Infectious Disease Compendium

Scabies

Microbiology

A mite, Sarcoptes scabiei var. hominis.

Epidemiologic Risks

Being human. Scabies is spread from person to person from contact. It cannot leap across the room.

Syndromes

Itchy itchy itchy. Severe infestation with chronic skin reaction is called Norwegian scabies, much to the eternal pride of the Norwegians.

From the 14th century: “I still have, and do not know how long it will torment me, a dry and ugly scabies.... Since five months ... this illness oppresses me so much that the hands are prevented to use the pen and to take the food, but they serve only to scratch and scrape it ... I certainly know only one thing about my illness, that it will soon leave me or I will leave it: we cannot be together for a long (PubMed). Sounds miserable.

Treatment

(NEJM review)

Regular scabies

Two applications — one on day 1 and one between day 8 and day 15 — of topical Permethrin 5%, applied in the evening and left on overnight

Can use 2 doses of po ivermectin (200 μg/kg/dose), taken with food — one on day 1 and one between day 8 and day 15.

Topical ivermectin is probably a better option, two applications a week apart (PubMed,Pubmed).

"A single dose of ivermectin provided a cure rate of 85.9% at a 2-week interval, which increased to 100% after crossing over to the Permethrin group at a 4-week interval. Twice application of Permethrin with a 1-week interval was effective in 92.5% of patients, which increased to 94.2% after crossing over to the ivermectin group at a 4-week interval. Permethrin-treated patients recovered earlier. Twice application of Permethrin with a 1-week interval is superior to a single dose of ivermectin (PubMed)."

Lindane (outpatient) 1% lotion; it is not recommended for pregnant women or very young children, apply to the entire skin and left on for 8 to 12 hours. Do not use immediately after a bath as this increases absorption and perhaps toxicity The treatment is repeated in 1 week.

Norwegian or crusted scabies

Both topical Permethrin 5% every 2 to 3 days for 1 to 2 weeks and oral ivermectin (200 μg/ kg/dose), taken with food, administered as three doses (days 1, 2, and 8), five doses (days 1, 2, 8, 9, and 15) or seven doses (days 1, 2, 8, 9, 15, 22, and 29), depending on severity of infection.

Topical benzyl benzoate 25% (with or without tea-tree oil 5%) instead of permethrin.

Notes

I itch just writing this. Can I get scabies from a computer? Treat all household contacts and clean all the clothes and bedding with hot water and hot dryer. In institutional outbreaks, need to treat all with skin to skin contact, which turns out to be everyone in the institution as you do not really know when the outbreak started. Everyone will freak and itch and demand therapy anyway. Trim the nails as the mites may hide under the nails.