Quantifying risk factors to guide progress towards leprosy elimination
Authors: Abhishek Pandey, Alison P Galvani
Journal: The Lancet Global Health (2019)

Although the widespread availability of multidrug therapy reduced the worldwide prevalence of leprosy by more than 99% since 1983, over 200 000 cases still occur every year.1WHO Regional Office for South-East AsiaLeprosy fact sheet.http://www.searo.who.int/entity/global_leprosy_programme/topics/factsheet/en/Date: 2017Date accessed: June 15, 2019Google Scholar, 2Smith CS Noordeen SK Richardus JH et al.A strategy to halt leprosy transmission.Lancet Infect Dis. 2014; 14: 96-98Summary Full Text Full Text PDF PubMed Scopus (54) Google Scholar As a consequence of associated nerve damage, disfigurement, and glaucoma, leprosy is the leading cause of disability due to an infectious disease.3Chaptini C Marshman G Leprosy: a review on elimination, reducing the disease burden, and future research.Lepr Rev. 2015; 86: 307-315Crossref PubMed Google Scholar Despite the severity of leprosy, progress towards elimination has stagnated over the last decade. Status-quo approaches rely on patients presenting themselves at health-care facilities with symptoms that can lead to delays in treatment. Such delays are exacerbated by stigma and misdiagnosis of the initial skin lesions. Accelerating diagnosis and treatment is instrumental both to avoid disabilities and to mitigate transmission. Even within the most affected countries—including India, Brazil, and Indonesia—leprosy risk across a country is often heterogeneous with the majority of cases occurring in high-risk regions.4Nery JS Ramond A Pescarini JM et al.Socioeconomic determinants of leprosy new case detection in the 100 Million Brazilian Cohort: a population-based linkage study.Lancet Glob Health. 2019; (published online July 19.)http://dx.doi.org/10.1016/S2214-109X(19)30260-8Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar Determining these high-risk regions is an essential first step in creating a robust surveillance–response system, which is imperative for making further progress towards a leprosy-free world. Poverty has often been associated with an elevated risk of leprosy.5Pescarini JM Strina A Nery JS et al.Socioeconomic risk markers of leprosy in high-burden countries: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2018; 12e0006622Crossref PubMed Scopus (55) Google Scholar However, there is inadequate quantification of specific socioeconomic, demographic, and geographical variables that contribute to leprosy risk. Advancing our understanding of these risk factors can be applied to identify the communities in which surveillance and control efforts would be most effectively and efficiently focused. Ascertaining risk factors is fundamental to implementing such targeted strategies. To investigate the spatial, socioeconomic, demographic, and household factors associated with the risk of leprosy incidence, Silva Nery and colleagues4Nery JS Ramond A Pescarini JM et al.Socioeconomic determinants of leprosy new case detection in the 100 Million Brazilian Cohort: a population-based linkage study.Lancet Glob Health. 2019; (published online July 19.)http://dx.doi.org/10.1016/S2214-109X(19)30260-8Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar analysed the health records and socioeconomic data of more than 23 million individuals, including over 18 000 leprosy cases across Brazil between 2007 and 2014. They introduced a comprehensive classification of risk factors into distal, intermediate, and proximal factors that underlie the hierarchical analytical framework developed in their study. At the highest level, distal factors reflected the broadest variables—eg, geographical location and urbanicity. Intermediate factors considered comprised ethnicity and socioeconomic variables, such as level of education and income. At the lowest level, proximal factors pertained to living conditions, including household size and sanitation. As proximal factors are influenced by intermediate factors, which are in turn influenced by distal variables, the authors assessed the associations between leprosy risk with distal variables first and then added layers of intermediate variables followed by proximal variables using the significant factors evaluated in the previous stage. This hierarchical analytic framework has the potential to be applied to other diseases affected by multiple levels of risk factors. WHO has established two 2020 goals for leprosy: the elimination of leprosy-attributable disabilities in children and reduction below one per million population in cases of grade-2 disabilities, defined as leprosy-related visible deformities.1WHO Regional Office for South-East AsiaLeprosy fact sheet.http://www.searo.who.int/entity/global_leprosy_programme/topics/factsheet/en/Date: 2017Date accessed: June 15, 2019Google Scholar A targeted, multifaceted strategy is most likely to be effective in realising these goals. To reduce leprosy-related stigma and thereby improve early consultation by patients for diagnosis and timely treatment, possible approaches include improving awareness, particularly within high-risk communities, and introducing socioeconomic rehabilitation programmes for leprosy patients with disabilities. Similarly, integrating leprosy services in primary health care can improve case finding and continuity of care. Diagnostic tests for early-stage or subclinical infection would be key tools for curbing transmission and averting the onset of disabilities. Currently, several serological tests are under development but are yet to attain sufficient sensitivity and specificity.6Rodrigues LC Lockwood DN Leprosy now: epidemiology, progress, challenges, and research gaps.Lancet Infect Dis. 2011; 11: 464-470Summary Full Text Full Text PDF PubMed Scopus (274) Google Scholar The substantial reduction in leprosy burden achieved worldwide a decade ago led to a misperception of leprosy no longer being a substantial threat to human health.6Rodrigues LC Lockwood DN Leprosy now: epidemiology, progress, challenges, and research gaps.Lancet Infect Dis. 2011; 11: 464-470Summary Full Text Full Text PDF PubMed Scopus (274) Google Scholar This fallacy resulted in the diversion of resources away from leprosy control programmes in many countries.6Rodrigues LC Lockwood DN Leprosy now: epidemiology, progress, challenges, and research gaps.Lancet Infect Dis. 2011; 11: 464-470Summary Full Text Full Text PDF PubMed Scopus (274) Google Scholar, 7Lockwood DNJ Shetty V Penna GO Hazards of setting targets to eliminate disease: lessons from the leprosy elimination campaign.BMJ. 2014; 348g1136Crossref PubMed Scopus (54) Google Scholar The ensuing loss of skill to recognise leprosy is contributing to preventable delays in diagnosis. Consequently, the last mile in the endgame towards leprosy elimination is proving to be the most challenging. Findings from Silva Nery and colleagues4Nery JS Ramond A Pescarini JM et al.Socioeconomic determinants of leprosy new case detection in the 100 Million Brazilian Cohort: a population-based linkage study.Lancet Glob Health. 2019; (published online July 19.)http://dx.doi.org/10.1016/S2214-109X(19)30260-8Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar could be applied to identify the areas and subpopulations in which building capacity for diagnosing and managing leprosy cases is urgent. For example, the authors found that individuals in most impoverished regions of Brazil were five to eight times more likely to contract leprosy than the rest of the population. Strategies aimed at the social development of these high-risk settings can play a crucial role in leprosy control. Despite the availability of effective treatment and impressive progress in reducing the burden of leprosy worldwide, the disease continues to impose significant morbidity and discrimination in affected societies. Declining global funding for leprosy7Lockwood DNJ Shetty V Penna GO Hazards of setting targets to eliminate disease: lessons from the leprosy elimination campaign.BMJ. 2014; 348g1136Crossref PubMed Scopus (54) Google Scholar has left the most marginalised populations at highest risk. Therefore, leprosy programmes need to be reenergised with resources and global commitment. In concert with bolstered investment, evidence-based interventions are required to implement optimal strategies for leprosy control. Silva Nery and colleagues4Nery JS Ramond A Pescarini JM et al.Socioeconomic determinants of leprosy new case detection in the 100 Million Brazilian Cohort: a population-based linkage study.Lancet Glob Health. 2019; (published online July 19.)http://dx.doi.org/10.1016/S2214-109X(19)30260-8Summary Full Text Full Text PDF PubMed Scopus (50) Google Scholar analysed data of an unprecedented sample size to quantify the factors associated with elevated leprosy risk. Their findings can guide policymakers to plan and implement targeted strategies aimed at early diagnosis, curbing stigma, and improving health-care access among the most vulnerable populations in leprosy-endemic regions. We declare no competing interests. Socioeconomic determinants of leprosy new case detection in the 100 Million Brazilian Cohort: a population-based linkage studyWithin the poorest half of the Brazilian population, the most deprived individuals have the greatest risk of leprosy. Strategies focusing on early detection and treatment in the poorest populations could contribute substantially to global disease control. Full-Text PDF Open Access