Scabies

Question 1

Cause of scabies

Answer 1

Sarcoptes scabeii vor hominis

Question 2

How long can burrows be seen on the stratum corneum?

Answer 2

4-6 weeks

Question 3

How soon can scabies penetrate the skin?

Answer 3

within 30 minutes of contact

Question 4

What is the life span of a scabies mite?

Answer 4

4-5 weeks

Question 5

How many eggs does a scabies mite lay per day?

Answer 5

1-3 eggs

Question 6

How long until the scabies eggs hatch and how long do the larvae take to develop?

Answer 6

Hatch after 3-4 days and develop over 10-15 days

Question 7

How is scabies transmitted?

Answer 7

Skin to skin
Fomites less common

Question 8

Scabies history features

Answer 8

Worse at night
Itching in close relations
Symmetrical symptoms

Question 9

What causes itching in scabies?

Answer 9

Host-mite interaction
Delayed type 4 sensitivity to the mite and its eggs/faeces

Question 10

What is the incubation period for scabies?

Answer 10

4-6 weeks
Quicker if re-infection (days) as already sensitised

Question 11

Where is spared in scabies

Answer 11

The back and head
Pilosebaceous follicles (scalp / beard)

Question 12

What is crusted scabies associated with?

Answer 12

Immunocompromise, leprosy, potent topical steroids, neurology which prevents scratching

Question 13

Why is crusted scabies more infectious?

Answer 13

Mites live on shed skin for 7 days
Mites can survive in nails as reservoir

Question 14

Diagnosis of scabies

Answer 14

Clinical - all other differentials less likely

Question 15

Definitive diagnosis of scabies

Answer 15

Visualisation of mite / egg or faeces (scybala) on microscopy

Question 16

How do you plate a skin scraping for scabies?

Answer 16

with 10% potassium hydroxide
or with mineral oil

Question 17

Scabies on dermatoscopy

Answer 17

Delta wing sign
Jet contrail sign
Mini triangle sign

Question 18

Scabies histology

Answer 18

eosinophils and lymphocytes in the dermis
pig tail shaped egg fragments in epidermis

Question 19

Clinical diagnosis of scabies

Answer 19

One of the following
1) Burrows (Burrow ink test)
2) Typical lesions on male genitals
3) Typical lesions and 2 x history features

Question 20

Scabies management (general advice)

Answer 20

Concurrent treatment with contacts
Wash linens at >50’ for at least 35 mins
or seal in bag for 4 days
or freeze <10’ for 5 hours
all on day of first permethrin application

Question 21

Scabies management (topical)

Answer 21

Permethrin 5% cream applied to whole body and left for 12 hours
Repeated 1-2 weeks later

Question 22

Scabies management (oral )

Answer 22

Ivermectin 200mcg/kg (round to nearest 3mg)
on day 1 + 8 (+15 if needed)
Max dose 120mg

Question 23

Scabies treatment (alternative topical)

Answer 23

Malathion applied on D1 and D8 for 24 hours
Benzy Benzoate 25% emulsion for 2 nights for 12 hours and on day 7

Question 24

Crusted scabies treatment

Answer 24

Ivermectin + topical agent
Thorough laundry and vacuuming of furnishings

Question 25

Follow up for scabies

Answer 25

4-6 weeks - check for new burrows

Question 26

Post scabies itch treatment

Answer 26

Emollients Crotamiton 10% cream Antihistamines Potent steroid (betametasone)

Question 27

PN for scabies

Answer 27

Partners and household members for last 2 months - treat all

Question 28

When to alert health protection in scabies?

Answer 28

2 linked cases in 8 weeks involving a closed setting e.g care home or prison