Scabies & Parasitic Infestations

1. Scabies and
Parasitic Infestations
Vishnu
Alexander
Jayavanth
Sim Yee

2. Scabies

3. Aetiology
● Scabies is caused by the mite, Sarcoptes scabiei var. hominis, which burrows into
the upper layer of the skin - the stratum corneum.
● The female lays eggs in the tracks of the burrows. The eggs and mite proteins
produce an allergic reaction and this reaction, is responsible for the characteristic
itching and rash.
● Scabies is normally acquired from skin-to-skin contact with another individual who
has scabies.
● It is frequently acquired among children and can also be sexually transmitted.It is
sometimes transmitted from care providers or beddings.
● The incubation period for those without previous exposure to scabies is 2 to 6
weeks. Individuals who have been previously infested with scabies develop
symptoms within 1 to 5 days of re-exposure.

6. Pathogenesis
● Both immediate and delayed types hypersensitivity occurs In the
development of lesions.
● During first infestation, pruritus occurs after sensitization to S. scabiei
usually within 4 to 6 weeks.
● After reinfestation. pruritus may occur within 24 h.
● With hyperinfestation. patient are often immunocompromised or have
neurologic disorders.

7. Symptoms
● The main symptom is itch, which usually develops within 2 to 6 weeks after
infestation.
● The itch is generalized, very intense and intractable.
● The itch is worst at night.
● History of itch among family members within the same period.

8. Cutaneous Findings
1. Lesions occurring at the sites of mite infestation
2. Cutaneous manifestations of hypersensitivity to mites
3. Lesions secondary to chronic rubbing and scratching
4. Secondary infection
5. Hyperinfestation
6. Variants of scabies in special hosts: those with an atopic diathesis,
nodular scabies, scabies in infants/ small children, and scabies in the
elderly.

9. Cutaneous Findings
● Intraepidermal Burrows
○ Skin-colored ridges, 0.5 to 1 cm in length, either linear or serpiginous, with minute
vesicle or papule at end of tunnel.
○ Each infesting female mite produces one burrow.
○ Mites are about 0.5 mm in length. Burrows average 5 mm in length but may be up
to 10 cm.
○ Distribution: Areas with few or no hair follicles, usually where stratum corneum is
thin and soft:
■ the interdigital webs of the hands
■ wrists, palms and soles in infants
■ shaft of penis
■ elbows, feet, buttocks or axillae.
○ In infants, infestation may also occur on head and neck.

12. Cutaneous Findings
● Intraepidermal Burrows
○ Scabies with nodules 5 to 20 mm in
diameter red, pink, tan or brown in color,
smooth; burrow sometimes seen on the
surface of a very early lesion.
○ Distribution: Scrotum, penis, axillae,
waist, buttocks or areolae.
○ Resolve with post inflammatory
hyperpigmentation.
○ May be more apparent after treatment,
as eczematous eruption resolves.

13. Cutaneous Findings
● Scabies With Hyperinfestation
○ May begin as ordinary scabies.
○ In others, clinical appearance is of chronic eczema, psoriasiform dermatitis,
seborrheic dermatitis or erythroderma.
○ Lesions often markedly hyperkeratotic and/or crusted.
○ Warty dermatosis of the hands/feet with nail bed hyperkeratosis.
○ Erythematous scaling eruptions occur on the face, neck, scalp and trunk.
○ Affected persons have a characteristic odor.
○ Distribution: Generalized or localized.
■ In patients with neurologic deficit, hyperinfestation may occur only in an
affected limb. May be localized only to the scalp, face, finger, toenail
bed, or sole.

15. Investigations
● Microscopy
○ Use highest yield to identify mite is in
typical burrows on the finger webs,
flexor aspects of wrists, and penis.
○ A drop of mineral oil is placed over a
burrow, and the burrow is scraped off
with a curette or scalpel blade and
placed on a microscope slide.
○ Three findings are diagnostic of
scabies: S. scabiei mites, eggs, and
fecal pellets (scybala)

16. Investigations
● Dermapathology
○ Scabietic burrow: Located within stratum corneum; female
mite with eggs situated in blind end of burrow. Spongiosis
(epidermal edema) near mite with vesicle formation
common.
○ Dermis shows infiltrate with eosinophils.
○ Nodules: cause by dense chronic inflammatory
infiltrate with eosinophils.
○ Hyperinfestation: Thickened stratum corneum
riddled with innumerable mites

17. Complications

18. Course Management
● Often persists up to several
weeks after successful
eradication of mite infections
● Pruritus becomes symptomatic
within few days if reinfestation
occurs
● Certain patients can have
delusions of parasitosis
● For patients with hyper
infestations:
- impossible for eradication
- recurrence more likely to
relapse
● GOAL of treatment:
Treat infected individuals &
close physical contacts at the
same time
Recommended regimens
- Permethrin 5% cream applied
to all areas of body
- Lindane 1% lotion or cream
applied thinly to all areas of
the body from the neck (wash
off thoroughly after 8 hrs)
* Lindane is contraindicated in
pregnancy, lactating women,
children < 2 years

19. ○ Symptomatic treatment of pruritus
■ Oral antihistamines
■ Possible topical corticosteroid (e.g., hydrocortisone) if severe
○ All close contacts should receive prophylactic treatment.
● General measures
○ Wash all textiles (e.g., clothing and bedding) (day 1 & day 8 post-
treatment)
○ All contacts within the household should be treated for scabies
infestation even if asymptomatic

20. Pediculosis

21. Introduction
● Pediculosis is infestation
with the human head-
and-body louse,
● They are ectoparasites
whose only known hosts
are humans
Types of species
1. Pediculus humanus capitis (head
louse)
2. Pediculus humanus corporis
(body louse)
3. Pthirus pubis (pubic or crab
louse)

22. Pediculus humanus capitis (head louse)
● Lice lay nits within 1-2 mm of
scalp
● Hatches within 1 week
passing through nymphal
stages and maturing to
adults over a period of 1
week
● MOT: head-to-head contact,
shared hats, caps, brushes,
combs, pillows
Clinical manifestations
● Pruritus of back and sides of
scalp
● Several patients can exhibit
OCD or delusions of
parasitosis after eradication of
lice and nits
Skin lesions
- Due to bite reactions
- Reactions related to immune
sensitivity/tolerance

24. Laboratory
examinations Treatment
● Microscopy
- Nits 0.5mm ova, whitish eggs
- Nonviable nits show an
absence of an embryo or
openulum.
- Louse:
Insect with six legs, 1 to 2 mm
in length, wingless,
translucent grayish-white
body that is red when
engorged with blood.
TOPICALLY APPLIED
INSECTICIDES:
- Permethrin. malathion,
pyrethrin, ivermectin, and
spinosad.
SYSTEMIC
- Oral Ivermectin, levamisole,
and albendazole.

25. Pediculus corporis (body louse)
Epidemiology and etiology
Etiological agent: Pediculus Humanus Humanus. Nits incubate for 8 to 10 days, nymphs
mature to adults in 14 days
Habitat: live in seams of clothing. Can survive without blood for meal up to 3 days.
Attaches to body parts to feed.
Risk factors: poverty, war, natural disasters, indigence, homelessness and refugee
camp population
Body lice as vectors of disease: body lice also may transmit infectious agents while
feeding. (Bartonella quintana causing trench fever and endocarditis, Rickettsia
prowazekii causing epidemic typhus)

26. Clinical manifestation
Infestation
Lice and nits being found in clothing seams. Lice
grabs onto body hairs to feed.
Reaction to bites
Bite reactions such as papular urticarial similar to
those of head lice. Changes secondary to rubbing
and scratching include excoriation, eczema, lichen
simplex, infection with S.aureus, and post-
inflammatory hyperpigmentation. Scabies,
pediculosis capitis, and Pulex irritans (the human
flea) can coexist.

27. Differential diagnosis
- Atopic dermatitis
- Contact dermatitis
- Scabies
- Adverse cutaneous drug reactions
Diagnosis
Lice and eggs found in clothing seams
Treatment
- Decontamination of clothing and bedding
- Hygiene measures
- Delousing by pyrethrin, permethrin

28. Pediculosis
pubis

29. Etiology & Epidemiology
● Phthirius pubis, the crab or pubic louse.
● Size 0.8 to 1.2 mm.
● First pair of legs vestigial; other two clawed.
● Life span 14 days.
● Female lays 25 ova.
● Nits incubate for 7 days
● Nymphs mature over 14 days.
● Mobility: Adults can crawl 10 cm/day.
● Prefer a humid environment; tend not to wander.
● Infestation most common in young males.
● Transmission during close physical contact: Sharing bed.
○ May coexist with other sexually transmitted diseases.

30. Clinical Manifestation
1. Often Asymptomatic
○ Mild-to-moderate pruritus for months.
○ With excoriation and secondary infection, lesions may
become tender & be associated with enlarged regional

31. Clinical Manifestation
2. Infestation
○ Lice appear as 1- to 2-mm brownish-gray specks in hairy
areas involved.
○ Remain stationary for days;
■ mouth parts embedded in skin;
■ claws grasping a hair on either
side.
○ Usually few in number.
Crab louse (arrow) on the skin In the pubic region.

32. Clinical Manifestation
2. Infestation
○ Nits attached to hair appear as tiny white-gray specks
○ Few to numerous.
○ Eggs at hairskin junction indicate active infestation.
○ Infestation:
■ Most common in pubic and axillary areas;
■ Others: perineum, thighs. lower legs, trunk, &
periumbilical.
■ In children eyelashes & eyebrows may be infested without
pubic involvement.
■ Maculae coeruleae most common on lower abdominal
wall. buttocks, & upper thlghs.

33. Clinical Manifestation
Crab lice (arrows) and nits on
the upper eyelashes of a 10-
year-old child; this was the
only site of infestation.

34. Clinical Manifestation
3. Skin lesions
○ Papular urticaria (small erythematous papules) at sites of
feeding, especially periumbilical
○ Changes secondary to rubbing lichenification & excoriations
○ Secondary S. aureus infection.
○ Maculae coeruleae (taches bleues) are slate-gray or bluish-
gray macules around 0.5 to 1 cm in diameter, non-blanching.
○ Result from crab louse bites.
○ With eyelid infestation, serous crusts may be present along
with lice & nits; occasionally, edema of eyelids with severe
infestation
○ With secondary impetiginization, regional lymphadenopathy.

35. Clinical Manifestation
Papular urticaria: A 25-year-old with pruritus.
Multiple inflammatory papules at sites of crab
lice bites on the abdomen and the inner aspects
of the thighs.
Maculae ceruleae are the blue spots
in the thigh. They are thought to be
secondary to anticoagulant activity
of louse saliva.

36. Differential Diagnosis
● Atopic dermatitis
● Seborrheic dermatitis
● Tinea cruris
● Molluscum contagiosum
● Scabies
These disorders may coexist with crab louse infestation.

37. Diagnosis
● Demonstration of live adult lice, nymphs, or nits in the pubic area
to diagnose active infestation.
● Because of the strong association between the presence of pubic
lice and sexually transmitted infections (STIs), affected people
require investigation for other STIs.
Course
● Treatment is usually effective.
● Reinfestation can occur.
● Retreatment may be necessary if lice are found or if eggs are
observed at the hair-skin junction.

38. Treatment
● Topically applied insecticides
○ Permethrin, malathion, pyrethrin, ivermectin, & spinosad.
● Systemic
○ Oral ivermectin, levamisole & albendazole.
● Removing nits with comb dipped in vinegar
● Decontaminate bedding and clothing
○ Wash in hot water kills the lice
● Treat sex partners.
○ Sexual contact should be avoided until all partners are
better.
● Eyes:
○ Lice can be removed with forceps or by removing or trimming
the lashes.
○ Eyelashes may be treated with a gentle petroleum jelly for

39. Thankyou