The method of transmission is particularly important when considering care for refugee populations. Scabies is found most often in those living in or traveling from tropical regions including East Asia, Southeast Asia, Oceania, and Latin America.17 In displaced or refugee populations, a lack of access to basic hygiene, extended travel in close quarters, and suboptimal health care access all may lead to an increased incidence of untreated scabies infestations.18 Scabies is more prevalent in children, with increased potential for secondary bacterial infections with Streptococcus and Staphylococcus species due to excoriation in unsanitary conditions. Secondary infection with Streptococcus pyogenes can lead to acute poststreptococcal glomerulonephritis, which accounts for a large burden of chronic kidney disease in affected populations.19 However, scabies may be found in any population, regardless of hygiene or health care access. Treating health care providers should keep a broad differential.
Presentation—The latency of scabies symptoms is 2 to 6 weeks in a primary outbreak and may be as short as 1 to 3 days with re-infestation, following the course of delayed-type hypersensitivity.20 The initial hallmark symptom is pruritus with increased severity in the evening. Visible lesions, excoriations, and burrows associated with scattered vesicles or pustules may be seen over the web spaces of the hands and feet, volar surfaces of the wrists, axillae, waist, genitalia, inner thighs, or buttocks.19 Chronic infestation often manifests with genital nodules. In populations with limited access to health care, there are reports of a sensitization phenomenon in which the individual may become less symptomatic after 4 to 6 weeks and yet be a potential carrier of the mite.21
Those with compromised immune function, such as individuals living with HIV or severe malnutrition, may present with crusted scabies, a variant that manifests as widespread hyperkeratotic scaling with more pronounced involvement of the head, neck, and acral areas. In contrast to classic scabies, crusted scabies is associated with minimal pruritus.22
Diagnosis—The diagnosis of scabies is largely clinical with confirmation through skin scrapings. The International Alliance for Control of Scabies has established diagnostic criteria that include a combination of clinical findings, history, and visualization of mites.23 A dermatologist working with refugee populations may employ any combination of history (eg, nocturnal itch, exposure to an affected individual) or clinical findings along with a high degree of suspicion in those with elevated risk. Visualization of mites is helpful to confirm the diagnosis and may be completed with the application of mineral oil at the terminal end of a burrow, skin scraping with a surgical blade or needle, and examination under light microscopy.
Treatment—First-line treatment for scabies consists of application of permethrin cream 5% on the skin of the neck to the soles of the feet, which is to be left on for 8 to 14 hours followed by rinsing. Re-application is recommended in 1 to 2 weeks. Oral ivermectin is a reasonable alternative to permethrin cream due to its low cost and easy administration in large affected groups. It is not labeled for use in pregnant women or children weighing less than 15 kg but has no selective fetal toxicity. Treatment of scabies with ivermectin has the benefit of treating many other parasitic infections. Both medications are on the World Health Organization Model List of Essential Medications and are widely available for treating providers, even in resource-limited settings.24
Much of the world still uses benzyl benzoate or precipitated sulfur ointment to treat scabies, and some botanicals used in folk medicine have genuine antiscabetic properties. Pruritus may persist for 1 to 4 weeks following treatment and does not indicate treatment failure. Topical camphor and menthol preparations, low-potency topical corticosteroids, or emollients all may be employed for relief.25 Sarna is a Spanish term for scabies and has become the proprietary name for topical antipruritic agents. Additional methods of treatment and prevention include washing clothes and linens in hot water and drying on high heat. If machine washing is not available, clothing and linens may be sealed in a plastic bag for 72 hours.
Pediculosis
Pediculosis is an infestation caused by the ectoparasite Pediculus humanus, an obligate, sesame seed–sized louse that feeds exclusively on the blood of its host (Figure 2).26 Of the lice species, 2 require humans as hosts; one is P humanus and the other is Pthirus pubis (pubic lice). Pediculus humanus may be further classified into morphologies based largely on the affected area: body (P humanus corporis) or head (P humanus capitis), both of which will be discussed.27
FIGURE 2. Pediculus humanus (louse), adult form.