Scabies (3)

Question 1

What is it?

How is it transmitted?

Answer 1

➊ A highly contagious mite infestation of the epidermis, leading to an incredibly itch rash

➋ Usually through close skin contact, such as holding hands for a prolonged time or sex.

N.B. Spread via fomites (clothing, towels, etc.) is very uncommon as the mite perishes within hours of leaving the host.

N.B. It can’t be caught from animals as the organism causing it is different.

Question 2

How does it present?

What is a pathognomonic feature here?

Answer 2

➊ Itchy rash that is symmetrical, and mainly affects the hands, wrists, axillae, thighs, buttocks, waist, and soles of the feet. The head and neck are usually spared.
→ Itch - It occurs 4-6 wks after the initial infection (host is still infectious), is worse at night, and may persist for several weeks after treatment

➋ Burrows - Thread-like tracks, typically found in the web spaces of the fingers/toes.

Question 3

How is it diagnosed?

Answer 3

Think scabies in a pt with a new widespread itchy rash, especially if they report itchy close contacts. The diagnosis is typically clinical and most easily confirmed using dermoscopy.

Investigations include:
* Dermoscopy
* Skin scrapings
* Burrow ink test - shows a classical zig-zag line where the ink has tracked into a burrow
* Ectoparasite preparation

Question 4

What is the more serious version of scabies?
→ How does this differ from normal scabies?

Answer 4

Crusted Scabies - Extremely contagious and serious infestation with scabies in the immunocompromised

→ * Rather than individual spots and burrows, they have patches of red skin that turn into scaly plaques due to dense hyperkeratosis (often misdiagnosed as psoriasis)
* Pts don’t present with an itch as they can’t form an immune response to the infestation
* Transmitted a lot more easily e.g. brief handshake/hug
* Can be spread via fomites e.g. clothing, towels, etc.

Question 5

What is the 1st line medical management option?
→ How is this applied?
→ What is 2nd line?

What else is important to do?

Answer 5

➊ Permethrin cream
→ Applied to the whole body, and left on for 8-12 hrs before washing it off. Should be repeated a wk later to kill all the eggs that survived the first treatment.
→ Oral Ivermectin if difficult to treat or crusted scabies

➋ * All household and close contacts should also be treated, even if asymptomatic
* All clothes, bedclothes, towels and other materials in contact with scabies need to be washed at very high heat
* Thoroughly hoover carpets and furniture