Scabies causes itching in 1-4 days for person previously infested. It takes 2-6 weeks before onset of itching if not previously infested. Itching is secondary to sensitization to the excreta of the mite. Itching is worst at night. Most lesions are between fingers & on the wrists, elbows, and penis.
CASES/YEAR
1,200,000 (US); 100,000,000 (Global)
INCUBATION
1-4 days for person previously infested; 2-6 weeks before onset of itching if not previously infested; [CCDM, p. 550]
INITIAL SYMPTOMS
Itching of lesions in finger webs, volar wrists and elbows, anterior axillary folds, belt line, thighs, and external genitalia (men), and nipples and lower buttocks (women); In infants (not usually adults), may affect head, neck, palms, and soles; [CCDM]
PRECAUTIONS
"For hospitalized patients, contact isolation for 24 hours after start of effective treatment. Twenty-four hours may be insufficient in crusted scabies because viable mites can remain after a single treatment." [CCDM, p. 551]
COMMENTS
Itching is secondary to sensitization to the excreta of the mite Sarcoptes scabiei. Itching is worst at night and after a hot shower. Most lesions (wavy dark lines <15 mm in length) are found between fingers, and on the volar wrists, elbows, and penis. Patients with immune deficiency diseases or taking glucocorticoids may become infested with thousands of mites producing Norwegian, or crusted, scabies. [Harrisons, p. 637] Skin lesions include papules, vesicles, and linear burrows. [CCDM, p. 550] The burrow is a serpiginous gray to white keratotic line 1 to 4 mm in length. The diagnosis can also be made by video-dermoscopy, PCR, or ELISA for mite products or specific IgE. [Cecil, p. 691] Atypical scabies include: 1.) Scalp scabies (infants); 2.) Crusted scabies (immunocompromised); and 3.) Nodular scabies (sexually transmitted). In AIDS patients, pruritic papules and scaly plaques occur on the palms, soles, trunk, and extremities. Crusts and pustules are typical in crusted scabies. [PPID, p. 1670, 3488] Glomerulonephritis is a complication when beta-hemolytic streptococci are present as a secondary infection. [CCDM, p. 550] Mites can live for only 72 hours after leaving the body. [ABX Guide: Sarcoptes scabiei]
DIAGNOSTIC
Unroof burrows or lift clear adhesive tape from lesions & study under microscope for mites, eggs, and fecal pellets. [Harrison ID, p. 1175] Applying mineral oil may facilitate specimen collection. Find burrows by applying ink & washing off. [CCDM]
SIGNS & SYMPTOMS
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S papules or plaques
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S pustule
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S rash on palms
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S skin blister or vesicles
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S skin or subcutaneous nodule
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S urticaria
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S skin lesion, linear or serpiginous
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*glomerulonephritis
ENTRY
Skin or Mucous Membranes (Includes Conjunctiva), Sexual Contact
TREATMENT
Patients should be informed that the itching may persist for 2 weeks after treatment. [ABX Guide: Sarcoptes scabiei]
REFERENCES FOR CASES/YEAR
1. (US) About 40 cases/10,000/year was the rate in a study of 1/2 million people observed every year from 1994-2003 in England and Wales; [PMID 16274495] Calculate: 40/10,000 X 300 million = 1,200,000;
2. (Global) Estimated global prevalence is 100 million cases; Risk factors include skin contact, poverty, tropical climates, and immunosuppression (AIDS); [5MCC-2020]