Scabies is a skininfection caused by Sarcoptes scabiei and the mite is transmitted mostly by direct skin-to-skin contact. Scabies can be classified into 2 major types depending on the resultant skin lesions into typical scabies infestation and crusted (or Norwegian scabies). Crusted scabies is usually associated with an immunocompromised status. The characteristic symptoms of scabies is that of intense itching, which is worse at night and erythema of the skin. Examination reveals skin lesions of various sizes in certain areas of predilection, which include the webs of fingers and toes and wrists. With appropriate antimicrobial therapy, scabies has an excellent prognosis. Treatment must be initiated for patients and individuals with close contact with the patient, even if they are asymptomatic.
In 1687, Giovan Cosimo Bonomo, an Italian physician, described the relationship between mites infestation and the resultant skin lesions.[1][2]
Cases of scabies have been described in literature as early as 1853.[3]
In the early days, the use of sulfur-containing products, whether in the form of baths, vapors or ointments was believed to be the treatment of choice for scabies.[4]
The most common mode of transmission of scabies is through direct skin-to-skin contact. However other methods of transmission include:[1][12][13][14][15][16]
Sexual transmission, especially among men who have sex with men
Fomites and shared clothing are a rare source of transmission of scabies; however, cases are more likely to occur with crusted scabies, due to the higher burden of mites
Cross infectivity from other mammals: this is a rare mode of transmission, however, cases of cross infectivity of humans from companion dogs were reported.
The following summarizes the lifecycle of the mite and the pathophysiology behind scabies infection:[17][1][13][18]
Away from the host, mites are viable for a period of 24-36 hours at a temperature of 21 C.
Once the female mite comes in contact with human skin, it digs a small tunnel (i.e.: burrow) at a rate of 0.5-5.0 mm per day through the layers of the epidermis.
A male mite searches for an unfertilized female, which lays 2-4 eggs per day and larvae hatches 2-4 days later. Larvae develop into adult mites 10-14 days later.
The clinical presentation of intense itching, redness of the skin and the multiple skin lesions are due to a delayed type hypersensitivity reaction by the host immune system.
Living in high-risk areas, such as Sub-Saharan Africa and indigenous communities in Australia and New Zealand
Living in crowded areas
Homeless or displaced children
Poor hygiene: the role of poor hygiene in the development of scabies is uncertain, as mites burrowed under the skin remain alive even after daily hot baths and are usually resistant to water and soap
Immunocompromised individuals, such as the elderly, malnourished and those with HIV, DM are at risk of developing Norwegian Scabies, which is the severe form
The prognosis of scabies is usually excellent. With prompt treatment with antimicrobial therapy, the infection and itching usually resolves within a matter of weeks.[12]
Burrows: are the tunnels which the female mite penetrates into the skin. Initially, they are not clinically visible and can only be seen several days later, when the host immune system forms a local reaction around the tunnel. Burrows are characterized by short, wavy lines.
Papules: they are usually small and erythematous. The distribution of the papules is variable; they can be sparse or very close to each other. Over the course of the infection, papules can transform into vesicles and/or bullae. Characteristic distribution of scabies usually involves the web spaces of fingers and toes, the wrists and areolae of breasts in females and penis in males. The back is usually spared, while face and neck involvement are usually only seen in infants and children.
Preferred regimen (1): Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours;
Preferred regimen (2): Ivermectin 200 ug/kg given orally, 4 times daily and repeated in 2 weeks as it has limited ovicidal activity;
Preferred regimen (3): Ivermectin 1% lotion - applied to all areas of the body from the neck down and washed off after 8–14 hours; repeat treatment in 1 week if symptoms persist;
Alternative regimen: Lindane (1%) 1 oz of lotion or 30 g of cream applied in a thin layer to all areas of the body from the neck down and thoroughly washed off after 8 hours
Lindane is an alternative choice because of its toxicity. Lindane is not recommended for pregnant and breastfeeding women, children aged <10 years, and persons with extensive dermatitis. Seizures have occurred when lindane was applied after a bath or used by patients who had extensive dermatitis. Aplastic anemia after lindane use also has been reported. Resistance has also been reported.
Note: Patients may experience worsening pruritus and erythema early during the administration of antimicrobial therapy
2. Infants and young children
Preferred regimen: Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours;
Note: Infants and young children aged< 10 years should not be treated with lindane.
3. Crusted Scabies
Preferred regimen: (Topical scabicide topical Benzyl benzoate 25% OR topical Permethrin 5% cream (full-body application to be repeated daily for 7 days then twice weekly until discharge or cure) AND treatment with Ivermectin 200 ug/kg PO on days 1,2,8,9, and 15. Additional Ivermectin treatment on days 22 and 29 might be required for severe cases;
4.Pregnant or Lactating Women
Preferred regimen: Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8–14 hours.
One of the most important means of preventing scabies is to encourage good hygiene and advocate healthy living conditions away from crowded conditions.[17]
Once a patient has been diagnosed with scabies, it is empirical to begin treatment with the appropriate antimicrobial therapy to eradicate the infection and prevent re-infection. However, the following measures must also be followed:[12][54]
Treatment of individuals who come in close contact with the patient, even if they are asymptomatic
Fomites, such as clothes, towels and bed linens, must be machine washed and dried at a high temperature (60 C)
Insecticide may be used for items that cannot be washed
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↑ 9.09.1Kartono F, Lee EW, Lanum D, Pham L, Maibach HI (2007). "Crusted Norwegian scabies in an adult with Langerhans cell histiocytosis: mishaps leading to systemic chemotherapy". Arch Dermatol. 143 (5): 626–8. doi:10.1001/archderm.143.5.626. PMID17515513.
↑ 11.011.1Lin S, Farber J, Lado L (2009). "A case report of crusted scabies with methicillin-resistant Staphylococcus aureus bacteremia". J Am Geriatr Soc. 57 (9): 1713–4. doi:10.1111/j.1532-5415.2009.02412.x. PMID19895437.
↑Arlian LG, Runyan RA, Achar S, Estes SA (1984). "Survival and infectivity of Sarcoptes scabiei var. canis and var. hominis". J. Am. Acad. Dermatol. 11 (2 Pt 1): 210–5. PMID6434601.
↑ 19.019.1Roberts LJ, Huffam SE, Walton SF, Currie BJ (2005). "Crusted scabies: clinical and immunological findings in seventy-eight patients and a review of the literature". J. Infect. 50 (5): 375–81. doi:10.1016/j.jinf.2004.08.033. PMID15907543.
↑ 20.020.1Arlian LG, Morgan MS, Estes SA, Walton SF, Kemp DJ, Currie BJ (2004). "Circulating IgE in patients with ordinary and crusted scabies". J. Med. Entomol. 41 (1): 74–7. PMID14989349.
↑Feldmeier H, Singh Chhatwal G, Guerra H (2005). "Pyoderma, group A streptococci and parasitic skin diseases -- a dangerous relationship". Trop. Med. Int. Health. 10 (8): 713–6. doi:10.1111/j.1365-3156.2005.01457.x. PMID16045456.
↑Brar BK, Pall A, Gupta RR (2003). "Bullous scabies mimicking bullous pemphigoid". J. Dermatol. 30 (9): 694–6. PMID14578561.
↑Burch JM, Krol A, Weston WL (2004). "Sarcoptes scabiei infestation misdiagnosed and treated as Langerhans cell histiocytosis". Pediatr Dermatol. 21 (1): 58–62. PMID14871329.
↑Mauleón-Fernandez C, Sáez-de-Ocariz M, Rodríguez-Jurado R, Durán-McKinster C, Orozco-Covarrubias L, Ruiz-Maldonado R (2005). "Nodular scabies mimicking urticaria pigmentosa in an infant". Clin. Exp. Dermatol. 30 (5): 595–6. doi:10.1111/j.1365-2230.2005.01832.x. PMID16045712.
↑Duran C, Tamayo L, de la Luz Orozco M, Ruiz-Maldonado R (1993). "Scabies of the scalp mimicking seborrheic dermatitis in immunocompromised patients". Pediatr Dermatol. 10 (2): 136–8. PMID8346105.
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↑Hengge UR, Currie BJ, Jäger G, Lupi O, Schwartz RA (2006). "Scabies: a ubiquitous neglected skin disease". Lancet Infect Dis. 6 (12): 769–79. doi:10.1016/S1473-3099(06)70654-5. PMID17123897.
↑ 30.030.1Hay RJ, Steer AC, Engelman D, Walton S (2012). "Scabies in the developing world--its prevalence, complications, and management". Clin. Microbiol. Infect. 18 (4): 313–23. doi:10.1111/j.1469-0691.2012.03798.x. PMID22429456.
↑Burkhart CG, Burkhart CN, Burkhart KM (2000). "An epidemiologic and therapeutic reassessment of scabies". Cutis. 65 (4): 233–40. PMID10795086.
↑Kristensen JK (1991). "Scabies and Pyoderma in Lilongwe, Malawi. Prevalence and seasonal fluctuation". Int. J. Dermatol. 30 (10): 699–702. PMID1955222.
↑Currie BJ, Connors CM, Krause VL (1994). "Scabies programs in aboriginal communities". Med. J. Aust. 161 (10): 636–7. PMID7968739.
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↑Usha V, Gopalakrishnan Nair TV (2000). "A comparative study of oral ivermectin and topical permethrin cream in the treatment of scabies". J. Am. Acad. Dermatol. 42 (2 Pt 1): 236–40. doi:10.1016/S0190-9622(00)90131-2. PMID10642678.
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