• Down Syndrome
• Underlying immunosuppression, such as patients with:
  • Diabetes mellitus
  • HIV
  • HTLV-1
  • Leukemia

Causes

The cause of scabies infection is Sarcoptes scabiei. For more information about the causative organism, click here.

Differentiating Scabies from Other Diseases

Scabies must be differentiated from the following pathologies:

Disease	Skin Lesions	Areas of Predilection	Crusting	Itching	Age Group
Atopic dermatitis	Edematous, erythematous papules or plaques May exhibit vesicles and oozing	Scalp in children Face (especially cheeks and around the eyes) in children Skin creases and flexural areas in adults	—	✔	Usually children
Eczema	Edematous, erythematous papules or plaques May exhibit Vesicles and oozing	Depends on the type of eczema	✔	✔	No specific age group
Arthropod bites	Papules Plaques Nodules	—	—	✔	No specific age group
Tinea corporis	Annular, erythematous plaques with central clearing Can also vesicular or verrucous	Trunk Extremities	—	✔	No specific age group
SLE	Red, scaly patches	Mostly sun-exposed areas	—	—	Usually middle-aged adults
Bullous pemphigoid	Tense bullae	Flexural areas: Armpits Lower abdomen Upper thighs	✔	✔	Usually older adults
Langerhans cell histiocytosis	Papules Pustules Vesicles	Scalp Postauricular area Diaper area	✔	—	Mostly children aged 1-3, but can occur at any age
Urticaria pigmentosa	Hyperpigmentation: red and brown spots of various sizes	Chest Forehead	✔	✔	Mostly children
Seborrheic dermatitis	Erythematous plaques with greasy, yellowish scales	Sebum-rich areas: Face Scalp Central chest	✔	✔	Can occur at any age, but most commonly in infancy and adults 30 to 60 years of age
Psoriasis	Erythematous plaques with silvery scales	Scalp Postauricular area Umbilicus Extensor surfaces over bony prominences, such as elbows and knees	✔	✔	Bimodal age distribution: 20-30 and 50-60 years of age

Epidemiology and Demographics

Epidemiology

Prevalence

The following data exists on the prevalence of scabies around the world:

• The prevalence of scabies worldwide varies greatly; it ranges from 200 to 71,400 per 100,00 cases.
• All regions had a prevalence of more than 10,000 per 100,000 cases, except in Europe and the Middle East.
• It is estimated that there are 300 million cases of scabies worldwide.

Demographics

Age

Scabies is more common in children and adolescents than adults.

Region

• The Pacific and Latin America have the highest prevalence of scabies worldwide, while it is the lowest in Europe and the Middle East.

Risk Factors

The following are believed to be risk factors for scabies:

• Living in high-risk areas, such as Sub-Saharan Africa and indigenous communities in Australia and New Zealand
• Living in crowded areas
• Homeless or displaced children
• Poor hygiene: the role of poor hygiene in the development of scabies is uncertain, as mites burrowed under the skin remain alive even after daily hot baths and are usually resistant to water and soap
• Immunocompromised individuals, such as the elderly, malnourished and those with HIV, DM are at risk of developing Norwegian Scabies, which is the severe form

Screening

There are no screening recommendations for scabies.

Natural History, Complications and Prognosis

Natural History

If left untreated, scabies infection can lead to secondary bacterial infection of the skin and underlying soft tissue. These can have severe complications, such as sepsis, post-streptococcal glomerulonephritis and rheumatic heart disease, especially in an immunocompromised host.

Complications

Major complications of scabies include:

• Secondary bacterial infection of the skin and soft tissue, caused mainly by S. aureus and S. pyogenes, which include:
  • Impetigo
  • Skin abscess
  • Cellulitis
  • Necrotizing fasciitis
• Secondary bacterial infection of the skin and soft tissue can progress to life-threatening complications such as:
  • Septicemia
  • Post-streptococcal glomerulonephritis
  • Renal failure
  • Rheumatic heart disease

Prognosis

The prognosis of scabies is usually excellent. With prompt treatment with antimicrobial therapy, the infection and itching usually resolves within a matter of weeks.

Diagnosis

History and Symptoms

• In suspected cases of scabies, make sure to enquire about the following:
  • History of exposure to a known case of scabies or coming in close contact with patients with a similar complaint (mainly itching)
  • In the case of children, ask about daycare attendance
  • History of hospitalization
  • Recent travel history

• The main symptoms in patients with scabies include:
  • Intense itching, which is worse at night
  • Skin lesions, which are typically red and of few millimeters in size, found mostly on finger webs, wrists, elbows, axillae, buttocks and groin

Physical Examination

In patients with scabies, skin should be carefully examined to look for:

• Burrows: are the tunnels which the female mite penetrates into the skin. Initially, they are not clinically visible and can only be seen several days later, when the host immune system forms a local reaction around the tunnel. Burrows are characterized by short, wavy lines.
• Papules: they are usually small and erythematous. The distribution of the papules is variable; they can be sparse or very close to each other. Over the course of the infection, papules can transform into vesicles and/or bullae. Characteristic distribution of scabies usually involves the web spaces of fingers and toes, the wrists and areolae of breasts in females and penis in males. The back is usually spared, while face and neck involvement are usually only seen in infants and children.
• Excoriations: skin excoriations are commonly seen in patients with scabies, due to the intense itching associated with the infection.

Skin

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=415>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  Scabies (common location in ventral wrist)

Ears

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

Extremities

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=415>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=415>
  

Trunk

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

• 

  Norwegian scabies. http://www.atlasdermatologico.com.br/ Adapted from Dermatology Atlas.

Genitales

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

• 

  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=414>
  

Laboratory Findings

• Serologic testing for Sarcoptes scabiei has a very high sensitivity and specificity.
• Peripheral IgE levels are elevated in patients with Norwegian Scabies.

Other Diagnostic Studies

Light Microscopy

The gold standard for diagnosis of scabies infection is visualization of the ova, feces or the mite itself on light microscopy.

Skin Biopsy

Skin biopsy is another means for diagnosing scabies. Visualization of the mites in the stratum corneum layer of the skin confirms the diagnosis.

Treatment

Medical Therapy

Medical therapy in patients with scabies consists of antimicrobial therapy, mainly either with topical permethrin or oral ivermectin. Patients may experience worsening pruritus and erythema early during the administration of antimicrobial therapy. However, the parasite is gradually eliminated during the body's natural shedding process. The following summarizes the preferred antimicrobial regimens in the treatment of scabies:

• Antimicrobial therapy

• 1. Adult

• Preferred regimen (1): Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours;
• Preferred regimen (2): Ivermectin 200 ug/kg given orally, 4 times daily and repeated in 2 weeks as it has limited ovicidal activity;
• Preferred regimen (3): Ivermectin 1% lotion - applied to all areas of the body from the neck down and washed off after 8–14 hours; repeat treatment in 1 week if symptoms persist;
• Alternative regimen: Lindane (1%) 1 oz of lotion or 30 g of cream applied in a thin layer to all areas of the body from the neck down and thoroughly washed off after 8 hours

• Lindane is an alternative choice because of its toxicity. Lindane is not recommended for pregnant and breastfeeding women, children aged <10 years, and persons with extensive dermatitis. Seizures have occurred when lindane was applied after a bath or used by patients who had extensive dermatitis. Aplastic anemia after lindane use also has been reported. Resistance has also been reported.

• Note: Patients may experience worsening pruritus and erythema early during the administration of antimicrobial therapy

• 2. Infants and young children

• Preferred regimen: Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours;
• Note: Infants and young children aged< 10 years should not be treated with lindane.

• 3. Crusted Scabies

• Preferred regimen: (Topical scabicide topical Benzyl benzoate 25% OR topical Permethrin 5% cream (full-body application to be repeated daily for 7 days then twice weekly until discharge or cure) AND treatment with Ivermectin 200 ug/kg PO on days 1,2,8,9, and 15. Additional Ivermectin treatment on days 22 and 29 might be required for severe cases;

• 4.Pregnant or Lactating Women

• Preferred regimen: Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours.

Primary Prevention

One of the most important means of preventing scabies is to encourage good hygiene and advocate healthy living conditions away from crowded conditions.

Secondary Prevention

Once a patient has been diagnosed with scabies, it is empirical to begin treatment with the appropriate antimicrobial therapy to eradicate the infection and prevent re-infection. However, the following measures must also be followed:

• Treatment of individuals who come in close contact with the patient, even if they are asymptomatic
• Fomites, such as clothes, towels and bed linens, must be machine washed and dried at a high temperature (60 C)
• Insecticide may be used for items that cannot be washed