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The Missing Millions: A Threat to the Elimination of Leprosy

PLOS Neglected Tropical Diseases

April 2015
9(4):e0003658

DOI:10.1371/journal.pntd.0003658

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Authors:

William Cairns S Smith

University of Aberdeen

W. H. Van Brakel

NLR International

Paul Saunderson

American Leprosy Missions

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Leprosy is a slow, chronic disease with a long incubation period caused by Mycobacterium leprae. The clinical presentation varies across a wide spectrum from tuberculoid to lepromatous leprosy. The condition is characterized by skin lesions and damage to peripheral nerves leading to physical disability and social problems. The past 50–60 years have witnessed remarkable progress in the fight against leprosy. The introduction of dapsone therapy in the late 1940s was the first effective treatment for leprosy, and this was followed by the move to short course multidrug therapy (MDT) in 1981. The World Health Assembly Resolution in 1991 [1] to “eliminate leprosy as a public health problem” by the year 2000 galvanised extraordinary international support resulting in the fall in the point prevalence of patients registered for treatment of leprosy by over 90% to less than 1 in 10,000 at the global level. The effort was led by the World Health Organization (WHO) and supported by national governments and their health service staff, the Nippon Foundation, Novartis, the International Federation of Anti-Leprosy Organizations (ILEP), local non-governmental organizations (NGOs), and by people affected by leprosy. Since 2000, the focus has moved from prevalence of leprosy to incidence as measured by reported new case detection to sustain the achievements and to reduce the burden of disease, particularly on reduction and prevention of disability associated with leprosy and rehabilitation of those facing the long-term consequences of the disease [2].

Number of new leprosy cases by year. The red continuous line represents the observed annual new case detection rate between 1985 and 2012, with extrapolation to 2020 based on the trend after 2005 (red dotted line). The blue continuous line is the predicted new case detection rate based on modeling with the SIMLEP model, applying an intermediate scenario in the presence of an infant BCG vaccination programme [7].

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VIEWPOINTS

The Missing Millions: A Threat to the

Elimination of Leprosy

William Cairns Smith

*, Wim van Brakel

, Tom Gillis

, Paul Saunderson

Jan Hendrik Richardus

1School of Medicine and Dentistry, University of Aberdeen, Aberdeen, United Kingdom, 2Netherlands

Leprosy Relief, Amsterdam, Netherlands, 3effect: hope, The Leprosy Mission, Markham, Ontario, Canada,

4American Leprosy Missions, Greenville, South Carolina, United States of America, 5Erasmus MC,

University Medical Center, Rotterdam, Netherlands

*w.c.s.smith@abdn.ac.uk

Introduction

Leprosy is a slow, chronic disease with a long incubation period caused by Mycobacterium

leprae. The clinical presentation varies across a wide spectrum from tuberculoid to leproma-

tous leprosy. The condition is characterized by skin lesions and damage to peripheral nerves

leading to physical disability and social problems. The past 50–60 years have witnessed remark-

able progress in the fight against leprosy. The introduction of dapsone therapy in the late 1940s

was the first effective treatment for leprosy, and this was followed by the move to short course

multidrug therapy (MDT) in 1981. The World Health Assembly Resolution in 1991 [1]to

“eliminate leprosy as a public health problem”by the year 2000 galvanised extraordinary inter-

national support resulting in the fall in the point prevalence of patients registered for treatment

of leprosy by over 90% to less than 1 in 10,000 at the global level. The effort was led by the

World Health Organization (WHO) and supported by national governments and their health

service staff, the Nippon Foundation, Novartis, the International Federation of Anti-Leprosy

Organizations (ILEP), local non-governmental organizations (NGOs), and by people affected

by leprosy. Since 2000, the focus has moved from prevalence of leprosy to incidence as mea-

sured by reported new case detection to sustain the achievements and to reduce the burden of

disease, particularly on reduction and prevention of disability associated with leprosy and reha-

bilitation of those facing the long-term consequences of the disease [2].

Understanding Transmission

Despite this remarkable progress, understanding of the pathogenesis of leprosy has remained

unclear. Basic knowledge of the transmission of M.leprae, portals of exit and entry, the role of

the environment and animal reservoirs, the development of immune responses following infec-

tion, and the pathogenesis of M.leprae infection to the disease of leprosy are all limited. A re-

cent expert group, hosted by effect: hope (The Leprosy Mission Canada) and the National

School of Tropical Medicine at Baylor College of Medicine in Houston, Texas, United States,

reviewed the evidence and recent research on transmission and how to block it. Novel methods

in strain typing M.leprae and recent findings in both host genetics and immune responses

open the potential for new solutions. However, the very long incubation period, the very low

incidence rates in those exposed, and the insidious clinical presentation create real challenges

to developing strategies to interrupt transmission [3].

PLOS Neglected Tropical Diseases | DOI:10.1371/journal.pntd.0003658 April 23, 2015 1 / 4

OPEN ACCESS

Citation: Smith WC, van Brakel W, Gillis T,

Saunderson P, Richardus JH (2015) The Missing

Millions: A Threat to the Elimination of Leprosy. PLoS

Negl Trop Dis 9(4): e0003658. doi:10.1371/journal.

pntd.0003658

Editor: Diana N. J. Lockwood, London School of

Hygiene and Tropical Medicine, UNITED KINGDOM

Published: April 23, 2015

access article distributed under the terms of the

Creative Commons Attribution License, which permits

unrestricted use, distribution, and reproduction in any

medium, provided the original author and source are

credited.

Funding: The authors have indicated that no funding

was recieved for this work.

Competing Interests: The authors have declared

that no competing interests exist

Global Trends in Leprosy

Global data on the trends in new case detection in leprosy are collated and published annually

by WHO [4]. There are concerns about the quality and completeness of these data [5,6]. These

data describe new case trends from detection through the completion of MDT at national, re-

gional, and global levels. Fig 1 plots the number of new leprosy cases by year. The red continu-

ous line represents the observed annual new case detection rate between 1985 and 2012, with

extrapolation to 2020 based on the trend after 2005 (red dotted line). The blue continuous line

is the predicted new case detection rate based on modeling with the SIMLEP model, applying

an intermediate scenario in the presence of an infant BCG vaccination programme [7]. These

trends in the last decade show a very striking feature (Fig 1, red line): a dramatic and sudden

decline in new case detection of over 60% over a short period of time (2001–2005). Under-

standing the possible explanations for this dramatic fall is very important. One explanation is

that this represents a true fall in the incidence of leprosy following reduction in transmission of

M.leprae infection. Disease modeling work [7] has suggested that the long-term underlying

trend in leprosy incidence in a good scenario including infant BCG immunization is a slow,

gradual decline of around 4.4% per year. A large, sudden fall in transmission seems biologically

implausible given the long and variable incubation period in leprosy and the evidence of con-

tinuing, significant rates of new cases in children [4]. A second explanation is that there was

substantial overdiagnosis of leprosy prior to 2001, which has inflated the previous levels of new

case detection. This may be a factor to explain the peak of new case detection between 1996

and 2001, a period of intensified case detection activities [8], such as Leprosy Elimination Cam-

paigns (LEC) and Special Action Projects for the Elimination of Leprosy (SAPEL). However,

the new case detection trends between 1985 and 1996 are remarkably stable and sustained

overdiagnosis seems unlikely over this period. The third, and most probable, explanation is

that the dramatic fall in new case detection is a result of a decline in leprosy activities following

the declaration of elimination as a public health problem globally, and in individual countries.

This decline includes reduced intensity and coverage of case detection activities, community

awareness, and training in the diagnosis and treatment of leprosy often associated with the

move from vertical leprosy control activities to integrated approaches. The recent rise in dis-

ability in new cases detected and the increasing delay in diagnosis reported by many countries

Fig 1. Number of new leprosy cases by year. The red continuous line represents the observed annual new case detection rate between 1985 and 2012,

with extrapolation to 2020 based on the trend after 2005 (red dotted line). The blue continuous line is the predicted new case detection rate based on

modeling with the SIMLEP model, applying an intermediate scenario in the presence of an infant BCG vaccination programme [7].

doi:10.1371/journal.pntd.0003658.g001

PLOS Neglected Tropical Diseases | DOI:10.1371/journal.pntd.0003658 April 23, 2015 2 / 4

supports this explanation [4]. WHO, along with the Nippon Foundation, called an Internation-

al Leprosy Summit in 2013 to address what they called “stagnation”in the leprosy control. This

resulted in the Bangkok Declaration [9], signed by the health ministers of the major leprosy en-

demic countries, calling for renewed political commitment to leprosy control.

The Implications of the Decline in New Case Detection for the

Elimination of Leprosy

Fig 1 shows how the model prediction of the long-term trend in new leprosy case detection

based on the observed figures before 2000 compares with the observed new case detection. The

resulting difference between the expected and observed numbers of new cases of leprosy be-

tween 2000 and 2012 is approximately over 2.6 million. This number will increase to over 4

million by 2020. This analysis implies that there may be a large accumulation of people with

leprosy in the community who remain undiagnosed and untreated. This assertion is supported

by evidence from recent sample surveys in endemic areas detecting many as yet untreated cases

in Bangladesh [10] and in India [11]. This large number of undetected cases represents a major

threat to leprosy control and contributes to the increased burden of infection in the community

and an increased pressure on transmission. This has major consequences for the road map for

NTDs in the London Declaration [12–14], which targets “interruption of transmission”and

“global elimination”of leprosy by 2020.

Response to This Threat to Leprosy Elimination

It is vital that all involved and concerned with leprosy control appreciate this situation and rec-

ognise that the London Declaration targets of “global elimination”of leprosy and “interruption

of transmission”by 2020 are likely to be unobtainable and that revised targets are needed.

Major commitments and resources need to be made available without delay. While local elimi-

nation (based on new cases detected in a defined locality) of leprosy through targeted leprosy

control activities as recommended by WHO is necessary in the short-term, the complete inter-

ruption of transmission at a global level will require new tools based on game-changing discov-

eries. A significant investment in complementary research efforts, designed to better understand

the basic elements of transmission, is necessary for achieving “interruption of transmission.”

The development of collaboration with other NTD programmes represents a real opportu-

nity to improve the coverage, quality, and cost-effectiveness of leprosy control with numerous

cross-cutting opportunities in drug delivery, surveillance, training, disability prevention, and

morbidity management. The commitment called for by health ministers in the Bangkok Decla-

ration is also essential at all levels, internationally, nationally, and locally by national govern-

ments and by all agencies that support national programmes, including Governmental and

non-governmental agencies, industry, and people affected by leprosy. The global introduction

of post-exposure prophylaxis [15–17] is a real opportunity to re-energise leprosy control activi-

ties through increased community awareness, capacity building, and active management of

contacts. The research opportunity recently launched by the Leprosy Research Initiative leads

the way to develop further innovations for leprosy control, but much more support is needed

for basic, as well as operational, research to develop strategies to interrupt transmission. For ex-

ample, recent findings have revealed new insights into zoonotic relationships, genetic markers

for host susceptibility and resistance, as well as environmental factors that continue to test our

long-held notions of the ecology of M.leprae and leprosy. Understanding these relationships

may provide the knowledge to move from management practices to strategies designed to

stop transmission.

PLOS Neglected Tropical Diseases | DOI:10.1371/journal.pntd.0003658 April 23, 2015 3 / 4

The WHO priority to promote early detection and to monitor this through measuring dis-

ability in new case detection is a vital component to evaluate enhanced initiatives designed to

reduce transmission. However, addressing the gap between the incidence and case detection of

leprosy requires improved strategies for case detection, new tools for early diagnosis, and

major efforts to improve community awareness and capacity of health staff to diagnose and

manage leprosy and its complications.

The challenge is to tackle the research gaps through novel collaborations, to improve opera-

tional collaborations with multiple players in all NTDs, and to incorporate new approaches in

community engagement that would enhance public health at the community level. The leprosy

world, including WHO, national governments, NGOs, the research community, and industry,

together with people affected by leprosy, must respond to this situation that, if left unaddressed,

could see all the past achievements in leprosy control reversed.

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Oct 2009
REV PANAM SALUD PUBL

To identify and summarize randomized clinical trials (RCTs) that assessed the effectiveness of chemoprophylaxis to prevent leprosy in contacts of patients newly diagnosed with the disease. All studies were extracted from Medline (PubMed 1966 to November 2008), the Cochrane Controlled Trials Register (number 3 2008), LILACS (1982 to November 2008), and Scirus (November 2008). Manual searches and searches of crossed references of assessed articles were also done. RCTs' risk of bias was assessed according to the methodology proposed by the Cochrane Collaboration. The main outcome measure was diagnosis of leprosy (secondary cases) in contacts of patients with the disease (primary cases). The search identified 320 references, from which 7 RCTs with a total of 66 311 participants were included and evaluated. The combined results from the RCTs favored chemoprophylaxis to placebo with 2-4 years of follow-up (6 RCTs, 66 107 participants, relative risk (RR) 0.59, 95% confidence interval (CI) 0.50-0.70, I(2) = 0 (I(2) describes percent total variation across studies caused by heterogeneity)). Single-dose rifampicin (21 711 participants, RR 0.43, 95% CI 0.28-0.67, number needed to treat 285), dapsone once or twice weekly for at least 2 years (3 RCTs, 43 137 participants, RR 0.60, 95% CI 0.48-0.76, I(2) = 0), and acedapsone every 10 weeks for 7 months (2 RCTs, 1 259 participants, RR 0.49, 95% CI 0.33-0.72, I(2) = 0) were significantly superior to placebo in preventing secondary cases of leprosy. Chemoprophylaxis is effective in lowering the incidence of leprosy in contacts of patients diagnosed with the disease.

The future incidence of leprosy: A scenario analysis

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Jun 2004
B WORLD HEALTH ORGAN

To investigate the impact of the current strategy for the elimination of leprosy on its incidence and to assess the consequences of failure to sustain this strategy. Scenarios for assessing the impact of the elimination strategy were implemented in a computer simulation program. The scenarios reflected the assumptions made regarding contagiousness, transmission and bacille Calmette-Guerin (BCG) vaccination. The trend in case detection rate for the main countries in which leprosy was endemic during 1985-98 was fitted, and incidence up to 2020 was projected. Owing to the gradual shortening of delays in detection up to 1998, and because of the low relapse rate that occurs with multidrug treatment MDT, incidence is predicted to decrease beyond 2000 in all scenarios. The annual decline was a few per cent higher when favourable assumptions were made about protection and coverage of BCG vaccination. Overall, the predicted annual decline in incidences ranged from 2% to 12%. The elimination strategy reduces transmission, but the decline may be slow. Relaxation of control after 2005 is unjustified given the uncertainty about the rate of decline and the adverse effects of longer delays in detection. A long-term strategy for leprosy control should be adopted.

Effectiveness of single dose rifampicin in preventing leprosy in close contacts of patients with newly diagnosed leprosy: Cluster randomised controlled trial

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May 2008
Br Med J

To determine the effectiveness of chemoprophylaxis using a single dose of rifampicin to prevent leprosy in close contacts. Single centre, double blind, cluster randomised, placebo controlled trial. Leprosy control programme in two districts of northwest Bangladesh with a population of more than four million. 28,092 close contacts of 1037 patients with newly diagnosed leprosy. 21,711 contacts fulfilled the study requirements. A single dose of rifampicin or placebo given to close contacts in the second month of starting the index patient's treatment, with follow-up for four years. Development of clinical leprosy. 18,869 of the 21,711 contacts (86.9%) were followed-up at four years. Ninety one of 9452 contacts in the placebo group and 59 of 9417 in the rifampicin group had developed leprosy. The overall reduction in incidence of leprosy using a single dose of rifampicin in the first two years was 57% (95% confidence interval 33% to 72%). The groups did not differ between two and four years. The overall number needed to treat (NNT) to prevent a single case of leprosy among contacts was 297 (95% confidence interval 176 to 537). Differences were found between subgroups at two years, both in reduction of incidence and in NNT. A single dose of rifampicin given to contacts of patients with newly diagnosed leprosy is effective at preventing the development of clinical leprosy at two years. The effect was maintained, but no difference was seen between the placebo and rifampicin groups beyond two years. Current Controlled Trials ISRCTN61223447 [controlled-trials.com].

[Present state of Hansen's disease between 2012 and 2013--weekly epidemiological record, no. 35, 2013, 88, 365-380 (translated by Shuichi Mori)]

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