Scabies

Scabies

introduction

Mite: Sarcoptes scabiei

scabies 

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Scabies is a parasitic infection of the skin caused by the burrowing of the ectoparasitic itch mite Sarcoptes scabiei. Mites burrow into the skin where they lay eggs. The resulting offspring crawl out onto the skin and make new burrows Any part of the body may be affected, and transmission is by skin-to-skin contact The absorption of mite excrement into skin capillaries generates a hypersensitivity reaction. The itching of scabies results from our body's allergic reaction to the mites, their eggs and their waste.

Clinical feature itchy papular, papular crusted, or vesicular lesions may present.  Classic sites include the interdigital folds, the wrists and elbows, and around breast nipples in women  An individual was defined to have scabies if at least two of the following 3 requirements were fulfilled: 

 Presence of one or more typical lesions for longer

than 2 weeks,  pruritus that intensified at night, or at least  one more family member with similar lesions

Complications Secondary infection of the skin lesions can occur following repeated scratching Vigorous scratching can break your skin and allow a secondary bacterial infection such as impetigo to occur A more severe form of scabies may develop called crusted scabies. This type tends to be crusty and scaly, and covers large areas of the body. It's very contagious and can be hard to treat.

Prevention & control 

To prevent re-infection Clean all clothes and linen ○ Potentially contaminated clothes and bedding should be washed at high temperature (>50°C) if possible Starve the mites ○ Mites separated from the human host die within 72 hours ○ Consider placing items you can't wash in a sealed plastic bag and leaving it in an out-of-the-way place for a couple of weeks Current sexual partners as well as other

members of the household should be examined and treated

treatment

These should be applied to the whole body from the neck downwards, and washed off after 12 hours, usually overnight  Itch may persist for several weeks. Application of crotamiton cream may give symptomatic relief, and antihistamines may also be helpful 

Follow up The appearance of new burrows at any stage post-treatment is indicative of a need for further therapy, although in re-infection symptoms of pruritus may recur before typical burrows have developed  Pruritus persisting more than 2 weeks after treatment may reflect treatment failure, reinfection or drug allergy to anti-scabetics 

medications

Benzyl benzoate 

Irritant & should be avoided in children  Less effective compared to malathion & permethrin  Side effects: Skin irritation, burning sensation, rashes

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Counseling points: Applied to the neck downwards, and washed off

after 12 hours, usually overnight Up to 3 application on consecutive days Reapply treatment to the hand if they are washed

Permethrin 

Permethrin cream 5%  Permethrin is approved by the US Food and Drug

Administration (FDA) for the treatment of scabies in persons who are at least 2 months of age.  Permethrin is safe and effective when used as directed. Permethrin kills the scabies mite and eggs.  Permethrin is the drug of choice for the treatment of scabies.  Two (or more) applications, each about a week apart, may be necessary to eliminate all mites, particularly when treating crusted (Norwegian) scabies

Crotamiton  Crotamiton

lotion 10% and Crotamiton cream 10%; Crotamiton is approved by the US Food and

Drug Administration (FDA) for the treatment of scabies in adults; it is considered safe when used as directed  Crotamiton is not FDA-approved for use in children. Frequent treatment failure has been reported with crotamiton

Lindane 

Lindane lotion 1%;  Although FDA-approved for the treatment of scabies,

lindane is not recommended as a first-line therapy.  Overuse, misuse, or accidentally swallowing lindane can be toxic to the brain and other parts of the nervous system; its use should be restricted to patients who have failed treatment with or cannot tolerate other medications that pose less risk  Lindane should not be used to treat premature infants, persons with a seizure disorder, women who are pregnant or breast-feeding, persons who have very irritated skin or sores where the lindane will be applied, infants, children, the elderly

Ivermectin 

Ivermectin  Ivermectin is an oral antiparasitic agent approved for

the treatment of worm infestations  Evidence suggests that oral ivermectin may be a safe and effective treatment for scabies; however, ivermectin is not FDA-approved for this use.  Oral ivermectin has been reported effective in the treatment of crusted (Norwegian) scabies; its use should be considered for patients who have failed treatment with or who cannot tolerate FDA-approved topical medications for the treatment of scabies.  A total of two or more doses of ivermectin may be necessary to eliminate a scabies infestation

Lifestyle and home remedies 

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Cool and soak your skin. Soaking in cool water or applying a cool, wet washcloth to irritated areas of your skin may minimize itching. Apply soothing lotion. Calamine lotion, available without a prescription, can effectively relieve the pain and itching of minor skin irritations. Take antihistamines. At your doctor's suggestion, you may find that over-the-counter antihistamines relieve the allergic symptoms caused by scabies. Ref: http://www.mayoclinic.com/health/scabies

references 1.

2. 3. 4. 5.

Feldmeier et. al. 2009. The epidemiology of scabies in an impoverished community in rural Brazil: Presence and severity of disease are associated with poor living conditions and illiteracy. J AM ACAD DERMATOL. (6) 436-444. Scott, G. 2008. United Kingdom National Guideline on the Management of Scabies infestation (2007) . Centers for Disease Control and Prevention. National Center for Zoonotic, VectorBorne, and Enteric Diseases (NCZVED). British National Formulary. 50th Edition. 2005. Anderson,P., Knoben, J. & Troutman, W. Handbook of clinical drug data. 10th edition. Mcgraw-Hill.