Get all the information about scabies in this study guide including its causes, how scabies look like, how it is transmitted, how it is tested, how it is being treated, and prevented.
Scabies is a highly contagious parasitic skin disease that usually affects people who live in poor communities where lack of access to treatment exist. Scabies also has high rates of infestation in tropical countries and in areas where there is frequent skin-to-skin contact among people such as in schools, hospitals, prisons, and nursing homes.
What is Scabies?
Human scabies is caused by an infestation of the skin by the human itch mite Sarcoptes scabiei var. hominis.
- The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs.
- A readily treatable infestation, scabies remains common primarily because of diagnostic difficulty, inadequate treatment of patients and their contacts, and improper environmental control measures.
- Scabies is a great clinical imitator; its spectrum of cutaneous manifestations and associated symptoms often results in delayed diagnosis.
- In fact, the term “7-year itch” was first used with reference to persistent, undiagnosed infestations with scabies
Transmission of scabies is predominantly through direct skin-to-skin contact, and for this reason scabies has been considered a sexually transmitted disease.
- The female S scabiei var hominis mite lays 60-90 eggs in her 30-day lifespan, although less than 10% of the eggs result in mature mites.
- Eggs incubate and hatch in 3-4 days (90% of the hatched mites die).
- Larvae (3 pairs of legs) migrate to the skin surface and burrow into the intact stratum corneum to make short burrows, called molting pouches (3-4 days).
- Larvae molt into nymphs (4 pairs of legs), which molt once into larger nymphs before becoming adults.
- Mating takes place once, and the female is fertile for the rest of her life; the male dies soon after mating.
- The female makes a serpentine burrow using proteolytic enzymes to dissolve the stratum corneum of the epidermis, laying eggs in the process; she continues to lengthen her burrow and lay eggs for the rest of her life, surviving 1-2 months.
- Transmission of impregnated females from person-to-person occurs through direct or indirect skin contact.
There are several types of scabies:
- Classic scabies. In classic scabies infection, typically 10-15 mites (range, 3-50) live on the host; little evidence of infection exists during the first month (range, 2-6 wk), but after 4 weeks and with subsequent infections, a delayed type IV hypersensitivity reaction to the mites, eggs, and scybala (feces) occurs.
- Crusted scabies. Crusted, or Norwegian, scabies (so named because the first description was from Norway in the mid-1800s) is a distinctive and highly contagious form of the disease; in this variant, hundreds to millions of mites infest the host individual, who is usually immunocompromised, elderly, or physically or mentally disabled and impaired.
- Nodular scabies. Nodules occur in 7-10% of patients with scabies, particularly young children; in neonates unable to scratch, pinkish brown nodules ranging in size from 2-20 mm in diameter may develop.
Human scabies is caused by the host-specific mite Sarcoptes scabiei var. hominis, an obligate human parasite.
- Sexually active individuals. Scabies in adults frequently is sexually acquired.
- Presence of many children in the household. Scabies can be passed easily by an infected person to his or her household members; child care facilities also are a common site of scabies infestations.
- Poor housing. Scabies can spread easily under crowded conditions where close body and skin contact is common.
Statistics and Incidences
An estimated 200 million people are affected by scabies at any given time, with prevalence rates ranging from 0.2% to 71%.
- A survey of children in a welfare home in Pulau Pinang, Malaysia found that the infestation rate for scabies was highest among children aged 10-12 years.
- The disease was more commonly evident in boys (50%) than in girls (16%).
- The overall prevalence rate for scabies was 31%.
- Scabies is clearly an endemic disease in many tropical and subtropical regions, being 1 of the 6 major epidermal parasitic skin diseases (EPSD) that are prevalent in resource-poor populations, as reported in the Bulletin of the World Health Organization in February 2009.
- Prevalence rates are extremely high in aboriginal tribes in Australia, Africa, South America, and other developing regions of the world.
- The World Health Organization reports a prevalence rate of 5-10% in children in resource-poor tropical countries.
When a person is infested with scabies mites the first time, symptoms usually do not appear for up to two months (2-6 weeks) after being infested; however, an infested person still can spread scabies during this time even though he/she does not have symptoms.
- Skin rash. The most common symptoms of scabies, itching and a skin rash, are caused by sensitization (a type of “allergic” reaction) to the proteins and feces of the parasite.
- Pruritus. Severe itching (pruritus), especially at night, is the earliest and most common symptom of scabies.
- Scabies rash. A pimple-like (papular) itchy (pruritic) “scabies rash” is also common.
- Burrows in skin. Tiny burrows sometimes are seen on the skin; these are caused by the female scabies mite tunneling just beneath the surface of the skin; these burrows appear as tiny raised and crooked (serpiginous) grayish-white or skin-colored lines on the skin surface; burrows are a pathognomonic sign and represent the intraepidermal tunnel created by the moving female mite.
Assessment and Diagnostic Findings
The diagnosis of scabies can often be made clinically in patients with a pruritic rash and characteristic linear burrows.
- Burrow ink test. A burrow can be located by rubbing a washable felt-tip marker across the suspected site and removing the ink with an alcohol wipe; when a burrow is present, the ink penetrates the stratum corneum and delineates the site; this technique is particularly useful in children and in individuals with very few burrows.
- Tetracycline. Topical tetracycline solution is an alternative to the burrow ink test; after application and removal of the excess tetracycline solution with alcohol, the burrow is examined under a Wood light; the remaining tetracycline within the burrow fluoresces a greenish color; this method is preferred because tetracycline is a colorless solution and large areas of skin can be examined.
- Skin scraping. Definitive testing relies on the identification of mites or their eggs, eggshell fragments, or scybala; this is best undertaken by placing a drop of mineral oil directly over the burrow on the skin and then superficially scraping longitudinally and laterally across the skin with a scalpel blade.
- Adhesive tape test. Strips of tape are applied to areas suspected of being burrows and then rapidly pulled off; these are then applied to microscope slides and examined; the adhesive tape test is easy to perform and had high positive and negative predictive values, making it a good screening test.
- Activity. Individuals affected by scabies should avoid skin-to-skin contact with others; patients with typical scabies may return to school or work 24 hours after the first treatment.
- Decontamination. Bedding, clothing, and towels used by infested persons or their household, sexual, and close contacts anytime during the three days before treatment should be decontaminated by washing in hot water and drying in a hot dryer, by dry-cleaning, or by sealing in a plastic bag for at least 72 hours.
The mainstay of scabies treatment is the application of topical scabicidal agents, with repeat application in 7 days.
- Antiparasitic agents. Treatment options include either topical or oral medication; topical options include permethrin cream (drug of choice), lindane, benzyl benzoate, crotamiton lotion and cream, sulfur, topical ivermectin, tea tree oil, or oil of the leaves of Lippia multiflora Moldenke, a shrub found growing in West African savanna; oral options include ivermectin, although it has not been approved by US Food and Drug Administration (FDA) for the treatment of scabies.
- Topical antibiotics. These agents are used to treat secondarily infected lesions.
- Topical corticosteroids. These agents may be applied to help control intense pruritus caused by scabies.
The nursing care of a patient with scabies include the following:
Assessment of a patient with scabies include:
- History. Patient history can reliably suggest the presence of scabies; lesion distribution and intractable pruritus that is worse at night, as well as scabies symptoms in close contacts (including multiple family members), should immediately rank scabies at the top of the clinical differential diagnosis.
- Physical exam. Clinical findings include primary and secondary lesions; primary lesions are the first manifestation of the infestation and typically include small papules, vesicles, and burrows; secondary lesions are the result of rubbing and scratching, and they may be the only clinical manifestation of the disease.
Based on the assessment data, the major nursing diagnosis for patient with scabies:
- Risk for infection related to tissue damage.
- Impaired skin integrity related to edema.
- Acute pain related to injury to biological agents.
- Disturbed sleep pattern related to itchiness and pain of lesions.
Nursing Care Planning and Goals
The major nursing care planning goals for a patient with scabies:
- Patient remains free of infection, as evidenced by normal vital signs and absence of signs and symptoms of infection.
- Patient and communities demonstrate understanding of plan to heal tissue and prevent injury.
- Patient and communities describe measures to protect and heal the tissue, including wound care.
- Patient describes satisfactory pain control at a level less than 3 to 4 on a rating scale of 0 to 10.
The following are the nursing interventions for a patient with scabies :
- Prevent infection. Wash hands and teach patient and SO to wash hands before contact with patients and between procedures with the patient; encourage fluid intake of 2,000 to 3,000 mL of water per day, unless contraindicated; teach the patient, family, and caregivers, the purpose and proper technique for maintaining isolation; if infection occurs, teach the patient to take antibiotics as prescribed. Instruct patient to take the full course of antibiotics even if symptoms improve or disappear.
- Restore skin integrity. Monitor status of skin around wound; monitor patient’s skin care practices, noting the type of soap or other cleansing agents used, temperature of water, and frequency of skin cleansing; tell patient to avoid rubbing and scratching; provide gloves or clip the nails if necessary; and instruct patient, significant others, and family in the proper care of the wound including hand washing, wound cleansing, dressing changes, and application of topical medications).
- Relieve pain. Acknowledge reports of pain immediately; provide rest periods to promote relief, sleep, and relaxation; provide analgesics as ordered, evaluating the effectiveness and inspecting for any signs and symptoms of adverse effects; and determine the appropriate pain relief method.
Nursing goals are met for a patient with scabies as evidenced by:
- Patient remained free of infection, as evidenced by normal vital signs and absence of signs and symptoms of infection.
- Patient and folks demonstrated an understanding of plan to heal tissue and prevent injury.
- Patient and folks described measures to protect and heal the tissue, including wound care.
- Patient described satisfactory pain control at a level less than 3 to 4 on a rating scale of 0 to 10.
Documentation in a patient with scabies include:
- Individual findings, including factors affecting, interactions, nature of social exchanges, specifics of individual behavior.
- Cultural and religious beliefs, and expectations.
- Plan of care.
- Teaching plan.
- Responses to interventions, teaching, and actions performed.
- Attainment or progress toward the desired outcome.
Here are some of the most important points about scabies:
- The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs.
- Transmission of scabies is predominantly through direct skin-to-skin contact, and for this reason, scabies has been considered a sexually transmitted disease.
- In classic scabies infection, typically 10-15 mites (range, 3-50) live on the host; incrusted or Norwegian scabies, hundreds to millions of mites infest the host individual, who is usually immunocompromised, elderly, or physically or mentally disabled and impaired; and in nodular scabies, nodules occur in 7-10% of patients with scabies, particularly young children.
- Human scabies is caused by the host-specific mite S. scabiei hominis, an obligate human parasite.
- An estimated 200 million people are affected by scabies at any given time, with prevalence rates ranging from 0.2% to 71%.
- When a person is infested with scabies mites the first time, symptoms usually do not appear for up to two months (2-6 weeks) after being infested.
- Symptoms include skin rash, pruritus, and burrows in the skin.
- The diagnosis of scabies can often be made clinically in patients with a pruritic rash and characteristic linear burrows.
- Scabies treatment includes administration of a scabicidal agent (eg, permethrin, lindane, or ivermectin), as well as an appropriate antimicrobial agent if a secondary infection has developed.
Sources and references for this scabies study guide:
- Centers for Disease Control and Prevention. (2010, Nov 2). Scabies. Retrieved from https://www.cdc.gov/parasites/scabies/index.html
- Barry, M. (2019, Jun 07). Scabies. Retrieved from https://emedicine.medscape.com/article/1109204-overview