Scabies- skin infestation Flashcards
what causes scabies
by a mite called sarcoptes scabei var hominis
what is the reservoir of the mite
human
who does scabies affect (3)
affects all :
1. ages
2. races
3. socio-economic classes.
there is a high prevalence of scabies in who (2)
- children
- sexually active people
what increases the spread of scabies (2)
- overcrowded places (prison, schools, refugee camps)
- delayed treatment of primary cases
how is scabies transmitted (2)
- Directly
- by close contact, which must be prolonged
- sexual (is the frequent cause in adults) - Indirectly
- via fomites.
NB: infested people that do not have symptoms can still spread it
how long can female mites survive up to, off the host in tropical climates
55-67 hours
what is the pathogenesis of scabies (6)
- Complete life cycle of the mite is in the human epidermis.
- A female mite lays eggs which mature in 10 days.
- Usually only a few mites 8-15 live on an infested host.
- however there are thousands in crusted scabies - Symptoms due to delayed hypersensitivity reaction to the mite and/or eggs.
- First infection: symptoms take a minimum of 3-4 weeks
- Re-infection: 1 – 2 days.
how long can the eggs survive up to in cooler environment
10 days
what type of patients have a high source of infection
those with crusted scabies
what are clinical features of crusted scabies (2)
- dry scales and crusts
- mostly marked over bony prominences dorsum of the fingers , wrists and ears.
what findings can you see on exam (5)
- Papules
- pustules
- burrows.
- excoriations
- secondary super-infection
what things do you get from the history (2)
- Intense pruritus, worse at night.
- Close personal contacts/household members may report itch
what areas does scabies affect (12)
- hands (interdigital space of fingers and toes)
- wrists
- elbows
- genital area (scrotum)
- breasts/ nipple area
- waistline
- buttocks
- axilla
- lower legs
- ankles
- around belly button
- fingers
in children what areas does scabies affect (6)
- face
- scalp
- neck
- fingers
- palms of hands
- soles of feet
who do you find crusted scabies in (2)
- immuno-compromised people
- people with decreased sensory function e.g. leprosy, paraplegia.
what causes crusted scabies
superinfection with thousands of mites
which type of scabies is the most contagious
crusted scabies, because of the superinfection with thousands of mites
for the international alliance for the control of scabies (IACS) what is the the criteria for suspected scabies diagnosis (2)
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
for the international alliance for the control of scabies (IACS) what is the the criteria for clinical scabies diagnosis (3)
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
for the international alliance for the control of scabies (IACS) what is the criteria for confirmed scabies diagnosis (3)
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
what are post scabitiec nodules
itchy larger, nodules seen after scabies treatment due to hypersensitivity to dead mites, eggs or feces left in the skin
where are post scabetic nodules common
genital area
what do post scabetic nodules lack
burrows
