Prospective Surveillance of Primary Healthcare Presentations for Scabies and Bacterial Skin Infections in Fiji, 2018-2019

Costs of primary healthcare presentations and hospital admissions for scabies and related skin infections in Fiji, 2018-2019

Scabies and related bacterial skin and soft tissue infections (SSTIs) are highly prevalent in many tropical, low- and middle-income settings. These skin conditions contribute to higher healthcare costs and burdens on healthcare systems. The Big Skin Health Intervention Fiji Trial ("Big SHIFT") carried out surveillance for scabies and SSTIs from July 2018 to June 2019 in the Northern Division of Fiji, an area with high prevalence of scabies, prior to a division-wide ivermectin-based mass drug administration (MDA) campaign. Using data from Big SHIFT, we sought to estimate the annual direct healthcare costs of scabies and related SSTIs for the Northern Division and extrapolate these costs to the national level. We categorized SSTIs as being potentially scabies-related or unlikely scabies-related, based on a previous study. The analysis used a health system perspective, with the main resource use categories of outpatient visits, bed days during admissions, medicines, and diagnostic tests. We extrapolated the total annual number of cases and direct healthcare costs for all divisions in Fiji based upon previous scabies and impetigo prevalence data across all divisions. The average cost per PHC presentation for scabies was US$17.7, and for potentially scabies-related SSTI was $18.3. The average cost per hospital admission for a potentially scabies-related SSTI case was $439. The estimated annual healthcare costs of scabies and related SSTIs in Fiji was US$3.0 million, with cost per capita of $3.3. Scabies and related SSTIs lead to a heavy economic burden in Fiji and prevention would reduce these healthcare costs.

Scabies, Bedbug, and Body Lice Infestations: A Review

Importance

Scabies, bedbug, and body lice infestations are caused by organisms that live on or in the skin, on clothing, or in the environment and commonly cause pruritus and rash. In 2021, approximately 622 million incident cases of scabies occurred globally. Data on bedbug infestations are limited. Body lice prevalence ranges from 4.1% to 35% among persons experiencing homelessness worldwide.

Observations

Scabies is caused by mites (Sarcoptes scabiei) that burrow into the epidermis. Transmission primarily occurs from prolonged skin-to-skin contact with an individual who has an infestation. Common scabies is characterized by excoriated pruritic papules, plaques, and pathognomonic burrows on finger/toe web spaces, volar wrists, ankles, axillae, buttocks, male genitalia, and areolae. Permethrin cream and oral ivermectin are first-line treatments for adults, with similar clearance rates by week 2 (74% with permethrin vs 68% with ivermectin; relative risk, 0.91; 95% CI, 0.76-1.08). Treatment failure can occur with oral ivermectin (11.8%; 95% CI, 8.4%-15.4%) and topical permethrin (10.8%; 95% CI, 7.5%-14.5%). Bedbugs (Cimex lectularius, Cimex hemipterus) are insects that live on mattresses and furniture and feed on blood nocturnally, causing linear pruritic erythematous papules. New skin lesions on waking, cohabitants with similar symptoms, and recently residing in a high-occupancy setting should raise suspicion. Treatment requires eradication with pest management. Body lice (Pediculus humanus humanus) are insects found on clothing that travel to the skin for blood meals. Body lice bites cause pruritic excoriated macules/papules and hyperpigmentation in areas where clothing seams contact skin. Treatment and prevention require at least once-weekly bathing and laundering of clothing and bedding.

Conclusions and Relevance

Scabies, bedbug, and body lice infestations are common. Accurate diagnosis requires taking a history, including social drivers of health (eg, housing status, living environment), and physical examination. First-line treatments include scabicides for patients with common scabies and their close contacts. Scabies, bedbug, and body lice infestations should be treated with decontamination measures.

Standardization of Epidemiological Surveillance of Group A Streptococcal Impetigo

Impetigo is a highly contagious bacterial infection of the superficial layer of skin. Impetigo is caused by group A Streptococcus (Strep A) and Staphylococcus aureus, alone or in combination, with the former predominating in many tropical climates. Strep A impetigo occurs mainly in early childhood, and the burden varies worldwide. It is an acute, self-limited disease, but many children experience frequent recurrences that make it a chronic illness in some endemic settings. We present a standardized surveillance protocol including case definitions for impetigo including both active (purulent, crusted) and resolving (flat, dry) phases and discuss the current tests used to detect Strep A among persons with impetigo. Case classifications that can be applied are detailed, including differentiating between incident (new) and prevalent (existing) cases of Strep A impetigo. The type of surveillance methodology depends on the burden of impetigo in the community. Active surveillance and laboratory confirmation is the preferred method for case detection, particularly in endemic settings. Participant eligibility, surveillance population and additional considerations for surveillance of impetigo, including examination of lesions, use of photographs to document lesions, and staff training requirements (including cultural awareness), are addressed. Finally, the core elements of case report forms for impetigo are presented and guidance for recording the course and severity of impetigo provided.

Scabies incidence and association with skin and soft tissue infection in Loyalty Islands Province, New Caledonia: A 15-year retrospective observational study using electronic health records

Background

Scabies and its complications are a public health problem in the low- and middle-income countries of the Western Pacific region. However, no data are available for the relatively wealthy French territory of New Caledonia. This study aimed to determine the incidence of scabies and its association with skin and soft tissue infection (SSTI) in Loyalty Islands Province (LIP) (20,000 inhabitants), New Caledonia.

Methodology/Principal findings

This retrospective observational study reviewed cases of scabies and SSTI extracted from the electronic health record databases of LIP clinics for the period 2004–2018. Data were validated through double sampling. The overall scabies incidence rate (IR) and scabies IRs by sex and age group were calculated. Scabies seasonality was evaluated. For children <5 years, the presence of SSTI was compared between the 3-month period preceding scabies diagnosis/treatment and the 3-month period preceding the 1-year anniversary of scabies diagnosis/treatment (self-matching).

A total of 16,843 scabies cases were extracted using a detection algorithm with a sensitivity of 96.7% and a specificity of 99.9%. From 2004 to 2018, the average overall scabies IR was 5.9% and the average scabies IR in children <1 year was 18.4%. Almost two-thirds of children aged 14 years had a history of scabies. Females were more affected, especially in the 20–39 age group (sex ratio>2). A strong seasonality was observed, with a 30% increase in winter. In children <5 years, SSTIs were 4.3 times more frequent in the 3 months preceding the scabies diagnosis than in the 3 months preceding the 1-year anniversary of scabies treatment (p<0.001).

Conclusions

Although health care is much better in New Caledonia than in neighboring countries, scabies is highly endemic in LIP. The disease is especially common in children <2 years and is associated with many SSTIs in children <5 years. Mass drug administration should be considered.

Scabies is a known public health problem in the Pacific region. This study aimed to determine the importance of scabies and associated skin infections in the Loyalty Island Province (LIP) of New Caledonia (20,000 inhabitants).

The provincial electronic medical database was searched for all cases of scabies and skin infection that occurred in the LIP population between 2004 and 2018. To evaluate the impact of scabies on skin infections, we measured the decrease in the number of skin infections in children <5 years one year after scabies treatment.

Over the study period, the average number of scabies cases occurring each year was 6 per 100 inhabitants. In children <1 year, this number was 18 per 100 inhabitants. We found that 80% of children aged 15 years had experienced at least one episode of scabies. We also observed a fourfold decrease in the number of skin infections in children <5 years 1 year after treatment. Scabies was more frequent (+30%) in winter.

The efficacy of sampling strategies for estimating scabies prevalence

Background

Estimating community level scabies prevalence is crucial for targeting interventions to areas of greatest need. The World Health Organisation recommends sampling at the unit of households or schools, but there is presently no standardised approach to scabies prevalence assessment. Consequently, a wide range of sampling sizes and methods have been used. As both prevalence and drivers of transmission vary across populations, there is a need to understand how sampling strategies for estimating scabies prevalence interact with local epidemiology to affect the accuracy of prevalence estimates.

Methods

We used a simulation-based approach to compare the efficacy of different scabies sampling strategies. First, we generated synthetic populations broadly representative of remote Australian Indigenous communities and assigned a scabies status to individuals to achieve a specified prevalence using different assumptions about scabies epidemiology. Second, we calculated an observed prevalence for different sampling methods and sizes.

Results

The distribution of prevalence in subpopulation groups can vary substantially when the underlying scabies assignment method changes. Across all of the scabies assignment methods combined, the simple random sampling method produces the narrowest 95% confidence interval for all sample sizes. The household sampling method introduces higher variance compared to simple random sampling when the assignment of scabies includes a household-specific component. The school sampling method overestimates community prevalence when the assignment of scabies includes an age-specific component.

Discussion

Our results indicate that there are interactions between transmission assumptions and surveillance strategies, emphasizing the need for understanding scabies transmission dynamics. We suggest using the simple random sampling method for estimating scabies prevalence. Our approach can be adapted to various populations and diseases.

Scabies is a parasitic infestation that is commonly observed in disadvantaged populations. A wide range of sampling sizes and methods have been used to estimate scabies prevalence. With differing key drivers of transmission and varying prevalence across populations, it can be challenging to determine an effective sampling strategy. In this study, we propose a simulation approach to compare the efficacy of different sampling methods and sizes. First, we generate synthetic populations and then assign a scabies status to individuals to achieve a specified prevalence using different assumptions about scabies epidemiology. Second, we calculate an observed prevalence for different sampling methods and sizes. Our results indicate that there are interactions between transmission assumptions and surveillance strategies. We suggest using the simple random sampling method for estimating prevalence as it produces the narrowest 95% confidence interval for all sampling sizes. We propose guidelines for determining a sample size to achieve a desired level of precision in 95 out 100 samples, given estimates of the population size and a priori estimates of true prevalence. Our approach can be adapted to various populations, informing an appropriate sampling strategy for estimating scabies prevalence with confidence.

Prevention of bacterial complications of scabies using mass drug administration: A population-based, before-after trial in Fiji, 2018-2020

BACKGROUND

Scabies is an important predisposing factor of impetigo which can lead to serious bacterial complications. Ivermectin-based mass drug administration can substantially reduce scabies and impetigo prevalence in endemic settings, but the impact on serious bacterial complications is not known.

METHODS

We conducted a before-after trial in the Northern Division of Fiji (population: 131,914) of mass drug administration for scabies control. Prospective surveillance was conducted from 2018 to 2020. Mass drug administration took place in 2019, involving two doses of oral ivermectin or topical permethrin, delivered alongside diethylcarbamazine and albendazole for lymphatic filariasis. The primary outcomes were incidence of hospitalisations with skin and soft tissue infections, and childhood invasive infections and post-streptococcal sequelae. Secondary outcomes included presentations to primary healthcare with skin infections and community prevalence of scabies and impetigo.

FINDINGS

The incidence of hospitalisations with skin and soft tissue infections was 17% lower after the intervention compared to baseline (388 vs 467 per 100,000 person-years; incidence rate ratio 0.83, 95% CI, 0.74 to 0.94; P = 0.002). There was no difference in incidence of childhood invasive infections and post-streptococcal sequelae. Incidence of primary healthcare presentations with scabies and skin infections was 21% lower (89.2 vs 108 per 1000 person-years, incidence rate ratio, IRR 0.79, 95% CI, 0.78 to 0.82). Crude community prevalence of scabies declined from 14.2% to 7.7% (cluster-adjusted prevalence 12.5% to 8.9%; prevalence ratio 0.71, 95% CI, 0.28 to 1.17). Cluster-adjusted prevalence of impetigo declined from 15.3% to 6.1% (prevalence ratio 0.4, 95% CI, 0.18 to 0.86).

INTERPRETATION

Mass drug administration for scabies control was associated with a substantial reduction in hospitalisations for skin and soft tissue infections.

FUNDING

National Health and Medical Research Council of Australia and Scobie and Claire Mackinnon Trust.

Estimation of scabies prevalence using simplified criteria and mapping procedures in three Pacific and southeast Asian countries

Background

Scabies causes considerable morbidity in disadvantaged populations. The International Alliance for the Control of Scabies (IACS) published consensus criteria in 2020 to standardize scabies diagnosis. However, these criteria are complex, and a WHO informal consultation proposed simplified criteria for mapping, to identify regions of high prevalence as targets for mass drug administration. We aimed to investigate the accuracy of simplified criteria in determining scabies prevalence, compared to the 2020 IACS criteria.

Methods

We obtained data relating to demographics, relevant history and skin lesions from all-age prevalence surveys from Fiji (n = 3365) and Solomon Islands (n = 5239), as well as school-aged children in Timor-Leste (n = 1043). We calculated prevalence using the 2020 IACS criteria and simplified criteria and compared these disease estimates.

Results

There was no significant difference in the pooled prevalence using the two methods (2020 IACS criteria: 16.6%; simplified criteria: 15.6%; difference = 0.9, [95% CI -0.1, 2.0]). In Timor-Leste, the prevalence using simplified criteria was lower (26.5% vs 33.8%). Simplified criteria had a sensitivity of 82.3% (95% CI 80.2, 84.2) and specificity of 97.6% (95% CI 97.2, 97.9) compared to the 2020 IACS criteria.

Conclusions

The scabies prevalence estimation using simplified criteria was similar to using the 2020 IACS criteria in high prevalence, tropical countries. The prevalence estimation was lower in the school-based survey in Timor-Leste. Mapping using simplified criteria may be a feasible and effective public health tool to identify priority regions for scabies control. Further work assessing use of simplified criteria for mapping in a field setting should be conducted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-12039-2.