Scabies

Ectoparasitesand parasites on humans skin/body surfaceParasitology DepartmentLearning ObjectivesParasites that causes infestation in the skin and human surface:Agents of disease: Sarcoptes scabiei, Pediculus humanus, Phtirus pubisPathogenesisPreventive treatmentCercarial dermatitis and filarial dermatitisCutaneous larva migrans:Agents of disease: hookworms larvae, Gnathostoma spinigerumPathogenesisPreventive treatmentMiasis

ReferenceRoberts LS, Janovy Jr J (ed): Gerald D. Schmidt & Larry S. Roberts Foundations of Parasitology, 7th edition, McGraw Hill, New York, 2005Sarcoptes scabieiSarcoptes scabieiAgent was already covered in BBS-ParasitologyCausing scabiesSynonims: seven-year itch, Norwegian itchContagious skin diseaseTransmitted by a close-prolonged contact with:Infested companionInfested bedding

5Sarcoptes scabiei

ScybalaMineral oil or Acry-Mount on a glass slide with cover slip on top7

malefemaleRash characteristicsEpidermal curved or linear ridgesFollicular papulesPruritus palms: more intense and unbearable at nightWhite visible epidermal ridges by mite burrowing into outer layers of skinHypersensitivity reactionExcoriated erythematous papulesPustules, crusted lesions8

99Distribution of rash

Circle of HebraImaginary circle intersecting sites of prediliction: wrists, finger webs, umbilicus, lower abdomen, genitalia, elbow flexures, areolae, axillae.

PathogenesisMites mate in hosts skin; males inseminating immature femalesImmature females move rapidly over the skin transmissible between hostsMales remain on the skin surface with nyhmphsMature females burrow tunnels in the skin with her mouthparts for about 2 monthsEggs are placed in the burrows with hatched larvae, ecdysed cuticles, excrementSymptoms are usually noticed in the well advanced casePathology Papular and burrow-type lesionsFace and scalp spared in adults, but not in infants or immunosuppressedBurrows may be barely visibleDull red nodules persist in groin, called nodular scabies, may persist after cure, histology is similar with pseudolymphomaNorwegian heavy crusting, scaling most common in malnourished, immuno-suppressed or patients with neurologic diseases.Treatment and preventionTreat the whole family or person in close contact with patientTopical sulfur preparationsOne-two applications dailyClean the house and fabrics used by the patients thoroughlyAvoid contact or cloths and fabrics with patients during illness13AnopluraAnopluraAgents (covered in BBS-Parasitology):Pediculus capitisPediculus corporisPediculus pubis (Phtirus pubis)Causing pediculosis/phtiriasis

15Pathology Attach to skin, hair, or clothes, and suck blood Saliva is antigenic and creates dermatitisPediculosis is not life threatenig, but lice may transmit endemic typhus, relapsing fever or trench feverPediculosis capitisAgent: Pediculus capitisMore common in children and womenSides and back of scalp, pruriticDiagnosis straight forward:Visible white flecks (nits)Matting and crusting of scalpFoul odor

Pediculosis capitis

Pediculosis corporisAgent: Pediculus corporisSynonims: pediculosis vestimenti or Vagabonds disease. Preferable sites: pressure areas beneath collar, belt or in bedding. Rarely found on skinLice live and lay eggs in clothingSigns & symptoms: generalized itching, parallel scratch marks, hyperpigmentation, red maculesAssess for excoriation on trunks, abdomen, and extremities

19Pediculosis pubisAgent: Pthirus pubis (crab louse)More common found in adults, STD patiensPreferable site is genitalia but may invade chest, hypogastrium, axilla or eyelashesLice commonly found on skinSigns & symptoms: intense pruritus, maculae ceruleae, bluish or slate colored papules, blancheable on sides of trunk or inner thighs, vulvar region and perirectal.

Treatment and preventionTreatmentPediculicides: apply Permethrin 1% Cream Rinse (Nix) to dry hair, then rinse out after 30-60 minutes. Do not shampoo for 24 hours afterwards.sHand pick or fine tooth comb to comb lice and nits outLaunder bed linens & vacuumSeal infested items (cloths, linen, fabrics) in plastic bags for 14 daysLaundering clothing and bedding, 1% Malathion powder, 10% DDT may be dusted onto inner surface of underwearBest to discard clothing altogether as lice may live in clothing for 1 month without a blood mealRepeat above in 10-14 daysAvoid contact or sharing clothes and fabrics with patients Treat social contacts22Filarial dermatitisSchistosomal dermatitisCutaneous leishmaniasisParasitic DermatitisParasitic dermatitisFilarial dermatitis is caused by Onchocerca volvulus, transmitted by black flies (Simulium sp.)Schistosomal dermatitis (swimmers itch):Cercarial penetration through the skinDevelops after 24 post exposure, and lasts within 2-3 daysCutaneous leishmaniasis:Caused by Leishmania tropica transmitted by sand fly (Phlebotomus sp.)Parasites found in the skin near lymph nodes

Cutaneous Larva MigransCutaneous larva migransSynonim: creeping eruption, ground itchCausativa agents: nematodes (zoonotic hookworms): Ancylostoma braziliense, Ancylostoma caninum, Ancylostoma ceylanicum, Strongyloides stercoralisFilariform larvae penetrate human skin, usually feet and hands invade epithellium aimless wandering through the skin red, itchy wound usually infected by pyogenic bacteriaPathogenesisContact with soil containing infective larvae (filariform larvae) that are capable of penetrating the skin.This cant occur after first exposure but follows reinfection only after several weeks, this infection suggests that the disease is due to hypersensitivity to larval secretions (Provic and Croese, 1996)The larva produces a number of enzymes which may assist in dermal invasion; such as metaloprotease, minor protease and hyluronidase (Hotez, Hawdon and Capello,1995)PathologyLesions may also become vesiculated, encrusted, or secondarily infected.The larvae eventually die and become absorbed without treatment.The cutaneous symptoms typically last for days to months.Only 29% of patients had lesions that persisted for 1 month, but in occasional patients had lesions in follicles and cause disease for as long as 2 years.Slightly increase of eosinophilia and normal IgE29

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TreatmentApplication of 15% thiabendazole ointment for 5 days.Systemic treatment with albendazole or ivermectin may also be used, especially in severe cases.MyiasisMyiasisDefinition: an infestation of the organs and tissue of human or animal by fly maggots that, at least for a period of time, feed on the hosts dead or living tissue, liquid body-substances or ingested food (Herms, 1971)Myiasis can occur in many organs: urogenital, dermal/subdermal, nasofaring, ophthalmic, furuncular, and cutaneous myiasis.Cutaneous myiasis

TreatmentSurgical debridement Surgical incision & extraction of the larvae is usually done under local anesthesia.

Suffocation approaches Several substance which may used to block larvaes respiratory such as Vaseline, or similar material.36

Thank You36