MEDICINE-DERMATOLOGY-DISEASES BY ARTHROPODS SCABIES HISTORY Reported for >2500 years Aristotle described Lice in the fleshCelsus recommended sulphur mixed with liquid as remedy Bonomo related mite to the disease First human disease known to be caused by a specific pathogen LIFECYCLE OF SARCOPTES SCABIEI: Eggs incubate and hatch (3-4 days) 90% of the hatched eggs die and 1% survive 3. Larva (3 pairs of legs) migrate to the skin surface Burrow into the intact Stratum Corneum Short Burrows (Molting Pouches) (3-4 days) 4. Larger Nymph 5. Adults 6. Mating takes place once a. Female fertile for life b. Male die 7. Female secrete proteolytic enzyme Dissolve stratum corneum further Serpentine burrows with Laying of eggs further burrowing (1-2 months) 8. Transmission of impregnated female 1. 2. 1. 2. 3. 4. 5. A. INTRO: a. Skin infestation caused by arthropod Sarcoptes scabiei var hominis b. Highly pruritic and contagious skin lesions B. INCIDENCE: a. 300 million cases annually b. One of the 6 major epidermal parasitic skin diseases (EPSD) c. Any age group d. M:F::1:1 C. ETIOPATHOGENESIS: a. Risk Factors: i. Young age ii. Illiteracy iii. Poor socioeconomic condition iv. Poor housing condition v. Overcrowding vi. Poor hygiene, irregular bathing vii. Sharing of clothes and towels viii. Homosexual Men b. Agent: i. Sarcoptes scabiei var hominis SARCOPTES SCABIEI VAR HOMINIS 1. Female infests the human a. Can be seen with naked eyes 2. Male is half the size of female 3. 4 pairs of legs 4. Unable to fly or jump 5. Crawl at the rate of 2.5 cm/min 6. Cannot penetrate deeper the outer layer of epidermis 7. Complete life cycle in human 8. Survive in the beddings and clothes for 2-3 days at room temp c. 9. <20 deg C remain immobile SASHMI-5TH BATCH OTHER VARIETIES OF SARCOPTES SCABIEI (Mange) 1. Infest dogs, cats, pigs, ferrets and horses 2. Unable to reproduce in humans 3. Cause irritation and transient dermatitis d. Mode of transmission: i. Direct skin to skin contact (common) ii. Sexual contact iii. Indirect fomites (Larger the no of the arthropod, more the chances) D. CLINICAL: a. History: i. Age: any ii. Sex: any iii. Socioeco:any iv. Itching 1. Short time or persistent (7 year itch) 2. More at night a. Sensation more in quiet env b. Steroid levels are low at night 3. Peak At 2- 3 weeks 4. Immunocompromised might not have itching v. Infestation in family members Page 1 MEDICINE-DERMATOLOGY-DISEASES BY ARTHROPODS b. Examination: i. Primary lesions: 1. Sites (Circle of Hebra): a. Head and face (in children) b. Webbed spaces of fingers c. Flexor area of wrist d. Axilla e. Antecubital area f. Breast and nipples (in female) g. Abdomen h. Umbilicus i. Genital areas (Glans penis, shaft and scortum involvement in males is typical) j. Gluteal folds (Involvement of back in old age) k. Feet 2. Lesions: a. Burrows b. Papules c. Pustules d. Nodules e. Utricarial papules and plaques 3. Burrows: a. Pathognomic of Scabies infestation b. Short (2-3 mm) and thin (width of a human hair) c. Straight or tortuous (serpentine) raised tract d. In the superficial epidermis e. With a vesicle at the tip (where the mite enters the burrow) 4. Mite may be visible as a small dot ii. Secondary lesions 1. Utricaria 2. Impetigo 3. Eczematous plaques 4. Pyoderma (Aerobic, anaerobic or mixed) E. VARIANTS: a. Infantile: i. Rare ii. Vesicopustules with eczematisation iii. May involve head and face 1. Because sebum secre is less in infants in head and face So no lysis of the org iv. H/O scabies in parents b. Nodular: i. Firm, red itchy nodules ii. >=0.5 cm iii. Due to hypersensitivity reaction to the mite iv. In the covered areas (Axillary folds and scotum) c. Crusted/ Norwegian: i. Thick hyperkeratotic crusted lesions with scales ii. Usually immunocompromised, elderly and retarded persons iii. Hundreds to millions mites iv. IgG and IgE are high v. CD8 predominance d. Scabies incognito: i. Modified by steroids e. Atypical/ Clean Scabies: i. Itching with few scattered papules Scabies galeusus: i. Development of primary lesions of syphilis in scabetic lesions of genetalia f. F. D/D: a. Insect bites b. Atopic dermatitis c. Contact dermatitis d. Psoriasis e. Utricaria SASHMI-5TH BATCH Page 2 MEDICINE-DERMATOLOGY-DISEASES BY ARTHROPODS necessary (Some dev larva survive the initial RX) b. 1% Lindane i. C/I in pediatrics ii. Transcutaneous absorption Neurotoxicity 2. Oral: a. Ivermectin, 0.2 mg/kg once; can repeat after 10-14 days IVERMECTIN: 1. Not FDA recommended for the RX 2. MOA: Binds selectively to glutamate gated chloride channel of nerve and muscle cells Paralysis and cell death 3. t1/2=16 hr, metabolized in the liver 4. C/I in infants G. INVESTIGATIONS: a. Diagnostic test: i. Identification of the mites, eggs, eggshell fragments and mite pellets (Scybala) ii. Drop of mineral oil over the burrow Longitudinal and lateral scrapping of skin with scalpel blade Study under microscope iii. Avoid using KOH as it can dissolve the pellets iv. Failure of the identification of eggs or mites does not rule out the diagnosis b. Localizing the burrow: i. Application of topical tetracycline Washing off the excess study under the Wood Lamp Fluorescence ii. Application of the washable ink c. Others: i. Dermatoscopy ii. PCR iii. IgE and eosinophilia iv. Skin biopsy Scabies in Pregnancy and lactating mother: 1. 6% Sulphur Cream 2. Ivermectin, Petmithrin and Lindane C/I ii. Antihistaminics: 1. To relief itching Hydroxyzine hydrochloride iii. Antibiotics: 1. For sec bac infections H. TREATMENT: a. General: i. Consultation with the dermatologist ii. Treatment of the family members and the people in close contact iii. Providing reassurance that the disease is not a reflection of poor hygiene b. Specific: i. Scabicide: 1. Topical: a. 5% Permethrin cream i. DOC, esp for >2m and small children ii. Dose: Application all over the body, except on the scalp; Shower after 8-14 hours; repeat the application after 7 days if I. COMPLICATIONS: a. Impetigo b. Furunculosis c. Cellulitis d. Pyelonephritis e. Post strep glomerulonephritis f. Abscess g. Sepsis h. Death SASHMI-5TH BATCH Page 3