Scabies

Raymond B. Otero, Ph.D.

Consultant

Introduction

Scabies is an infectious disease of the skin caused by a mite whose penetration is visible as papules or vesicles or as tiny linear burrows containing mites and their eggs. It occurs worldwide and specifically in institutions where hygiene procedures are suspect. It is also associated with overcrowding and poor hygiene. Published reports of outbreaks linked to AIDS patients have been documented^1,2. Scabies outbreaks can last for several months if proper surveillance and outbreak controls are not followed³. There has been as many as 300 million cases of scabies occurring annually around the world⁴.

Lesions

Lesions are prominent around the webs, anterior surfaces or wrists and elbows, anterior axillary folds, belt line, thighs and external genitalia in men, nipples, abdomen, and lower portion of buttocks in women⁵. In infants, the head, neck, palms and soles may be involved⁶. When infestations occur in the nursing home residents who have been bedridden for many days or weeks, lesions can occur in the back⁷.

Itching

Itching is intense, especially at night, but complications are limited to lesions secondarily infected from scratching⁸.

Agent

Infestation with Sacroptes scabiei var. hominis, a mite, causes scabies.

Transmission

Transfer of parasites is by direct contact only (skin-to-skin). Transfer from undergarment or bedclothes may occur only if these have been contaminated by infected persons immediately beforehand. Scabies can be transmitted sexually. Mites can burrow beneath the skin surface in 2.5 minutes⁶. Norwegian scabies is highly infectious due to large numbers of mites in the exfoliating scales.

Reservoir

Humans are the most common reservoir for scabies infestation⁶.

Incubation period

Incubation period is 2 to 6 weeks before onset of itching in persons without previous exposure⁶. Persons who have been previously infested may develop symptoms almost immediately⁹.

Period of communicability

A person remains communicable until mites and eggs are destroyed by effective treatment⁶.

Complications

Persistent pruritus caused my secondary mite sensitization is a complication of scabies. Intense scratching can lead to severe excoriation, tissue trauma and secondary bacteremia with Staphylococcus aureus, especially in AIDS patients⁸.

Diagnostic tests

Potassium hydroxide wet mounts of burrows scraping may reveal adults, larvae and eggs⁵. For optimal results a dermatologist or microbiologist/technologist should perform this on site.

Equipment needed for skin scraping¹⁰

gloves

magnifying glass

gooseneck lamp or flashlight (bright)

felt tip pen-green or blue washable ink

alcohol swabs

#15 scalpel blades, glass slides for scraping, or curettes

scalpel holder

Kelly clamp or other forceps

slides and cover slips

mineral oil

requisition form, if slides are being sent to a clinical lab (private, hospital, state)

sharp

Procedures for doing skin scrapings¹⁰:

Establish and confirm the diagnosis by skin scraping and microsopic identification of mites, eggs, or scybala (fecal pellets). A nurse from the healthcare facility can be taught this procedure by a dermatologist, the consulting physician or by a nurse or technician who has had professional training in doing the procedure.

Mass treatment should not be initiated unless a definite diagnosis has been made in at least 1 of the symptomatic cases.

Scrape those persons with the most severe rash first. Elderly may present with severe urticaria and bullous lesions.

Shoulders, back and abdomen are choice areas for scraping in the elderly. Other sites; hands, wrists, elbows, feet, ankles, buttocks, axillae, knees, thighs, and breasts.

Use hand magnifying lens to identify recent burrows or papules. A bright light and magnifying glass will assist in visualizing the tiny dark speck (the mite) at the end of the burrow.

Identify these high yield lesions by applying mineral oil (best used over dry scaly areas) or by applying the burrow ink test to possible burrows. The burrow ink test is done by using a wide felt tip pen (blue or green are best) over burrows and then wiping off with an alcohol swab. The alcohol will remove most of the surface ink, but will not remove the ink taken up by the burrow, thus leaving a dark irregular line.

Apply mineral oil or preferably microscope immersion oil to lesions or scalpel blade and glass slides.

Scrape non-excoriated, non-inflamed areas (burrows and papules) vigorously with a #15 scalpel blade or glass slide held at a 90 angle to the skin and while holding the skin taut until the stratum corneum is removed. (Vigorous scraping appropriately results in a few red blood cells visible under the microscope, but there should not be frank bleeding.) Some practitioners prefer using a small curette. Change blades or curettes between scraping on different persons. Blades can be placed and removed from the handle with forceps. Used blades must be placed in a sharps container.

Transfer skin scrapings from 6 different sites to a single slide or to 6 different slides per patient. These scrapings can be pushed onto the slide edge and then moved to the center of the slide.

Place the cover slip over the slide.

Examine entire slide methodically under low power at 25-50 x magnification for at least 5 minutes. Low power (1.5-4 x) is useful initially. The microscope should be taken to the facility; however, if the practitioner is not trained in reading the slides, the cover slip should be secured to the slide at all edges with clear nail polish and transported personally, by courier, or by mail (in a secure mailer) to:

A hospital or rural clinic laboratory with pre-arrangements; or a physician’s office with pre-arrangements.

Method of Control

Preventive measures

Education of the public, healthcare workers, patients/ resident and immediate families on modes of transmission and treatment should be performed on a regular schedule.

Control of patient¹¹

The use of Standard Precautions (formerly called Universal Precautions) is satisfactory. If the patient/resident is unable to be taught and is a threat to other patients/residents, a private room (Contact Isolation) should be considered for 24 hours after start of medication.

Laundering

Normal laundering procedures at temperatures of 120 - 140 F is more than adequate to destroy the mite and their eggs. There is no need to bag items of clothing or linens for 48 hours or longer prior to washing. Thoroughly drying the textiles after washing increases the effectiveness of the decontamination process.

Search for contacts

Search for unreported or unrecognized cases among companions or household members. Treat persons prophylactically who has had skin-to-skin or sexual contact with infested person. Check with medical staff on the possibility of infestation. If a staff member has become infested by a patient/resident and is treated, then an OSHA 200 form must be completed.

Treatment ^{8,10,12,13,14}

a. Permethrin (5% cream-Elimite)- thoroughly massage into skin covering the entire body (except the head) from the soles of the feet to the neck. For infants, young toddlers, and geriatric patients, it should be applied to the entire body including the scalp, neck, temples and forehead because the mite often infests these areas in those age groups. Underneath the nails should also be treated in the elderly patient⁸.

After 8-14 hours, shower to remove. Contact with eyes and mouth should be avoided. One application is almost curative.

b. Crotamiton 10% (Eurax)- apply from neck down. Cream must be thoroughly massage into skin. Apply twice a day for 5 days.

c. Lindane 1% (gamma benezene hexachloride- Kwell cream)- apply to all areas from neck down. Wash off after 8 hours. Retreat after one week if no improvement. Lindane should not be used after a bath, and it should not be used by persons who have extensive dermatitis, pregnant or lactating women and children less than 2 years¹³.

            Note¹⁰: Pruritus and rash may persist for 1 to 4 weeks after treatment. Pruritus and residual rash should not be considered treatment failure until 1 month after last treatment. To prevent or lessen the possibility of these signs and symptoms, some dermatologists use 1% hydrocortisone cream or triamcinocolone cream (0.1% - 0.025%) applied to the most intense rash and a lubricating agent or emollient to the lesser rash for children. A 1% hydrocortisone cream or triamcinolone creame (0.1%) can be used on adults. Steriod creams should not be applied until after the first scabicide treatment. Overtreatment is common and should be avoided because of toxicity, especially with Lindane. Close supervision of treatment including bathing is necessary of residents in a long-term care to prevent toxicity because of poor application.

Reasons for treatment failures¹⁰

Infected or crusted lesions did not allow penetration of scabicide – need to soften scaliness;

Reinfestation from untreated contacts;

Cell-mediated immunodeficiency;

Resistance of mites to the scabicide.

Nursing interventions

Have the patient’s fingernails cut short to access treatment and to minimize skin breaks from scratching, which may lead to secondary bacterial infections⁸.

Suggests that the patient/resident’s family and other close personal contacts be checked for symptoms⁸.

Have the patient notify sexual contact(s) since scabies is known to be sexually transmitted⁸.

If the patient is a school child, notify the school of his/her condition.

Be alert for any complications that may be associated with treatment.

Encourage the patient/resident to verbalize his/her feelings about the infestation, including embarrassment, fear of rejection by others and any physical body image affects.

Patient teaching

Teach the patient and his/ her family to identify the characteristic lesions and how this disease is transmitted.

Assure the patient and his/her family that the infestation can be treated successfully with good hygiene and proper application of a scabicide.

Stress the importance of good hand washing and nail cleaning to prevent the Infection's and recurrence.

Teach the patient/resident the signs of skin irritation and hypersensitivity reactions that may occur from treatment or from the mites’ themselves⁸.

Advise the patient/resident to report to the nurse or to his/her physician immediately if these signs develop.

References

¹Moss, V. A., Salisbury, J. Scabies in an AIDS hospice unit. Br J Clin Pract. 1991. 45:35-36.

²Sirera, G., et al. Hospital outbreak of scabies stemming from two AIDS patients with Norwegian scabies. Lancet 1990. 335:1227.

³Pasternak, J., et al. Scabies epidemic: price and prejudice. Infect Control Hosp Epidemiol. 1994. 15:540-542.

⁴Reid, A. F., Poonking, T. Epidemic scabies and associated glomerulonephritis in Trinidad. Bull Am Health Organ. 1988. 22:103.

⁵Murray, P. R., et al. In: Manual of Clinical Microbiology. ASM Press. 6^th Edition. 1995. Pp. 1271-1273.

⁶Chin, J. In: Control of Communicable Diseases. American Public Health Association. 17^th Edition. 2000. Pp. 445-447.

⁷Wenzel, R. P. In: Prevention and Control of Nosocomial Infections. Williams and Wilkins. 3^rd Edition. 1997. Pp. 299-301.

⁸Pien, F. D. Ectoparasites. In: Infection Control and Applied Epidemiology – Principles and Practice. Mosby. 1996. Chapter 55. Pp. 1-3.

⁹Arlian L. G. Biology, host relations and epidemiology of Sarcoptes scabiei. Ann Rev Entomol. 1989. 34:139.

¹⁰Treatment of Scabies. 1996. Kentucky Department of Health Services, Communicable Disease Branch. Frankfort, KY.

¹¹CDC. Guideline for isolation precautions in hospitals. Amer J Inf Control. 1996. 24(1)32-52.

¹²Rakel, R. E. In: Conn’s Current Therapy. W. B. Saunders. 2001. Pp. 855.

¹³CDC. Guidelines for treatment of sexually transmitted diseases. MMWR. 1998. 47(RR-1):1-118.

¹⁴The Medical Letter. 1998. Volume 40, Issue 1017. January 2.