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Medical dermatology Dan > Bites & Infestations Dan > Flashcards

Bites & Infestations Dan Flashcards

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USMLE® Step 1 flashcards Dermatology Board Prep flashcards
1
Q

T/F

Scabies is acquired from domestic dosg

A

False
dogs have different species
human scabies lives whole life in the epidermis
dog scabies cause itch in humans but do not establish infection

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2
Q

T/F

scabies is due to sarcoptes scabeii var hominis

A

True

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3
Q

How long do scabies mite survive off a human host?

A

ABTSI module says 56 hrs
Rook says 24-36
both agree depends on temp and humidity

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4
Q

T/F

scabies mites have 4 pairs of legs

A

True

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5
Q

T/F

The male scabies mite is larger than the female

A

False
female is larger and may see eggs and feaces associated with female mite
females rear 2 sets of legs are closer to the middle of the body, males are closer to the rear of the body

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6
Q

T/F

It takes 2-6 weeks after infestation for symptoms of scabies to appear

A

True
when symptomatic it is said the pt is sensitized - they are mounting a low level immune response against the mites resulting in the itch - immediate and delayed type hypersensitivity
Pts who develop crusted scabies are often not completely sensitized

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7
Q

T/F

A scabies mite lives for 2-3 months

A

False

4-6 weeks

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8
Q

T/F

A person will become itchy within 1-2 days of reinfested with scabies after previous sensitization

A

True

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9
Q

T/F

The scalp and face are commonly involved in scabies infestation

A

False

usually spared in adults but involved in children, elderly or immuncompromised

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10
Q

T/F

secondary staph infection is common in crusted scabies

A

True

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11
Q

T/F

KOH is helpful for identifying scabies on slides

A

False

mineral oil should be used

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12
Q

T/F

Pink pigtail like structures are a clue to the diagnosis of scabies on histology

A

True

thought to be empty egg shell cases or perhaps adult mite exoskeleton

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13
Q

What are Scybala?

A

scabies feaces pellets - round amorphous structures on histo

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14
Q

T/F

a pt with scabies infestation typically has hundreds of adult mites on them at any time

A

False
usually not many mites
hundreds present in crusted scabies

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15
Q

How is scabies treated in adults and children

A

Adults, kids over 2 months and preg and breastfeeding women should all be treated with lyclear 2 treatments
Kids under 2 months can be treated with 5% precipitated sulphur in WSP
In kids, elderly and immune suppressed must apply topicals to face and scalp, not just neck down

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16
Q

T/F

Nits and head lice are the same thing

A

False
although ‘Nits’ is often used to refer to head lice the nits are actually the eggs attached to the hairshaft
white nits are hatched eggs, brown nits are viable eggs

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17
Q

What is the organism responsible for head lice

A

Pediculus capitis

Infestation is called pediculois capitis

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18
Q

T/F

head lice have 8 legs

A

False

6 legs

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19
Q

T/F

girls get head lice more than boys

A

True

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20
Q

T/F

head lice are common amongst afro-caribbean kids

A

False

rare as dont like coarse curly hair

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21
Q

How are head lice identified?

A

Wet hair and apply conditioner to stun lice and allow comb to pass easily
comb hair with fine nit comb and wipe off on paper towel to look for lice and nits

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22
Q

What measures should be taken if head lice are suspected?

A

Make diagnosis
check all household members and close contacts
Notify school so other kids can be assessed
treat case and family members
hot wash pillow cases, wash or discard hair brushes etc
child can go to school if treatment started
Permethrin or malathion are Rx of choice + repeated combing
some lice are resistant to permethrin and even malathion
Ivermectin can be used in resistant cases - single dose usually works well

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23
Q

T/F

Body lice may be found in large numbers on human skin

A

False
usually live mainly in clothing esp in seams
esp affect homeless and people unable to wash or change their clothes for a long period

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24
Q

T/F

Body lice may transmit endemic typhus

A

True

also trench fever and relapsing fever

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25
Q

What is the organism responsible for body lice

A

Pediculus humanis var corporis

pediculus corporis

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26
Q

T/F

body lice are smaller than head lice

A

False
larger
otherwise look the same

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27
Q

what are the features of body lice infestation

pediculosis corporis

A

Very itchy papules or pinpoint red lesions esp on neck, shoulders, back and waist
may have LNs
may skin sores/ impetigo
see stains on clothes and sheets from blood and foeacal pellets

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28
Q

How is body lice managed?

A

incinerate clothes, sheets and towels
if not possible hot wash and machine dry then hot iron seams or leave in sealed plastic bag for 2 weeks before wearing again
alternative is to fumigate clothes with DDT, permethrin or malathion
good wash of body repeated regularly is usually sufficient
sometimes topical pediculicide is used in same way as for head lice but usually not necessary

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29
Q

what is the organism responsible for pubic lice?

A

pthirus pubis
(crab louse)
shorter, wider body than head/body lice, with 6 legs with hooks on ends of 4 of them - resemble crabs
about 1mm long

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30
Q

T/F

pubic lice usually affect at least 2 hairy regions and not always pubic area

A

True

can be perianal hair, beard, eyelashes or axillae

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31
Q

T/F

pubic lice are always spread by sexual contact

A

False

can be just close contact or from contaminated clothing or linen

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32
Q

T/F

women are affected by pubic lice less often than men

A

True

? due to less body hair

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33
Q

T/F

Lice usually cannot survive more than 36 hrs off a human host

A

True

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34
Q

T/F

pubic lice present with itch and both lice and nits may be seen on hair shafts typically near the base

A

True
can be erythema around follicles
rare blue-grey macules on trunk and thighs in chronic cases due to bites - macula cerulea

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35
Q

T/F
Pts with pubic lice should be treated with topical insecticide such as permethrin but pt with body lice usually only need treatment of their clothes and basic hygeine measures

A

True

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36
Q

T/F

Tungiasis occurs in C America, africa and asia due to jumping flea called Tunga penetrans

A

True
burrows into dermis then releases eggs then dies
presents with small black lesion which enlarges into nodule
can get secondary infection including tetanus and gangrene
self resolves or Rx w/ curette or topical ivermectin. Oral ivermectin not effective

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37
Q

T/F

Botfly infection is synonymous with cutaneous myiasis

A

True
is infestation of the skin by the larvae (maggots) of one of several species of fly in the family Diptera
e.g. human botfly (dermatobia hominis), Tumbu fly

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38
Q

T/F
botfly larvae infecting a wound is known as wound myiasis, and when the larvae invades intact skin causing a boil-like lesion it is called furuncular myiasis

A

True

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39
Q

T/F

botfly infestation is self limiting

A

True
but can be serious if close to nose, eyes, sinuses or on scalp
can treat with oral or topical ivermectin or suffocate larva with vaseline occlusion of air hole and remove with forceps when it emerges

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40
Q

T/F

Botfly larvae are easily removed when in the skin

A

False
have barbs and tapered body to prevent extraction
need to kill then remove or suffocate so it exits the burrow
e.g. LN2, curettage
or vaseline or steak occlusion

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41
Q

What is creeping myiasis?

A

Due to cattle or horse fly larvae in skin

like larva migrans but moves more slowly and persists longer

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42
Q

what disease are transmitted by mosquitos?

A 
malaria
filariasis
yellow fever
West Nile virus
dengue fever
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43
Q

T/F

exagerrated bite reaction with bullae or necrosis are associated with chronic EBV infection

A

True
Asian or Hispanic children and adolescents with chronic EBV infection and proliferation of EBV-carrying NK cells
In widespread or severe rcns consider HIV or CLL (eosinophilic dermatosis of haematological malignancy)

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44
Q

T/F

Animal fleas rarely bite humans

A

false
commonly do bite but dont cause established infestations
esp bite lower legs and feet/ankles
human fleas are very rare and most flea bites in humans are from domestic animal fleas

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45
Q

T/F

The human flea is called pulex irritans

A

true

occurs in high density low hygeine groups

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46
Q

what are the organisms known as bed bugs?

A

Cimex lectularius or C. hemipterus

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47
Q

T/F

bed bugs are most active at night

A

True
nocturnal
hide in cracks in floor, walls and mattress etc in day and come out at night to feed on blood by biting
adult mites only feed once a week

48
Q

T/F

bed bug bites appear immedietely after the bites have occured

A

False
bite and itch due to immune rcn to bug saliva
often take several days to appear

49
Q

T/F

If bed bugs are suspected professional pest control experts should be sought to examine and treat the home

A

True
the bugs do not live on people but in the surroundings such as parts of the mattress, bed frame, under furniture and in cracks in walls and floors
hot wash, tumble dry and steam clean linens and treat home thoroughly

50
Q

T/F

bed bugs live for 4-6 weeks

A 
False
take 4-6 wks to reach adult from egg
live for 4-6 months
Pass through 5 developmental stages (nymphs) to reach adulthood and need a blood meal each time to molt and progress to next stage
adult female lays up to 5 eggs per day
51
Q

what is stingose gel/spray?

A

aluminium sulphate
available OTC
neutralises bites and stings to relieve pain

52
Q

How do you get rid of bed bugs?

A

Need to treat the whole house with particular attention to the bed and bedroom or anywhere people sleep
mattresses are hard to treat and may need to be discarded or sealed in plastic for more than 13 months to ensure bugs are all dead
must pull apart bed and nearby furniture and search in cracks in walls and floor boards - vacuum all areas with hepa filtered vac and steam clean surfaces, cracks and carpets to kill bugs and eggs
treat with professional insecticide and repeat after 2 weeks
tea tree oil solution can be used as a spray insecticide on all carpets and surfaces and in cracks and crevices
should hot wash all linens and sheets then hot tumble dry and steam iron
repair crack in walls and skirting boards to eliminate hiding places

53
Q

T/F

bed bugs can transmit Hep B

A

True

consider this for an outbreak in a homeless shelter

54
Q

T/F

bed bugs can bite birds and animals as well as humans

A

True
these are not preferred but it is sensible to remove birds nests or other animal presence from the dwelling when trying to eradicate bed bugs

55
Q

How are bed bug bites treated?

A 
The same as any other insect bite/sting
do nothing
topical or oral antihistamine
topical aluminium sulphate gel/spray (stingose)
topical steroid
menthol or camphor preparations
56
Q

T/F

both fleas and bed bugs have 6 legs

A

True

57
Q

T/F

fleas survive off the host in cocoons and are alerted to the presence of an animal/human by the vibrations of foot steps

A

True

58
Q

how are pubic lice of the eyelashes treated?

A

apply WSP liberally BD for 8 days to suffocate lice then remove eggs with fine forceps - may need ophthalmologist to do this with slit lamp

59
Q

What is urticaria multiformis endemica?

A

Rarely seen severe skin eruption due to delayed hypersensitivity to bites from old world sandfly, phlebotomus papatasi
also called Harara
lesions look like papular urticaria, may be haemorrhagic bullae
can persist for months

60
Q

T/F sandlfys are found in the tropics and in the mediterranean and middle east and usually bite animals

A

True
Also in C and S America and southern Texas
and can transmit leishmoniasis or sandfly fever

61
Q

T/F

ticks are arachnids

A

True
have mouthparts, capitulum and unsegmented body
+ 4 pairs of legs
(larval stage have 3 pairs of legs)

62
Q

T/F

Argasids are hard ticks

A

False
Argasids are soft ticks
Ixodidae are hard ticks - have a dorsal chitinous shield

63
Q

T/F

adult Ixodidae ticks attach to host and feed for several days before detaching and searching for a new host

A

True
so can easily transmit disease
soft ticks feed at night for a few mins only

64
Q

T/F

The mouth parts of soft ticks can only be seen from below and the sexes are not easily distinguished

A

True

65
Q

T/F

Ixodes holocyclus is responsible for most human and animal tick bites in Australia

A

True
This is the australian paralysis tick and is most dense in a 20km wide band following the eastern australian coastline
causes an ascending flaccid paralysis due to a neurotoxin; animals and children affected more than adults - improves if tick removed promptly

66
Q

T/F

tick bites can cause marked local reactions

A

True
pruritic papular, nodular or vesiculobullous lesions
can be papular urticaria or local eczematous rcn
can be nodule with pseudolymphomatous histology or necrosis or granulomatous histo w/ fb giant cells

67
Q

T/F

ticks can be removed by grasping the body

A

False
likely to break off body and leave mouth parts behind
can use forceps to remove with mouthparts intact by grasping as close to skin surface as possible and pull directly up in single steady motion

68
Q

How is rickettsial disease treated?

A

Doxy 100mg daily for 7-10 days usually sufficient - if tick bite and rickettsial disease suspected can take serology and treat without waiting for result

69
Q

What organisms are transmitted by human bites?

A

staph, strep, anaerobes

70
Q

What organisms are transmited by marine animal bites?

A

Vibrio spp, aeromonas hydrophilia, pseudomonas spp

71
Q

T/F

arachnidism is the clinical syndrome that occurs from a spider bite

A

True

72
Q

T/F

Red back spiders are responsible for most spider bites requiring antivenom in Aus

A

True
Latrodectus hasseltii
lactodectrus spp are the widow spiders

73
Q

T/F

pressure-immobilization is recommended first aid for all spider bites suspected to be from a dangerous spider

A

True
splint limb to limit movement and wrap in crepe bandage - significantly reduces spread of toxin
should only remove when medical Rx is established
for all bites from large black spiders (could be funnel webs) and red backs

74
Q

T/F
lepidopterism is the clinical syndrome resulting from the hairs or spines of caterpillars, moths or butterflies on the skin

A

True
The spines often have barbs and venom
can cause immediate or delayed symptoms
can cause localised itch or urticated papules
can cause widespread urticria with perioccular or orofacial oedema, fever and malaise

75
Q

T/F

cellotape is useful to remove setae (hairs) of caterpillars from the skin

A

True

76
Q

T/F

Swimmers itch is due to sea lice

A

False
sea lice is another name for sea-bathers eruption
swimmers itch or schistosome cercarial dermatitis is due to contact with non-human schistosomes (free-swimming larvae) of certain parasitic flatworms whos usual host is a bird or animal
Cercariae are tadpole shaped larvae

77
Q

T/F

swimmers itch is most commonly acquired from fresh water

A

True
but there are salt water types
esp in summer in temperate climates including southern Aus

78
Q

T/F

swimmers itch mainly affects exposed parts of the body

A

True

as opposed to sea bathers eruption which mainly affects areas under the bathers or hairy areas

79
Q

What are the symptoms of swimmers itch?

A

get prickling sensation and urticarial lesions 30mins after contact mainly in exposed areas
develop severe pruritus 10-12hrs later
symptoms usually subside in 12 hrs if pt not sensitized
If sensitized;
24hrs after exposure get papulopustular rash, can be pain and swelling and lymphadenopthy, fever and headache
itch and rash often peak after 48 hrs then settle over 1-2 weeks

80
Q

T/F

swimmers itch can be avoided by swimming in clothing or with exposed skin covered with vaseline

A

True

81
Q

T/F swimmers it is self limiting and minimal Rx is usually required

A

True
aspirin for pain and swelling
hygeine measures to secondary bacterial infection
topical steroids if symptoms severe

82
Q

T/F

Biopsies are not helpful in the diagnosis of swimmers itch

A

False
spongiosis with collections of neuts and eos in epi is supportive of the diagnosis
if Bx taken within 48 hrs of exposure can see cercariae in outer epidermis = tadpole shaped larvae

83
Q

TF

nematocyst dermatitis is called sea bathers eruption

A

True

also called sea lice or marine dermatitis

84
Q

sea bathers eruption is due to the larval form of marine nematocysts

A

True

85
Q

T/F

sea bathers eruption only occurs after swimming in salt water

A

True

86
Q

T/F

In sea bather eruption there are itchy papules on the areas not covered by the swimsuit

A

False
mainly affects the covered areas
sea bathers eruption heppens under the bathers
as organisms trapped under the clothing
can occur elsewhere esp hairy areas as organisms become trapped in hair
can be weals as well as papules

87
Q

T/F

vigorous towelling after swimming in lakes or sea may prevent cercariae from penetrating the skin

A

True

should shower with swimwear removed after sea bathing to prevent sea bathers eruption

88
Q

T/F pts with a sea bathers eruption can get significant systemic symptoms

A

True
fever/chills, nausea, vomiting, diarrhoea, headache, weakness, malaise, muscle spasms
more common in kids or if previous episode so sensitized

89
Q

What are the treatments for sea bathers eruption?

A 
TCS, menthol, camphor
colloidal baths (bicarb or oatmeal to reduce itch)
antihistamines
may need pred if severe
manage secondary infection
90
Q

T/F

Most stings from jellyfish are caused by sea nettle type jellyfish

A

True

91
Q

T/F

Jellyfish stings are painful but rarely lethal

A

True
But need good first aid and emergency medical attention
immobilise affected area
try to identify jellyfish type if possible
may need antivenom

92
Q

T/F

A sting from a portuguese man of war is the most dangerous marine sting injury

A

False
is not very dangerous but extremely painful
contact with the tentacles causes sharp burning pain like an electric shock
a broken off tentacle continues to sting even after detached from the animal

93
Q

T/F

The australian box jellyfish is the most venemous marine animal

A

True
Chironex Fleckeri- not a true jellyfish
has a 4-sided body and tentacles 2-3m long
tentacles tear off and attach to the skin when it stings humans
causes severe local reactions and cause cardiac arrest within minutes

94
Q

T/F

Vinegar should immediately be applied to jelly fish stings to neutralise the venom

A

True

95
Q

T/F

jelly fish stings usually heal up quickly and completely

A

False
prone to necrosis and secondary infections
heal slowly

96
Q

T/F

The australian box jellyfish is also known as Irukandji

A

False
This is a tiny jellyfish the size of a thumbnail and is sometimes also called box jellyfish
It has a severe sting and has caused death. The symptoms of its sting are known as Iukandji syndrome

97
Q

What is Irukandji syndrome?

A

Due to sting from small Irukandji jellyfish
onset 30mins after sting
back pain, muscle cramps, sweating, goosebumps, headace, nausea, vomiting, palpitations
can develop severe HTN and can be fatal
often sting site is also extremely painful

98
Q

T/F

Only one species of demodex mite lives on humans

A

False
2 species;
D follicularum
D brevis

99
Q

T/F

demodex mites emerge from the hair follicle at night to mate

A

True

100
Q

T/F
D follicularum buries itself face down near the root of the eyelashes or brow hairs with the tail protruding from the follicular orifice

A

True
D Brevis lives inside the sebaceous glands of the face including glands associated with follicles and free Meibomian glands

101
Q

T/F

some clinical syndromes may result mainly from extensive demodex infestation and are known as primary demodicoses

A

True

102
Q

What are the primary demodicoses?

A

Spinulate demodicosis (ptyriasis follicularum)
Papulopustular demodicosis
Nodulocystic/conglobate demodicosis
Periorbital/ periauricular/ perioral demodicosis

103
Q

What are risk factors for demodicosis?

A 
Local or systemic immune suppression;
E.g;
HIV
leukaemia
TCS use
CRF
TCNI use
EGFR inhibitors
Phototherapy
104
Q

T/F

what are the features of Spinulate demodicosis (ptyriasis follicularum)?

A

white-yellow fine spiky change of the sebaceous hair follicles
ay be some subtle erythema

105
Q

How do demodex affect the eyes?

A

Can cause blepharitis, chalazia and rarely keratoconjuntivits

106
Q

T/F

Auricular demodicosis can cause otitis externa or myringitis

A

True

myringitis is acute vesicles on the TM

107
Q

What are the features of papulopustular (rosacea-like) demodicosis?

A

Can be primary or secondary
In both cases there is a papulopustular facial eruption
can be widespread or mainly periorbital, perioral or periauricular
In primary types there is no pre-existing dermatosis
In secondary type there is a pre-existing rash such as rosacea or perioral dermatitis

108
Q

What are the features of nodulocystic demodicosis?

A

Intense follicular inflammation due to demodex proliferation with suppurative folliculitis

109
Q

T/F

Primary demodicosis usually present later in life, especially in elderly and rarely before age 40

A

True

110
Q

T/F

primary demodicoses are follicle-bound and limited to the face

A

True

secondary demodecosis can occur on trunk as well as diffusely on the face and may be seen in younger adults

111
Q

T/F

primary demodicoses are very pruritic

A

False

rash is asymptomatic or mildly pruritic

112
Q

T/F
Absence of the classical features of rosacea including flushing and telys is important to distinguish primary demodicosis

A

True

113
Q

What are diagnostic criteria for primary demodicosis?

A

Absence of a pre-existing or concurrent dermatosis
Abnormal increase in mite colonization; >5 mites per cm squaed on biopsy
disease remits only after Rx with anti-demodex therapy (arachnicides/ acaricides) and not with anti-inflammatory antibiotics

114
Q

T/F

demodex mites are related to spiders

A

True

type of arachnid

115
Q

How are demodex mites treated?

A 
Can use oral ivermectin single dose - Rx of choice
topical options;
Ivermectin cream
permethrin cream
benzyl benzoate 10-25% lotion
Crotamiton/lindane/malathion
116
Q

T/F

Only female Phlebotomus sandflys bite animals including humans to get blood meal

A

True

Medical dermatology Dan (41 decks)

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