Transcript Slide 1

Infestations and Bites
Medical Student Core Curriculum
in Dermatology
Last updated August, 2011
1
Goals and Objectives
 The purpose of this module is to help medical students
develop a clinical approach to the evaluation and initial
management of patients presenting with bites and
infestations
 After completing this module, the learner will be able to:
•
•
•
•
Recognize risk factors for lice infestation and scabies
Identify nits and adult lice as diagnostic of pediculosis
Identify a burrow as the primary morphology of scabies
Identify common causes and clinical presentations of insect bite
reactions, with an emphasis on bedbugs and brown recluse spider
bites
• Discuss treatment options and patient education for pediculosis
capitis, scabies, and insect bite reactions
2
Case One
Mary Thompson
3
Case One: History
 HPI: Mary is a 6-year-old girl with a two week history of an
itchy scalp. It has not been relieved by over-the-counter
dandruff shampoo. She recently stayed over at her
cousin’s house who now has the same problem.
 PMH: no chronic illnesses or prior hospitalizations
 Allergies: no known allergies
 Medications: none
 Family history: noncontributory
 Social history: lives at home with parents and attends first
grade
 ROS: negative
4
Case One, Question 1
 What information is relevant in Mary’s
history?
a.
b.
c.
d.
Recent contact with similar complaint
Scalp pruritus (itching)
School-aged child
All of the above
5
Case One, Question 1
Answer: d
 What information is relevant in Mary’s
history?
a.
b.
c.
d.
Recent contact with similar complaint
Scalp pruritus
School-aged child
All of the above
6
Pediculosis (Lice): The Basics
 Three different varieties of lice may infest humans
• Head louse – Pediculus humanus var. capitis
• Body louse – Pediculus humanus var. corporis
• Pubic or crab louse – Phthirus pubis
 Head lice are spread by close physical contact
and may be transferred by use of head gear,
combs, brushes, and pillows
 Commonly affects school-age children
7
Pediculosis Capitis: The Basics
 Affects all ethnic and socioeconomic groups, but is less
common in African-Americans.
 Frequently has associated scalp pruritus and may also have
posterior cervical lymphadenopathy.
 Live adult lice and nits (ova or eggs) may be noted on
examination.
• Most common sites to find nits are the retroauricular and
occipital scalp.
• Nits within 0.6 cm of the scalp are typically viable. In warm
environments the distance may be greater.
• Nits must be distinguished from hair casts. Hair casts encircle
the hair shaft and move freely in contrast to the nit which is
cemented to the hair.
8
Back to
Case One
9
Skin Exam Findings
Exam of occipital scalp: Structures
on the hair are not freely movable
10
Case One, Question 2
 How would you describe Mary’s exam?
a. Multiple hair casts present in the occipital
scalp. No nits or lice noted.
b. Multiple nits present in the occipital scalp. No
lice noted.
c. Negative exam, no nits or lice noted.
11
Case One, Question 2
Answer: b
 How would you describe Mary’s exam?
a. Multiple hair casts present in the occipital
scalp. No nits or lice noted.
b. Multiple nits present in the occipital
scalp. No lice noted.
c. Negative exam, no nits or lice noted.
12
Skin Exam Findings
Exam of occipital scalp: numerous nits
13
Pediculosis: Pathogenesis
 Female adult lice live 30 days and lay 5-10 eggs (nits) per
day at the base of the hair where it meets the scalp.
 Eggs hatch in 8-12 days.
 Lice typically survive 1-2 days away from the scalp. Eggs
may survive up to 10 days away from the scalp.
 Live eggs remain close to the scalp to maintain warmth
and moisture but as the hair grows, the nits move off the
scalp with the hair.
 Because hair grows at a rate of ~ 1cm per month, the
duration of infestation can be estimated by the distance of
the nit from the scalp.
14
Pediculosis: Pathogenesis
 The adult louse at
the right typically is
2-3 mm in length.
 The presence of live
adult lice, immature
nymphs, and/or
viable eggs indicates
active infection.
15
Back to
Case One
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Follow-up
 Mary returns to clinic in four weeks for
follow-up. Therapy was completed as
directed but she still has nits present on
exam which are approximately one inch
from the scalp. A sample is on the slide
that follows.
17
Hair Mount
This image shows a nit
without an intact cap
(operculum) and is not
viable (no larva inside).
Continued presence of
nits does not always
represent treatment
failure.
18
Pediculosis: Treatment
 Physical removal of nits may be facilitated by
using a fine-toothed comb (or nit picker) on wet,
well-conditioned hair.
 Occlusive methods have also been used to
suffocate head lice using substances such as
petroleum jelly and mayonnaise, but study results
have been variable.
 Over-the-counter and prescription topical
therapies are listed on the following slide.
19
Pediculosis: Treatment
Therapy
Over-the counter
pyrethrins (natural
botanical)
1% permethrin lotion
Use
Risks
+resistance
Topically to clean, dry
hair for 10 minutes
Allergic reaction
(chrysanthemum,
ragweed, etc)
Other
Lotion, shampoo,
foam mousse,
cream rinse
(synthetic pyrethrin)
Topically to clean, dry
hair for 10 minutes
+resistance
Over age 2 months
5% permethrin cream
(synthetic pyrethrin)
Topically to clean, dry
hair overnight
+resistance
Over age 2 months
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0.5% malathion lotion
Topically to clean, dry
hair for 8-12 hours
Alcohol base is
flammable
Over age 6 years
Pediculosis: Treatment
 Individual patient risks should be assessed
prior to choosing a topical therapy (age,
allergy history, prior treatment, etc.).
 It is prudent to retreat with topical therapies
one week after initial therapy to kill the newly
hatched lice.
 Patients with refractory lice should be
referred to a dermatologist.
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Back to
Case One
22
Case One, Question 3
 If Mary had live lice in the scalp on follow-up,
what would be possible causes of treatment
failure?
a.
b.
c.
d.
e.
f.
Not treating contacts (reinfestation)
Not properly cleaning the environment
Not retreating in 7-10 days
Incorrect application of the medication
Resistance of the organism to medication
All of the above
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Case One, Question 3
Answer: f
 If Mary had live lice in the scalp on follow-up, what
would be possible causes of treatment failure?
a.
b.
c.
d.
e.
f.
Not treating contacts (reinfestation)
Not properly cleaning the environment
Not retreating in 7-10 days
Incorrect application of the medication
Resistance of the organism to medication
All of the above
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Pediculosis: Patient Education
 All persons living in the home should be
examined to avoid reinfestation.
• If it is not possible to examine household members,
treat without an exam if the treatment is not
contraindicated.
 Clothing and bedding should be washed and
dried on the hot cycle.
 Non-washable items may be placed in the dryer
or stored in a sealed plastic bag for two weeks.
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Pediculosis: Patient Education
 Combs and brushes should also be
washed in hot water and may be treated
with a pediculocide.
 Floors, furniture, and vehicles should be
vacuumed to remove hair with potentially
viable nits attached.
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Case Two
Michael Miller
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Case Two: History
 HPI: Mike is a 21-month-old boy who was referred
to the dermatology clinic for a rash that has been
present for two weeks. He has been having
problems sleeping due to itching.
 PMH: no history of major illness or hospitalizations
 Allergies: no known drug allergies
 Medications: none
 Family history: noncontributory
 Social history: lives in the city and attends day
care
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 ROS: pruritus
Case Two: Skin Exam
 Multiple
erythematous
papules throughout
the trunk, extremities.
Also involving the
scrotum.
 Burrows present in
the 2nd-3rd web space
on the right hand.
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Case Two, Question 1
 What in-office procedure would best help
to confirm the diagnosis?
a.
b.
c.
d.
KOH preparation
Nail clipping
Skin scraping (mineral oil prep)
Wood’s light examination
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Case Two, Question 1
Answer: c
 What in-office procedure would best help
to confirm the diagnosis?
a.
b.
c.
d.
KOH preparation
Nail clipping
Skin scraping (mineral oil prep)
Wood’s lamp examination
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Case Two, Question 2
 You perform a skin scraping on the patient
and see the image on the following slide
when you look through the microscope.
What is present on the slide?
a.
b.
c.
d.
Eggs
Scabies mite
Scybala (scabies feces)
All of the above
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Case Two, Question 2
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Case Two, Question 2
Answer: d
 You perform a skin scraping on the patient and
see the image on the following slide when you
look through the microscope. What is present
on the slide?
a.
b.
c.
d.
Eggs
Scabies mite
Scybala (scabies feces)
All of the above
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Case Two,
Question 2
mite
scybala (feces)
egg
35
Scabies: The Basics
 Sarcoptes scabiei (scabies) affects patients of all ages
and all socioeconomic classes, although more
common in women and children.
 Patients in congregated facilities are more prone to
the infestation, such as nursing homes.
 Most infections occur from direct contact with an
infected individual. However, fomites can transmit the
infection.
 Females lay about three eggs per day, which hatch in
four days. Most patients have less than 20 mites on
the skin at a time.
36
Scabies: The Basics
 The time from initial infestation to
symptoms is 3-4 weeks because
the rash is caused by
hypersensitivity to the mites.
 Papules may commonly involve
the breasts, umbilicus, penis,
scrotum, finger webs, wrists, and
axilla.
 The scalp and head are more
frequently involved in infants,
elderly, and immunosuppressed.
37
Case Two, Question 3
 Which of the following clinical findings are
considered pathognomonic for scabies?
a.
b.
c.
d.
Burrows
Diffuse involvement
Erythematous papules
Sparing of the groin
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Case Two, Question 3
Answer: a
 Which of the following clinical findings are
considered pathognomonic for scabies?
a.
b.
c.
d.
Burrows
Diffuse involvement
Erythematous papules
Sparing of the groin
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Scabies
 Burrows are linear
markings in the skin
due to the movement
of the mite. They are
1-10 mm in length and
may be found most
readily in the
interdigital spaces,
wrists, and elbows.
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Back to
Case Two
41
Case Two, Question 4
 Mike’s mother tells you his uncle has AIDS and
is currently hospitalized. Why is this important?
a. His uncle may have been the source of
infection
b. If his uncle has scabies, it could cause an
institutional outbreak
c. If his uncle gets scabies, it may be a more
severe form
d. All of the above
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Case Two, Question 4
Answer: d
 Mike’s mother tells you his uncle has AIDS and is
currently hospitalized. Why is this important?
a. His uncle may have been the source of infection
(Immunosuppressed patients are at increased risk for
infection)
b. If his uncle has scabies, it could cause an institutional
outbreak (Patients with crusted scabies harbor more mites)
c. If his uncle gets scabies, it may be a more severe form
(Immunosuppressed patients may develop crusted
scabies)
d. All of the above
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Crusted Scabies
Refer to the HIV
Dermatology
module for more
information on
crusted scabies
44
Scabies: Treatment
 As in pediculosis, scabies treatment
includes a two-pronged approach. The
patient and the environment must both be
treated.
 Environmental care includes washing all
clothing and linens in hot water, sealing
items which may not be washed in bags
for two weeks, and vacuuming.
45
Scabies: Treatment
Therapy
Use
Risks/Side effects
Other
5% permethrin
cream
Apply from the neck
down, leave on
overnight
Low, only 2% systemic
absorption. May burn
or sting on application.
First-line treatment in
patients over 2 months old.
Pregnancy category B
5-10% precipitated
sulfur
Apply for three days,
then wash off
Greasy, strong odor,
stains clothing
Safe in pregnancy and
children under 2 months.
Must be compounded
Diarrhea, itching, joint
pain, skin irritation
Most useful for
immunocompromised
patients or when topical
therapy is impractical
(outbreaks). Not
recommended for pregnant
or lactating women.
Oral Ivermectin
200mcg/kg by mouth,
repeat dose two
weeks later
For difficult to treat or severe scabies, refer to a dermatologist
Case Three
Mrs. Marsha Koehler
47
Case Three: History
 HPI: Mrs. Koehler is a 33-year-old woman who
presented to clinic with “itchy bumps” which started
over the weekend. No one else at home has a
similar complaint.
 PMH: GERD
 Allergies: none
 Medications: Omeprazole
 Family history: not contributory
 Social history: works in a diner as a waitress
 ROS: negative
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Case Three: Skin Exam
Edematous papules scattered over the body. Some
with signs of excoriation.
49
Case Three, Question 1
 What is the most likely diagnosis?
a.
b.
c.
d.
e.
Bedbug bites
Brown recluse spider bite
Chickenpox
Methicillin-resistant S. aureus folliculitis
Pediculosis corporis
50
Case Three, Question 1
Answer: a
 What is the most likely diagnosis?
a. Bedbug bites
b. Brown recluse spider bite (normally single site)
c. Chickenpox (presents as dewdrop on a rose petal
papules, vesicles, crusts in various stages more
common in children)
d. Methicillin-resistant S. aureus folliculitis (follicularbased, may be pustular)
e. Pediculosis corporis (body lice) (normally blue-colored
macules or excoriations are seen)
51
Bedbugs: The Basics
 Cimex lectularius (most common type) affect
people from all racial and socioeconomic
groups
 May be spread via clothing and bedding while
traveling, on mattresses, laundry, etc.
 Stay hidden during the day and feed at night
 Attracted to the warmth and carbon dioxide
emitted by the patient
 Bites may be multiple in a linear array
referred to as “breakfast, lunch, and dinner”
52
Bedbugs: Pathogenesis
 Typically have a blood meal every 3-5 days for
4-10 minutes
 Saliva keeps blood meal flowing due to:
• Nitrophorin, leading to vasodilation
• An anticoagulant which prevents conversion of
factor X to factor Xa
• Apyrase, leading to inhibition of platelet
aggregation
 May live over a year without feeding
53
Cimex lectularius
54
Back to
Case Three
55
Case Three, Question 2
 Which finding favors a diagnosis of bedbug
bites?
a.
b.
c.
d.
Flecks of blood or feces on the bed sheets
Nocturnal assault
Sweet, pungent odor in the room
All of the above
56
Case Three, Question 2
Answer: d
 Which finding favors a diagnosis of bedbug
bites?
a.
b.
c.
d.
Flecks of blood or feces on the bed sheets
Nocturnal assault
Sweet, pungent odor in the room
All of the above
57
Bedbugs: Treatment
 Bites will typically resolve within 1-2 weeks
 Symptomatic care may include topical.
antipruritics such as corticosteroids and/or
antibiotics (if secondary infection occurs).
 Bed linens should be laundered and
furniture vacuumed.
 A professional exterminator may be needed
to treat the home.
58
Insect Bites: Differential
Insect
Presentation
Characteristics
Risks
Flea (rat flea:
Xenopsylla
cheopis, X.
brasiliensis
cat flea:
Ctenocephalides
felis)
Linear or
clustered pruritic
papules. May be
bullous.
Frequently on
lower legs
Wingless. May
jump 18 cm
May transmit
disease such as
bubonic plague (rat
flea), endemic
typhus (cat flea)
Mosquito bites
Papular urticaria
typically
Males lack
mouthparts.
Females inflict
human bites
Pruritus, secondary
infection. May
transmit malaria,
Dengue fever, etc.
Other
Gypsy moth
Erythematous
caterpillar
papules in a
(Lymantria dispar) linear streak
Keratoconjunctivitis
and respiratory
symptoms from
airborne hairs
Hairs cause
clinical findings
Harvest mite
(chigger –
Trombicula)
Intense pruritus
hours after bites
Southern states
in U.S.
Erythematous
Less than 0.5 mm
macules, papules long, reddish
on waist, ankles,
folds
Case Four
Miss Stacey Dean
60
Case Four: History
 HPI: Miss Dean is a 23-year-old woman who
presented to clinic with a “painful bump” which
started yesterday in the evening. She was cleaning
out her attic earlier that day.
 PMH: Asthma
 Allergies: Penicillin
 Medications: Albuterol inhaler
 Family history: not contributory
 Social history: college student
 ROS: malaise
61
Case Four: Skin Exam
 Hemorrhagic bulla
with surrounding
ischemia and
peripheral erythema
62
Case Four, Question 1
 What is the most likely diagnosis?
a.
b.
c.
d.
Brown recluse spider bite
Ecthyma gangrenosum
MRSA infection
Snake bite
63
Case Four, Question 1
Answer: a
 What is the most likely diagnosis?
a.
b.
c.
d.
Brown recluse spider bite
Ecthyma gangrenosum
MRSA infection
Snake bite
64
Arachnid Bites: The Basics
 Only three genera of spiders found in the United
States have bites toxic to humans: Latrodectus,
Loxosceles, and Tegeneria.
 Approximately 12,500 spider bites were reported
to the American Association of Poison Control
Centers and zero deaths secondary to spider
bites in 2008.
 This module will review the characteristics of the
Loxosceles reclusa, or brown recluse spider.
65
Brown Recluse: The Basics
 Characteristic violinshaped dark brown
marking on the
cephalothorax seen at
the left
 Found in the Midwest
and Southeast
66
Brown Recluse: The Basics
 As noted by the name, the spider is typically
not aggressive, but is reclusive.
 Bites frequently occur when patients are
disturbing areas where the spiders seek
shelter (attics, closets, etc.) or putting on
clothing containing the spiders.
 Cardboard boxes may harbor the spiders as
the corrugated structure mimics their natural
habitat.
67
Back to
Case Four
68
Brown Recluse:
Clinical Presentation
This case shows the
characteristic
“Red (peripheral erythema),
White (blanching), and
Blue (central violaceous area)”
sign of the brown recluse bite.
69
Brown Recluse:
Clinical Presentation
 The initial wound may progress to necrosis and deep ulcer
formation.
70
Brown Recluse: Differential
History/Finding
MRSA Infection
Brown Recluse Bite
Insect seen
-
-/+
History of similar
occurrence
Common
Uncommon
Close personal contacts
affected
Common
Uncommon
Multiple areas affected on
exam
Common
Uncommon
Progression
Days to weeks
Hours to days
Red, white, and blue sign
-
+
Geographic location
Throughout the U.S.
Southeast and Midwest
(endemic areas)
MRSA infections may frequently be mistaken for spider bites. Pyoderma
gangrenosum and erythema migrans (Lyme disease) may be considered also.
71
Back to
Case Four
72
Case Four, Question 2
 What leads to tissue destruction in the
brown recluse bite?
a.
b.
c.
d.
Amylase
Keratolytics
Solenopsin D
Sphingomyelinase D
73
Case Four, Question 2
Answer: d
 What leads to tissue destruction in the
brown recluse bite?
a.
b.
c.
d.
Amylase
Keratolytics
Solenopsin D
Sphingomyelinase D
74
Brown Recluse: Complications
 Tissue necrosis may occur due to the
presence of multiple proteins in the venom.
 In addition, some patients may develop
systemic symptoms including malaise,
nausea, vomiting, etc.
 Uncommonly significant hemolysis, renal
failure, anemia, and/or hypotension may
occur.
75
Brown Recluse: Management
 Supportive care including cleansing
the wound, cold compresses, and
pain control is important.
 Multiple treatments have been
suggested, but not consistently
shown to be beneficial.
 The wound at right healed with
close monitoring, topical therapy
with antibiotic ointment, and
nonstick wound dressings without
requiring surgical debridement.
76
Take Home Points
 Pediculosis capitis commonly affects school-aged children.
 Nits and/or adult lice are diagnostic of pediculosis capitis.
 Pediculosis capitis therapy includes physical removal and overthe-counter or prescription topical therapy.
 Scabies affects all classes of patients, but those in group settings
or in an immunocompromised state are at increased risk of
infestation.
 The primary morphology of scabies is a burrow. Pruritic papules
and areas of crusting may be seen as well.
 The primary diagnostic test for scabies is the skin scraping, or
mineral oil prep.
 First-line treatment for scabies in patients over two months of age
who are not pregnant is permethrin 5% cream.
77
Take Home Points
 Bedbugs infest all populations. They typically feed at night.
 Bedbug bites cause edematous papules which are frequently
arranged in a “breakfast, lunch, and dinner” pattern.
 Insect bite reactions may be treated with topical corticosteroids and
antibiotics if indicated.
 Brown recluse spiders are only found in the Midwest and
Southeast. They have a characteristic violin-shaped marking on
their cephalothorax.
 MRSA infection is frequently misdiagnosed as brown recluse
spider bites.
 The primary therapy for a brown recluse spider bite is supportive
care.
78
Acknowledgements
 This module was developed by the American Academy of
Dermatology Medical Student Core Curriculum Workgroup from
2008-2012.
 Primary author: Jennifer Swearingen, MD.
 Peer reviewers: Susan K. Ailor, MD, FAAD; Cory A. Dunnick, MD,
FAAD, Timothy G. Berger, MD, FAAD.
 Revisions and editing: Jennifer Swearingen, MD; Sarah D.
Cipriano, MD, MPH; Jillian W. Wong. Last revised in August 2011.
 Thank you to Dr. Bahar Dasgeb, Dr. Steven Daveluy, Dr.
Stephanie Diamond,Dr. Dirk Elston, Dr. Darius Mehregan, Dr.
David Mehregan, and Dr. Robert Schoenfeld for their assistance
in obtaining images for the module.
79
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