The public health control of scabies: priorities for research and action

doi:10.1016/S0140-6736(19)31136-5

The Lancet

Volume 394, Issue 10192, 6–12 July 2019, Pages 81-92

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https://doi.org/10.1016/S0140-6736(19)31136-5 Get rights and content

Summary

Scabies is a parasitic disease of the skin that disproportionately affects disadvantaged populations. The disease causes considerable morbidity and leads to severe bacterial infection and immune-mediated disease. Scientific advances from the past 5 years suggest that scabies is amenable to population-level control, particularly through mass drug administration. In recognition of these issues, WHO added scabies to the list of neglected tropical diseases in 2017. To develop a global control programme, key operational research questions must now be addressed. Standardised approaches to diagnosis and methods for mapping are required to further understand the burden of disease. The safety of treatments for young children, including with ivermectin and moxidectin, should be investigated. Studies are needed to inform optimum implementation of mass treatment, including the threshold for intervention, target, dosing, and frequency. Frameworks for surveillance, monitoring, and evaluation of control strategies are also necessary.

Introduction

In 2017, scabies was added to the WHO list of neglected tropical diseases (NTDs). Scabies was recommended to be included as a category A NTD, defined as those conditions that fulfil all four specified criteria, and are recommended for large-scale action in the portfolio of the NTD Department.¹ In reaching this recommendation, the WHO NTD Strategic and Technical Advisory Group noted the need for further research to inform control strategy and key issues for programmatic implementation, including ensuring affordable access to oral medications and developing guidelines for their public health use.² In March, 2018, the WHO NTD Global Working Group on Monitoring and Evaluation discussed scabies for the first time.³ Key recommendations from that meeting included the need to better define the global burden, to integrate control efforts to capitalise on ivermectin-based programmes for other NTDs, and to establish interim guidelines for public health interventions for scabies control. In this rapidly evolving context, we review major advances in the science of control of human scabies from the past 5 years and identify key operational research questions that need to be addressed to develop a global scabies control programme.

Section snippets

The burden of scabies

Scabies is caused by infestation with the microscopic ectoparasite Sarcoptes scabiei var hominis, and leads to severe itch, skin lesions, and more serious complications due to bacterial superinfection (figure 1). Transmission requires skin-to-skin contact, and no non-human reservoir exists. Scabies occurs in all countries, but its distribution is not uniform. In high-income settings, most cases are sporadic, and the predominant public health issue is the management of outbreaks in institutions

Diagnosis

Both the mapping of scabies and population-level control are hampered by the absence of a reliable, reproducible, and standardised approach to diagnosis. Two systematic reviews of diagnostic methods found inconsistency in approaches to scabies diagnosis.34, 35 Microscopy of skin scrapings to visualise mites and eggs is highly specific but insensitive and operator dependent, and therefore generally not useful for field settings. To address this gap, an international panel of experts, convened by

Epidemiology and mapping

Despite an expansion of research on scabies in the past decade, the development of a global strategy has been constrained by the scarcity of prevalence data, including from those countries suspected to be at risk on the basis of routinely reported clinical data or geographical or socioeconomic characteristics. For example, a worldwide systematic review of published scabies prevalence estimates found 48 studies, of variable quality, with over-representation of countries in the Pacific region and

Transmission and complications

Despite scabies being an ancient disease, our understanding of the drivers of transmission remains poor. Understanding transmission dynamics is important for investigating the comparative effects of different control strategies, including through mathematical modelling.74, 75 The observed cycles of scabies prevalence in some temperate settings (leading to the misnomer the 7-year itch) previously raised the possibility of herd immunity. However, in many tropical settings, recurrent infestations

Social and economic issues

As a disease that affects the skin, scabies is a potent cause of stigma and reduced quality of life.9, 92, 93 Increasingly, the chronic disfigurement caused by scabies and other NTDs is understood to adversely affect mental health,56, 94 although this aspect has not been factored into current GBD estimates of DALYs. Understanding the conception of scabies, itch, and impetigo within various cultures will help define what scabies as a public health problem means to the most affected communities.

Treatment

Although various effective, topical preparations exist for treatment of individual cases, for multiple reasons these agents are poorly suited to population-level control interventions. Reasons include the prolonged duration of application required and local irritation, resulting in inadequate adherence.⁹⁹ Permethrin 5% cream is the most effective topical treatment,¹⁰⁰ but is expensive and unavailable in most countries.²¹ Topical treatments that are available in some low-income and middle-income

Population-level control

The strategy of individual case management has not appreciably reduced the transmission of scabies in high-prevalence settings.6, 150 Data from studies using MDA have led to renewed interest in the potential of MDA to contribute to sustained population-level control.151, 152 Programmes of mass treatment combined with additional screening and case management in Panama and Australia (using permethrin)6, 17, 153 and the Solomon Islands (using ivermectin)¹⁵⁴ considerably reduced scabies prevalence.

Developing a global strategy

Despite some deficiencies in the evidence for scabies control strategies, preliminary recommendations are needed for countries wishing to commence control measures, alongside pursuit of the research agenda described here. Initial guidance is required on the threshold of scabies prevalence above which MDA could be recommended and other health-system-related, geographical, sociopolitical, or pragmatic factors that might affect this decision. In lower-prevalence settings, intensified case

Conclusions

Scabies is a common illness and major health issue affecting communities in many resource-poor settings, warranting public health intervention. Strong evidence suggests that ivermectin-based MDA strategies can be highly effective in reducing the burden of scabies and impetigo in some settings. Future research priorities include further defining the burden of disease, development of standardised approaches to diagnosis and population burden estimation, novel diagnostics, and treatments, and

Search strategy and selection criteria

References for this Review were identified through searches of PubMed for articles published between Jan 1, 1990, and March 31, 2019, using the terms “scabies” and “Sarcoptes scabiei”. Reference lists of identified manuscripts were reviewed to identify additional relevant material. No language restrictions were imposed.

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Cited by (91)

Spanish Academy of Dermatology and Venereology (AEDV) expert recommendations for the management of sexual transmitted parasitosis. Scabies, and pediculosis pubis
2024, Actas Dermo-Sifiliograficas
Las enfermedades transmisibles en las que el patógeno se transmite por contacto sexual se denominan infecciones de transmisión sexual. La Academia Española de Dermatología (AEDV), a través de su grupo de trabajo de infecciones de transmisión sexual, se ha propuesto elaborar documentos de recomendaciones, destinados a la orientación de los dermatólogos y del personal sanitario que atiende en España a personas afectadas de estas infecciones. El presente documento analiza las características epidemiológicas, clínicas, terapéuticas y de control de 2 parasitosis consideradas de transmisión sexual: la escabiosis, causada por Sarcoptes scabiei var. hominis, y la pediculosis púbica, causada por el Pthirus pubis. Ambas parasitosis tienen en común que pueden diseminarse de forma mixta, por vía sexual y comunitaria, independientemente del modo de adquisición de la infestación. Esta peculiaridad genera particularidades en el control de la infestación.
Sexually transmitted infections are communicable diseases where the pathogen is transmitted through sexual contact. The Sexually Transmitted Infections Working Group of the Spanish Academy of Dermatology and Venereology (AEDV) is engaged in the drafting of documents to guide dermatologists and health care personnel who treat Spanish patients with these infections. This document analyzes the epidemiological, clinical, therapeutic, and control characteristics of 2 sexually transmitted parasitosis: scabies due to Sarcoptes scabiei var. hominis, and pubic pediculosis due to Phthirus pubis. Both parasitoses share a sort of mixed spread through sexual and community transmission regardless of the route through which the infection was initially acquired. This specific feature creates particularities in the management and control of the infestation.
Efficacy and safety of moxidectin and albendazole compared with ivermectin and albendazole coadministration in adolescents infected with Trichuris trichiura in Tanzania: an open-label, non-inferiority, randomised, controlled, phase 2/3 trial
2023, The Lancet Infectious Diseases
Control efforts against soil-transmitted helminths focus on preventive chemotherapy with albendazole and mebendazole, however these drugs yield unsatisfactory results against Trichuris trichiura infections. We aimed to assess the efficacy and safety of moxidectin and albendazole compared with ivermectin and albendazole against T trichiura in adolescents living on Pemba Island, Tanzania.
This open-label, non-inferiority, randomised, controlled, phase 2/3 trial was done in four secondary schools (Kilindi, Kwale, Ndagoni [Chake Chake District], and Kiuyu [Wete District]) on Pemba Island, Tanzania. Adolescents aged 12–19 years who tested positive for T trichiura in at least two of four Kato-Katz slides with a mean infection intensity of 48 eggs per gram (EPG) of stool or higher were considered for inclusion. Participants were randomly assigned (21:21:2:2:8) to five treatment groups (8 mg moxidectin and 400 mg albendazole [group 1], 200 μg/kg ivermectin and 400 mg albendazole [group 2], 400 mg albendazole [group 3], 200 μg/kg ivermectin [group 4], or 8 mg moxidectin [group 5]) using a computer-generated randomisation code, stratified by baseline T trichiura infection intensity. Study site investigators and participants were not masked to study treatment; however, allocation was concealed to participants. The primary outcome was egg reduction rate (ERR) of T trichiura 14–21 days after treatment in the available case population. Moxidectin and albendazole was considered non-inferior to ivermectin and albendazole (control group) when the lower limit of the two-sided 95% CI of the difference was higher than the non-inferiority margin of –2 percentage points. This study is registered with ClinicalTrials.gov, NCT04700423.
Between March 1 and April 30, 2021, 771 participants were assessed for eligibility. 221 (29%) of 771 participants were ineligible and a further 14 (2%) were excluded. 207 (39%) of 536 participants were randomly assigned to moxidectin and albendazole, 211 (39%) to ivermectin and albendazole, 19 (4%) to albendazole, 19 (4%) to ivermectin, and 80 (15%) to moxidectin. Primary outcome data were available for all 536 participants. The geometric mean ERR of T trichiura after 14–21 days was 96·8% (95% CI 95·8 to 97·6) with moxidectin and albendazole and 99·0% (98·7 to 99·3) with ivermectin and albendazole (difference of –2·2 percentage points [–4·2 to –1·4]). No serious adverse events were reported during the study. The most reported adverse events were headache (160 [34%] of 465), abdominal pain (78 [17%]), itching (44 [9%]), and dizziness (26 [6%]).
Our findings show inferiority of moxidectin and albendazole to ivermectin and albendazole against T trichiura. However, given the high efficacy, moxidectin coadministration might complement treatment progammes, particularly in areas in which ivermectin is not available
Bill and Melinda Gates Foundation, reference number OPP1153928.
[Translated article] Epidemic Scabies: New Treatment Challenges in an Ancient Disease
2023, Actas Dermo-Sifiliograficas
Scabies which is among the most prevalent diseases worldwide, is becoming more frequent in Spain. The problems of this epidemic can be explained by several factors: improper application or prescription of treatments, resistance or reduced sensitivity to topical treatments, and poor understanding of the parasite and contagion. We require a new evidence-based approach to therapy that takes these problems into consideration. If symptoms persist after proper treatment, it is important to identify the reason for failure and standardize our approach. In refractory cases, the prescriber should prioritize oral medication, indicate a higher dose, combine treatments, or evaluate the use of off-label treatments in certain populations. The availability of new medications, such as spinosad or, especially, moxidectin, offer hope for bringing this disease under control.
La escabiosis es una de las enfermedades transmisibles más prevalentes en el mundo, actualmente en auge en nuestro entorno. Existen diferentes causas que explican la problemática de esta epidemia: una incorrecta aplicación o pauta del tratamiento; la disminución de la sensibilidad o la resistencia al tratamiento tópico y las carencias en el conocimiento del parásito y su transmisibilidad. Por este motivo es necesario un nuevo enfoque en el tratamiento de esta enfermedad que contemple los problemas y la evidencia actual. Si hay una persistencia de la clínica tras un correcto tratamiento es importante corroborar el fracaso terapéutico y estandarizar la actitud. Por último, ante un caso recalcitrante cabría plantear la posibilidad de priorizar el tratamiento oral, aumentar su dosis, realizar tratamientos combinados o plantear su uso fuera de ficha técnica en poblaciones especiales. La aparición de nuevos tratamientos, como el spinosad o, sobre todo, la moxidectina, aportan esperanza en el control de esta enfermedad.
Pruritic papules and nodules as sign of persistent scabies infestation despite treatment according to current guidelines evidence for treatment resistance to ivermectin, benzylbenzoat and permethrin proven by videomicroscopy
2023, IDCases
Scabies infestation is a growing public health issue due to its world wide increase of incidence. The objective of this study was to proof treatment resistance towards treatment, which was applied according to international guidelines. This is a controversial issue since treatment failures were believed to be due to false application oft he treatment. Here, we proof fort he first time this treatment resistance by videomicroscopic evaluation. Additionally an escalation therapy is described, which led to an effective treatment.
Modelling mass drug administration strategies for reducing scabies burden in Monrovia, Liberia
2023, Epidemiology and Infection
Effects of weather and air pollution on outpatient visits for insect-and-mite-caused dermatitis: an empirical and predictive analysis
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ReviewThe public health control of scabies: priorities for research and action

Summary

Introduction

Section snippets

The burden of scabies

Diagnosis

Epidemiology and mapping

Transmission and complications

Social and economic issues

Treatment

Population-level control

Developing a global strategy

Conclusions

Search strategy and selection criteria

Lancet Infect Dis

Lancet

Lancet Infect Dis

Clin Microbiol Infect

Lancet Infect Dis

Trends Parasitol

Lancet Infect Dis

Lancet Infect Dis

Math Biosci

J Infect

Lancet Infect Dis

Kidney Int

Parasitol Int

Lancet

Trends Parasitol

Lancet Infect Dis

Recommendations for the adoption of additional diseases as neglected tropical diseases

Report of the tenth meeting of the WHO Strategic and Technical Advisory Group for Neglected Tropical Diseases

9th NTD-STAG Global Working Group Meeting on Monitoring and Evaluation of Neglected Tropical Diseases

The global epidemiology of impetigo: a systematic review of the population prevalence of impetigo and pyoderma

PLoS One

The prevalence of scabies and impetigo in the solomon islands: a population-based survey

PLoS Negl Trop Dis

Scabies and impetigo in Timor-Leste: a school screening study in two districts

PLoS Negl Trop Dis

The prevalence and association with health-related quality of life of tungiasis and scabies in schoolchildren in southern Ethiopia

PLoS Negl Trop Dis

Skin disease prevalence study in schoolchildren in rural Cote d'Ivoire: implications for integration of neglected skin diseases (skin NTDs)

PLoS Negl Trop Dis

Prevalence and drivers of human scabies among children and adolescents living and studying in Cameroonian boarding schools

Parasit Vectors

Scabies in resource-poor communities in Nasarawa State, Nigeria: epidemiology, clinical features and factors associated with infestation

Trop Med Infect Dis

Impact of ivermectin mass drug administration for lymphatic filariasis on scabies in eight villages in Kongwa District, Tanzania

Am J Trop Med Hyg

Scabies among primary schoolchildren in Egypt: sociomedical environmental study in Kafr El-Sheikh administrative area

Clin Cosmet Investig Dermatol

Scabies and impetigo prevalence and risk factors in Fiji: a national survey

PLoS Negl Trop Dis

Success of a scabies control program in an Australian Aboriginal community

Pediatr Infect Dis J

Impact of climate change on dermatological conditions related to flooding: update from the International Society of Dermatology Climate Change Committee

Int J Dermatol

Ethiopia—scabies outbreak response in Amhara regional state

Investigation of a scabies outbreak in drought-affected areas in Ethiopia

Trop Med Infect Dis

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

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Global, regional, and national disability-adjusted life-years (DALYs) for 333 diseases and injuries and healthy life expectancy (HALE) for 195 countries and territories, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016

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The importance of scabies coinfection in the treatment considerations for impetigo

Pediatr Infect Dis J

Scabies and risk of skin sores in remote Australian Aboriginal communities: a self-controlled case series study

PLoS Negl Trop Dis

Is impetigo a missed opportunity for scabies treatment?

N Z Med J

Parasitic scabies mites and associated bacteria joining forces against host complement defence

Parasite Immunol

Scabies mite inactive serine proteases are potent inhibitors of the human complement lectin pathway

PLoS Negl Trop Dis

A scabies mite serpin interferes with complement-mediated neutrophil functions and promotes staphylococcal growth

PLoS Negl Trop Dis

Scabies mites alter the skin microbiome and promote growth of opportunistic pathogens in a porcine model

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Toward the global control of human scabies: introducing the International Alliance for the Control of Scabies

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Review
The public health control of scabies: priorities for research and action