Distribution and persistence of Mycobacterium leprae nasal carriage among a population in which leprosy is endemic in Indonesia

Infections of the Peripheral Nervous System

PURPOSE OF REVIEW

This article describes infections that affect the peripheral nervous system, including their clinical features, differential diagnoses, and treatments.

RECENT FINDINGS

Rates of pyomyositis have increased recently in the United States, possibly because of an increase in risk factors such as IV drug use, obesity, and diabetes. Other peripheral nervous system infections, such as diphtheria, have become more common in older patients secondary to a lack of revaccination or waning immunity. Although recommended treatment regimens for most infections remain unchanged over recent years, debate over the ideal dosing and route of administration continues for some infections such as tetanus and leprosy (Hansen disease).

SUMMARY

Infections of the peripheral nervous system are varied in terms of the type of infection, localization, and potential treatment. Nerve conduction studies and EMG can help determine localization, which is key to determining an initial differential diagnosis. It is important to recognize infections quickly to minimize diagnostic delays that could lead to patient morbidity and mortality.

Efficacy of chemoprophylaxis and immunoprophylaxis in leprosy prevention: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND

Vaccination and single-dose rifampin are the main proven effective intervention types for preventing leprosy among contacts of Mycobacterium leprae endemic areas. Currently, no high-quality evidence is available regarding the best prophylactic intervention.

OBJECTIVES

Our primary study aim is to detect the most effective prophylactic intervention for the prevention of leprosy.

METHODS

In May 2019, 12 databases were searched systematically. Updated search terms were developed in March 2020 to complete an updated search. All randomized controlled trials (RCTs) comparing the different types of chemoprophylactic and immunoprophylactic interventions in leprosy prevention were included. Our participants were contacts of patients with leprosy or people residing in leprosy endemic communities. We searched for different types of chemoprophylactic and immunoprophylactic interventions used in leprosy prevention. We used network meta-analysis and meta-analysis. Quality assessment was performed using Cochrane Risk of Bias for included RCTs, in which all included RCTs were rated to be low to moderate risk. We registered our protocol in Prospero with ID CRD42019143207.

RESULTS

Among 11 included studies (326 264 patients) from original and updated search terms, eight were eligible for network meta-analysis (NMA) while four were eligible for MA. Findings suggest that Bacillus Calmette-Guérin (BCG) vaccination was the most effective intervention compared to placebo (risk ratios (RRs) 0.49 (0.30, 0.80), p 0.77), followed by combined BCG vaccination and single-dose rifampicin (SDR) with similarly low values (RR 48%, p 0.77). BCG revaccination was the least effective intervention compared to placebo (RR 1.08 (0.36, 3.22), p 0.26).

CONCLUSION

Compared to placebo, the BCG vaccine was the most effective prophylactic intervention. The combination of BCG vaccination + SDR had nearly the same efficacy as BCG vaccination alone, while BCG revaccination was the least effective. Thus, vaccination proved to be a more effective treatment than SDR alone. A well-designed multicenter RCT is warranted to evaluate the safety of these vaccines.

The long-term impact of the Leprosy Post-Exposure Prophylaxis (LPEP) program on leprosy incidence: A modelling study

Background

The Leprosy Post-Exposure Prophylaxis (LPEP) program explored the feasibility and impact of contact tracing and the provision of single dose rifampicin (SDR) to eligible contacts of newly diagnosed leprosy patients in Brazil, India, Indonesia, Myanmar, Nepal, Sri Lanka and Tanzania. As the impact of the programme is difficult to establish in the short term, we apply mathematical modelling to predict its long-term impact on the leprosy incidence.

Methodology

The individual-based model SIMCOLEP was calibrated and validated to the historic leprosy incidence data in the study areas. For each area, we assessed two scenarios: 1) continuation of existing routine activities as in 2014; and 2) routine activities combined with LPEP starting in 2015. The number of contacts per index patient screened varied from 1 to 36 between areas. Projections were made until 2040.

Principal findings

In all areas, the LPEP program increased the number of detected cases in the first year(s) of the programme as compared to the routine programme, followed by a faster reduction afterwards with increasing benefit over time. LPEP could accelerate the reduction of the leprosy incidence by up to six years as compared to the routine programme. The impact of LPEP varied by area due to differences in the number of contacts per index patient included and differences in leprosy epidemiology and routine control programme.

Conclusions

The LPEP program contributes significantly to the reduction of the leprosy incidence and could potentially accelerate the interruption of transmission. It would be advisable to include contact tracing/screening and SDR in routine leprosy programmes.

The Leprosy Post-Exposure Prophylaxis (LPEP) program explored the feasibility and impact of contact tracing and the provision of SDR to eligible contacts of newly diagnosed leprosy patients in states or districts of Brazil, India, Indonesia, Myanmar, Nepal, Sri Lanka and Tanzania. This study investigated the long-term impact of the LPEP program on the leprosy new case detection rate (NCDR). Our results show that LPEP could reduce the NCDR beyond the impact of the routine leprosy control programme and that many new cases could be prevented. The benefit of LPEP increases gradually over time. LPEP could accelerate the time of reaching predicted NCDR levels of 2040 under routine program by up to six years. Furthermore, we highlighted how the impact varies between countries due to differences in the number of contacts per index patient screened and differences in leprosy epidemiology and national control programme. Generally, including both household contacts and neighbours (> 20 contacts per index patient) would yield the highest impact.

Forecasting the new case detection rate of leprosy in four states of Brazil: A comparison of modelling approaches

Background:

Brazil has the second highest annual number of new leprosy cases. The aim of this study is to formally compare predictions of future new case detection rate (NCDR) trends and the annual probability of NCDR falling below 10/100,000 of four different modelling approaches in four states of Brazil: Rio Grande do Norte, Amazonas, Ceará, Tocantins.

Methods:

A linear mixed model, a back-calculation approach, a deterministic compartmental model and an individual-based model were used. All models were fitted to leprosy data obtained from the Brazilian national database (SINAN). First, models were fitted to the data up to 2011, and predictions were made for NCDR for 2012–2014. Second, data up to 2014 were considered and forecasts of NCDR were generated for each year from 2015 to 2040. The resulting distributions of NCDR and the probability of NCDR being below 10/100,000 of the population for each year were then compared between approaches.

Results:

Each model performed well in model fitting and the short-term forecasting of future NCDR. Long-term forecasting of NCDR and the probability of NCDR falling below 10/100,000 differed between models. All agree that the trend of NCDR will continue to decrease in all states until 2040. Reaching a NCDR of less than 10/100,000 by 2020 was only likely in Rio Grande do Norte. Prediction until 2040 showed that the target was also achieved in Amazonas, while in Ceará and Tocantins the NCDR most likely remain (far) above 10/100,000.

Conclusions:

All models agree that, while incidence is likely to decline, achieving a NCDR below 10/100,000 by 2020 is unlikely in some states. Long-term prediction showed a downward trend with more variation between models, but highlights the need for further control measures to reduce the incidence of new infections if leprosy is to be eliminated.

Minimum requirements and optimal testing strategies of a diagnostic test for leprosy as a tool towards zero transmission: A modeling study

Background

The availability of a diagnostic test to detect subclinical leprosy cases is crucial to interrupt the transmission of M. leprae. In this study we assessed the minimum sensitivity level of such a (hypothetical) diagnostic test and the optimal testing strategy in order to effectively reduce the new case detection rate (NCDR) of leprosy.

Methods and findings

We used the individual-based model SIMCOLEP, and based it on previous quantification using COLEP data, a cohort study of leprosy cases in Bangladesh. The baseline consisted of treatment with Multidrug therapy of clinically diagnosed leprosy cases, passive case detection and household contact tracing. We examined the use of a leprosy diagnostic test for subclinical leprosy in four strategies: testing in 1) household contacts, 2) household contacts with a 3-year follow-up, 3) a population survey with coverage 50%, and 4) a population survey (100%). For each strategy, we varied the test sensitivity between 50% and 100%. All analyses were conducted for a high, medium, and low (i.e. 25, 5 and 1 per 100,000) endemic setting over a period of 50 years.

In all strategies, the use of a diagnostic test further reduces the NCDR of leprosy compared to the no test strategy. A substantial reduction could already be achieved at a test sensitivity as low as 50%. In a high endemic setting, a NCDR of 10 per 100,000 could be reached within 8–10 years in household contact testing, and 2–6 years in a population testing. Testing in a population survey could also yield the highest number of prevented new cases, but requires a large number needed to test and treat. In contrast, household contact testing has a smaller impact on the NCDR but requires a substantially lower number needed to test and treat.

Conclusions

A diagnostic test for subclinical leprosy with a sensitivity of at least 50% could substantially reduce M. leprae transmission. To effectively reduce NCDR in the short run, a population survey is preferred over household contact tracing. However, this is only favorable in high endemic settings.

The annual number of new leprosy cases has been stable in the past decade, indicating that transmission has not been yet been interrupted. As current control seems to be insufficient to bring down the number of cases, there is a need for novel tools to interrupt transmission. A diagnostic that permitted diagnosis of subclinical cases will likely be fundamental to achieve elimination and ultimately eradication. In this study we assessed the minimum sensitivity level of such a (hypothetical) diagnostic test and the optimal testing strategy in order to effectively reduce the new case detection rate (NCDR) of leprosy. We showed that a diagnostic test for subclinical leprosy could substantially reduce the NCDR in a high, medium and low endemic population. A significant impact could already be achieved at a test sensitivity level of 50%. To effectively reduce the NCDR in the short run, a population survey is preferred over household contact tracing. However, this is only favorable in high endemic settings, as in medium and low endemic settings testing in a population survey requires many more people to be tested and treated to prevent one new leprosy case.

Presence of viable Mycobacterium leprae in environmental specimens around houses of leprosy patients

PURPOSE

Leprosy is a chronic systemic infectious disease caused by Mycobacterium leprae, one of the first organisms to be established as the cause for disease in humans. Because of high prevalence pockets of leprosy in the endemic regions, it is necessary to identify the possible sources of M. leprae in the environment and its mode of transmission.

MATERIALS AND METHODS

Slit skin smears (SSSs) from lesions were collected in 70% ethanol from 50 leprosy cases staying in the leprosy resettlement village and hospital from a high endemic area. One hundred and sixty soil samples were collected from different areas around the leprosy hospital and from the resettlement village of cured leprosy patients where active cases also resided at the time of sample collection. M. leprae specific gene region (RLEP 129 bp) and 16S rRNA targets were used for polymerase chain reaction (PCR) based detection for the presence and viability of M. leprae. An rpoT region was also amplified to determine presence of numbers of 6 bp tandem repeats.

RESULTS

All the SSS samples collected from patients showed three copies of rpoT region (6 bp tandem repeat, an ancient Indian type). Fifty-two soil samples showed presence of M. leprae DNA whereas M. leprae specific 16S rRNA gene was amplified in sixteen of these samples. PCR amplification and fragment length analysis showed 91 bp, i.e., three copies of the rpoT 6 bp tandem repeats from soil samples and similar three copies observed in patient samples.

CONCLUSION

Presence of viable M. leprae in the soil having same rpoT genotype of M. leprae noted in patients suggests that it could be the same strain of M. leprae. M. leprae found in the soil could be the one that is excreted out by the patient. Significance of its viability in the environment and its pathogenicity with respect to transmission needs to be further explored. Findings of this study might provide possible insights for further exploration into understanding transmission patterns in leprosy and also will throw light on identifying potential for existence of extra human source or reservoirs of M. leprae, if any.

Nasal PCR assay for the detection of Mycobacterium leprae pra gene to study subclinical infection in a community

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. Identification of Mycobacterium leprae is difficult in part due to the inability of the leprosy bacillus to grow in vitro. A number of diagnostic methods for leprosy diagnosis have been proposed. Both serological tests and molecular probes have shown certain potential for detection and identification of Mycobacterium leprae in patients. In this study, we have investigated whether Mycobacterium leprae DNA from the nasal secretion of healthy household contacts and the non contacts could be detected through PCR amplification as a method to study the sub clinical infection in a community. A total of 200 samples, 100 each from contacts and non contacts representing all age groups and sex were included in this study. The M. leprae specific primer (proline-rich region) of pra gene was selected and PCR was performed using extracted DNA from the sample. A total of 13 samples were found to be positive for nasal PCR for pra gene among the male and female contacts out of which 7% were males and 6% were females. Even though several diagnostic tools are available to detect the cases of leprosy, they lack the specificity and sensitivity. PCR technology has demonstrated the improved diagnostic accuracy for epidemiological studies and requires minimal time. Although nasal PCR studies have been reported from many countries it is not usually recommended due to the high percentage of negative results in the contact.

Mathematical modelling of leprosy and its control

Leprosy or Hansen's disease is an infectious disease caused by the bacterium Mycobacterium leprae. The annual number of new leprosy cases registered worldwide has remained stable over the past years at over 200,000. Early case finding and multidrug therapy have not been able interrupt transmission completely. Elimination requires innovation in control and sustained commitment. Mathematical models can be used to predict the course of leprosy incidence and the effect of intervention strategies. Two compartmental models and one individual-based model have been described in the literature. Both compartmental models investigate the course of leprosy in populations and the long-term impact of control strategies. The individual-based model focusses on transmission within households and the impact of case finding among contacts of new leprosy patients. Major improvement of these models should result from a better understanding of individual differences in exposure to infection and developing leprosy after exposure. Most relevant are contact heterogeneity, heterogeneity in susceptibility and spatial heterogeneity. Furthermore, the existing models have only been applied to a limited number of countries. Parameterization of the models for other areas, in particular those with high incidence, is essential to support current initiatives for the global elimination of leprosy. Many challenges remain in understanding and dealing with leprosy. The support of mathematical models for understanding leprosy epidemiology and supporting policy decision making remains vital.

Leprosy: review of the epidemiological, clinical, and etiopathogenic aspects - part 1

Leprosy is caused by Mycobacterium leprae and has been known since biblical times. It is still endemic in many regions of the world and a public health problem in Brazil. The prevalence rate in 2011 reached 1.54 cases per 10,000 inhabitants in Brazil. The mechanism of transmission of leprosy consists of prolonged close contact between susceptible and genetically predisposed individuals and untreated multibacillary patients. Transmission occurs through inhalation of bacilli present in upper airway secretion. The nasal mucosa is the main entry or exit route of M. leprae. The deeper understanding of the structural and biological characteristics of M. leprae, the sequencing of its genome, along with the advances in understanding the mechanisms of host immune response against the bacilli, dependent on genetic susceptibility, have contributed to the understanding of the pathogenesis, variations in the clinical characteristics, and progression of the disease. This article aims to update dermatologist on epidemiological, clinical, and etiopathogenic leprosy aspects.

Socio-economic and environmental effects influencing the development of leprosy in Bahia, north-eastern Brazil

OBJECTIVES

To investigate spatial clusters and possible associations between relative risks of leprosy with socio-economic and environmental factors, taking into account diagnosed cases in children under 15 years old.

METHODS

An ecological study was conceived using data aggregated by municipality to identify possible spatial clusters of leprosy from 2005 to 2011. Relative risks were calculated accounting for the respective covariate gender. The second stage of the analysis consisted of verifying possible associations between the relative risks of leprosy as a dependent variable, and socio-economic and environmental variables as independent. This was performed using a multivariate regression analysis according to a previously defined conceptual framework.

RESULTS

Overall rates have decreased from 0.88/10 000 in 2005 to 0.52 in 2011. Spatial scan statistics identified 4 high-risk and 6 low-risk clusters. In the regression model, after allowing for spatial dependence, relative risks were associated with higher percentage of water bodies, higher Gini index, higher percentage of urban population, larger average number of dwellers by permanent residence and smaller percentage of residents born in Bahia.

CONCLUSIONS

Although relative risks of leprosy in Bahia have been decreasing, they remain very high. The association between relative risks of leprosy and water bodies in the proposed geographic scale indicates that hypothesis linking M. leprae and humid environments cannot be discarded. Socio-economic conditions such as inequality, a greater number of dwellers by residence and migration are derived from the urbanisation process carried out in this State. Precarious settlements and poor living conditions in the cities would favour the continuity of leprosy transmission.

Unveiling healthy carriers and subclinical infections among household contacts of leprosy patients who play potential roles in the disease chain of transmission

Leprosy transmission still occurs despite the availability of highly effective treatment. The next step towards successfully eliminating leprosy is interrupting the chain of transmission of the aetiological agent, Mycobacterium leprae. In this investigation, we provide evidence that household contacts (HHCs) of leprosy patients might not only have subclinical infections, but may also be actively involved in bacilli transmission. We studied 444 patients and 1,352 contacts using anti-phenolic glycolipid-I (PGL-I) serology and quantitative polymerase chain reaction (qPCR) to test for M. leprae DNA in nasal swabs. We classified the patients according to the clinical form of their disease and the contacts according to the characteristics of their index case. Overall, 63.3% and 34.2% of patients tested positive by ELISA and PCR, respectively. For HHCs, 13.3% had a positive ELISA test result and 4.7% had a positive PCR test result. The presence of circulating anti-PGL-I among healthy contacts (with or without a positive PCR test result from nasal swabs) was considered to indicate a subclinical infection. DNA detected in nasal swabs also indicates the presence of bacilli at the site of transmission and bacterial entrance. We suggest that the concomitant use of both assays may allow us to detect subclinical infection in HHCs and to identify possible bacilli carriers who may transmit and disseminate disease in endemic regions. Chemoprophylaxis of these contacts is suggested.

Leprosy. An update: definition, pathogenesis, classification, diagnosis, and treatment

Leprosy is a chronic granulomatous disease caused by the bacillus Mycobacterium leprae. It primarily affects the skin and peripheral nerves and is still endemic in various regions of the world. Clinical presentation depends on the patient's immune status at the time of infection and during the course of the disease. Leprosy is associated with disability and marginalization. Diagnosis is clinical and is made when the patient has at least 1 of the following cardinal signs specified by the World Health Organization: hypopigmented or erythematous macules with sensory loss; thickened peripheral nerves; or positive acid-fast skin smear or skin biopsy with loss of adnexa at affected sites. Leprosy is treated with a multidrug combination of rifampicin, clofazimine, and dapsone. Two main regimens are used depending on whether the patient has paucibacillary or multibacillary disease.

Kinship and Leprosy in the Contacts of Leprosy Patients: Cohort at the Souza Araújo Outpatient Clinic, Rio de Janeiro, RJ, 1987-2010

A broad variety of factors have been associated with leprosy among contacts, including socioeconomic, epidemiological, and genetic characteristics. Data from 7,174 contacts of leprosy patients from a leprosy outpatient clinic in Rio de Janeiro, Brazil, 1987–2010, were analyzed to investigate the effects of kinship, individual, and contextual factors on leprosy. Multivariate analyses were performed using a robust estimation method. In the prevalence analysis, close kinship (sibling OR = 2.75, offspring OR = 2.00, and other relatives OR = 1.70), socioeconomic factors, and the duration of exposure to the bacillus were associated to leprosy. In the incidence analysis, significant risks were found for all categories of kinship (parents RR = 10.93, spouse, boyfriend/girlfriend, and bride/groom RR = 7.53, sibling RR = 7.03, offspring RR = 5.34, and other relatives RR = 3.71). Once the treatment of the index case was initiated, other factors lost their significance, and the index case bacteriological index and BCG (Bacillus Calmette-Guérin vaccine) protection had a greater impact. Our findings suggested that both genetic susceptibility and physical exposure play an important role in the epidemiology of leprosy, but it was not possible establishing the role of genetic factor. Analyses of other factors related to the genotype of individuals, such as genetic polymorphisms, are needed.

The meaning of leprosy and everyday experiences: an exploration in cirebon, indonesia

It is imperative to consider the meaning of leprosy and everyday experiences of people affected by leprosy and key persons in the community if one aims to make leprosy services more effective, which appears necessary in Indonesia given the large numbers of new cases detected annually. However, little is written in the international literature about the experiences of people currently being treated for leprosy, those cured, or other key informants. This paper analyses the narratives of the people by drawing upon in-depth interviews with 53 participants and 20 focus groups discussions. The participants were purposively selected. We provide insights into the experiences of people and the meaning they give to leprosy and highlight aspect of aetiology, spirituality, religion, darkening of the skin, and sorcery. We also examine experiences of seeking care and focused on the impact of the disease in particular on the elderly and children. In conclusion, the continued need for implementation of leprosy services in Indonesia is very evident. The diversities in people's experiences with leprosy indicate a demand for responsive leprosy services to serve the diverse needs, including services for those formally declared to be “cured.”

Cohort study of the seasonal effect on nasal carriage and the presence of Mycobacterium leprae in an endemic area in the general population

Leprosy continues to be a significant health problem in certain pockets in developing countries. Better understanding of the transmission and source of the infection would help to decipher the transmission link, leading to control of the spread of the disease. The nose is considered to be a portal of entry, suggesting an aerial route for transmission through droplet infection. The evidence suggests that many individuals from endemic countries carry Mycobacterium leprae in their nasal cavities without having obvious symptoms of leprosy. The objective of the present study was to assess the presence of M. leprae on the nasal mucosa in the general population from a leprosy-endemic pocket. M. leprae detection was carried out using PCR targeting RLEP. Four hundred subjects from an area highly endemic for leprosy were included in the study and followed up during three different seasons--winter, summer, and monsoon--for evidence of nasal exposure to M. leprae. PCR positivity for M. leprae was observed in 29%, 21% and 31% of the samples collected in winter, summer and the monsoon season, respectively. Twenty-six individuals from the cohort showed amplification for M. leprae for all seasons. Our results are consistent with reports in the literature showing widespread exposure to M. leprae in the endemic community. The results also suggest possible association of the environmental conditions (climate) with the transmission pattern and levels of exposure to M. leprae. However, the present study indicated that the population from highly endemic pockets will have exposure to M. leprae irrespective of season.

Pathogen-specific epitopes as epidemiological tools for defining the magnitude of Mycobacterium leprae transmission in areas endemic for leprosy

During recent years, comparative genomic analysis has allowed the identification of Mycobacterium leprae-specific genes with potential application for the diagnosis of leprosy. In a previous study, 58 synthetic peptides derived from these sequences were tested for their ability to induce production of IFN-γ in PBMC from endemic controls (EC) with unknown exposure to M. leprae, household contacts of leprosy patients and patients, indicating the potential of these synthetic peptides for the diagnosis of sub- or preclinical forms of leprosy. In the present study, the patterns of IFN-γ release of the individuals exposed or non-exposed to M. leprae were compared using an Artificial Neural Network algorithm, and the most promising M. leprae peptides for the identification of exposed people were selected. This subset of M. leprae-specific peptides allowed the differentiation of groups of individuals from sites hyperendemic for leprosy versus those from areas with lower level detection rates. A progressive reduction in the IFN-γ levels in response to the peptides was seen when contacts of multibacillary (MB) patients were compared to other less exposed groups, suggesting a down modulation of IFN-γ production with an increase in bacillary load or exposure to M. leprae. The data generated indicate that an IFN-γ assay based on these peptides applied individually or as a pool can be used as a new tool for predicting the magnitude of M. leprae transmission in a given population.

New biomarkers with relevance to leprosy diagnosis applicable in areas hyperendemic for leprosy

Leprosy is not eradicable with currently available diagnostics or interventions, as evidenced by its stable incidence. Early diagnosis of Mycobacterium leprae infection should therefore be emphasized in leprosy research. It remains challenging to develop tests based on immunological biomarkers that distinguish individuals controlling bacterial replication from those developing disease. To identify biomarkers for field-applicable diagnostics, we determined cytokines/chemokines induced by M. leprae proteins in blood of leprosy patients and endemic controls (EC) from high leprosy-prevalence areas (Bangladesh, Brazil, Ethiopia) and from South Korea, where leprosy is not endemic anymore. M. leprae-sonicate-induced IFN-γ was similar for all groups, excluding M. leprae/IFN-γ as a diagnostic readout. By contrast, ML2478 and ML0840 induced high IFN-γ concentrations in Bangladeshi EC, which were completely absent for South Korean controls. Importantly, ML2478/IFN-γ could indicate distinct degrees of M. leprae exposure, and thereby the risk of infection and transmission, in different parts of Brazilian and Ethiopian cities. Notwithstanding these discriminatory responses, M. leprae proteins did not distinguish patients from EC in one leprosy-endemic area based on IFN-γ. Analyses of additional cytokines/chemokines showed that M. leprae and ML2478 induced significantly higher concentrations of MCP-1, MIP-1β, and IL-1β in patients compared with EC, whereas IFN-inducible protein-10, like IFN-γ, differed between EC from areas with dissimilar leprosy prevalence. This study identifies M. leprae-unique Ags, particularly ML2478, as biomarker tools to measure M. leprae exposure using IFN-γ or IFN-inducible protein-10, and also shows that MCP-1, MIP-1β, and IL-1β can potentially distinguish pathogenic immune responses from those induced during asymptomatic exposure to M. leprae.

Leprosy now: epidemiology, progress, challenges, and research gaps

Leprosy continues to be a challenge to health worldwide, with about 250,000 new cases being detected every year. Despite widespread implementation of effective multidrug therapy, leprosy has not been eliminated. A third of newly diagnosed patients have nerve damage and might develop disabilities, although the proportion varies according to several factors, including level of self-care. Women who develop leprosy continue to be especially disadvantaged, with rates of late diagnosis and disability remaining high in this subgroup. Leprosy was not a specified disease in the Millennium Development Goals, but improvements in the other areas they cover, such as education and levels of poverty, will help leprosy patients and services. We review data and make recommendations for research on diagnosis, treatment, and prevention, such as further use of molecular analysis of the Mycobacterium leprae genome, implementation of BCG vaccination, and administration of chemoprophylaxis to household contacts. We also suggest development of tools for early diagnosis and detection of infection and nerve damage, and formulation of strategies to manage the chronic complications of leprosy, such as immune-mediated reactions and neuropathy.

How to prevent immunological reactions in leprosy patients and interrupt transmission of Mycobacterium leprae to healthy subjects: two hypotheses

The basis of World Health Organization strategy for leprosy elimination is that the only source and reservoir for infection are patients with the disease. It was assumed that multi drug therapy (MDT) would reduce transmission of Mycobacterium leprae, but there is no convincing evidence for this. Furthermore, even if MDT has been proved to be extremely effective against the infectious disease, a noticeable proportion of leprosy patients can suffer from immunologic hypersensitivity reactions which are now the most significant issue in the managements of the disease. In endemic areas it was found that: M. leprae survives outside human body; healthy individuals harbor M. leprae bacilli in nasal cavity and shed micro-organisms in environment; there is widespread subclinical transmission of M. leprae with transient infection of the nose resulting in the development of a mucosal immune response. This disparate clinical, epidemiologic, and microbiologic evidence leads to the first hypothesis: that antigenic load in local tissues, sufficient to trigger the immune response, comes from external supply of M. leprae organisms. The hypothiocyanite anion (OSCN-) is generated in vivo by the reaction of thiocyanate with hydrogen peroxide catalyzed by lactoperoxidase. OSCN- is an antimicrobial oxidizing agent that prevents growth of bacteria, fungi, and viruses. OSNC- exists in lower airway secretions and lung has never been reported to be affected by leprosy. There is a sufficient concentration of OSCN- in the saliva, and accordingly mouth is rarely affected by leprosy. By contrast, the concentration of this compound is low or nil in nasal and lacrimal secretions and leprosy very often affects nose and eyes. The second hypothesis is that OSCN- may also protect from leprosy. Recently a method of OSCN- production, not involving enzymatic steps or use of toxic heavy-metal salts, has been patented. Studies on the susceptibility of M. leprae to hypothiocyanite could be carried out and, in case of positive results, the substance might be used in order to sterilize the nasal cavity of healthy carriers and prevent transmission of M. leprae to healthy subjects and to leprosy patients in whom it may trigger an immune response.

Seroprevalence of ML Flow test in leprosy contacts from State of Minas Gerais, Brazil

Leprosy is a public health problem in Brazil. Epidemiological control actions are based on the diagnosis and treatment of leprosy patients and household contact surveillance. Serological tests for leprosy could identify from among the contacts those at greater risk of developing leprosy in the future. ML Flow was administered to 2,840 household contacts of new leprosy cases diagnosed from October 2002 to March 2004, in State of Minas Gerais. ML Flow was positive in 20.5% of leprosy contacts, with high seropositivity among males (22.4%), individuals aged over 15 years-old (21.7%) and individuals in contact with multibacillary cases (23.9%). The chances of a household contact presenting a seropositive test was related to household contact with a multibacillary index case (OR=1.75), age over 15 years-old (OR=1.38) and male gender (OR=1.25). Follow-up of these contacts is necessary to evaluate the real role of seropositivity in the development of leprosy disease.

Genetic susceptibility to mycobacterial disease in humans

Mycobacterial disease remains a serious global health problem. Tuberculosis causes more than 2 million deaths a year, and leprosy is still a cause of severe disability in many parts of the world. As a result of the study of individuals with marked susceptibility to usually nonpathogenic mycobacteria, as well as case-control studies with candidate genes and genome-wide screens of affected populations, there is substantial evidence for the role of genetic factors in the susceptibility to mycobacterial disease. These studies have defined immunological processes essential for the control of mycobacteria infections in humans.

ML0405 and ML2331 are antigens of Mycobacterium leprae with potential for diagnosis of leprosy

Despite the success of multidrug therapy in reducing the number of registered leprosy cases worldwide, evidence suggests that Mycobacterium leprae continues to be transmitted. A serological diagnostic test capable of identifying and allowing treatment of early-stage disease could reduce transmission and prevent the onset of the disability, a common complication of the disease in later stages. Serological diagnosis based on antibody recognition of phenolic glycolipid I (PGL-I) cannot reliably identify individuals with lower bacterial indices (BI). One strategy that might improve this situation is the provision of highly specific serological antigens that may be combined with PGL-I to improve the sensitivity of diagnosis. Using serological expression cloning with a serum pool of untreated lepromatous leprosy (LL) patients, we identified 14 strongly reactive M. leprae proteins, 5 of which were previously unstudied. We present results suggesting that two of these proteins, ML0405 and ML2331, demonstrate the ability to specifically identify LL/borderline lepromatous (BL) patients on the basis of immunoglobulin G (IgG) reactivity. In a household contact study, LL index cases were identified on the basis of this reactivity, while household contacts of these patients demonstrated undetectable reactivity. At a serum dilution of 1:800, suitable to reduce background PGL-I IgM reactivity, two BL patients with a BI of <4 showed anti-human polyvalent immunoglobulin G, A, and M reactivity measured with a combination of ML0405, ML2331, and natural disaccharide O-linked human serum albumin (NDOHSA) (synthetic PGL-I) that was markedly higher than IgM reactivity to NDOHSA alone. We suggest that ML0405 and ML2331 may have utility in serological leprosy diagnosis.

Leprosy

Leprosy remains an important health problem worldwide. The disease is caused by a chronic granulomatous infection of the skin and peripheral nerves with Mycobacterium leprae. The clinical range from tuberculoid to lepromatous leprosy is a result of variation in the cellular immune response to the mycobacterium. The resulting impairment of nerve function causes the disabilities associated with leprosy. This review summarises recent advances in understanding of the biology of leprosy, clinical features of the disease, the current diagnostic criteria, and the new approaches to treatment of the infection and the immune-mediated complications. Supervised multi-drug therapy (MDT) for fixed durations is highly effective for all forms of the disease. The widespread implementation of MDT has been associated with a fall in the prevalence of the leprosy but as yet no reduction in the case-detection rate globally. Thus, leprosy control activities must be maintained for decades to interrupt transmission of infection.

Chemoprophylaxis is effective in the prevention of leprosy in endemic countries: a systematic review and meta-analysis. MILEP2 Study Group. Mucosal Immunology of Leprosy

OBJECTIVE

To quantify the efficacy of chemoprophylaxis against leprosy.

METHOD

Literature searching of Medline and Embase databases, hand-searching of references and correspondence with investigators.

STUDY SELECTION

published papers relating to the prevention of leprosy and the use of chemotherapy in leprosy were identified for critical appraisal. Trials were selected and grouped into three categories according to study design and control groups.

DATA ANALYSIS

the relative risks (RR) with 95% confidence intervals were calculated from the original data using a random effects model. To assess the cost-effectiveness of chemoprophylaxis, a further analysis of the rates of disease in the trial and control groups was done based on the numbers needed to be treated (NNT) to prevent one new case of leprosy.

RESULTS

A total of 14 trials were identified from 127 published papers on chemoprophylaxis of leprosy. The trials were categorized into randomized controlled trials, non-randomized controlled trials, and uncontrolled trials. The overall results of the meta-analysis shows that chemoprophylaxis gives around 60% protection against leprosy. The NNT are low in trials of household contacts.

CONCLUSIONS

The evidence shows that chemoprophylaxis against leprosy is an effective way to reduce the incidence of leprosy, particularly in household contacts. The role of chemoprophylaxis needs to be re-examined using newer drugs given the continuing case detection rates globally.

Mycobacterium leprae--millennium resistant! Leprosy control on the threshold of a new era

Over the past decades, the conditions of leprosy control implementation have changed dramatically. Introduction of multidrug therapy, together with the global effort of the World Health Organization to eliminate leprosy as a public health problem, had a tremendous impact on leprosy control, particularly by decreasing the registered prevalence of the disease. At the beginning of the new millennium, leprosy control programmes face several new challenges. These relate not only to changes in the prevalence of the disease, but also to changes in the context of leprosy control, such as those created by health sector reforms and other disease control programmes. This review discusses current knowledge on the epidemiology of Mycobacterium leprae and some important aspects of leprosy control. It is argued that our understanding is still insufficient and that, so far, no consistent evidence exists that the transmission of leprosy has been substantially reduced. Sustainable leprosy control, rather than elimination, should be our goal for the foreseeable future, which also includes care for patients on treatment and for those released from treatment. This, however, requires new strategies.

Development of a polymerase chain reaction dot-blotting system for detecting cutaneous tuberculosis

For a definitive diagnosis of cutaneous tuberculosis the demonstration of mycobacteria is essential, but this is generally not possible in skin lesions. Routinely available techniques have poor sensitivity and are time consuming, therefore, delaying the institution of timely therapy. The high sensitivity and speed of polymerase chain reaction (PCR) for the detection of infectious agents has prompted investigators to use this technique for the detection of Mycobacterium tuberculosis in body fluids such as cerebrospinal fluid or pleural fluid. In the present study, PCR was used to examine punch biopsy specimens from the affected skin of 10 patients with clinical diagnoses of tuberculosis verrucosa cutis, lupus vulgaris, scrofuloderma, papulonecrotic tuberculide and erythema induratum. A control group of 20 patients included individuals having skin manifestations with definite clinical diagnoses other than cutaneous tuberculosis, such as leprosy, fungal mycetoma, chronic bullous disease of childhood and pemphigus vulgaris. The PCR amplified products were dot hybridized with a probe which was random prime labelled with 32P. The results were compared with routine microbiological and histological findings. Among the test group, six of 10 (60%) were positive for M. tuberculosis by PCR, although their histopathology showed non-specific chronic inflammation with no definite diagnosis. Microbiological investigations, including acid-fast bacillus smear and culture, were positive in a single case of scrofuloderma. All patients in the control group were negative by PCR for M. tuberculosis. The data indicate that the combination of dot hybridization with PCR markedly increased the sensitivity and specificity of PCR. This may be a useful tool in the diagnosis of tuberculosis when conventional methods fail.

Mucosa-associated lymphoid tissues as sites for uptake, carriage and excretion of tubercle bacilli and other pathogenic mycobacteria

Pathogenic mycobacteria, including those that cause tuberculosis and paratuberculosis, cross mucosal barriers by endocytosis within mucosal lymphoepithelial sites. These entry sites commonly include oropharyngeal and nasopharyngeal tonsils and Peyer's patches. Bacilli discharged at the basolateral surfaces of engulfing epithelial M cells are taken up by professional antigen-presenting cells associated with T lymphocytes of the parafollicular area. Dendritic cells and macrophages in these sites allow mycobacterial replication, due to the permissive immunological environment in lymphoepithelial tissues. Abrogation of local delayed-type hypersensitivity reactions generally ensures continuing integrity and function of these tissues. Phagocytes containing intracellular mycobacteria disseminate infection to other parts of the body and also probably migrate back onto the mucosal surface to shed bacilli.

Evaluation of PCR for diagnosis of visceral leishmaniasis

An evaluation of Leishmania PCR was performed with bone marrow, lymph node, and blood samples from 492 patients, 60 positive controls, and 90 negative controls. Results were compared with microscopy results for Giemsa-stained smears. PCR and microscopy of lymph node and bone marrow aspirates from patients with microscopically confirmed visceral leishmaniasis (VL) were equally sensitive. However, in patients clinically suspected of having VL and in whom parasites could not be demonstrated by microscopy, PCR was positive for 12 of 23 (52.2%) lymph node aspirates and 8 of 12 (66.7%) bone marrow aspirates, thus confirming the clinical diagnosis of VL. With PCR on filter paper, Leishmania DNA was detected in the blood of 33 of 47 (70%) patients with confirmed VL and in 2 of 11 (19%) patients suspected of having VL. Positive PCR results were more frequently found for blood samples on filter paper than for samples stored in EDTA. In conclusion, PCR is a more sensitive method than microscopy for the detection of Leishmania in lymph node and bone marrow aspirates, being especially useful for the confirmation of cases of suspected VL. Blood from a finger prick may be used for the initial PCR screening of people suspected of having VL. If the PCR of blood is negative, one should perform PCR with lymph node and/or bone marrow material, because PCR with these materials is more often positive.

The epidemiology of Mycobacterium leprae: recent insight

Leprosy is still a health problem in many countries. Because the causative organism, Mycobacterium leprae cannot be cultured in vitro, it is virtually impossible to assess exposure, and the onset of infection and disease. As a consequence, the chain of infection, considered as the relationships between M. leprae, transmission and human host, is poorly understood. Here, we discuss a number of organism-, host- and environmental-related factors which may be incriminated in the dynamic process of the development of leprosy disease. The use of modern molecular and immunological tools has become a valuable addition to epidemiological research. Understanding of the epidemiology of leprosy is a prerequisite for effective control of the disease.