Scabies

Question 1

What is scabies?

Answer 1

“the itch”

• parasitic caused by arachnid mite SARCOTOPES SCABEI
• particular problem in developing world

Question 2

How can you catch scabies?

Pathology and spread?

Answer 2

Can come from pets eg dogs
Other family members (highly contagious)
Can be SEXUALLY transmitted

0.2-0.4mm size
Mites mate on skin surface, female burrows into skin to lay eggs, 10-15 days for eggs to mature
Live on skin for 4-6 weeks, move 2.5cm a minute

INCUBATION period of 6 weeks! During which time person is sensitised to might saliva and faeces, immune response and papules then appear.

Spread through shared bedding, towels, clothes (crusted scabies)

Can survive days without a host

Question 3

Presentation of scabies?

Complications?

Answer 3

• papular rash (abdomen, inner thigh, web spaces, flexor surface of wrist)
• itch worse at night

Complications:

• bacterial infection
• flare up of eczema and psoriasis

Question 4

Diagnosis of scabies?

Answer 4

Usually clinical.

If there is doubt then skin scrapings sent for MC+S will show:
- find a burrow, tease out a mite for miscroscopy. Or find eggs or faeces.

Question 5

What is crusted scabies?

Answer 5

also called Norweigen scabies, found in immunosuppressed.

• HIV lack of T-cells
• peripheral neuropathy and elderly may be affected
• 1000s of mites shed in flakes of skin
• rash is HYPERKERATOTIC and resembles psoriasis
• often secondary infection
• hard to treat
• generalised lympadenopathy

Question 6

Differential diagnosis in scabies?

Answer 6

• insect bites
• atopic dermatitis
• tinea
• impetigo
• psoriasis
• folliculitis
• lichen planus
• lots of other things with a red rash!

Question 7

Treatment of scabies?

Answer 7

need a parasitical agent eg PERMETHRIN

• treat all household and sexual contacts
• PERMETHRIN 5%, apply to affected area and wash of 8-12hrs later. Repeat every 7 days until cleared.
• some apply liberally, get under the nails
  (alternatives: malathion, crotamiton, ivermectin PO)
• children can return to SCHOOL day after first treatment

CLOTHES:

• wash clothes, bedding etc at >50C and tumble dry at >50C
• or seal in bags for 72 hrs to kill mites (especially in sun or heat)

ITCH:

• antihistamines eg PHENERGAN 10-25mg
• steroid cream
• emollients (keep in fridge)