12 - parasitic skin disease.pdf

8/16/2019 12 - parasitic skin disease.pdf

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Parasitic Skin DiseasesParasitic Skin DiseasesArthropoda:Scabies

Pediculosis

Helminth:

Creeping eruption

(Cutaneous Larva Migrans)


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Order : ACARINA

• Family Ixodidae = Hard ticks

• Family Argasidae = Soft ticks

• Family Trombiculidae = Chiggers

• Family Sarcoptidae• Family Demodicidae

• Family Tyroglyphidae


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• round, transluscent, dirty white

• six legged larvae

• eight short legged nymphs andadults

Male 0.2 mm

•1st , 2nd legs sucker ended

• 3rd

legs bristle ended• 4th legs sucker ended

Female 0.3-0.4 mm:

• 1st and 2nd legs sucker ended,

• 3rd and 4th legs bristle ended

Order : ACARINA

Family : Sarcoptidae

Species : Sarcoptesscabiei


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Mite, feeds on skin and blood

Distribution

• World wide usually associated with:

– unhygienic life-style,

– poor personal hygiene insufficient watersupply

• Wide spread in the tropics, especially chi ldren

Transmission• direct skin contact

• Through bedding and clothing


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Mite life cycle

• Eggs Hatch

• 1st instar, nymphs dig into

stratum corneum with

mandibles, moult after 3-4

days

• 2nd instar, protonymphs,

moult after 2-5 days

• 3rd instar, tritonymphs,

moult after 5-6 days

• Adult males and females

• Females moult once more


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LIFE CYCLE

• the period from eggs to mature adults takes 10 – 14 days

• both male and female make short burrows in hornysuperficial layer of the skin.

• The gravid female lays her eggs in a burrow.

• The larvae hatch out after 3-4 days, leave the burrow to theskin surface and shelter in the hair follicles.

• After 4-5 days The mites burrow into the upper layer of theskin but never below the stratum corneum. The adult live for4-5 weeks.

• Itch mites are active mainly overnight.


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Clinical features:

• The activities and secretions cause

intense itching of affecting area.

• Small vesicles and rash may be seen

on the skin surface.

• Scratching may convert the papule

into pustule (bleeding, secondary

bacterial infection)

Norwegian Scabies => crusted

scabies

• Prefered sites

• axilla, around the waist, inner

aspect of thighs, back of the legs,

interdigital and popliteal folds and

also all over the body


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Mites burrowing under theskin cause a rash, which ismost frequently found on:

•hands, particularly thewebbing between the

fingers;•the folds of the wrist,

•elbow or knee;

•the penis;

•the breast;•and/or the shoulder blades.


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Pediculosis

Causative agent:

- Pediculus humanus

- Phtirus pubis


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OrdoOrdo ANOPLURAANOPLURA

(Sucking lice)(Sucking lice)

OrdoOrdo ANOPLURAANOPLURA

(Sucking lice)(Sucking lice)

•• Wingless ,Wingless , dorsodorso--ventrally flattenedventrally flattened

•• The body is notThe body is not chitinizedchitinized..

•• Head is longer than it’s wideHead is longer than it’s wide•• well adapted to an existence on the body /bodywell adapted to an existence on the body /body--hairs.hairs.

•• Lice are host and site specific.Lice are host and site specific.


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Fam.Fam. PediculidaePediculidaeFam.Fam. PediculidaePediculidae

• Pediculus humanus var. capitis

• Pediculus humanus var. corporis

• Phthirus pubis

P. humanus var. capitis P. humanus var. corporis


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P. humanus var. corporis

P. humanus var. capitis


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Pediculus humanus Pediculus humanus

The Morphology of Adult liceThe Morphology of Adult lice•• Female is bigger than maleFemale is bigger than male•• HaveHave greyishgreyish colour colour •• Head :Head :

-- rectangular rectangular--ovoidovoid from the dorsal aspectfrom the dorsal aspect

-- piercing and sucking proboscispiercing and sucking proboscis•• Thorax : 3 segmentsThorax : 3 segments externally indistinctexternally indistinct3 pairs legs, each ending in a claw3 pairs legs, each ending in a claw

•• Abdomen : 9 segments Abdomen : 9 segmentsthe terminal segments :the terminal segments :

femalefemale inverted Vinverted V-- shapedshaped

gonopodsgonopods in ventral sidein ventral sidemalemale roundedrounded

havehave aedeagusaedeagus

The Morphology of Adult liceThe Morphology of Adult lice•• Female is bigger than maleFemale is bigger than male•• HaveHave greyishgreyish colour colour •• Head :Head :

-- rectangular rectangular--ovoidovoid from the dorsal aspectfrom the dorsal aspect

-- piercing and sucking proboscispiercing and sucking proboscis•• Thorax : 3 segmentsThorax : 3 segments externally indistinctexternally indistinct3 pairs legs, each ending in a claw3 pairs legs, each ending in a claw

•• Abdomen : 9 segments Abdomen : 9 segmentsthe terminal segments :the terminal segments :

femalefemale inverted Vinverted V-- shapedshaped

gonopodsgonopods in ventral sidein ventral sidemalemale roundedrounded

havehave aedeagusaedeagus


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Lice eggHair Louse


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Life CycleLife Cycle

• Incomplete metamorphose

• Eggs :

– Ovoid, operculated, white, cemented to the hair or

fiber• At body temperature they hatch in 4-14 days Nymph

Adult within 2 weeks

• The adult live about 30 days


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Medical ImportanceMedical Importance


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• Habitat : – Pubic hair,

– Axillary, chest and body hair,

– Eyelashes and eyebrows

• Life cycle ~ Pediculus spp. (Phthirus: 15 d)

• symptomscaused by a bite, saliva

• Transmission: direct contact

• Tx ~ Pediculus spp.

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12 - parasitic skin disease.pdf