Ectoparisites

Digafe Tsegaye

MD ,Dermato-venerologist

Ectoparisites

Pediculosis

Scabies

Myiasis

Tungiasis

Pediculosis

• Pediculosis capitis / (head louse)

• Pediculosis corporis/ (body or clothing

louse)

• Phitriasis pubis / (crab)

Introduction

• Lice are wingless,dorsoventrally flattened blood-sucking insects

• Lice have three pairs of legs

• Head and body lice, which travel up to 23 cm/min, crab lice are sluggish and travel a maximum of 10 cm/day

• Head and body lice develop in adults in 19 to 25 days from the time the egg is laid and crab lice in 22 to 27 days.

Medical importance of lice

• Pruritis

• Hypersensitivity reaction

• Endemic typhus , relapsing fever

• Excoriations frequently lead to pyoderma

• Parasitophobia

Pediculosis capitis / (head louse)

• Transmission is head-to-head contact ,

shared towels ,brushes, and combs

• DX :

– Active infestation is based on finding live adult

lice, immature nymphs, and/or viable-

appearing eggs.

– Empty shells (nits) are not

diagnostic of active infestation.

Pediculosis capitis. Myriads of oval, grayish-white egg capsules

(nits) are firmly attached to the hair shafts.

Pediculosis corporis (body or

clothing louse)

• Infestations of body lice are found mainly in low income ,poor hygiene, homeless ,refugees living in crowded conditions.

• The infestation is transmitted chiefly by contaminated clothing or bedding

• Clinical feature :

• macules or papules at the site where the louse punctures the skin to obtain blood

• Vertical excoriations xic

• Crusts and at times pus or serum may stain the underclothing.

• Transitory wheals and bacterial infections may complicate the process

• Post inflammatory pigmentation is common.

• Few or no adult organisms are seen except in heavily infested persons

• Numerous nits are found in clothing seams, particularly in contact with the crotch, armpits, belt line, and collar

Phitriasis pubis / (crab)

• Transmitted sexually, frequently coexisting

with other sexually transmitted diseases.

• Most are self-diagnosed

Pediculosis pubis. Eyelash infestation with Pthirus pubis. Nits can be

seen attached to the eyelashes.

Treatment

• Pediculosis capitis

5 % PERMETHRINE

• Method of application

– Hair is first washed with a regular

shampoo, rinsed with water, and towel-dried.

– Sufficient permethrin cream rinse is supplied

to coat the hair and scalp thoroughly.

– Left on for 10 min and rinsed off with water

Lindane shampoo

• The hair should then be rinsed thoroughly with water and dried.

• The patient should lather the scalp thoroughly for 4 min with 30 to 40 mL of lindane shampoo .

• Unlike permethrine ,lindaine leaves the hair tangled and difficult to comb.

• Toxic ….single application / not suitable for infants

Scabies

• Caused by Sarcoptes scabies Var

humanis

• Fertilized female burrows in to the stratum

corneum and depoits her eggs .

• Sensitization begins 2-4weeks after the

infection

• But with days if patient were already

sensitized already

Clinical feature

(burrow is a pathognomonic lesion)

• Pruritic papular erruptions worse at bed time

– Excoriations

– Lichenification

• Burrows : slightly elevated ,grayish ,tortous lines

• Vesicle or pustule containing the mite may be noted

• Site : finger webs,wrist,axillae, areola,

umblicus, lower abdomen, genitalia

and buttocks.

• Circle of Hebra .

• In adults face and scalp are spared

• Impetigo / furunclosis if not treated

Secondary bacterial infection

Scabies in infants

• Generalized (face and scalp are involved )

• Bullous lesions are seen on the palms and

soles

Norwegian scabies

• Also called Crusted scabies

• Seen in immunocompromised or debilitated patients

• Also patients with neurological abnormality like down syndrome , leprosy

• C / F : contains millions of mites

• Heavy scaling and crusting on face ,scalp ,pressure bearing sites

• Psoriasis like changes are noted on the nail or under it ,,,, nail deformity

Crusted scabies

Nodular scabies

• An itchy nodule on the scrotum is

to be considered like Scabies

unless proved other wise !!!!

Treatment

5 % perimethrine is a DOC

• Single application , wash after 8 hours

• You may repeat after a week

• Treat close contacts

1 % Lindane (GHCB) : toxic to the nerve

BBL 25 % for three consecutive days

10 % Sulphur PPt in white Petrolatum

Crotamiton for 5 consecutive nights

• Ivermectin 200 microgram / kg Q for crusted Scabies

• IL steroide / excision for Nodular Scabies

Myiasis

Etiology

- Myiasis can be caused by

several spp of arthropods

of the order Diptera

- Worldwide, the most

common flies in human

infestation :

○Dermatobia hominis

○ Cordylobia

anthropophaga /(tumbu

fly)

Cordylobia anthropophaga ( tumbu fly) :Deposit

eggs on soiled clothing → when a person in

contact eggs hatch, larvae burrow into the skin.

Clinical presenation of cutaneous myasis

- Furuncular : itchy papule- painful or tender

papule :

- Lesions consist of one or few larvae

- May feel sensation of movement

Treatment

surgical extraction

suffocation with Occlsuion

Inject lidocaine at the base of the tissue cavity → local swelling force it to the surface

Tungiasis

- Infestation caused by the flea; Tunga

penetrans

- Endemic in certain area of the world

• T. penetrans lives in warm, dry soil

- After contact, invade the unprotected skin ,

feet /interdigital, subungal

- C / F

- No symptom , pruritic , painful

- a black furuncular nodule surrounded by a white halo

Complication

o Bacterial superinfection

o Tetanus

o Gangrene

o Autoamputation of a digit

RX

Removal of the gravid female flea

In early case, lift by enlarging the orifice with a sterile needle

Late, curettage, electrodessication or excision

Topical Rx- alternatives

ivermectin

thiabendazole

TAT prophylaxis