Scabies

Aka: Scabies, Sarcoptes scabiei

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II. Epidemiology

  1. Most common in children under age 2 years
  2. Endemic to tropical areas
  3. Incidence: Affects 100-300 million persons per year (worldwide)

III. Risk Factors

  1. Young children
  2. Crowded living conditions (Nursing Homes, shelters)
  3. Poor hygiene
  4. Poor nutritional status
  5. Homelessness
  6. Dementia
  7. Sexually Transmitted Disease
  8. Immunocompromised
  9. Tropical region

IV. Pathophysiology

  1. Images
    1. scabiesMite.jpg
  2. Caused by mite infestation: Sarcoptes scabiei
  3. Life cycle of female mite (30 days)
    1. Male and female mite mate on skin and then male mite dies
    2. Female mite burrows into skin to lay eggs
      1. Lays 10 to 25 eggs over 4-6 weeks (1-3 eggs/day)
      2. Female dies after laying eggs
    3. Eggs hatch within 3-4 days
      1. Scabies larvae mature into adults in 14-17 days
    4. New mites cut through burrow to skin surface to begin cycle again
      1. Scabies mite can travel 2.5 cm/minute
      2. Mites cannot jump or fly
    5. Mites can live up to 3 days without a human host
    6. Mites can complete life cycle without host symptoms
  4. Transmission with any contact including with fomites
    1. Prolonged skin contact for at least 15-20 minutes (usually not a handshake)
      1. Exception: Hyperkeratotic Crusted Scabies can be transmitted with brief contact
      2. Hospitals and Nursing Homes
      3. Day cares
    2. Household contact
    3. Sexual contact
    4. Shared clothing or bedding
    5. Fomite transmission is rare
  5. No significant transmission from pets with Scabies (mange)
    1. Mite may be passed from pet (esp. dogs) but they do not survive
    2. Short-term itching may occur but resolves in days

V. Symptoms

  1. Severe, intense diffuse itch at incubation (Hypersensitivity Reaction to mite feces)
  2. Symptoms worse at night, interfering with sleep
    1. Few other pruritic dermatoses cause such intense night Pruritus
  3. Failure to Thrive in Infants
    1. Infants have worse course with diffuse involvement

VI. Signs

  1. Characteristics
    1. Onset or incubation
      1. Initial infestation: Symptoms occur 6-8 weeks after exposure (delayed Hypersensitivity Reaction)
      2. Subsequent infestation: Symptoms may occur within 2 days of exposure
    2. Initial: Tiny to small erythematous Papules (<5 mm)
    3. Next: Vesicles or Pustules may form
    4. Pathognomonic: Burrow (present in 10-20% of cases)
      1. May appear as short, Scaling, 1-10 mm long, wavy gray lines on surface of skin
        1. Marks the course of mite tunneling through Epidermis (typically Stratum Corneum)
        2. Most easily seen on web spaces, wrists and elbows
      2. Burrow Ink Test (BIT Test)
        1. Color burrows with magic marker and then washing the area
        2. Marker will infiltrate the burrows, and the burrows will be more evident
    5. Secondary to scratching
      1. Excoriations, crusts
      2. Secondary Skin Infections
    6. More intense inflammatory response in some cases
      1. Background erythema
      2. Deep Nodules
  2. Distribution
    1. Infants
      1. Vesicles, Pustules, bullae, erosions and ulcerations are more common in infants than Papules
      2. Pustules and vessicles on palms and soles
      3. Face and scalp involvement (not seen at other ages)
      4. Diffuse involvement may occur
      5. Pruritus may be absent
    2. Children and adults (especially flexor surfaces)
      1. Spares face and scalp
      2. Hands and wrists
        1. Digital web spaces
        2. Sides of fingers
        3. Volar wrist
        4. Lateral palm
      3. Axillae
      4. Elbow and Antecubital fossa
      5. Trunk (may appear as a diffuse erythematous rash as Hypersensitivity Reaction)
    3. Adults (includes sites for children above)
      1. Genitalia (including Scrotum and penis)
      2. Female Breast (especially areola)
      3. Gluteal crease
      4. Waistband
  3. Variant: Hyperkeratotic Crusted Scabies (Norwegian Scabies)
    1. Pathophysiology
      1. Very contagious
      2. Occurs in older, debilitated, Immunocompromised patients living in close quarters (e.g. Nursing Home)
      3. Infestations involve hundreds to more than a thousand mites (contrast with 10-15 typically)
    2. Symptoms
      1. Pruritus is paradoxically mild or absent despite the severity of the infestation
      2. Lack of inflammatory response
    3. Signs
      1. Thick (hyperkeratotic) crusted Plaques on hands and feet (especially palmar and plantar surfaces)
      2. Thick, dystrophic Fingernails and Toenails
      3. Red, Scaling lesions with generalized distribution may appear as Xerotic Eczema (Dry Skin)
      4. Scalp is often involved

VII. Diagnosis

  1. Precautions
    1. Scabies is misdiagnosed in 45% of cases (often when made without microscopy or Dermoscopy)
    2. Preferred diagnosis is based on identifying a mite, eggs or scybala
    3. Alternative diagnostic criteria (empiric treatment criteria)
      1. Pruritus AND
      2. Lesions typical of Scabies on at least two body sites OR other household members have Pruritus
      3. Page (2007) J Fam Pract 56(7): 570-2 [PubMed]
  2. Search for burrows holding gravid female mite
    1. Consider Burrow Ink Test (BIT Test) in signs as above
    2. Typical infestations involve 10-15 mites
    3. Often found on nipples, axillae, hands and genitalia
    4. Find newest lesions and least disturbed skin
    5. Check beneath finger nail edge
  3. Scrape Burrow or other lesions
    1. Technique
      1. Apply drop of Mineral Oil to skin burrow
      2. Scrape burrow longitudinally with #15 blade along length of burrow (avoid causing bleeding)
      3. Transfer the skin scraping with oil to a glass slide
    2. Microscopy under low power in oil for:
      1. Mite (female is 0.4 mm, male is 0.2 mm)
      2. Eggs
      3. Scybala (Mite feces)
    3. Potassium Hydroxide (KOH)
      1. Dissolves scybala
  4. Dermoscopy
    1. Fewer False Negatives than microscopy
  5. Skin Biopsy
    1. Consider in refractory cases in which the diagnosis is elusive

VIII. Differential Diagnosis

  1. See Pruritus
  2. Other cutaneous infestations
    1. Bed Bugs
    2. Lice
    3. Cutaneous Larva Migrans
  3. Miscellaneous conditions
    1. Atopic Dermatitis
    2. Contact Dermatitis
    3. Dermatitis Herpetiformis
    4. Lichen Planus
    5. Papular Urticaria
    6. Pityriasis Rosea
    7. Psoriasis
    8. Seborrhea
    9. Secondary Syphilis
    10. Superficial Folliculitis
    11. Impetigo
    12. Insect Bites
    13. Tinea Corporis

IX. Management

  1. General
    1. Treat all household contacts who sleep in same room
    2. Treat sexual partners for the last 2 months
    3. Environmental control measures (start on the morning after the treatment application)
      1. Wash in hot water (122-140 F or 50-60 C) and dry all clothing and bedding used in the last 48 hours
      2. Items that cannot be washed can be placed in a plastic bag for at least 1 week
      3. Vacuuming may be helpful
    4. Itching will persist up to 2-6 weeks after treatment
      1. Pruritus clears as skin sloughs mite debris
      2. See Pruritus Management for general measures
      3. Consider Pruritus Management after treatment
        1. Topical Corticosteroids (low to medium potency such as Triamcinolone)
        2. Oral Antihistamine (e.g. Benadryl, Atarax or Zyrtec)
        3. Oral Corticosteroids for 5-7 days (severe diffuse Pruritus)
  2. Body or Genital Scabies (follow links to agents below regarding usage)
    1. First Line
      1. Permethrin (Elimite) 5% cream
        1. Apply to all areas of body from neck down
          1. Apply to all cracks and crevices (including perineum)
          2. Infants (age<1 year old) and Immunocompromised should also apply to face and head
            1. Healthy adults and children >1 year old need not apply to face and head
          3. Leave on overnight for 8-14 hours
          4. Wash off in morning
        2. Reapply in one week
        3. Supply adults with 60 grams (30 grams per application)
        4. Two doses typically cost $25 in 2019
        5. May be used in infants over age 2 months
        6. Pregnancy Category B
    2. Second Line
      1. Ivermectin (Stremectol)
        1. Avoid in pregnancy and children under 15 kg (33 lb)
        2. May be used during Lactation
        3. Give 200 mcg/kg orally now and repeat in 7-14 days
          1. Adults will typically require 4-6 tablets per dose
          2. Total cost of 2 doses in 2019 is approximately $50
        4. Indications
          1. Patients unable to apply the cream (bed-ridden, institutionalized)
          2. Scabies refractory to Permethrin
          3. Generalized crusted Scabies
    3. Other agents
      1. Benzyl Benzoate 25%
        1. Available OTC
        2. In studies, applied daily for 3 days
        3. Adverse effects include mild stinging and burning Sensation
        4. Efficacy
          1. In one study, was found significantly more effective than 5% Permethrin
          2. Meyersburg (2024) Br J Dermatol 190(4): 486-91 [PubMed]
      2. Precipitated Sulfur in petrolatum or other ointment at 6% (compounded)
        1. Has been used in newborns, pregnancy, Lactation
        2. No safety or efficacy data available
        3. Applied head to toe
          1. Leave on 24 hours
          2. Repeat application daily for 3 days total
        4. Change bed linen as treatment is completed
        5. Stings!
      3. Crotamiton (Eurax) 10% cream
        1. Used in nodular Scabies or as an alternative to other agents
        2. Apply and leave on for 24 hours, then wash and reapply for up to 3-5 days
        3. Safe in pregnancy, Lactation and infants
        4. Efficacy: 50-70%
    4. Agents not recommended
      1. Permethrin 1% (OTC Nix Creme Rinse)
        1. Too low a concentration to be effective (use the 5% Permethrin instead)
      2. Lindane (Kwell, Gamma Benzene Hexachloride) 1% Lotion
        1. Avoid due to neurotoxicity (systemic absorption is 10 fold more than Permethrin)
        2. Higher risk with broken skin and young children
        3. Higher resistance rates than other agents
  3. Crusted Scabies (Norwegian Scabies)
    1. Environmental control measures
      1. See general measures as above
      2. Use barrier protection (gloves)
      3. Treat exposures
    2. Dual medication therapy
      1. Permethrin 5% cream daily to full body for 7 days, then twice weekly until cure AND
      2. Ivermectin 200 mcg/kg orally on days 1, 2, 8, 9, and 15

X. References

  1. DeClerck and Swadron in Herbert (2015) EM:Rap 15(10):18-19
  2. Marco (2013) Crit Dec in Emerg Med 27(1): 2-7
  3. Angel (2000) Pediatr Clin North Am 47(4):921-35 [PubMed]
  4. Finders (2004) Am Fam Physician 69(2):341-50 [PubMed]
  5. Gunning (2012) Am Fam Physician 86(6): 535-41 [PubMed]
  6. Potts (2001) Postgrad Med 110(1):57-64 [PubMed]
  7. Roos (2001) Drugs 61(8):1067-88 [PubMed]

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Related Studies

Ontology: Sarcoptes scabiei (C0036227)

Definition (MSH) A species of mite that causes SCABIES in humans and sarcoptic mange in other animals. Specific variants of S. scabiei exist for humans and animals, but many have the ability to cross species and cause disease.
Concepts Eukaryote (T204)
MSH D012520
SnomedCT 264427009, 67333007
LNC LP18000-7
English Sarcoptes scabiei, Sarcoptes scabieus, scabiei, Sarcoptes, scabieus, Sarcoptes, itch mites, itching mite, sarcoptes scabiei, scabiei sarcoptes, mites scabies, itch mite, scabies mite, Sarcoptes scabiei hominis (organism), Itch mite, Sarcoptic mange mite, Sarcoptes scabiei hominis, Scabies mite, Sarcoptes scabiei (organism), Sarcoptes scabiei, NOS
French Sarcopte de la gale, Sarcopte scabiei
Swedish Skabbkvalster
Czech Sarcoptes scabiei, zákožka svrabová
Finnish Syyhypunkki
Russian CHESOTOCHNYI KLESHCH, ЧЕСОТОЧНЫЙ КЛЕЩ
Polish Świerzbowiec drążący
Norwegian Skabbmidd, Sarcoptes scabiei
Spanish Sarcoptes scabiei (organismo), Sarcoptes scabiei, SAI, pica ácaro, sarcoptic ácaro de sarna, Sarcoptes scabiei
German Sarcoptes scabiei
Italian Sarcoptes scabiei
Dutch Acarus scabiei, Sarcoptes scabiei, Schurftmijt
Portuguese Sarcoptes scabiei
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Scabies (C0036262)

Definition (CHV) A contagious skin inflammation caused by the bite of the mite
Definition (MEDLINEPLUS)

Scabies is an itchy skin condition caused by the microscopic mite Sarcoptes scabei. It is common all over the world, and can affect anyone. Scabies spreads quickly in crowded conditions where there is frequent skin-to-skin contact between people. Hospitals, child-care centers, and nursing homes are examples. Scabies can easily infect sex partners and other household members. Sharing clothes, towels, and bedding can also spread scabies. You cannot get scabies from a pet. Pets get a different mite infection called mange.

Symptoms are

  • Pimple-like irritations or a rash
  • Intense itching, especially at night
  • Sores caused by scratching

Your health care provider diagnoses scabies by looking at the skin rash and finding burrows in the skin.

Several lotions are available to treat scabies. The infected person's clothes, bedding and towels should be washed in hot water and dried in a hot dryer. Treatment is also recommended for household members and sexual partners.

Centers for Disease Control and Prevention
Definition (MSHCZE) Parazitární kožní onemocnění vyvolané roztočem zákožkou svrabovou (Sarcoptes scabiei). Samička vrtá v kůži až několik milimetrů dlouhé chodbičky, v nichž klade vajíčka. Člověk se nakazí obv. nepřímo (např. ložním prádlem). Po inkubaci 2–6 týdnů se objeví silné svědění, které zesílí po ulehnutí (v teple). Na kůži se objevují červené pupínky (často dvojice – začátek a konec chodbičky), které se mohou druhotně infikovat. Časté je postižení meziprstních prostor, okolí pohlavních orgánů, kolen, podpaží aj. Nález u osob s dobrou hygienou však nemusí být takto typický. K léčbě se používají skabicidní přípravky (např. lindan), ev. magistraliter přípravky obsahující mj. síru. (cit. Velký lékařský slovník online, 2013 http://lekarske.slovniky.cz/ )
Definition (NCI) A contagious skin infection that is caused by the burrowing parasitic mite, sarcoptes scabiei, and is characterized by intense itching and small, raised red spots in the area of the mite burrows.
Definition (MSH) A contagious cutaneous inflammation caused by the bite of the mite SARCOPTES SCABIEI. It is characterized by pruritic papular eruptions and burrows and affects primarily the axillae, elbows, wrists, and genitalia, although it can spread to cover the entire body.
Concepts Disease or Syndrome (T047)
MSH D012532
ICD9 133.0
ICD10 B86
SnomedCT 266224002, 154422001, 187215008, 67172004, 128869009
English Scabies, scabies, scabies (diagnosis), Scabies [Disease/Finding], Infestation by Sarcoptes scabiei (disorder), Sarcoptic itch, Infestation by Sarcoptes scabiei var hominis (disorder), Infestation by Sarcoptes scabiei var hominis, Sarcoptes scabiei; acariasis, Sarcoptes scabiei; infestation, infestation; Sarcoptes scabiei, infestation; mites, scabic, infestation; scabies, acariasis; Sarcoptes scabiei, mites; infestation, scabic, scabies; infestation, Sarcoptes scabeii infestation, Scabies infestation, Infestation by Sarcoptes scabiei
Dutch Sarcoptes scabeii-infestatie, scabies, scabiesinfestatie, Sarcoptes scabiei; acariasis, Sarcoptes scabiei; infestatie, acariasis; Sarcoptes scabiei, infestatie; Sarcoptes scabiei, infestatie; mijten, schurft, infestatie; scabies, mijten; infestatie, schurft, scabies; infestatie, Scabies, Scabiretinopathie bijes
French Infestation par Sarcoptes scabeii, Gale, Psore, Scabiose
German Befall durch Sarcoptes scabeii, Skabies, Krätze
Italian Infestazione da Sarcoptes scabeii, Infestazione da scabbia, Scabbia
Portuguese Sarna, Infestão por Sarcoptes scabeii, Infestação por Sarcoptes scabiei, Escabiose
Spanish Sarna, Infestación por Sarcoptes scabeii, infestación por Sarcoptes scabiei (trastorno), infestación por Sarcoptes scabiei, Infección por Sarcoptes scabiei, sarna, sarna (trastorno), infestación por Sarcoptes scabiei, variedad hominis (trastorno), infestación por Sarcoptes scabiei, variedad hominis, prurito sarcóptico, prurito, Escabiosis
Japanese 疥癬寄生, 疥癬, ヒト疥癬感染, ｶｲｾﾝ, ﾋﾄｶｲｾﾝｶﾝｾﾝ, ｶｲｾﾝｷｾｲ
Swedish Skabb
Czech svrab, Infestace parazitem Sarcoptes scabiei, Svrab, Infestace svrabem, scabies, skabies
Finnish Syyhy
Russian CHESOTKA ZUDNEVAIA, CHESOTKA, ЧЕСОТКА, ЧЕСОТКА ЗУДНЕВАЯ
Korean 옴
Polish Świerzb
Hungarian scabies infestatio, Sarcoptes scabeii infestatio, scabies
Norwegian Skabb
Derived from the NIH UMLS (Unified Medical Language System)

Related Topics in Parasitic Infections

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