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.
