Scabies

11.20 Scabies

Presentation
Patients may rush to the emergency department shortly after having gone to bed, unable to sleep because of severe itching. Papules and vesicles (marking deposition of eggs) along thread-like tracks (mite burrows) are chiefly found in the interdigital web spaces as well as on the volar aspects of the wrists, antecubital fossa, olecranon area, nipples, umbilicus, lower abdomen, genitalia and gluteal cleft. Secondary bacterial infection is often present.
What to do:



Attempt identification of the mite by placing mineral oil over the papule or vesicle at the proximal end of a track and scraping it with a # 15 scalpel blade onto a microscope slide. Examine it under low magnification for either the mite or its oval eggs or fecal concretions.



If the clinical picture is convincing, treatment should be instituted without the help of microscopic examination, or even in the face of negative scrapings.



Treat with lindane (Kwell) lotion to the entire body from the neck down. Concentrate on the affected areas. The patient should apply this prescription medication and leave it on for 24 hours before washing it off (60-120ml is required for the average adult). It may be necessary to repeat this treatment after 1 week, but not sooner. Tell the patient that the itching will not go away at once, but that this does not mean the Kwell was ineffective. Dead mites and eggs continue to itch as they are absorbed by the body. An antipruritic agent such as hydroxyzine (Atarax) 25mg q6h can be prescribed for comfort.



Alternatively, treat with a similar application of crotamiton (Eurax) lotion or cream to the body after bathing, repeated after 24 hours. This treatment can also reduce itching.



Clothing, bedding, and towels should be washed with hot water or dry cleaned to prevent reinfection.
What not to do:



Do not use Kwell on infants, young children, or pregnant women. Up to 10% of this pesticide may be absorbed percutaneously, producing seizures or CNS toxicity, and therefore an alternative treatment should be sought. Crotamiton (Eurax) cream applied twice during a 48 hr period will be effective and also acts as an antipruritic agent.
Discussion
Scabies is caused by infestation with the mite Sarcoptes scabiei. The female mite, which is just visible to the human eye, excavates a burrow in the stratum corneum and travels about 2mm a day for about 1-2 months before dying. During this time she lays eggs which reach maturity in about 3 weeks. Scabies is transmitted principally through close personal contact, but may be transmitted through clothing, linens, or towels. Severe pruritis is probably caused by an acquired sensitivity to the organism and is first noted 2-4 weeks after primary infestation. Sometimes nonspecific, pruritic, generalized maculopapular excoriated rash, turns out, after a therapeutic trial of Kwell, to have heen an atypical case of scabies.