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Symposium Report: Developing Strategies to Block the Transmission of Leprosy



Remarkable progress has been made in the treatment and management of leprosy over the last 60 years. Current control strategies rest on early detection of disease and appropriate multidrug therapy (MDT) to cure the patient and halt transmission within the community. These strategies are built on a solid understanding of therapeutics for mycobacterial diseases but suffer from an incomplete understanding of transmission of Mycobacterium leprae and a shortage of tools that can truly diagnose leprosy at an early stage. Accordingly, transmission continues in many areas of the world. To clarify the current state of our knowledge of M. leprae transmission and to establish a research agenda to address gaps in our understanding of transmission, an international symposium entitled “Developing Strategies to Block the Transmission of Leprosy” was organized and sponsored by effect:hope (The Leprosy Mission Canada) and held on May 29–30, 2014. The meeting was hosted by the National School of Tropical Medicine, Baylor College of Medicine in Houston, Texas.
Symposium Report: Developing Strategies to Block
the Transmission of Leprosy
*effect:hope, Markham, Canada
**Swiss Tropical and Public Health Institute, Basel, Switzerland
***University of Basel, Basel, Switzerland
****Emory School of Medicine, Atlanta, GA, USA
Accepted for publication 24 May 2015
Remarkable progress has been made in the treatment and management of leprosy over the
last 60 years. Current control strategies rest on early detection of disease and appropriate
multidrug therapy (MDT) to cure the patient and halt transmission within the community.
These strategies are built on a solid understanding of therapeutics for mycobacterial diseases
but suffer from an incomplete understanding of transmission of Mycobacterium leprae and a
shortage of tools that can truly diagnose leprosy at an early stage. Accordingly, transmission
continues in many areas of the world.
To clarify the current state of our knowledge of M. leprae transmission and to establish
a research agenda to address gaps in our understanding of transmission, an international
symposium entitled “Developing Strategies to Block the Transmission of Leprosy” was
organized and sponsored by effect:hope (The Leprosy Mission Canada) and held on May
2930, 2014. The meeting was hosted by the National School of Tropical Medicine, Baylor
College of Medicine in Houston, Texas.
The goal of the symposium was to establish a research agenda, aimed at bridging the gaps
in our understanding of M. leprae transmission, which will complement a global research
strategy focused on eliminating leprosy.
Correspondence to: Thomas P. Gillis, Effect:hope, Markham, Ontario, Canada (e-mail:;
Lepr Rev (2015) 86, 156–164
156 0305-7518/15/064053+09 $1.00 qLepra
The objectives were:
1. To identify the key gaps in our understanding of M. leprae transmission
2. To organise gaps into priority areas
3. To propose specific areas of investigation to address these priority areas
Keynote speakers
The NTDs: Prospects for Elimination.” Peter Hotez, National School of Tropical Medicine,
Peter Hotez presented an overview of the global burden of Neglected Tropical Diseases
(NTDs) and their impact on health and on exacerbating the effects of poverty. Dr. Hotez
discussed the current strategies in place for NTD control and elimination such as Mass Drug
Administration and the impact it has had on reducing NTD prevalence. He highlighted the
issues surrounding Disability-Adjusted Life Years (DALY) and how leprosy’s very low
DALY may not accurately reflect its sustained effect on people affected by leprosy. Dr. Hotez
suggested that the London Declaration
may be overly simplistic when considering leprosy
with regard to its road map and he supports focusing efforts on interrupting transmission for
eventual elimination of leprosy.
“Tracing Our Path to Today.” Paul Fine, London School of Hygiene and Tropical Medicine,
Paul Fine described the history of leprosy as a disease including its disappearance
from Northern Europe and the first attempts to estimate the global burden of the disease.
Prof. Fine also shared current data on leprosy prevalence citing India, Brazil and Indonesia
as the countries that account for 80% of new cases as of 2012. Prof. Fine discussed some
of the possible theories related to M. leprae transmission and the reasons for the decline in
leprosy prevalence globally. He also shared some of the issues related to semantics facing
those working in the leprosy field and the impact this has on addressing M. leprae
“Systematic literature review on current knowledge regarding the transmission of leprosy
(Hansen’s disease).” Martin Bratschi, Swiss Tropical and Public Health Institute,
Martin Bratschi presented the findings from the systematic review of the peer-reviewed
literature pertaining to M. leprae transmission which was carried out to assess the current state
of knowledge on this topic. Dr. Bratschi showed that the systematic literature review identified
a total of 79 relevant articles providing solid evidence for M. leprae transmission among
contacts and for zoonotic leprosy in the Southern States of the USA. He also reported that based
on the extant evidence, skin-to-skin contact, aerosols/droplets and shedding of bacteria into the
environment and subsequent infection, all remain possible options and there is no study which
has unequivocally demonstrated the mechanisms by which M. leprae bacteria are transmitted.
The full literature review entitled “Current knowledge on Mycobacterium leprae transmission:
a systematic literature review” is published concurrently with this article.
Blocking transmission of leprosy 157
“Modeling Leprosy: How mathematical models help us understand transmission and the
effect of interventions.” Jan Hendrik Richardus, Netherlands.
Jan Hendrik Richardus stated that the primary purposes of current leprosy models are to
predict the course of leprosy incidence and to analyse the impact of various intervention
strategies. He gave an overview of the Lechat, SIMLEP and SIMCOLEP mathematical
models used for leprosy. He also highlighted some of the results from current leprosy
modeling efforts including the cost-effectiveness of single-dose rifampin chemoprophylaxis
and the impact of early diagnosis and treatment.
Representatives from five countries discussed the current trends in M. leprae transmission
and control in their respective countries.
Brazil (Rosa Castillia Soares, Ministry of Health, Sao Paulo, Brazil)
India (Sunil Anand, TLMI India, Delhi, India)
Ethiopia (Abraham Aseffa, AHRI/ALERT, Addis Ababa, Ethiopia)
Bangladesh (Shaikh Hossain, ICDDR,B, Bangladesh)
Philippines (Marivic Balagon, LWM Center for TB & Leprosy Research, Cebu,
The general themes were:
1. Leprosy control programmes have become decentralised and integrated into general
health systems
2. Reduced numbers of cases were reported in the early 2000’s
3. A high proportion of MB cases remain in Ethiopia and the Philippines
4. All five countries noted stable transmission in children
5. The rate of grade 2 disabilities overall has shown no significant change
6. There is decreasing expertise in case finding
7. High endemic pockets remain in most countries and appear to be related to lack of access
to care, and poverty
Breakout sessions were held to discuss the following key topics related to M. leprae
transmission: reservoir, parasite and host. Each breakout session began with a panel of experts
speaking on key topics related to the session. Discussion groups were then formed around
specific sub-topics and a rapporteur for each group was selected. Dr. Edith Bahmanyar of the
Novartis Foundation then facilitated plenary discussions around the key findings presented by
each rapporteur. The goal of the sessions was to identify and define the gaps in knowledge and
needs within the key topic areas that would lead to an improved understanding of M. leprae
transmission and provide new tools and strategies to block M. leprae transmission.
Expert Panel: Active cases (Paul Saunderson), Occult human reservoir (Cairns Smith),
Animal reservoir (Richard Truman) and Environmental reservoir (Ravindra Turankar)
D. Mensah-Awere et al.158
Sub-topics: 1. Active cases/occult human reservoirs (Saunderson/Smith)
2. Animal/Environmental reservoirs (Truman/Turankar)
Expert Panel: M. leprae genome (Pushpendra Singh); M. lepromatosis (Xiang-Yang Han)
Sub-topics: 1. Pathogen characteristics (Singh/Han)
2. Genotyping (Singh/Han)
Expert Panel: Genetics (Erwin Schurr), Immunology (Tom Hawn), Vaccines (Steve Reed),
Diagnostics (Annemiek Geluk), Portal of exit/entry of M. leprae (Eric Brenner)
Sub-topics: 1. Genetics, Immunology (Shurr, Hawn)
2. Vaccines/Diagnostics (Reed, Geluk)
3. Portals of exit-entry of M. leprae (Brenner)
Partners from an array of government and nongovernment research and research funding
organizations presented their current research priorities and funding commitments as well as
successful projects related to leprosy research and control. The partners represented were; National
Institute of Allergy and Infectious Disease (NIAID, USA), Pan-American Health Organization
(PAHO), The Leprosy Research Initiative (LRI) and Novartis Foundation (Switzerland).
Based on the breakout sessions and the literature review on M. leprae transmission (see
Keynote Speakers and 2) the following gaps in our understanding of M. leprae transmission
and needs to fill these gaps were identified.
1. Human-to-human transmission of M. leprae
Studies have clearly shown that close proximity to leprosy patients increases the risk of
contracting the disease. However, other members of endemic communities who are potentially
asymptomatically infected carriers may also contribute to the transmission of M. leprae.
Gap 1: Human Reservoirs
We do not understand the full extent of the human reservoir of M. leprae; specifically the
roles of undiagnosed patients, patient contacts and other members of endemic
communities in perpetuating M. leprae transmission are unknown.
Needs to fill gap 1:
a) Discovery of biomarkers for: all clinical cases of leprosy, subclinical infections
and asymptomatic carriers.
b) Develop platforms for field-friendly diagnostic tests.
Blocking transmission of leprosy 159
2. Route of entry/exit of M. leprae in humans
A series of case reports appear to show that injection of M. leprae at the site of skin trauma
(e.g. by tattoo or accident) can lead to localised as well as disseminated manifestations of
leprosy. For most leprosy cases, there is however no clear sign that entry of the pathogen
occurred through skin trauma, and the available evidence points more towards the
involvement of the upper respiratory tract.
3. Role of animals, the environment or insects in the transmission of M. leprae
In the Southern USA, leprosy has been shown to exist as a zoonosis, based on M. leprae strain
identification, indicating that there is transmission of M. leprae between armadillos and
humans. However, in other parts of the world, the role of animals as reservoirs or vectors in
M. leprae transmission remains unclear. It is also unknown how the recently described
existence of M. leprae in the environment contributes to the spread of the disease.
Gap 2: Entry and exit route
We do not understand the route of entry and exit of M. leprae in humans.
Needs to fill gap 2:
a) Assess the role of colonization and route of entry (e.g. nasal-oral mucosa, skin and
gastrointestinal tract) of M. leprae into the human host.
b) Investigate potential roles of co-infections on the entry/exit of M. leprae from the
human host (e.g. amoebiasis).
c) Study the stages of pathogenicity of M. leprae to understand the migration (port of
entry to the site of initial lesion to point of exit) of M. leprae inside the human host.
Gap 3a: Roles of animals or vectors
We do not understand the role animals (armadillos outside of the southern USA and other
animals) or vectors (e.g. insects or amoeba) play in the transmission of M. leprae.
Needs to fill gap 3a:
a) Investigate how the distribution of M. leprae infection in armadillos is spreading in the
Americas and how this affects the occurrence of human leprosy.
b) Investigate the genetic diversity of M. leprae in armadillos to better understand
zoonotic and cross-species transmission.
c) Systematically investigate the possible role of animals (e.g. by serological
surveillance) other than armadillos in M. leprae transmission in different endemic
areas worldwide.
d) Investigate the biological relationship between M. leprae and amoeba.
D. Mensah-Awere et al.160
4. Role of Poverty in Transmission
It has been demonstrated that the socio-economic status of an individual appears to affect the
risk of contracting leprosy. However, the driver of this correlation is not clear. Whilst there
was not a breakout session dedicated to the topic of poverty and M. leprae transmission,
it was a reoccurring theme discussed in several sessions of the symposium.
5. Role of Host-Parasite Interaction in Transmission
Despite recent advances in our understanding of M. leprae genetic diversity and the cellular
immune response of leprosy patients, there are considerable gaps in our understanding of the
interaction between M. leprae and the human host.
Gap 4: Role of poverty
We do not understand how poverty acts as a risk factor for M. leprae transmission.
Needs to fill gap 4:
a) Investigate the role of poverty-related factors, such as nutrition, hygiene and crowding
on M. leprae transmission.
Gap 3b: Role of environmental sources
We do not understand the source and relevance for transmission of M. leprae in the
environment (e.g. in soil or water).
Needs to fill gap 3b:
a) Systematically investigate the presence of M. leprae in the environment in different
endemic settings.
b) Use genotyping to characterize environmental M. leprae to determine how it relates to
genotypes found in human infections in the same area.
c) Demonstrate viability and role in transmission of environmental M. leprae.
Gap 5: Host-pathogen interaction
We do not sufficiently understand the impact of the interaction between M. leprae and the
human host on M. leprae transmission.
Needs to fill gap 5:
a) Investigate relationship between M. leprae genetic characteristics and virulence,
growth kinetics, drug resistance, tropism for nerves and the tendency to cause reactions.
b) Understand the role of host genetic risk factors in susceptibility and resistance to
M. leprae infection, clinical progression of leprosy and reactions.
c) Understand how the immune response affects the manifestation of the M. leprae
infection (including establishing of infection, progression of disease, nasal carriage and
reactions) and eventually transmission of M. leprae.
d) Increase understanding of similarities/differences between M. leprae and M. lepromatosis.
Blocking transmission of leprosy 161
6. Transmission Networks
Recent evidence has shown that depending on the endemic setting, there are various types of
M. leprae transmission networks.
7. Improving Epidemiology Data
Despite the elimination of leprosy in many countries, hot-spots of transmission with more
than 1 case per 10 000 inhabitants and active transmission remain.
Conclusion and way forward
The Developing Strategies to Block the Transmission of Leprosy symposium brought together
a broad spectrum of expertise in the field of infectious diseases (Table 1), in order to identify
the key gaps that exist in our knowledge of M. leprae transmission as well as associated needs
to close those gaps. Key overarching research principles that will help to improve our
Gap 6: Transmission networks
We do not understand the diversity and relevance of the various M. leprae transmission
Needs to fill gap 6:
a) Increase collection of genome sequenced M. leprae strains with isolates from various
origins (e.g. worldwide, PB patients) which are complemented with detailed
epidemiological data.
b) Investigate genetic diversity of M. leprae from different sources (patients, nasal
carriers, zoonotic and environmental) and various settings (e.g. high and low endemic)
to study the transmission ecology at the community level.
c) Develop molecular epidemiology tools which are customised to a region to allow for
fine typing from primary samples and investigation of transmission links.
Gap 7: Enhanced epidemiological data
We do not fully understand the geographic distribution of leprosy, especially at a
sub-national level.
Needs to fill gap 7:
a) Improve the quality of national epidemiological surveillance data including
sub-national geographic variation and prevalence data based on local population
b) Implement contact tracing and active case finding strategies to identify transmission
c) Digitalize leprosy surveillance to improve data access and timely identification of
areas with high case numbers.
D. Mensah-Awere et al.162
understanding of M. leprae transmission were further identified from both the literature
review on M. leprae transmission and during discussions at the symposium. These research
principles are related to study design, the type of data to be collected in the course of studies
and the capacity to conduct research in endemic areas. Specifically, it was concluded, that
it is of great importance that long-term studies are performed and aspects of M. leprae
transmission are monitored over several years. Only such longitudinal studies will have the
potential to demonstrate how any novel tool, intervention or control measures can potentially
affect the transmission of M. leprae. Furthermore, the degree of detail and types of data
collected in different studies vary considerably and make comparison between findings from
different studies difficult. The leprosy research and control communities should strive to
define a minimal and standardised set of high quality clinical and demographic data that
should be collected about participants in all studies. Researchers should further consider
establishing a biobank of samples relevant for M. leprae transmission research. Finally, for
the long-term research efforts required to eventually block the transmission of M. leprae it is
of utmost importance to continue to support, expand and maintain research infrastructure and
capacity in leprosy endemic areas. Likewise, government entities involved in leprosy control
should continue to receive technical and other support so as to collect high quality
epidemiological data about trends in the number of leprosy cases detected and how
interventions are affecting the spread of the disease.
The key gaps and needs identified during this symposium and reported here are essential
in shaping a global research agenda designed to block transmission of M. leprae and move
toward eliminating the disease. These research priorities will form the foundation of the
Transmission Research Initiative (TRI) which will be launched in October 2015 by
effect:hope and partners, with a goal to support research aimed at closing gaps in our
understanding of M. leprae transmission.
We would like to thank all participants for their time and effort in helping to make this
symposium a success. We would also like to specifically extend our gratitude to National
School of Tropical Medicine, Baylor College of Medicine for hosting the symposium. The
symposium organizers Peter Hotez, Tom Gillis, Anna Wickenden, Kenneth Wong, Monica
Cazares, and Cynthia Johnson wish to thank all plenary speakers and the symposium
facilitator Edith Bahmanyar for their contributions. The symposium and participant costs
were funded by effect:hope (The Leprosy Mission Canada).
Uniting to combat neglected tropical diseases. London Declaration on Neglected Tropical Diseases. http:// ds.pdf.
Bratschi MW, Steinmann P, Wickenden A, Gillis TP. Current knowledge on M. leprae transmission: a systematic
literature review. Lepr Rev, 2015; 86: 142–155.
Blocking transmission of leprosy 163
Table 1. List of Participants affiliations
Participant Affiliation
Erwin Schurr McGill University, Montreal, Canada
Thomas Hawn University of Washington, Seattle, WA, USA
Steve Reed Infectious Disease Research Institute, Seattle, WA, USA
Annemiek Geluk Leiden University Medical Center, Leiden, The Netherlands
Pushpendrah Singh Ecole Polytechnique Federale de Laisanne (EPFL), Lausanne, Switzerland
Gerd Pluschke Swiss Tropical and Public Health Institute, Basel, Switzerland
W. Cairns Smith University of Aberdeen, Aberdeen, Scotland
Paul Fine London School of Hygiene and Tropical Medicine, London, UK
Peter Hotez National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, USA
Jan Hendrik Richardus Erasmus MC, University Medical Center, Rotterdam, The Netherlands
Eric Brenner University of South Carolina, Columbia, SC, USA
Masanori Matsuoka Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan
Ravindra Turanka The Leprosy Mission India and Stanley Browne Laboratory, Delhi, India
Marivic Balagon Leonard Wood Memorial Center for TB and Leprosy Research, Cebu, The Philippines
Edith Bahmanyar Novartis Foundation, Basel, Switzerland
Rosa Castalia Soares Leprosy Program, Ministry of Health, Sao Paulo, Brazil
Sunil Anand The Leprosy Mission Trust India, Delhi, India
Ruth Butlin Nilphamari, Bangladesh
Abraham Aseffa Armauer Hansen Research Institute and ALERT, Addis Ababa, Ethiopia
Shaikh Shahed Hossain International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
Jessica Fairley Emory School of Medicine, Atlanta, GA, USA
Martin Bratschi Swiss Tropical and Public Health Institute, Basel, Switzerland
Anna Wickenden effect:hope (The Leprosy Mission Canada), Markham, Canada
Peter Derrick effect:hope (The Leprosy Mission Canada), Markham, Canada
Tom Gillis effect:hope (The Leprosy Mission Canada), Markham, Canada
Kenneth Wong effect:hope (The Leprosy Mission Canada), Markham, Canada
Paul Saunderson American Leprosy Mission, Greenville, SC, USA
Christa Kasang German Leprosy and TB Relief Association, Wurzburg, Germany
Wim van Brakel Netherlands Leprosy Relief, Amsterdam, The Netherlands
Tamara Prinsenberg Netherlands Leprosy Relief, Amsterdam, The Netherlands
Ken Gibson The Leprosy Mission Ireland, Dublin, Ireland
Xiang-Yang Han MD Anderson, Houston, TX, USA
Bide Landry WHO-AFRO, Brazzaville, Republic of Congo
David Scollard National Hansen’s Disease Programs, Baton Rouge, LA, USA
Rahul Sharma National Hansen’s Disease Programs, Baton Rouge, LA, USA
Richard Truman National Hansen’s Disease Programs, Baton Rouge, LA, USA
Christine Sizemore NIAID, National Institutes of Health, Bethesda, MD, USA
Terry Williams Houston Department of Health and Human Services, Houston TX, USA
Steven Mays Houston Department of Health and Human Services, Houston TX, USA
D. Mensah-Awere et al.164
... None of the studies have given a structured elimination plan or framework, which is a gap to be filled while building an investment case for leprosy . Knowledge on transmission of M. leprae is limited 102 . Operational research is required to assess the feasibility of chemoprophylaxis in different settings 33,34 Box 1 Continued. ...
... It concludes that prospective longterm studies are needed to understand the transmission of M. leprae. 102 Further, the recommendations in this paper can be helpful in designing a framework or plan for elimination. Sufficient evidence exists in support of chemoprophylaxis. ...
Full-text available
Introduction: Leprosy continues to be a global public health problem, but draws less attention because 'prevalence based elimination' has been misinterpreted as eradication. The ongoing transmission of M. leprae has renewed interest in complete elimination. The aim of our study is to review systematically the literature regarding the elimination of leprosy, and to assess this information on its applicability for defining a Leprosy Elimination Investment Case (LEIC) based on Eradication Investment Case guidelines. Methodology: A literature search was conducted using the MeSH subheadings and synonyms of leprosy. A total of 1007 articles were considered and 112 were included in the final selection. The search focused on the literature covering leprosy elimination and its public health aspects. The LEIC framework was adapted from an existing "Guide to Preparing an Eradication Investment Case". Results: The LEIC framework provided 11 topics under which information was synthesized from the literature. The fields were categorised under sections: 1) Proposed investment; 2) Rationale for investing; 3) Issues to consider when moving from control to eradication; 4) Management and governance. Scanty quantitative data are available for developing a LEIC, particularly regarding disease burden, and new interventions that could contribute to elimination are not yet applied routinely. Discussion: For monitoring global elimination, it is necessary to measure disease burden comprehensively, and contact centered preventive interventions should be part of a global elimination strategy. The biological and technical feasibility of elimination is not certain and advanced microbiological and operational research is necessary to understand transmission better. The current WHO road map for leprosy elimination is too vague and needs further structuring through a thoroughly prepared LEIC.
... Additionally, national efforts are also needed to involve dermatologists in private sector to sustain high-quality leprosy services especially providing treatment. Although many member states declared leprosy elimination at the national level, leprosy as a public health problem has remained at sub-national levels [13][14][15], and many other leprosy concerns were unrecognized and unresolved [16,17]. In our study we found that Muscat and north Batinah Governorates are reporting highest leprosy cases, these two urban governorates are the most populated governorates and comprise of 49% of the total population with highest population density 346 and 87 /square kilometer in Muscat and North Batinah Governorates respectively, therefore, implementation of targeted active case search in high-risk governorates is required. ...
Full-text available
The World Health Organization (WHO) released the Global Leprosy Strategy 2016-2020 towards a leprosy-free world. The author described the progress made towards the elimination of leprosy and suggested recommendations for the acceleration towards a Leprosy-free country according to WHO laid out criterion.Case record review of Leprosy patients managed between the years 1992 to 2015 were registered and analyzed. Data were collected from annual reports of the Ministry of Health including demographics, classification of leprosy new cases, relapse, childhood, grades of disability (GD) and multidrug therapy (MDT) completion rates.Leprosy prevalence rate declined from 1.64 to 0.09 per 10,000 population during the period 1992 and 2015 (p
... Improved understanding of M leprae transmission and the risk factors for infection, as well as improved possibilities for studying M leprae, are needed to develop more effective tools and interventions to interrupt transmission. 24 This Personal View summarises recent work to develop new strategies and tools that we consider to be crucial for halting the transmission of M leprae. These strategies and tools include targeted screening with diagnostic tools to identify patients with leprosy; innovative strategies for prevention of the disease, such as administration of chemoprophylaxis or immuno prophylaxis to individuals at risk of infection; and transmission models and investment cases for elucidation of new pathways to interrupt M leprae transmission. ...
Leprosy control has seen little innovation and only limited progress in the past decade. However, research on the disease has increased and important innovations are underway. Here, we comment on efforts to develop tools and approaches to detect leprosy and to stop the transmission of Mycobacterium leprae, the causative bacillus of the disease. The tracing and screening of contacts of known patients with leprosy promises to strengthen early diagnosis, while preventive chemotherapy will reduce the risk of contacts developing the disease by 50–60% within 2 years of administration. Until now, diagnosis has been mainly based on the presence of signs and symptoms, but efforts are underway to develop inexpensive, reliable, point-of-care tests to diagnose infection. Development of a leprosy-specific vaccine that boosts long-lasting T-cell responses is also a research objective. As for launching a programme to interrupt transmission, two interlinked tools—epidemiological modelling and the concept of an investment case—are being developed to explore the feasibility and costs of such a programme and its overall effect on individuals and society. We believe that sustained innovation is needed and that only a combination of tools and approaches holds promise to end M leprae transmission.
... It is assumed that the main route of entry to the body is through the respiratory tract, although there are case studies suggestive of transmission through skin by wounds and tattoos, but the review also showed that no study has unequivocally demonstrated the mechanisms by which M. leprae bacteria travel from one case of leprosy to another (23). A recent expert group has identified the major gaps in knowledge about transmission and prioritized the research questions about transmission (24). ...
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Leprosy is a curable infectious disease. The causative agent, Mycobacterium leprae, has the unique capability to infect peripheral nerves, which may lead to varying degrees of neuropathy. In the most severe circumstances, this infection may result in an inability to feel pain in the hands or feet, a loss of digits, and blindness.Paradoxically, as treatment has become more successful, many specialized centers have closed and few physicians have adequate knowledge about the disease. A strong stigma, based on fear, still contributes to prolonged suffering and delayed diagnosis. Today, the diagnosis and treatment of leprosy also is often impeded by a lack of knowledge and awareness in the healthcare community. This textbook attempts to address the deficiency.The International Textbook of Leprosy is dedicated to the physicians and health workers caring for their first patient with leprosy, and to all of those in the research community who have encountered some of the fascinating scientific aspects of leprosy and wish to learn more.
... At the end of 2000, the WHO announced the elimination of leprosy as a public health problem globally and in 107 out of 122 countries that were considered endemic in 1985 [14]. Despite elimination at the national level, leprosy has remained a public health problem at sub-national levels in many countries [7,20], and many other concerns were unresolved [21,22]. ...
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Background Cameroon achieved the elimination target of leprosy in 2000, and has maintained this status ever since. However, a number of health districts in the country continue to report significant numbers of leprosy cases. The aim of this study was to assess the burden of leprosy in Cameroon from 2000 to 2014. Methods We obtained and analysed using the new leprosy burden concept of analysis, leprosy surveillance data collected between 2000 and 2014 from the National Leprosy Control Programme. Principal findings Cameroon achieved leprosy elimination in 2000, registering a prevalence rate of 0.94/10,000 population. The prevalence rate dropped further to reach 0.20/10,000 population (78% reduction) in 2014. Similarly, the new case detection rate dropped from 4.88/100,000 population in 2000 to 1.46/100,000 population (85.3% reduction) in 2014. All 10 regions of the country achieved leprosy elimination between 2000 and 2014; however, 10 health districts were still to do so by 2014. The number of high-leprosy-burden regions decreased from 8 in 2000 to 1 in 2014. Seven and two regions were respectively medium and low-burdened at the end of 2014. At the health districts level, 18 remained at the high-leprosy-burdened level in 2014. Conclusion The leprosy prevalence and detection rates as well as the overall leprosy burden in Cameroon have dropped significantly between 2000 and 2014. However, a good number of health districts remain high-leprosy-burdened. The National Leprosy Control Programme should focus efforts on these health districts in the next coming years in order to further reduce the burden of leprosy in the country.
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Leprosy is caused by Mycobacterium leprae (M. leprae) and M. lepromatosis, an obligate intracellular organism, and over 200,000 new cases occur every year. M. leprae parasitizes histiocytes (skin macrophages) and Schwann cells in the peripheral nerves. Although leprosy can be treated by multidrug therapy, some patients relapse or have a prolonged clinical course and/or experience leprosy reaction. These varying outcomes depend on host factors such as immune responses against bacterial components that determine a range of symptoms. To understand these host responses, knowledge of the mechanisms by which M. leprae parasitizes host cells is important. This article describes the characteristics of leprosy through bacteriology, genetics, epidemiology, immunology, animal models, routes of infection, and clinical findings. It also discusses recent diagnostic methods, treatment, and measures according to the World Health Organization (WHO), including prevention. Recently, the antibacterial activities of anti-hyperlipidaemia agents against other pathogens, such as M. tuberculosis and Staphylococcus aureus have been investigated. Our laboratory has been focused on the metabolism of lipids which constitute the cell wall of M. leprae. Our findings may be useful for the development of future treatments.
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Background Leprosy control achieved dramatic success in the 1980s–1990s with the implementation of short course multidrug therapy, which reduced the global prevalence of leprosy to less than 1 in 10 000 population. However, a period of relative stagnation in leprosy control followed this achievement, and only limited further declines in the global number of new cases reported have been achieved over the past decade. Main text In 2016, major stakeholders called for the development of an innovative and comprehensive leprosy strategy aimed at reducing the incidence of leprosy, lowering the burden of disability and discrimination, and interrupting transmission. This led to the establishment of the Global Partnership for Zero Leprosy (GPZL) in 2018, with partners aligned around a shared Action Framework committed to achieving the WHO targets by 2030 through national leprosy program capacity-building, resource mobilisation and an enabling research agenda. GPZL convened over 140 experts from more than 20 countries to develop a research agenda to achieve zero leprosy. The result is a detailed research agenda focusing on diagnostics, mapping, digital technology and innovation, disability, epidemiological modelling and investment case, implementation research, stigma, post exposure prophylaxis and transmission, and vaccines. This research agenda is aligned with the research priorities identified by other stakeholders. Conclusions Developing and achieving consensus on the research agenda for zero leprosy is a significant step forward for the leprosy community. In a next step, research programmes must be developed, with individual components of the research agenda requiring distinct expertise, varying in resource needs, and operating over different timescales. Moving toward zero leprosy now requires partner alignment and new investments at all stages of the research process, from discovery to implementation.
Over the past few decades, the prevalence of leprosy cases has decreased with ongoing efforts at a global level; however, the incidence of this infection remains relatively constant. With currently available antimicrobials, many individuals recover from a microbiologic perspective, but many of them suffer from long‐term neurologic sequelae due to peripheral nerve dysfunction. The current armamentarium of antimycobacterial drugs and inflammatory therapies is insufficient to decrease the overall burden of disease and suffering caused by this infection. There is an unmet need for further pharmacologic and immunotherapeutic strategies to preserve neurologic function in those affected by this ancient plague.
Humans encounter mycobacterial species due to their ubiquity in different environmental niches. In many individuals, pathogenic mycobacterial species may breach our first-line barrier defenses of the innate immune system and modulate the activation of phagocytes to cause disease of the respiratory tract or the skin and soft tissues, sometimes resulting in disseminated infection. Cutaneous mycobacterial infections may cause a wide range of clinical manifestations, which are divided into four main disease categories: (i) cutaneous manifestations of Mycobacterium tuberculosis infection, (ii) Buruli ulcer caused by Mycobacterium ulcerans and other related slowly growing mycobacteria, (iii) leprosy caused by Mycobacterium leprae and Mycobacterium lepromatosis, and (iv) cutaneous infections caused by rapidly growing mycobacteria. Clinically, cutaneous mycobacterial infections present with widely different clinical presentations, including cellulitis, nonhealing ulcers, subacute or chronic nodular lesions, abscesses, superficial lymphadenitis, verrucous lesions, and other types of findings. Mycobacterial infections of the skin and subcutaneous tissue are associated with important stigma, deformity, and disability. Geography-based environmental exposures influence the epidemiology of cutaneous mycobacterial infections. Cutaneous tuberculosis exhibits different clinical phenotypes acquired through different routes, including via extrinsic inoculation of the tuberculous bacilli and dissemination to the skin from other sites, or represents hypersensitivity reactions to M. tuberculosis infection. In many settings, leprosy remains an important cause of neurological impairment, deformity, limb loss, and stigma. Mycobacterium lepromatosis, a mycobacterial species related to M. leprae, is linked to diffuse lepromatous leprosy of Lucio and Latapí. Mycobacterium ulcerans produces a mycolactone toxin that leads to subcutaneous tissue destruction and immunosuppression, resulting in deep ulcerations that often produce substantial disfigurement and disability. Mycobacterium marinum, a close relative of M. ulcerans, is an important cause of cutaneous sporotrichoid nodular lymphangitic lesions. Among patients with advanced immunosuppression, Mycobacterium kansasii, the Mycobacterium avium-intracellulare complex, and Mycobacterium haemophilum may cause cutaneous or disseminated disease. Rapidly growing mycobacteria, including the Mycobacterium abscessus group, Mycobacterium chelonei, and Mycobacterium fortuitum, are increasingly recognized pathogens in cutaneous infections associated particularly with plastic surgery and cosmetic procedures. Skin biopsies of cutaneous lesions to identify acid-fast staining bacilli and cultures represent the cornerstone of diagnosis. Additionally, histopathological evaluation of skin biopsy specimens may be useful in identifying leprosy, Buruli ulcer, and cutaneous tuberculosis. Molecular assays are useful in some cases. The treatment for cutaneous mycobacterial infections depends on the specific pathogen and therefore requires a careful consideration of antimicrobial choices based on official treatment guidelines.
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Recent mathematical and statistical modeling of leprosy incidence data provides estimates of the current undiagnosed population and projections of diagnosed cases, as well as ongoing transmission. Furthermore, modeling studies have been used to evaluate the effectiveness of proposed intervention strategies, such as postleprosy exposure prophylaxis and novel diagnostics, relative to current approaches. Such modeling studies have revealed both a slow decline of new cases and a substantial pool of undiagnosed infections. These findings highlight the need for active case detection, particularly targeting leprosy foci, as well as for continued research into innovative accurate, rapid, and cost-effective diagnostics. As leprosy incidence continues to decline, targeted active case detection primarily in foci and connected areas will likely become increasingly important.