Sarcoptes scabiei: Difference between revisions
From IDWiki
Sarcoptes scabiei
mNo edit summary |
No edit summary |
||
(2 intermediate revisions by the same user not shown) | |||
Line 1: | Line 1: | ||
+ | ==Background== |
||
− | * A mite that causes '''scabies''' |
||
+ | *A mite that causes '''scabies''' |
||
− | == Microbiology == |
||
+ | ===Microbiology=== |
||
− | * Eight-legged mite |
||
− | * Lives on human skin, but can survive 24 hours on clothes and linens |
||
+ | *Eight-legged mite (arachnid) |
||
− | == Epidemiology == |
||
+ | *Lives on human skin, but can survive 24 hours on clothes and linens |
||
+ | ===Epidemiology=== |
||
− | * Transmitted by direct contact |
||
− | * In the case of crusted scabies, may also have transmission via fomites |
||
+ | *Transmitted by person-to-person direct contact |
||
− | == Management == |
||
+ | **They don't jump |
||
+ | **Transmission via unwashed bed sheets or heavily contaminated clothing |
||
+ | **Animal scabies ([[mange]]) can transiently infect humans |
||
+ | *Common worldwide |
||
+ | *More common in: |
||
+ | **Crowded conditions |
||
+ | **Institutional setting |
||
+ | **Children less than 2 years of age |
||
+ | ***School transmission unlikely given contact is not typically close enough |
||
+ | **Winter time in Northern hemisphere |
||
+ | **Periods of civil unrest |
||
+ | *In the case of crusted scabies, may also have transmission via fomites |
||
+ | === Pathophysiology === |
||
− | * 5% permethrin applied from hairline of neck down entire body, left for 12 hours, then washed off |
||
− | ** Must be reapplied on any areas (like hands) that are washed during the 12 hours |
||
− | * All clothes/beddings must either be washed in 50+ ºC water, or placed in a sealed plastic bag for 3 to 7 days |
||
− | * Household contacts should be treated as well |
||
+ | * Male and female crawl around on the skin and mate either on the skin or in a burrow |
||
+ | * Female, once fertiziled, burrows into epidermis and lays 2-3 eggs daily along the path of the burrow |
||
+ | ** Lays up to 20-25 eggs before she dies |
||
+ | ** Moults about every 5 days |
||
+ | * Eggs hatch into larvae in 3 to 4 days |
||
+ | * Mites can live off of human host for 24 to 36 hours (longer if cold) |
||
+ | |||
+ | == Clinical Manifestations == |
||
+ | |||
+ | === Classical Scabies === |
||
+ | |||
+ | * Low burden (5 to 15 mites) |
||
+ | * Only symptom is intense pruritis, which is caused by delayed type IV hypersensitivity reaction |
||
+ | ** Usually appears after after 4 to 6 weeks on first infection, but within 24 to 48 hours on repeat infestation |
||
+ | ** Often worse at night |
||
+ | * Can see burrows, but not always |
||
+ | ** Classically in webs of fingers |
||
+ | ** They can be subtle and atypical |
||
+ | |||
+ | === Crusted Scabies === |
||
+ | |||
+ | * Sometimes called Norwegian scabies |
||
+ | * Seen in cellular immunocompromise, including advanced [[HIV]], [[leprosy]], [[lymphoma]], and the elderly |
||
+ | * Starts as areas of erythema anywhere on the body (most commonly scalp, hands, and feet) |
||
+ | * Develops into crusted or scaly areas |
||
+ | * No or minimal itching, due to lack of cell-mediated hypersensitivity |
||
+ | * Heavy mite burden, with thousands |
||
+ | |||
+ | === Atypical Scabies === |
||
+ | |||
+ | * Scalp, seen in infants and young children |
||
+ | * More generalized lesions, in infants and children |
||
+ | * Nodular scabies (violacenous, pruritic nodules) |
||
+ | ** Typically on scrotum or genetalia, or breasts |
||
+ | |||
+ | == Differential Diagnosis == |
||
+ | |||
+ | * [[Eczema]] |
||
+ | * [[Tinea]] |
||
+ | * [[Atopic dermatitis]] or [[contact dermatitis]] |
||
+ | * [[Papular urticaria]] |
||
+ | * [[Seborrheic dermatitis]] |
||
+ | * [[Bullous pemphigoid]] |
||
+ | |||
+ | == Diagnosis == |
||
+ | |||
+ | * Usually made clinically |
||
+ | * If sending a skin scraping, use the leading edge of the burrow |
||
+ | |||
+ | ==Management== |
||
+ | |||
+ | *5% [[Is treated by::permethrin]] applied from hairline of neck down entire body, left for 12 hours, then washed off |
||
+ | **Must be reapplied on any areas (like hands) that are washed during the 12 hours |
||
+ | *For clinical failure or more extensive infestations, [[Is treated by::ivermectin]] 200 μg/kg, repeated once at day 14 |
||
+ | **Treatments are not ovacidal |
||
+ | *For crusted scabies, consider combination topical plus oral |
||
+ | **[[Permethrin]] applied daily for 7 days, repeated weekly for 2 weeks |
||
+ | **[[Ivermectin]] 200 μg/kg p.o. on day 1, 2, 8, 9, and 15; can be extended to include days 22 and 29 for severe cases |
||
+ | *Alternatives include lindane 1% lotion, benzyl benzoate 10-25%, and others |
||
+ | *Household management |
||
+ | **All clothes/beddings must either be washed in 50+ ºC water, ironed, dry-cleaned, or placed in a sealed plastic bag for 3 to 7 days |
||
+ | **Household contacts should be treated as well |
||
+ | *Itching may continue for 4 to 6 weeks due to the cell-mediated hypersensitivity reaction to dead mites and eggs |
||
+ | |||
+ | == Prevention == |
||
+ | |||
+ | === Infection Prevention and Control === |
||
+ | |||
+ | * For crusted scabies, strict contact precautions |
||
+ | * Contacts should be treated empirically, including family, patient care staff, etc. |
||
{{DISPLAYTITLE:''Sarcoptes scabiei''}} |
{{DISPLAYTITLE:''Sarcoptes scabiei''}} |
||
[[Category:Ectoparasites]] |
[[Category:Ectoparasites]] |
Latest revision as of 11:27, 15 May 2023
Background
- A mite that causes scabies
Microbiology
- Eight-legged mite (arachnid)
- Lives on human skin, but can survive 24 hours on clothes and linens
Epidemiology
- Transmitted by person-to-person direct contact
- They don't jump
- Transmission via unwashed bed sheets or heavily contaminated clothing
- Animal scabies (mange) can transiently infect humans
- Common worldwide
- More common in:
- Crowded conditions
- Institutional setting
- Children less than 2 years of age
- School transmission unlikely given contact is not typically close enough
- Winter time in Northern hemisphere
- Periods of civil unrest
- In the case of crusted scabies, may also have transmission via fomites
Pathophysiology
- Male and female crawl around on the skin and mate either on the skin or in a burrow
- Female, once fertiziled, burrows into epidermis and lays 2-3 eggs daily along the path of the burrow
- Lays up to 20-25 eggs before she dies
- Moults about every 5 days
- Eggs hatch into larvae in 3 to 4 days
- Mites can live off of human host for 24 to 36 hours (longer if cold)
Clinical Manifestations
Classical Scabies
- Low burden (5 to 15 mites)
- Only symptom is intense pruritis, which is caused by delayed type IV hypersensitivity reaction
- Usually appears after after 4 to 6 weeks on first infection, but within 24 to 48 hours on repeat infestation
- Often worse at night
- Can see burrows, but not always
- Classically in webs of fingers
- They can be subtle and atypical
Crusted Scabies
- Sometimes called Norwegian scabies
- Seen in cellular immunocompromise, including advanced HIV, leprosy, lymphoma, and the elderly
- Starts as areas of erythema anywhere on the body (most commonly scalp, hands, and feet)
- Develops into crusted or scaly areas
- No or minimal itching, due to lack of cell-mediated hypersensitivity
- Heavy mite burden, with thousands
Atypical Scabies
- Scalp, seen in infants and young children
- More generalized lesions, in infants and children
- Nodular scabies (violacenous, pruritic nodules)
- Typically on scrotum or genetalia, or breasts
Differential Diagnosis
- Eczema
- Tinea
- Atopic dermatitis or contact dermatitis
- Papular urticaria
- Seborrheic dermatitis
- Bullous pemphigoid
Diagnosis
- Usually made clinically
- If sending a skin scraping, use the leading edge of the burrow
Management
- 5% permethrin applied from hairline of neck down entire body, left for 12 hours, then washed off
- Must be reapplied on any areas (like hands) that are washed during the 12 hours
- For clinical failure or more extensive infestations, ivermectin 200 μg/kg, repeated once at day 14
- Treatments are not ovacidal
- For crusted scabies, consider combination topical plus oral
- Permethrin applied daily for 7 days, repeated weekly for 2 weeks
- Ivermectin 200 μg/kg p.o. on day 1, 2, 8, 9, and 15; can be extended to include days 22 and 29 for severe cases
- Alternatives include lindane 1% lotion, benzyl benzoate 10-25%, and others
- Household management
- All clothes/beddings must either be washed in 50+ ºC water, ironed, dry-cleaned, or placed in a sealed plastic bag for 3 to 7 days
- Household contacts should be treated as well
- Itching may continue for 4 to 6 weeks due to the cell-mediated hypersensitivity reaction to dead mites and eggs
Prevention
Infection Prevention and Control
- For crusted scabies, strict contact precautions
- Contacts should be treated empirically, including family, patient care staff, etc.