A Spreading Problem

Outbreaks of scabies are common worldwide and difficult to resolve. Once isolated to specific regions, scabies is becoming a more generalized concern due to the many mass migrations of refugees to other countries. “To be honest, I do not know whether the overall incidence has changed over the past few years,” Dr. Mueller said.  “However, we certainly see increasing clusters of outbreaks among refugees, due to poor sanitary conditions during escape.”

Many obstacles have prevented eradication of scabies. Primary among them is a lack of consistently effective diagnostic methods. In a review of scabies therapeutic trials, Thompson, et al4 reported that only half of the studies reviewed designated clinical observation of a rash, pruritis, and mite burrows for diagnosis, while the rest were poorly defined. Parasitic testing was used in just more than half of the trials as well. Of note, they concluded that “no predominant combination of diagnostic criteria emerged through the review.”

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Current treatments also present obstacles to the eradication of the mites on both the individual and mass scale. Topical permethrin 5% is the most commonly used treatment worldwide, and although effective and readily available, its use is associated with a high rate of allergic reactions and escalating drug resistance leading to non-response to treatment.6,7 The requirement that the patient be covered from the neck down with permethrin 5% cream for 8 hours before being rinsed off contributes to a high incidence of nonadherence by caregivers.6

Oral ivermectin has not been approved in the United States for treatment of scabies, but has been widely implemented as well, although a 2019 Cochran review found that it was associated with a higher treatment failure rate than topical permethrin.8

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Seeking Effective Solutions

As the immigrant crises continue in the United States and other countries, the problem of scabies becomes more generalized, and new investigations have begun to take a broader approach to solutions. Mueller and colleagues published a study in BMC Infectious Diseases of a triaging algorithm for the treatment of large numbers of Syrian refugees with known or suspected scabies.9 The study randomly assigned 48 infected individuals to one of three groups according to diagnostic criteria (no signs, itch only, and skin lesions with itching). All were treated with one dose of oral ivermectin or two doses seven days apart. Patients in group 3 were given two doses of oral ivermectin with two doses of topical permethrin seven days apart. At four weeks, the algorithm was reapplied to four patients who had not fully recovered. At the end of eight weeks, all patients were symptom-free and required no further treatment.9

The researchers wrote that their algorithm “proved to be both highly efficient for treatment of large numbers of patients with suspected or diagnosed scabies infestation as well as for prevention of spreading of the disease.” They believe this algorithm is well suited for the management of scabies mass outbreaks.

References

  1. World Health Organization. Report of the tenth meeting of the WHO Strategic and Technical Advisory Group for neglected tropical diseases. 2017 [cited 17 March 2018].  http://www.who.int/ neglected diseases/NTD_ST AG_report_2017.pdf?ua=1. Accessed August 14, 2019.
  2. Engelman D, Cantey PT, Marks M, et al. The public health control of scabies: priorities for research and action [published online June 6, 2019]. Lancet. doi:10.1016/S0140-6736(19)31136-5
  3. GBD 2016 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet. 2017;390:1211-1259.
  1. Thompson MJ, Engelman D, Gholam K, Fuller LC, Steer AC. Systematic review of the diagnosis of scabies in therapeutic trials. Clin Exp Dermatol. 2017;42:481-487.
  2. Ong CY, Vasanwala FF. Infected with scabies again? Focus in management in long-term care facilities. Diseases. 2019;29:7.
  3. Anderson KL, Strowd LC. Epidemiology, diagnosis, and treatment of scabies in a dermatology office. J Am Board Fam Med. 20172;30:78-84.
  4. Thomas J, Peterson  GM, Walton SF, et al. Scabies: an ancient global disease with a need for new therapies.. BMC Infect Dis. 2015;15:250. 
  5. Dhana A, Yen H, Okhovat JP, et al. Ivermectin versus permethrin in the treatment of scabies: A systematic review and meta-analysis of randomized controlled trials. J Am Acad Dermatol. 2018;78194-78198.
  6. Mueller SM, Gysin S, Schweitzer M, et al. Implementation and evalution of an algorithm for the management of scabies outbreaks. BMC Infect Dis. 2019;19:200.

This article originally appeared on Dermatology Advisor

Topics:

General Dermatology Infectious Disease Medicine