parsitic skin diseases

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PARSITIC SKIN DISEASES

BY

DrNagatSobhy

Assistant prof .of dermatology

Scabies

Scabies is an ectoparasite infestation.

It is caused by the mite Sarcoptesscabieivariety hominisan obligate human parasite that

burrows tunnels downwards into the epidermis (not deeper than the stratum granulosum).

Mites of all developmental stages tunnel into the stratum corneum and deposit faeces behind

them; the female also lays eggs in the tunnels.

A photomicrograph of an itch mite (Sarcoptesscabiei).

Photograph of the mite, S. scabiei, seen on a skin scraping from scabetic patient

In classic scabies, there are only about 11-12 female mites per case.

Hypersensitivity of both immediate and delayed types to the mite or its products has been

implicated in the development of lesions other than burrows.

Mode of transmission

:

-Close person-to-person contact.

-Sexual intercourse .

-Fomites may transmit the infection.

Clinical picture

Itching : Nocturnal , scratching ..

The affected sites : Delicate skin as ..

Morphology of the lesion : poly morphic .

A scabies burrow under magnification

Clinical variations of scabies

1-Scabies incognito .


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2-Scabies in infants and young children .

3-Nodular scabies .

4-Crusted ( Norwegian ) scabies .

5-Animal scabies .

Crusted (Norwegian) scabies

This type represents an abnormal host immune response to the sarcoptesscabiei.The condition

is primarily seen in the following groups:

1-The mentally retarded ( Down,s syndrome )

2-Patients with poor cutaneous sensation ( leprosy ,syringomelia ,and tabesdorsalis . )

3-Patients with severe systemic diseases ( leukemia diabetes )

4-Patients with severe immunesuppression.

Crusted scabies in a patient with no overt immunosuppressive illness

Photograph of patient with hyperkeratotic rash typical of crusted (Norwegian) scabies.

Crusted scabies in a patient with claw hand

from past leprosy.

Bullous Scabies

-These scabies can be seen in adults over 65 years of age.

-There is no linkage to an underlying condition or disease.

-It can mimic bullous pemphigoid clinically, pathologically,andimmunopathologically.

Diagnosis of scabies

History

Examination

Investigations : Scraping

Complications of scabies

-Bacterial infections

- Eczematization


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-Urticaria

-Acarophobia

Treatment of scabies

-Instructions

-Drugs : Topical and systemic .

Topical scabicides

1-Benzyl benzoate 10% and 25% lotions

2-Pyrethrins: permethrin 5% cream, lotion

3-Malathion 05% lotion

4-Sulphur (precipitated) 210% in petrolatum

5-Crotamiton 10% cream (Eurax )

6-Gamma benzene hexachloride 1% cream or emulsion .

Special care fore Infant------ Pregnant

Systemic drug for scabies

Ivermectin. (200 g/kg once and repeated after 1-2 weeks) .

Ivermectin

1-The full benefit becomes evident when

eradication of scabies in epidemic or endemic situations

2-in nursing homes and prisons is needed since ivermectin leads to reliable disease control.

3-Along the same lines, crusted scabies has been effectively treated with ivermectin in adults

and children, sometimes in combination with topical permethrin.

Mechanism of action

Ivermectininterrupts the GABA-induced neurotransmission of many parasites.leading to

paralysis of the parasites.

Novel drug

Recently, the essential oil of the tea tree (Melaleucaalternifolia), containing

oxygeneticterpenoids, was found to have rapid scabicidal and antibacterial activity.


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vaccine development

The multifunctional enzyme glutathione S-transferase ofS scabieicould represent a specific

target for vaccination against human scabies.

Pediculosis

Pediculosis is an infestation oflice blood-feeding ectoparasiticinsects of the order

Phthiraptera. The condition can occur in almost any species of warm-blooded animal (i.e.,

mammals and birds), including humans.Although "pediculosis" in humans may properly refer to

lice infestation of any part of the body, the term is sometimes used loosely to refer to

pediculosiscapitis, the infestation of the human head with the specific head louse.

Pediculushumanuscapitis () Lice are small gray brown,blood sucking insects which crawl among

the hairs

Classification

Pediculosis may be divided into the following types

1- Pediculosiscapitis (Head lice infestation)

2- Pediculosiscorporis (Pediculosisvestimenti, Vagabond's disease) typhus $relapsing fever

3- Pediculosis pubis (Crabs) STD

Pediculosis, or louse infestation, remains a

worldwide problem. The lice that infest human beings are almost always sucking lice that live in

close association with the host and lay their eggs on hair shafts or in the seams of clothing

A and B, Identifying characteristics of a head louse.

Head louse nit attached to hair shaft

Identifying characteristics of a crab louse

Treatment

Malathion o.5 % lotion

Anti scabetic drugs

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