Systematic Review of Institutional Scabies Outbreaks in Sub Saharan Africa

Background

Scabies is a global health problem largely affecting low and middle-income countries with a disproportionate burden on children and the elderly living in poor and overcrowded areas [1]. Globally, it has been estimated to affect over 200 million people with the prevalence rate of scabies infections variying between 0.2% to 71.4 % [2].

Up until recently, there has been paucity of data on the epidemiology of scabies in Sub-Saharan Africa and in particular community and facility based level estimates of disease burden [3]. There is more recent data from Ethiopia, Liberia, Nigeria, Cameroon, Malawi and Ghana which all suggest that scabies is a major public health problem in sub-Saharan Africa [4, 5, 6, 7, 8, 9]. The predisposing factors are overcrowding, poor personal hygiene, low socio-economic standards and impaired host immunity [5, 10]. The clinical features of scabies follow the invasion of the adult female S scabiei var hominis mites into the top layer of epidermis causing serpentine burrows using proteolytic enzymes to dissolve the stratum corneum .This results in the infected individual developing an allergic hypersensitive reaction to the presence of mite proteins and faeces in the scabies burrow, causing intense itch and rash [1, 11]. The persistent itch may lead to excoriations from scratches, exposing the skin to secondary bacterial infections that result in cellulitis, impetigo, and pyoderma [12, 13, 14].

Apart from the clinical manifestations, this disease is associated with reduced quality of life causing psychosocial, and emotional consequences to the affected populations [8, 9]. Scabies is a significant cause of morbidity and a potential source of economic burden in most low and middle- income countries. It imposes a considerable financial burden on individuals, families, communities, and the country`s health systems [1]. Early diagnosis of scabies is crucial in avoiding outbreaks, preventing exposure to unnecessary treatment, significant morbidity, and increased economic burden [1, 15]. The diagnosis has been quite challenging in most low income countries, as clinical diagnosis is still the most common method of disease confirmation [6]. In the past decade, evidence from literature has shown that there was no standardized technique for diagnosing scabies to facilitate communication and comparison of epidemiological and clinical findings and the development of scabies control strategies [16].

To address this issue, The International Alliance for the Control of Scabies (IACS) Criteria [17] was developed through a Delphi study with international experts panel where detailed expert opinions and recommendations were obtained and combined with a comprehensive review of the available literature to develop uniform, evidence‐based definitions and consistent diagnostic methods [17, 18].

The main public health interventions for scabies control are intensified disease management (IDM) and preventive chemotherapy [19]. The magnitude of community and institutional scabies outbreaks is still being underestimated. Evidence from literature has reported scabies outbreaks to have occurred in the hospitals, prisons, orphanages, schools, army barracks and nursery homes across the world [20]. The aim of this systematic review is to identify and describe the literature on scabies outbreaks within facility based settings, explore epidemiological risk factors, its progression and response across Sub Saharan African countries.

Eligibility Criteria

Inclusion criteria were defined according to the populations, interventions, comparisons, outcomes and study type (PICOS) framework, a model adopted by the Cochrane Library to structure rigorous reviews on health- related questions. The inclusion and exclusion criteria were as follows (Table 1).

Quality assessment and Study Selection

The Critical Appraisals Skills Programme (CASP) checklists were used for case control and cohort studies [22]. The AXIS tool was employed for cross sectional study. Mixed method was used for Newcastle Ottawa Scale (NOS) was used to grade all the studies into low (0-3), moderate (4- 7), or high risk of bias (8-10). Two reviewers independently provided quality assessment of the articles at all stages. At the initial step, the two reviewers independently scanned through the titles and abstracts of the articles retrieved from the databases. The relevance of the studies was assessed, and the articles selected were further screened. After screening for eligibility, the remaining full texts were assessed for quality. For studies with unclear methods, the authors were contacted to seek clarification.

These checklists assessed the aim, risk of bias, statistical methods, measurement of exposures/outcomes, and relevance, among other criteria. The overall sections ask: “Are the results valid?”, “what are the results?” and “will the results help locally?” If the study failed to respond to these initial questions or a large flaw regarding a criterion was found, the study was rejected.

Risk Factors Affecting Scabies Outbreaks

Most of the reviewed studies pointed out several risk factors that might have facilitated the occurrence and spread of outbreaks. The most frequently observed cause was person to person transmission through contact with infected person or via sharing of clothing or sleeping in the same quarters. Three studies identified index cases who had travel history from scabies epidemic areas within last two months prior to the onset of symptoms [24, 27, 29].

Kaburi, et al. [9] reported seating in pairs due to overcrowded classes and sharing of sleeping mats during siesta as contributing factors towards propagation of the outbreak among pre-school children [9]. Sara, et al. [28] described home being affected by flood as a significant risk factor citing displacement, overcrowding and poor personal hygiene which in turn leads to increased susceptibility to scabies infestation. Additionally, suboptimal hand hygiene became a more critical factor that facilitated the transmission of secondary bacterial infections including pyoderma in 60% of the cases. Two of the studies listed family size greater than 5 as a significant risk factor (Figure 2).

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Diagnosis and Clinical Presentation of Scabies

‘Suspected case’ definitions were described in 5 papers. Three papers were identified in which no case definitions were evaluated; one was a conference abstract. There were no consistent criteria used for diagnosis in the included studies for scabies. Three studies reported clinical diagnosis made by trained healthcare professionals [9, 25, 26]. To avoid inter- and intra-operative error of reliability, at least two public health personnel had to agree on the case definition and clinical diagnosis for scabies to be added to the line list.

The diagnosis was based on the presence of the typical clinical signs and symptoms using a structured checklist developed by trained healthcare professionals. However, only two studies Kaburi, et al. [9] had a confirmed case definition of scabies demonstrating the presence of mite and its products on skin scraping. Regarding the distribution of scabies rash on the body parts, interdigital space (n=4) was the most affected area followed by the flexor aspect of the wrists, elbows, buttocks, and abdomen (n=2) as shown in Figure 3. Figure 4 illustrates the most reported clinical presentation among the cases.

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Treatment and Management of Scabies Outbreaks

Most facilities notified public health authorities about the outbreaks and received advice and assistance to manage the outbreaks. Following the detection of the index cases, four reports on scabies outbreaks conducted active case finding among residents and staff by contact tracing. Responding to the outbreaks, treatment measures for the cases and its contacts included mass drug treatment with benzoyl benzoate (n=4), 5% permethrin dermal cream (n=3), single oral dose of ivermectin 150 mgkg (n=1) and 1% lindane as seen in Figure X below. Only one study reported that 64% of cases refused treatment at the nearest health facility [28]. Control measures included referral and transfer to a municipal hospital in two studies [9, 28]. Other measures included were health education and dissemination with emphasis on personal hygiene, sharing of beds and clothes.

The personal hygiene week was declared and performed in two studies [27, 29]. Alebachew, et al. [29] highlighted church community mobilisation and communal cleaning of the shared clothing, bedding, and linens used by an infested individual.

Kaburi, et al. [9] further conducted environmental assessment of the state of classrooms, average class occupancy, seating arrangement, sleeping conditions during siesta, washroom hygiene, and the general state of cleanliness of the school premises. Close follow-up of cases and re-screening was reported only in two studies. The overall highest attack rate was recorded in Tanzanian prison 81.8% (followed by Ethiopian church and primary schools with an attack rate of 35 and 25% respectively. The lowest attack rate was recorded in Ghana and Ethiopia in the basic and primary schools. No case mortality was recorded in any of the studies (Figure 5).

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Risk of Bias

The quality of 8 studies was assessed and the results are summarized in Figure 4. Six studies scored high risk of bias for all the criteria points. Two studies were at low and medium risk for all criteria respectively [9, 25]. Problems related to recall bias and standardization of self-reported measurement created a high risk of bias for the measurement of the exposure domain in six studies. The problem related to missing data resulted in a high risk of bias.

Figure 6 demonstrates a preponderance of low-quality studies, which limits the strength of recommendations that this report can make due to the high potential for biased outcomes. The main problems were small sample sizes, subjective measures, missing information, and no adjustment for confounding.

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Discussion

Infectious disease outbreaks cause millions of deaths across the African region annually [30]. This systematic review includes published studies from the past 20 years illuminating the continuous burden that scabies has presented to the Sub Saharan African region. Scabies outbreaks were most reported in rural communities. With lack of easy access to health facilities and poorer health infrastructure than urban communities, this can create a cyclical burden where most infected people will either receive delayed treatment or no treatment at al thus worsening the outbreak progression as observed in an institution based extended to community outbreak in Ethiopia [28].

Globally, most of the research on scabies outbreaks has been carried out in urban settings, and has focused mainly on prevalence and socio economic aspects [23]. However, these crucial data on scabies outbreaks in both rural and urban communities are greatly lacking in Sub Saharan region and is vital for control of institutional outbreaks [10].

The duration of outbreaks varied for each facility with the churches and prison recording the highest duration of outbreaks of more than 4 months. The possible reasons for the prolonged outbreak may be due to delay in identification of the index case, delayed diagnosis and prompt treatment of contacts and cases. Thereby, suggesting that accurate identification of how scabies spread is a fundamental step in outbreak control.

In the current systematic review, overall incidence (attack rate) in the general population ranged from 11-88%. Few papers presented a breakdown of scabies outbreaks prevalence rates by smaller age groups, making a reliable comparison of the disease distribution across age groups difficult between studies. However, the highest scabies incidence was described in preschool children less than 3 years (17%), in older children aged 5-14 (56%) and adults aged 20-29 (47%) years in prison.

Children in primary school were most affected populations, and most of them had sign of secondary infection attributable to scabies. This might be due to the fact that younger children, particularly, those at school are at high risk of scabies infestations as the school environments may increase the susceptibility of cross-infestation and increase contacts which can be passed to family members and others.

This high burden of scabies seems to support the hypothesis that infections occur more often in young children as it has been observed in other low and middle- income countries, where scabies is an endemic disease [10]. The high incidence of scabies among young adults in prison may be due to the frequent close interpersonal contact and overcrowding.

Another objective of this study was to identify factors associated with scabies outbreaks in institutions. Most of the reviewed studies pointed out several issues in practice that might have facilitated the occurrence and spread of outbreaks. The most frequently observed cause was person to person transmission through contact with infected person or sleeping in the same quarters. This result is consistent with the systemic review conducted on scabies in developing countries showing that overcrowding especially sleeping with scabies case is an important risk factor [1] and a systematic review on prevalence and associated risk factors in Ethiopia showing that sharing of bed with an infected person is a risk factor [5]. The diagnosis was mostly made clinically with no clear details on the criteria used. Only five studies reported a case definition and only two studies on specific diagnostic criteria for the health professionals to follow. No standardized method such as IACS was used.

It was also observed that there was lack of dermatologists or experienced doctors available to make accurate diagnosis relying heavily on community extension workers which may have led to delay in diagnosis. As the diagnosis of scabies was made clinically, false- positive and false-negative diagnoses may have occurred.