One versus two doses of ivermectin-based mass drug administration for the control of scabies: A cluster randomised non-inferiority trial.

BACKGROUND: Mass drug administration (MDA) based on two doses of ivermectin, one week apart, substantially reduces prevalence of both scabies and impetigo. The Regimens of Ivermectin for Scabies Elimination (RISE) trial assessed whether one-dose ivermectin-based MDA would be as effective. METHODS: RISE was a cluster-randomised trial in Solomon Islands. We assigned 20 villages in a 1:1 ratio to one- or two-dose ivermectin-based MDA. We planned to test whether the impact of one dose on scabies prevalence at 12 and 24 months was non-inferior to two, at a 5% non-inferiority margin. RESULTS: We deferred endpoint assessment to 21 months due to COVID-19. We enrolled 5239 participants in 20 villages at baseline and 3369 at 21 months from an estimated population of 5500. At baseline scabies prevalence was similar in the two arms (one-dose 17·2%; two-dose 13·2%). At 21 months, there was no reduction in scabies prevalence (one-dose 18·7%; two-dose 13·4%), and the confidence interval around the difference included values substantially greater than 5%. There was however a reduction in prevalence among those who had been present at the baseline assessment (one-dose 15·9%; two-dose 10·8%). Additionally, we found a reduction in both scabies severity and impetigo prevalence in both arms, to a similar degree. CONCLUSIONS: There was no indication of an overall decline in scabies prevalence in either arm. The reduction in scabies prevalence in those present at baseline suggests that the unexpectedly high influx of people into the trial villages, likely related to the COVID-19 pandemic, may have compromised the effectiveness of the MDA. Despite the lack of effect there are important lessons to be learnt from this trial about conducting MDA for scabies in high prevalence settings. TRIAL REGISTRATION: Registered with Australian New Zealand Clinical Trials Registry ACTRN12618001086257.

Defining the need for public health control of scabies in Solomon Islands.

Pacific Island countries have a high burden of scabies and impetigo. Understanding of the epidemiology of these diseases is needed to target public health interventions such as mass drug administration (MDA). The aim of this study is to determine the prevalence of scabies and impetigo in Solomon Islands as well as the relationship between them and their distribution. We conducted a prevalence study in 20 villages in Western Province in Solomon Islands. All residents of the village were eligible to participate. Nurses conducted clinical assessments including history features and skin examination. Diagnosis of scabies was made using the 2020 International Alliance for the Control of Scabies diagnostic criteria. Assessments were completed on 5239 participants across 20 villages. Overall scabies prevalence was 15.0% (95%CI 11.8-19.1). There was considerable variation by village with a range of 3.3% to 42.6%. There was a higher prevalence of scabies in males (16.7%) than females (13.5%, adjusted relative risk 1.2, 95%CI 1.1-1.4). Children aged under two years had the highest prevalence (27%). Overall impetigo prevalence was 5.6% (95%CI 4.2-7.3), ranging from 1.4% to 19% by village. The population attributable risk of impetigo associated with scabies was 16.1% (95% CI 9.8-22.4). The prevalence of scabies in our study is comparable to previous studies in Solomon Islands, highlighting a persistent high burden of disease in the country, and the need for public health strategies for disease control.

Protocol for a cluster-randomised non-inferiority trial of one versus two doses of ivermectin for the control of scabies using a mass drug administration strategy (the RISE study).

INTRODUCTION: Scabies is a significant contributor to global morbidity, affecting approximately 200 million people at any time. Scabies is endemic in many resource-limited tropical settings. Bacterial skin infection (impetigo) frequently complicates scabies infestation in these settings. Community-wide ivermectin-based mass drug administration (MDA) is an effective control strategy for scabies in island settings, with a single round of MDA reducing population prevalence by around 90%. However, current two-dose regimens present a number of barriers to programmatic MDA implementation. We designed the Regimens of Ivermectin for Scabies Elimination (RISE) trial to investigate whether one-dose MDA may be as effective as two-dose MDA in controlling scabies in high-prevalence settings. METHODS AND ANALYSIS: RISE is a cluster-randomised non-inferiority trial. The study will be conducted in 20 isolated villages in Western Province of Solomon Islands where population prevalence of scabies is approximately 20%. Villages will be randomly allocated to receive either one dose or two doses of ivermectin-based MDA in a 1:1 ratio. The primary objective of the study is to determine if ivermectin-based MDA with one dose is as effective as MDA with two doses in reducing the prevalence of scabies after 12 months. Secondary objectives include the effect of ivermectin-based MDA on impetigo prevalence after 12 and 24 months, the prevalence of scabies at 24 months after the intervention, the impact on presentation to health facilities with scabies and impetigo, and the safety of one-dose and two-dose MDA. ETHICS AND DISSEMINATION: This trial has been approved by the ethics review committees of the Solomon Islands and the Royal Children's Hospital, Australia. Results will be disseminated in peer-reviewed publications and in meetings with the Solomon Islands Ministry of Health and Medical Services and participating communities. TRIAL REGISTRATION DETAILS: Australian New Zealand Clinical Trials Registry: ACTRN12618001086257. Date registered: 28 June 2018.

Prevalence of scabies and impetigo in the Solomon Islands: a school survey.

BACKGROUND: Scabies, a parasitic disease of the skin, is a major public health problem, largely affecting children. Scabies is often complicated by impetigo which can result in serious complications including invasive infections and immune mediated diseases. Scabies and impetigo are reported to have high prevalence in tropical settings including the Solomon Islands. METHODS: We conducted a cross-sectional prevalence survey at Gizo Primary School in the Western Province of the Solomon Islands in August 2018. The diagnosis of scabies was based on criteria developed by the International Alliance for the Control of Scabies in 2018. Population attributable risk was calculated to determine the effect of scabies on the prevalence of impetigo, and both adjusted and unadjusted risk ratios were calculated to identify differences between sexes and age groups. RESULTS: A total of 324 students were assessed (47.5% of those enrolled at the school). The prevalence of scabies was 54.3% (95% confidence interval [CI] 48.7-59.8) and most disease was mild (68.8%). The prevalence was higher in males (63.5%; adjusted risk ratio [ARR] 1.4, 95% CI 1.1-1.7), and in those aged 10-12 years (61.4%; ARR 1.8, 95% CI 1.1-2.9 when compared to those aged 4-6 years). The prevalence of impetigo was 32.1%, with males more likely to be affected (41.7%, ARR 1.7, 95% CI 1.2-2.4) but with no significant differences between age groups. 63.5% of those with impetigo had scabies, corresponding to a population attributable risk of 11.8%. CONCLUSIONS: There is a very high burden of scabies and impetigo among primary school students in Gizo. There is a critical need for the development and implementation of control programs in areas where scabies is endemic.

The diagnosis of scabies by non-expert examiners: A study of diagnostic accuracy.

BACKGROUND: Although scabies is estimated to be one of the most common skin conditions globally, prevalence data is not available in most settings. Disease mapping is required to develop and monitor successful control programs. Non-expert health workers are likely to play an important role in scabies mapping activities in endemic settings. METHODOLOGY: Four non-expert health workers were trained in the diagnosis of scabies and impetigo. The health worker diagnosis was compared to a reference consensus diagnosis of two doctors experienced in diagnosis. The study was conducted in a primary school in Gizo, Solomon Islands, in August 2018. The six examiners consecutively assessed school students, blinded to each other's findings. Training and diagnostic procedures followed criteria for scabies diagnosis established by the International Alliance for the Control of Scabies in 2018. PRINCIPAL FINDINGS: Amongst the 171 students who underwent clinical assessment the prevalence of scabies and impetigo according to the reference standard was 55% and 45% respectively. Sensitivity of the non-expert health workers' diagnosis compared to the reference standard was 55.3% for scabies (95% confidence interval [CI], 50.1-60.4) with a specificity of 89.9% (95% CI 86-93.1) and 52.6% for impetigo (95% CI 46.9-58.3) with a specificity 97.8% (95% CI 95.7-99). Sensitivity for moderate to severe scabies was 93.5% (95% CI 86.3-97.6) with a specificity of 74% (95% CI 70.2-77.5). CONCLUSIONS: Following brief training, the diagnostic accuracy of non-expert health workers for scabies and impetigo was promising, especially for moderate to severe disease. Modifications to training and processes are recommended to further improve accuracy. The diagnosis by non-expert health workers may be acceptable for scabies and impetigo mapping in endemic areas.