SCABIES & PEDICULOSIS

INFESTATION

Infestation is the presence of animal parasites on or in the body, is common in tropical countries and less so in temperate ones.

Infestations fall into two main groups:

1 those caused by arthropods; and

2 those caused by worms.

MECHANISMS OF SKIN INJURY BY ARTHROPODS

Mechanical traumaInjection of irritant, cytotoxic or pharmacologically active substances

Injection of potential allergens Invasion of the host's tissuesReactions to retained mouthparts

Secondary infection

HISTORY

2500 yrs Sarcoptes scabiei is derived from the

Greek words sarx (the flesh) koptein (to smite or cut) and

the Latin scabere (to scratch). first ascribed to the mite by Giovan

Cosimo Bonomo in 1687. Over 300 million people worldwide

are infected

EPIDEMOLOGY

women & children

urban areas,

winter Prevalence 4 – 100%

TRANSMISSION

directly by close personal contact, sexual or

indirectly via fomites

factorsovercrowding,delayed treatment of primary

cases, and public awareness

highly host-specific an arthropod a member of the

class Arachnida, subclass Acari, order Astigmata, and family Sarcoptidae.

Too small to be seen by the naked eyeAdult female measures ~

0.4 - 0.3 mm, & the smaller male 0.2 - O.15

mm

body is creamy white & is marked by transverse corrugations,

ovoid

four-pairs of legs - anterior two pairs end in elongated

peduncles tipped with small suckers, In the female, the rear two pairs of legs

end in long bristles, whereas in the male bristles are present on the third pair and peduncles with suckers on the fourth.

crawl at a rate of 2.5 cm/min, burrow through the stratum corneum at the rate of about 2 mm per day(0.5 - 5 mm/day)

At temperatures below 20°C, S scabiei are immobile, although they can survive

number - <20 & with crusted scabies can be thousands to millions

live mites can survive for up to a week in the environment, feeding on the sloughed stratum corneum

cannot fly or jump

PATHOGENESIS

F (within 20 min) burrows into the stratum corneum (traverses at a rate of 0.5 - 5 mm/day)

avoid areas with a high density of pilosebaceous follicles

Mating takes place once, and the female is fertile for the rest of her life (1 mo),

Copulation in a small burrow---------the male, falls off the skin & perishes--------- Fertilized female enlarges the burrow using proteolytic enzymes to dissolve the stratum corneum of the epidermis ----- begins egg laying (3 eggs a day each)

Six-legged larvae emerge from the eggs after 3-4 days

90% of the hatched mites die

Escape from the burrow by cutting through its roof------then dig short burrows called moulting pouches & transform into nymphs-------------After further moult into larger nymphs , adult males and females develop(in 2-3 weeks)

CLINICAL FEATURES IP- 2-6 weeks immediate symptoms –in re infection

Triad`sPruritic papular lesions, Excoriations, andBurrowsSite- The circle of Hebra ~ an

imaginary circle intersecting the main sites of involvement - axillae, elbow flexures, wrists & hands, & crotch

CONT...... Pruritis

○ accentuate at night & exacerbated by a hot bath or shower

Primary lesions of scabies - burrows, papules, pustules,

nodules, occasionally urticarial papules and plaques

interdigital webbing of the hands,

flexural aspect of the wrists, behind the ears, axilla, waist, ankles, feet, buttocks & belt area

penile & scrotal in men, areola, nipples & genital area in women

DISTRIBUTION OF LESIONS

In very young children, infants, elderly and immunocompromised hosts, a widespread eczematous eruption primarily on the trunk is common , scalp & face can also be affected.

CONTD... P/E The burrow

pathognomonic sign and represent the intraepidermal tunnel created by the moving female mite. a 1-10 mm tunnel serpiginous, greyish-white thread-like elevations

At the end of it a vesicle/pustule containing

the mite may be noted, especially in infants & children

at entry, slight scale

In infants, commonly located on the palms & soles : F

To identify burrows quickly: apply a drop of India ink or gentian violet to the infested area, remove it with alcohol Thin threadlike burrows retain the ink

CONTD... Erythematous Papules & Vesicles (filled

with serous fluid) rarely contain mites and most likely are due to a hypersensitivity reactionPapules= on the shaft of the penis &

scrotum in men & on nipples in women

Vesicles= on the palms & soles

Animal Scabies: Zoonotic scabiesaffect humans who come in close contact

with the animalincubation period is shorter, the symptoms

are transientusually manifests with vesicles & papules

with atypical distributionBurrows are usually absentruns a self-limited course, require no

treatment Mites from animals are not a source of

human infestation, but they can produce bite reactions

Asymptomatic infestationnot uncommon considered ‘carriers’

SECONDARY SCABIES LESIONS

With rubbing- secondary infection, - the host immune response against the mites and their products.

Excoriations, Lichenification, widespread eczema, honey-colored crusting, postinflammatory hyperpigmentation, erythroderma, and frank pyoderma

DDX

Atopic dermatitis Insect bites Contact dermtitis Autosensitization ('id' reaction)

Drug eruptions PPE

VARIANTSVARIANTS

Nodular scabies in 7-10% of patients with active scabies Pink, tan, brown, or dull red nodules (2-20 mms)

May or may not itch Persist on the scrotum, penis, and vulva and In neonates unable to scratch, pinkish-brown nodules

may develop usually sterile

Intralesional steroids, tar, or excision are methods of treatment

DDXNODULAR SCABIES

Papular urticaria (insect bites)

Prurigo nodularis

Secondary syphilis

BULLOUS SCABIES

Mimics BP both clinically & histologically (contain many eosinophils)

Vesicles and bullae-, particularly on the palms & fingers

Immunofluorescent

In immunocompromised / debilitated patients, including those with: neurologic disorders, Down syndrome,

organ transplants, graft-versus-host disease, adult T-cell leukemia, leprosy, or AIDS and institutionalized populations

Risk factors for profound infestation -an inability to mount an immune

response, perceive pruritis, and/or physically scratch the skin

Crusted scabies (Norwegian/hyperkeratotic scabies)

* marked thickening and crusting of the skin.

* Hyperkeratotic, crusted/scaling lesions teem with mites

* large areas with prominent scalp lesions,

hands and arms are usual locations * Swollen & crusted finger tips;

& dystrophic nails * Pruritis- minimal/absent

CONTD...The rest of the skin usually appears

diffusely xerotichighly contagiousSevere fissuring & scaling of the

genitalia & buttocks may be presentOral agent should be used in

conjunction with a topical agent

DDXCRUSTED SCABIES

Psoriasis

Seborrheic dermatitis

COMPLICATIONS

Secondary impetiginization

Lymphangitis & septicemia ~ particularly in crusted scabies

Post-streptococcal glomerulonephritis

'post-scabietic pruritus‘ represent the body's response to dead mites that

are eventually sloughed off (within 4 wks) along with natural epidermal exfoliation

Tx- antihistamines or a short course of topical or oral corticosteroids

SCABIES AND HIV frequent unusual features head and neck occur with minimal or no

pruritis but with an extensive papulosquamous eruption( i.e.,hyperkeratotic,

Crusted scabies- soles - should arouse suspicion

of underline HIV difficult to eradicate Oral ivermectin (200

1Micg/kg weekly) is the most effective

DIAGNOSIS

Mainly clinicalPruritus with typical lesions & distributionContact Hx

Microscope

○ Skin scrapings obtained from the finger webs, wrists, or ankles is most likely to be positive

○ In Norwegian scabies, scraping of the thick scales will often yield several viable mites(100)

○ Excoriated lesions are often negative

Dermoscopy PCR Biopsy

CONTD...

H/pH/p A patchy to diffuse infiltrate with

eosinophils is noted in the reticular dermis

On transection, a scabies mite may occasionally be seen within the epidermis

fragments of the adult mite exoskeleton

serve as a clue to the Dx when mites, scybala or eggs are not identified

TREATMENT

Age cost severity ? previous treatment status

In infants with extensive involvement, several re treatments a week apart occasionally be required

second application of topical medication.......

Treat simultaneously all household contacts (even with no symptoms)

CONTD...

MEDICATIONS 1) 1) Permethrin

5% cream applied for 8 -14 hrs

standard first line topical scabicide

MoA= produce nerve paralysis & death in ectoparasites by causing delayed repolarization by disrupting Na+ current~ ovicidal

2) Benzyl benzoate(BBL)

Derivatives of balsam of peru 12.5% & 25% emulsion

lotion overnight application for three consecutive nights or left to the skin for 48hrs

MOA= ?kills the adult scabies mite with yet unclear action

exerts toxic effects on the nervous system of the parasite, resulting toxic to mite ova, though its exact mechanism of action is unknown.

CONTD...

3) Precipitated sulfur

6-10% precipitated sulfur ointment in a petrolatum base (for children 2.5%)

Applied to the entire body for three successive nights~ 2wks

MOA= kills adult scabies mite

interact with cysteine, present in the stratum corneum, to form hydrogen sulfide---

safe in preg and neonates

Efficacy = as high as 92%

4) ivermectin Structurally similar to

macrolide antibiotics,

MoA= blocks neurotransmission across nerve synapses that utilize glutamate or GABA(y-aminobutyrica cid) --- cause paralysis of peripheral motor function in insects

Age specific

CONTD...

Ivermectindosage- 200

micg/kg; often the dose is repeated in 10 to 14 days

LINDANE 1% lotion or cream applied only in a thin

coat to dry skin should not be applied

immediately after bathing

M/A= ?? Inhibits inositol in scabies mite to produce CNS excitation & death of the parasite

Inhibits GABA

C/I= children < 2 yrs of age, pregnant & lactationWeight --

FOLLOW-UP VISITS

In 2 weeks is important to ascertain success or failure of therapy

Any new lesions 'post-scabietic pruritus‘

body's response to dead mites- till 4th week after treatment.

steroids

PREVENTION

PEDICULOSIS

Phthiraptera family Order Anoplura-blood-sucking

(***solenophages) ectoparasites of mammals

Pediculus capitis, the head louse Pediculus humanus, the clothing or body

louse & Pthitrus pubis, the pubic or crab louse

ingest blood, & produce skin lesions by mechanical puncture( stylet, haustellum) & injecting toxic secretions

PEDICULOSIS CAPITIS

Head lice in school-aged children, 3-12yr, 10%of

children : F affect all levels of society & all ethnic

groupsPrevalence= 6 to 12 million

infestations/year incidence is low among African Americans

spread by close physical contactsharing of head gear, combs, brushes, &

pillows

ETIOLOGY & PATHOGENESIS

is 1 to 2 mm long, elongated, greyish white flattened dorsoventrally, & wingless three pairs of sharp clow- grasp hairs and for feeding feed approximately five times each day

5 - 10 eggs a day can travel up to 23 cm/min The larva, called a nymyh/instar, looks like a miniature

adult louse 1 - 2 days (4 days) away from the scalp (Nits up to 10

days) 30 days *Head lice do not carry or transmit any human disease. hatches in 8 to 10 days, and reaches maturity in

approximately 18 days. Nits are .8mm, with operculum

CLINICAL FINDINGS

Louse - occipital and retro auricular regions <20 but in 5% >100

Itching or can be asymptomatica result of hypersensitivity reaction

to the saliva & faecal matter produced by the louse during feeding

Sensitization - 3-8month

hemorrhagic crust Excoriations, lymphadenopathy, &

conjunctivitis(redness &swelling) may be observed

CONTD...Diagnosis Identification of live adult lice, immature

nymphs, and/or viable-appearing eggs

Live nits(egg cases) placed in close proximity to the scalp(parietal & occipital)

Have proteinaceou sheath

cemented to the hair shaft with chitinous material secreted by the female accessory glands

C0MPLICATIONS Excoriation ----- Secondary bacterial

infections

DDX

Seborrheic piedra Delusion parasitosis Artifacts on the hair Hair casts (pseudonitis)

PEDICULOSIS CORPORIS (BODY/CLOTHING LICE)

EPIDEMIOLOGY low of socio-economic in urban public hospitals

No predilection for race, age, or sex

contaminated clothing or bedding

ETIOPATHOGENESIS

Body Iouse/P. humanus var humanus

lifespan -18 days 270 to 300 ova

2-4mm

3 day,with out meal comes to the surface only for meal

CLINICAL FEATURES

linear excoriations primarily

Occasionally, a macula ceruleae (Iiterally, sky-blues pot)a blue to slightly slate-colored

macule.............bruise-like lesion (~1.5 cm) & often with a central punctum 2nd to altered blood pigments in clothing binds (waistband, buttocks & thighs) & is asymptomatic to slightly pruritic

CONTD...

Diagnosis examining the lining

of the clothing seams for the presence of nits

By shaking out the

clothing over a sheet of newsprint,

Nits that contain an unborn louse fluoresce white.

Nits that are empty fluoresce gray.

DDx Scabies AD ACD Drug reaction Viral exanthem Systemic cause of pruritus

COMPLICATIONS

Excoriation

secondary infection with S. aureus, S. pyogenes & other bacteria (impetigo & furunculosis)

act as vectors for R.prowazekaii (epidemic typhus), Bartonella quintana (trench fevers or endocarditis) & Borrelia recurrentis (relapsing fever)

PEDICULOSIS PUBIS (PUBIC LICE)

EPIDEMIOLOGY most often are

a sexually transmitted disease

~ 30 % of patients have another concurrent STI

from one sexual exposure with an infested partner is more than 90%

contaminated clothing, towels, or beddings

ETIOPATH0GENESIS

Pthiridae

crab - naming second and third pairs of -to cling on to hair

(pincer like claws) light brown 0.8 to 1.2 mm in length ambulate up to 10 cm/day

lifespan of 2 wks 25 ova

away from the human host for up to 36 hrs dog

CLINICAL FEATURES

Pruritus

Maculae ceruleae (sky-blue spots, (tache bleu), on inner thighs or sides of trunk

Bullous lesion

adult organisms on the body ( ~ 10 - 25 or more) pubic hair, any hair bearing site can be affected, eyelashes

((phthiriasis palpebrarum○ in hirsute ~ short hairs of the thighs, trunk, & perianal

area

nits near the base of the hair the duration of infestation can be approximated by the

distance

of the nit from the skin surface

CONTD...

Diagnosis louse in the pubic

area coexisting STI

microscopic examination Empty nits may

indicate a prior infestation

COMPLICATIONS excoriation Secondary

infection -lymphadenitis & fever

. generalized exanthem (pityriasis rosealike pediculid).

DDx Scabies Extensive excoriation Contact dermatitis

White piedraTrichosporon cutaneum

Trichomycosis pubis

Hair casts

TREATMENTS

Block Na+ channel repolarization

Topically for 10min, repeat a wk later for body louse

100% cidal- 10min

Topically 8 -12 hrs repeat in 7 -10 days

Currently treatment of choice for body louse

Pyrethrin (synergized/synthetic= permethrin/piperonyl butoxide) 1%, 5% shampoo

Permethrin 1% cream

Organophosphate cholinesterase inhibitor

Topically for 8-12hrs (20-30min)

Organochloride acts as GABA inhibitor

Topically for 5-10min, not to be repeated

Malathion 0.5% lotion Lindane shampoo 1%

CONTD...

Ivermectin, oralInhibit GABA release & cause respiratory paralysis

250micro gm/kg a week apart

not ovicidal

Wet combing Occlusive or

suffocation Boiling of clothing(65 *C), bedding, &

other possible fomites is ovicidal & lousicidal

cotimoxazole acctylcholincsterasei

nhibiting insecticides Robi comb, Tea tree

oil and lavender oil

EYE TX

thick layer of petrolatum twice a day for 2 weeks (interere respiratory function –block)

mechanical removal cryotherapy flurescein 10-20% mercuric oxide physiostigmine ointment!!!!!!!!! Oral ivermectin argon laser photo therapy aqueous pediculicide

CONTD...

Patients with HIV/AIDShave more severe infestations with p. pubis &

unresponsive to conventional therapy

REFERENCES

emedicineRook'sTextbook of Dermatology

THANK U!

Malathion, carbaryl and permethrin preparation are probably the treatments of choice now. They kill lice and eggs effectively;

malathion has the extra value of sticking to the hair and so Lotions should remain on the scalp for at least

12 h, and are more effective than shampoos. The application should be repeated after 1 week so that any lice that survive the first application and hatch out in that interval can be killed.protecting against reinfection for 6 weeks.

Intralesional steroids, tar, or excision are methods of treatment for this troublesome condition, termed nodular scabies.

Sensitization majority of mites are found on the hands and

wrists, Children have often gathered mites and ova under the nails when scratching.

Permethrin 5% cream (Elimite) is the most widely used medication for scabies. It is a synthetic pyrethroid that is lethal to mites and has low toxicity for humans.

Lindane (y-benzene hexachloride) is also effective, with a low incidence of adverse effects when used properly. Because of

the availability of less toxic agents, lindane is rarely used as a first-line agent. In much of the world, benzyl benzoate and 10% precipitated sulfur in white petrolatum are used to treat

scabies. The scabicide should be thoroughly rubbed into theskin from the neck to the feet, with particular attention given to the creases, perianal areas, umbilicus, and free nail edge and folds. It is washed off 8 to 10 h later. Clothing and bedlinen are changed and laundered thoroughly.

Crotamiton (Eurax) has a lower cure rate than other available agents.

When used, it should be applied on 5 successive nights and washed off 24 h after the last use.

it usually takes 2-6 weeks before the host's immune system becomes sensitized

to the mite or its by product 'post-scabietic pmritus'. body's response to dead mites second application of topical medication is performed

in order to reduce the potential for reinfestation from fomites as well as to ensure killing of any nymphs that may have hatched as a result of thesemi-protective environment within the egg that allowed them to survive

Lotions should remain on the scalp for at least 12 h, and are more effective than shampoos. The application should be repeated after 1 week so that any lice that survive the first application and hatch out in that interval can be killed. A systemic antibiotic may be needed to deal with severe secondary Infection a head louse repellent, containing 2% piperonal, is available over the counter and may be worth a trial for those who are repeatedly reinfested. Systemic ivermectin therapy is reserved for infestations resisting the treatments listed

th e head and body lice may be variants within a single species, but are thought by most biologists to represent two distinct species that can hybridize or interbreed under special

circumstances.

peri pilar keratin casts ('pseudonits'; hair muffs) [21,221 or dried

globules of cheap hair lacquer. The acctylcholincsteraseinhibiting insecticides malathion and carbaryl (carbaril) Robi comb, co-trimoxazole, Tea tree oil and

lavender oil prophylaxis

TREATMENT FAILURE

Evidence the presence of adult organisms

should be suspected if live lice are still present 12 to 24 hours after treatment

Failure to follow instructions changing formulations, dilution of the pediculicide subtheraputic doses or duration

Neglecting to treat sexual contacts

Treating only the pubic area in hairy individuals

Re-infestation