A presentation on the cutaneous manifestations of scabies

1. Scabies
A. Awajo

2. Scabies
• Sarcoptes scabei var hominis: specific for humans
• Sarcoptes scabei var canis: animal mite, rarely causes infection in
humans
• Tramsmission
1. Acquired through direct, prolonged, skin-to-skin contact with an
infected person(i.e., same household).
2. Sexual contact.
3. ?Fomite ( infected clothing, bedding)

3. • Female lifespan 4–6 weeks; lays 40–50 eggs.
• Lays 3 eggs per day in tunnels; eggs hatchin 4 days. Burrow 2–3 mm
daily, usually at night, and lay eggs during the day.
• Hatched larvae migrate to skin surface and mature into adults.
• Males and females copulate. Gravid female burrows back under
stratum corneum; male falls off skin.

4. Epidemiology
• Estimated at 300 million cases/year worldwide.
• Epidemics ocured in 15 year cycles, latest 1960
• Children (often ≤5 years). Nodular scabies
more common in children.
• Young adults (body contact).
• Elderly and bedridden patients

5. Pathogenesis
• Hypersensitivity of both immediate and delayed types occurs in the
development of lesions other than burrows.
• First infestation: For pruritus to occur, sensitization to S. scabiei must
take place -takes several weeks to develop if 1st infestation.
• Reinfestation: After reinfestation, pruritus may occur within 24 h

6. Clinical features
Pruritic papular lesions- Intense, widespread, usually sparing head and
neck.
Lesions at Site of Infestation
• Intraepidermal Burrows-grey, slightly elevated
• Scabietic (Scabious) Nodule
• Hyperkeratosis/Crusting Psoriasiform
Hypersensitivity lesion:
• Small erythematous papules / papulovesicles
• Persistent nodular lesions (penis)
Secondary changes
• Pustules: due to secondary infection
• Eczematised : common infants, children

7. Sites
• Burrows – finger webs, sides of finger, flexural aspects of wrists, feet, male genitalia
• Hypersensitivity –
Excoriated papules,
papulovesicles
Infants: scalp, face,
palms, soles
Line Of Hebra

8. R.H., a 26 year old woman comes to see you with a seven week history
of a rash which is worse on her hands. It is extremely itchy, particularly at
night. She is worried that she could give “this itching” to her 4 year old
son

10. • Diagnosis of scabies is made by looking at the burrows or rash.
• Confirmation of diagnosis
Skin scraping papule/ pustule microscopy : mites, eggs, or feces

11. Treatment
TOPICAL
• 5% permethrin : apply for 8 hours on days 1 & 8
• 1% GBHC: apply for 8 hours on days 1 & 8
• 25% Benzyl benzoate: 3 application for 12 hourly
• 10% Crotamiton: apply for 8 hours on days 1,2,3 & 8
• 10% Precipated Sulphur: twice daily for 14 days; DOC in pregnancy
• 1% Lindane Solution-Apply only once. Wash off in 8 to 12 hours.
ORAL
• Ivermectin 200μg/kg body weight on day 1, 8 and 15

12. General principles
1. Apply to whole body below jaw line including genitals, soles, under
free edge of nails
2. Treat all family members simultaneously
3. Ordinary laundering of linen
4. Antihistamines: for 4-6 weeks
5. Persistent nodular lesion – topical steroid may be required

13. Norwegian scabies or crusted scabies
• Immunocomprised patients
• Mentally challenged
• The number of infesting mites may be >1 million.
C/F: widespread crusted, hyperkeratotic lesion
• Innumerable mites (hundreds)
• Very contagious
Treatment - Topical 5% permethrin or
topical 5% benzoyl benzoate
applied daily for seven days, then twice weekly until cure
Keratolytic creams on alternate days to scabicide
Oral ivermectin on days 1, 2, 8, 9, and 15
(add days 22, 29 if infestation is severe).

14. Animal scabies
• Mite - Sarcoptes Scabiei var Canis
• Transmission - Infected animal to human;
human to human transmission does not occur
• Source – horses, cattle, dogs, cats; (this infection in animals is called
Mange)
• C/F – small, pruritic papules “ temprorary”
no burrows
site - front of trunk,
medial aspect of upper extremities
• Treatment – antihistamines
• specific antiscabetic not required

15. THANK YOU