Scabies- skin infestation

Question 1

what causes scabies

Answer 1

by a mite called sarcoptes scabei var hominis

Question 2

what is the reservoir of the mite

Answer 2

human

Question 3

who does scabies affect (3)

Answer 3

affects all :
1. ages
2. races
3. socio-economic classes.

Question 4

there is a high prevalence of scabies in who (2)

Answer 4

1. children
2. sexually active people

Question 5

what increases the spread of scabies (2)

Answer 5

1. overcrowded places (prison, schools, refugee camps)
2. delayed treatment of primary cases

Question 6

how is scabies transmitted (2)

Answer 6

1. Directly
   - by close contact, which must be prolonged
   - sexual (is the frequent cause in adults)
2. Indirectly
   - via fomites.

NB: infested people that do not have symptoms can still spread it

Question 7

how long can female mites survive up to, off the host in tropical climates

Answer 7

55-67 hours

Question 8

what is the pathogenesis of scabies (6)

Answer 8

1. Complete life cycle of the mite is in the human epidermis.
2. A female mite lays eggs which mature in 10 days.
3. Usually only a few mites 8-15 live on an infested host.
   - however there are thousands in crusted scabies
4. Symptoms due to delayed hypersensitivity reaction to the mite and/or eggs.
5. First infection: symptoms take a minimum of 3-4 weeks
6. Re-infection: 1 – 2 days.

Question 8

how long can the eggs survive up to in cooler environment

Answer 8

10 days

Question 9

what type of patients have a high source of infection

Answer 9

those with crusted scabies

Question 10

what are clinical features of crusted scabies (2)

Answer 10

1. dry scales and crusts
2. mostly marked over bony prominences dorsum of the fingers , wrists and ears.

Question 10

what findings can you see on exam (5)

Answer 10

1. Papules
2. pustules
3. burrows.
4. excoriations
5. secondary super-infection

Question 10

what things do you get from the history (2)

Answer 10

1. Intense pruritus, worse at night.
2. Close personal contacts/household members may report itch

Question 11

what areas does scabies affect (12)

Answer 11

1. hands (interdigital space of fingers and toes)
2. wrists
3. elbows
4. genital area (scrotum)
5. breasts/ nipple area
6. waistline
7. buttocks
8. axilla
9. lower legs
10. ankles
11. around belly button
12. fingers

Question 11

in children what areas does scabies affect (6)

Answer 11

1. face
2. scalp
3. neck
4. fingers
5. palms of hands
6. soles of feet

Question 12

who do you find crusted scabies in (2)

Answer 12

1. immuno-compromised people
2. people with decreased sensory function e.g. leprosy, paraplegia.

Question 13

what causes crusted scabies

Answer 13

superinfection with thousands of mites

Question 14

which type of scabies is the most contagious

Answer 14

crusted scabies, because of the superinfection with thousands of mites

Question 14

for the international alliance for the control of scabies (IACS) what is the the criteria for suspected scabies diagnosis (2)

Answer 14

one criterion

C1
typical lesions affecting typical distribution along with one history feature
- either itch/ positive contact hx
C2
atypical lesions affecting atypical distribution along with 2 history features
- itch
- positive contact history

Question 15

for the international alliance for the control of scabies (IACS) what is the the criteria for clinical scabies diagnosis (3)

Answer 15

minimum fulfil one criterion

B1
scabies burrows
B2
typical lesions involving make genitalia
B3
typical lesions affecting typical distribution along with 2 history features:
- itch
- positive contact history

Question 15

for the international alliance for the control of scabies (IACS) what is the criteria for confirmed scabies diagnosis (3)

Answer 15

minimum fulfil one criterion

A1
mites, eggs, or feces depicted through light microscope on skin specimen
A2
mites, eggs, or feces visualized in vivo through high powered imaging device e.g. video dermoscopy
A3
mites identified in vivo through dermoscopy

Question 16

what are post scabitiec nodules

Answer 16

itchy larger, nodules seen after scabies treatment due to hypersensitivity to dead mites, eggs or feces left in the skin

Question 16

where are post scabetic nodules common

Answer 16

genital area

Question 17

what do post scabetic nodules lack

Answer 17

burrows

Question 18

what is the general management of scabies (4)

Answer 18

1. Treat all contacts and household members as the patient regardless of symptoms.
2. Identify and immediately treat crusted scabies patients.
3. Patients should be given specific instruction about use of the drugs.
4. All clothing used in the past week be stored unused for at least 10 days
   - NB washing in hot water and ironing clothes, though commonly advised, may be impractical, and little evidence available.

Question 19

what are complications of scabies (3)

Answer 19

1. Secondary infection with grp A streptococci which has lead to cases of post streptococcal glomerulonephritis, rheumatic fever.
2. Stigma
3. discrimination

Question 20

what are some medical treatments that can be used (3)

Answer 20

1. Benzyl Benzoate Emulsion (BBE)
2. permethrin 5%
   - is an expensive topical agent
3. oral ivermectin

Question 21

how should you use benzyl benzoate emulsion (BBE) (3)

Answer 21

1. Apply overnight for 3 consecutive days, then repeat cycle after 7 days (i.e 6 nights in 2 wks)
2. Irritating. For the first 30min – 1 hr
3. Dilute the 25 % emulsion in children and infants, even though this reduces efficacy.

Question 22

how do you treat crusted scabies (2)

Answer 22

1. Oral ivermectin 200μg/kg on day 1, repeat day 14.
2. Salicylic acid 10 % and emollients to shed scales.