Sarcoptes scabiei: Difference between revisions

Latest revision as of 11:27, 15 May 2023

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

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)

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

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

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

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

For crusted scabies, strict contact precautions
Contacts should be treated empirically, including family, patient care staff, etc.

@@ Line 79: / Line 79: @@
 *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 crusted scabies, [[Is treated by::ivermectin]] 200 μg/kg, repeated once at day 14
+*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