Scabies and pediculosis

Dermatology

1. SCABIES & PEDICULOSIS - Nivetha C

2. INTRODUCTION An ancient world wide disease caused by Sarcoptes scabiei It is considered as a important health problem worldwide especially for indegenous population and immunocompromused individuals

3. BIOLOGY OF SCABIES Sarcoptes scabiei is a member of family Sarcoptidae It has a creamy white color with brown sclerotised legs and mouth parts Adult female is larger than male It has 4 pairs of legs Unlike other arthropods it cannot fly ,they crawl as fast as 2.5cm per minute on warm skin

4. LIFE CYCLE & PATHOGENESIS

5. CLINICAL FEATURES Incubation period is usually several weeks in a person exposed to scabies for the first time Itching – most common symptom which is generalised and severe Worsens more at night . Due to delayed type IV hypersensitivity reaction Lesion- Due to the presence of mite and it’s burrows It may be erythematous papules, papulovesicles , nodules, erythematous rash , scratching( excoriation / eczematization ) secondary infection ( pyoderma)

6. CLASSICAL SCABIES Burrows are pathognomic lesion but are not easily seen They appear as serpiginous or S shaped greyish thread like elevation with a vesicle at one end indicating the presence of mite Sites- interdigital webs, front of wrist, elbows, axilla,feet, areola and scrotum. Palms and soles in infants Erythematous papules and papulo-vesicles – Excoriated found in webspace , front of wrist, ulnar border of forearm , elbow , axilla , areola , umbilicus, lower abdomen , upper medial sides of thigh and genitals . An imaginary circle formed by these sites of predilection is called “ Circle of Hebra”

7. CIRCLE OF HEBRA

8. CLASSICAL SCABIES ( contd) A diffuse papular erythematous rash or urticarial lesion on the trunk, buttock, scapular region and abdomen represents a hypersensitivity reaction to mite

9. CLINICAL VARIANTS NODULAR SCABIES Erythematous nodules found during infestation or after treatment Seen in axilla or scrotum INFANTILE SCABIES Lesions are found on face, scalp, palms, soles

10. SCABIES IN CLEAN- Fewer lesion seen at atypical and covered sites GENITAL SCABIES – Maybe sexually transmitted. Papule seen on penile shaft, scrotum and inner aspects of thigh CRUSTED SCABIES/ NORWEGIAN SCABIES- seen in people with poor sensory perception such as leprosy and individuals with decreased immunity like HIV , old aged or transplant recipients Other risk factors – Neurologic disorders such as Parkinson’s disease , down’s syndrome , systemic corticosteroids , chemotherapy Diffuse hyperkeratotic papules and plaques develop on the palms and soles Itching is mild. Xerosis of skin and nail dystrophy maybe present

11. COMPLICATIONS Impetiginisation Lymphangitis Septicemia Phimosis and paraphimosis ( Genital scabies) Eczematization – erythema , oozing, crusted lesion ( Infantile scabies)

12. INVESTIGATIONS Scraping and Microscopy A drop of mineral oil applied to a burrow and skin scraping are examined under a microscope for identification of mite , eggs, egg casings or faecal pellets Uncommonly performed investigations burrow ink test , needle extraction of the mite, Histopathology

13. DIFFERENTIAL DIAGNOSIS Pompholyx Prurigo mitis Atopic dermatitis Lichen planus Id eruptions Vasculitis Senile eczema HIV pruritus Erythroderma Neurotic excoriations Dermatitis herpetiformis Bullous pemphigoid

14. TREATMENT Treat secondary complications first Treat all household members Treat all inmates and caretakers in institution Treat fomites by putting in hot water, insecticides for 2-4 days Scabicides to be applied throughly behind ears and from neck to toes; repeat application depending upon scabicides used

15. SYSTEMIC TREATMENT Ivermectin: 200 microgms/kg single dose; 56% cure; repeat 14 days later, 96% cure Act by interrupting glutamate and aminobutyric acid induced neurotransmission in parasite causing paralysis & death Lacks ovicidal action Better with eczematised patients

16. SUPPORTIVE TREATMENT Antihistaminics Antibiotics: systemic, local Emollients Soaps Steroids: Topical /Systemic (in eczematised scabies) Keratolytics in crusted scabies Future trends: Local Ivermectin, tea tree oil

17. PEDICULOSIS Types 1.Pediculus humanus : Two varieties a. Pediculus humanus corporis b. Pediculus humanus capitis 2. Phthirus pubis : The gravid louse lays a few egg daily, these eggs are called nits. They are small oval greyish white & 0.5 mm in length. Morphology Head louse & body louse morphology identical (Thin & long) Crab louse (broad & short)

18. PEDICULOSIS CAPITIS It is the infestation of the scalp by pediculosa humanu capitis. It localizes in the scalp , favouring the occiput & temporal area. They are laid close to the scalp surface, at the bottom of the hair. Clinical features : Itching Scratching causes trauma with result into oozing. Secondary infection usually resulting in pustulation & absscess formation

19. PEDICULOSIS CORPORIS It is the infestation of the body by pediculosa humanus corporis. The body louse inhibbits from the clothings. Lice bites the skin to suck blood Release of mild toxin Produces pruritic spot & strong itching Results in excoriations ( Hall mark of the disease) Sites : Shoulder Trunk Buttocks

20. PEDICULOSIS PUBIS This is the infestation of the pubic & perianal hairs by phthirus pubis. It is usually transmitted by sexual contact. The adult female lays eggs & nits remain firmly adhered to the pubic hair. Clinical features : The patients complains of itching which results in scratching. The hairs may be matted in the thick crusts of dried pus, serum & blood. The patients may also notice tiny blood spot on the underwear.

21. DIAGNOSIS The diagnosis is usually suspected on clinical examination & finding the nits or the adult louse on the hair of the fibers in the seams of the clothing, if necessary the hair of the fibers may be observed under the low power microscope

22. TREATMENT Pediculosis capitis : a. 1% Gamma benzene hexacholoride b. 25% Benzyl benzoate c. 0.5 % malathion Mode of applications : Three applications on the consecutive days followed by tying a cloth on the scalp. Shampoo after 7 days.

23. 2.Pediculosis corporis : Patients needs a scrub bath. Insecticidal dusting powder should be applied to the garments lying close to the skin. Laundering & ironing of the clothes. 3. Pediculosis pubis : a. 1% Gamma benzene hexachloride b. 25% Benxyl benzoate c. 0.5% malathion Since application is usually sufficient, if necessary repeat after 3 days.

24. OTHER TREATMENT MODALITIES Maintain good hygiene Secondary bacterial infection treated with broad spectrum antibiotics Itching controlled by antihistaminics