Geographic distribution, age pattern and sites of lesions in a cohort of Buruli ulcer patients from the Mapé Basin of Cameroon

Pseudogenomic insights into the evolution of Mycobacterium ulcerans

BACKGROUND

Buruli ulcer (BU) disease, caused by Mycobacterium ulcerans (MU), and characterized by necrotic ulcers is still a health problem in Africa and Australia. The genome of the bacterium has several pseudogenes due to recent evolutionary events and environmental pressures. Pseudogenes are genetic elements regarded as nonessential in bacteria, however, they are less studied due to limited available tools to provide understanding of their evolution and roles in MU pathogenicity.

RESULTS

This study developed a bioinformatic pipeline to profile the pseudogenomes of sequenced MU clinical isolates from different countries. One hundred and seventy-two MU genomes analyzed revealed that pseudogenomes of African strains corresponded to the two African lineages 1 and 2. Pseudogenomes were lineage and location specific and African lineage 1 was further divided into A and B. Lineage 2 had less relaxation in positive selection than lineage 1 which may signify different evolutionary points. Based on the Gil-Latorre model, African MU strains may be in the latter stages of evolutionary adaption and are adapting to an environment rich in metabolic resources with a lower temperature and decreased UV radiation. The environment fosters oxidative metabolism and MU may be less reliant on some secondary metabolites. In-house pseudogenomes from Ghana and Cote d'Ivoire were different from other African strains, however, they were identified as African strains.

CONCLUSION

Our bioinformatic pipeline provides pseudogenomic insights to complement other whole genome analyses, providing a better view of the evolution of the genome of MU and suggest an adaptation model which is important in understanding transmission. MU pseudogene profiles vary based on lineage and country, and an apparent reduction in insertion sequences used for the detection of MU which may adversely affect the sensitivity of diagnosis.

Comprehensive Case-Control Study of Protective and Risk Factors for Buruli Ulcer, Southeastern Australia

To examine protective and risk factors for Buruli ulcer (BU), we conducted a case-control study of 245 adult BU cases and 481 postcode-matched controls across BU-endemic areas of Victoria, Australia. We calculated age- and sex-adjusted odds ratios for socio-environmental, host, and behavioral factors associated with BU by using conditional logistic regression. Odds of BU were >2-fold for persons with diabetes mellitus and persons working outdoors who had soil contact in BU-endemic areas (compared with indoor work) but were lower among persons who had bacillus Calmette-Guérin vaccinations. BU was associated with increasing numbers of possums and with ponds and bore water use at residences. Using insect repellent, covering arms and legs outdoors, and immediately washing wounds were protective; undertaking multiple protective behaviors was associated with the lowest odds of BU. Skin hygiene/protection behaviors and previous bacillus Calmette-Guérin vaccination might provide protection against BU in BU-endemic areas.

Perceived water-related risk factors of Buruli ulcer in two villages of south-central Côte d'Ivoire

BACKGROUND

Buruli ulcer, caused by Mycobacterium ulcerans, is a neglected tropical skin disease that is primarily endemic in West and Central Africa, including Côte d'Ivoire. Studies indicate that M. ulcerans infections are caused by contact with an environmental reservoir of the bacteria, governed by specific human biological conditions. Yet, the nature of this reservoir and the exact mode of transmission remain unknown.

METHODOLOGY

To identify ecologic risk factors of Buruli ulcer in south-central Côte d'Ivoire, we pursued a qualitative study matched with geo-referencing inquiry. Embedded in a broader integrated wound management research project, we (i) mapped households and water sources of laboratory confirmed Buruli ulcer cases and (ii) interviewed 12 patients and four health care workers to assess exposure to surface water and to deepen the understanding of perceived transmission pathways.

PRINCIPAL FINDINGS

Water availability, accessibility, and affordability were reported as key determinants for choosing water resources. Furthermore, perceived risks were related to environmental, structural, and individual factors. Despite the presence of improved water sources (e.g., drilled wells), communities heavily relied on unprotected surface water for a multitude of activities. The nearby Bandama River and seasonal waterbodies were frequently used for washing, bathing, and collection of water for drinking and cooking. Many residents also reported to cross the river on a daily basis for agricultural chores, and hence, are exposed to stagnant water during farming activities.

CONCLUSIONS/SIGNIFICANCE

Our study in two Buruli ulcer endemic villages in south-central Côte d'Ivoire revealed a wide range of water-related domestic activities that might expose people to an increased risk of contracting the disease. Environmental, biological, social, and cultural risk factors are closely interlinked and should be considered in future investigations of Buruli ulcer transmission. Active participation of the communities is key to better understand their circumstances to advance research and fight against Buruli ulcer and other neglected tropical diseases.

Quantifying Population Burden and Effectiveness of Decentralized Surveillance Strategies for Skin-Presenting Neglected Tropical Diseases, Liberia

We evaluated programmatic approaches for skin neglected tropical disease (NTD) surveillance and completed a robust estimation of the burden of skin NTDs endemic to West Africa (Buruli ulcer, leprosy, lymphatic filariasis morbidity, and yaws). In Maryland, Liberia, exhaustive case finding by community health workers of 56,285 persons across 92 clusters identified 3,241 suspected cases. A total of 236 skin NTDs (34.0 [95% CI 29.1–38.9]/10,000 persons) were confirmed by midlevel healthcare workers trained using a tailored program. Cases showed a focal and spatially heterogeneous distribution. This community health worker‒led approach showed a higher skin NTD burden than prevailing surveillance mechanisms, but also showed high (95.1%) and equitable population coverage. Specialized training and task-shifting of diagnoses to midlevel health workers led to reliable identification of skin NTDs, but reliability of individual diagnoses varied. This multifaceted evaluation of skin NTD surveillance strategies quantifies benefits and limitations of key approaches promoted by the 2030 NTD roadmap of the World Health Organization.

A need for null models in understanding disease transmission: the example of Mycobacterium ulcerans (Buruli ulcer disease)

Understanding the interactions of ecosystems, humans and pathogens is important for disease risk estimation. This is particularly true for neglected and newly emerging diseases where modes and efficiencies of transmission leading to epidemics are not well understood. Using a model for other emerging diseases, the neglected tropical skin disease Buruli ulcer (BU), we systematically review the literature on transmission of the etiologic agent, Mycobacterium ulcerans (MU), within a One Health/EcoHealth framework and against Hill's nine criteria and Koch's postulates for making strong inference in disease systems. Using this strong inference approach, we advocate a null hypothesis for MU transmission and other understudied disease systems. The null should be tested against alternative vector or host roles in pathogen transmission to better inform disease management. We propose a re-evaluation of what is necessary to identify and confirm hosts, reservoirs and vectors associated with environmental pathogen replication, dispersal and transmission; critically review alternative environmental sources of MU that may be important for transmission, including invertebrate and vertebrate species, plants and biofilms on aquatic substrates; and conclude with placing BU within the context of other neglected and emerging infectious diseases with intricate ecological relationships that lead to disease in humans, wildlife and domestic animals.

Methods and Approaches for Buruli Ulcer Surveillance in Africa: Lessons Learnt and Future Directions

Over 95% of the global burden of Buruli ulcer disease (BU) caused by Mycobacterium ulcerans occurs in equatorial Africa. National and sub-national programs have implemented various approaches to improve detection and reporting of incident cases over recent decades. Regional incidence rates are currently in decline; however, surveillance targets outlined in 2012 by WHO have been missed and detection bias may contribute to these trends. In light of the new 2030 NTD roadmap and disease-specific targets, BU programs are required to strengthen case detection and begin a transition towards integration with other skin-NTDs. This transition comes with new opportunities to enhance existing BU surveillance systems and develop novel approaches for implementation and evaluation.In this review, we present a breakdown and assessment of the methods and approaches that have been the pillars of BU surveillance systems in Africa: (1) Passive case detection, (2) Data systems, (3) Clinical training, (4) Active case finding, (5) Burden estimation, and (6) Laboratory confirmation pathways. We discuss successes, challenges, and relevant case studies before highlighting opportunities for future development and evaluation including novel data collection tools, risk-based surveillance, and integrated skin-NTD surveillance. We draw on both experience and available literature to critically evaluate methods of BU surveillance in Africa and highlight new approaches to help achieve 2030 roadmap targets.

Introduction of Mycobacterium ulcerans disease in the Bankim Health District of Cameroon follows damming of the Mapé River

Buruli ulcer (BU) is an emerging ulcerative skin disease caused by infection with Mycobacterium ulcerans. Efforts to control its spread have been hampered by our limited understanding of M. ulcerans reservoirs and transmission, and the factors leading to the emergence of BU disease in a particular region. In this report we investigate an anecdotal link between damming the Mapé River in Cameroon and the emergence of BU in the Health Districts bordering Lake Bankim, the impoundment created by the Mapé dam. We used bacterial population genomics and molecular dating to find compelling support for a 2000 M. ulcerans introduction event that followed about 10 years after the filling of the newly created impoundment in 1988. We compared the genomic reconstructions with high-resolution satellite imagery to investigate what major environmental alterations might have driven the emergence of the new focus.

High antibody titres induced by protein subunit vaccines using Mycobacterium ulcerans antigens Hsp18 and MUL_3720 with a TLR-2 agonist fail to protect against Buruli ulcer in mice

Background

Mycobacterium ulcerans is the causative agent of a debilitating skin and soft tissue infection known as Buruli ulcer (BU). There is no vaccine against BU. The purpose of this study was to investigate the vaccine potential of two previously described immunogenic M. ulcerans proteins, MUL_3720 and Hsp18, using a mouse tail infection model of BU.

Methods

Recombinant versions of the two proteins were each electrostatically coupled with a previously described lipopeptide adjuvant. Seven C57BL/6 and seven BALB/c mice were vaccinated and boosted with each of the formulations. Vaccinated mice were then challenged with M. ulcerans via subcutaneous tail inoculation. Vaccine performance was assessed by time-to-ulceration compared to unvaccinated mice.

Results

The MUL_3720 and Hsp18 vaccines induced high titres of antigen-specific antibodies that were predominately subtype IgG₁. However, all mice developed ulcers by day-40 post-M. ulcerans challenge. No significant difference was observed in the time-to-onset of ulceration between the experimental vaccine groups and unvaccinated animals.

Conclusions

These data align with previous vaccine experiments using Hsp18 and MUL_3720 that indicated these proteins may not be appropriate vaccine antigens. This work highlights the need to explore alternative vaccine targets and different approaches to understand the role antibodies might play in controlling BU.

The immunology of other mycobacteria: M. ulcerans, M. leprae

Mycobacterial pathogens can be categorized into three broad groups: Mycobacterium tuberculosis complex causing tuberculosis, M. leprae and M. lepromatosis causing leprosy, and atypical mycobacteria, or non-tuberculous mycobacteria (NTM), responsible for a wide range of diseases. Among the NTMs, M. ulcerans is responsible for the neglected tropical skin disease Buruli ulcer (BU). Most pathogenic mycobacteria, including M. leprae, evade effector mechanisms of the humoral immune system by hiding and replicating inside host cells and are furthermore excellent modulators of host immune responses. In contrast, M. ulcerans replicates predominantly extracellularly, sheltered from host immune responses through the cytotoxic and immunosuppressive effects of mycolactone, a macrolide produced by the bacteria. In the year 2018, 208,613 new cases of leprosy and 2713 new cases of BU were reported to WHO, figures which are notoriously skewed by vast underreporting of these diseases.

Buruli ulcer: The Efficacy of Innate Immune Defense May Be a Key Determinant for the Outcome of Infection With Mycobacterium ulcerans

Buruli ulcer (BU) is a neglected, tropical infectious disease of the skin and the subcutaneous tissue caused by Mycobacterium ulcerans. This pathogen has emerged as a new species from a common ancestor with Mycobacterium marinum by acquisition of the virulence plasmid pMUM. The plasmid encodes enzymes required for the synthesis of the macrolide toxin mycolactone, which has cytotoxic and immunosuppressive activities. In advanced BU lesions, extracellular clusters of M. ulcerans reside in necrotic subcutaneous tissue and are protected from infiltrating leukocytes by the cytotoxic activity of secreted mycolactone. Several lines of evidence indicate that elements of the innate immune system eliminate in many cases the initial inoculum before bacterial clusters can form and that therefore exposure to M. ulcerans leads only in a minority of individuals to the characteristic chronic necrotizing BU lesions. It is assumed that phagocytes play a key role in early host defense against M. ulcerans. Antibodies against bacterial surface structures seem to have less potential to enhance innate immunity than T_H1 cell responses. Precise innate and adaptive immune effector mechanisms leading to protective immunity are however unclear, complicating the development of effective vaccines, the most desired solution to control BU. The tuberculosis vaccine Mycobacterium bovis Bacillus Calmette–Guérin (BCG) has limited short-term protective activity against BU. Whether this effect is due to the broad antigenic cross-reactivity between M. bovis and M. ulcerans or is at least partly mediated by a non-specific enhanced responsiveness of innate immune cells to secondary stimulation, recently described as “trained immunity” or “innate immune memory” is unknown but has major implications for vaccine design. Current vaccine research and development activities are focusing on recombinant BCG, subunit vaccines with selected M. ulcerans proteins, and the neutralization of mycolactone.

Does skin surface temperature variation account for Buruli ulcer lesion distribution?

Background

Buruli ulcer is a necrotising infection of skin and soft tissue caused by Mycobacterium ulcerans (M. ulcerans). Buruli ulcer most often occurs on limbs, and it is hypothesized this is explained by direct exposure to the environment. However, even on exposed areas Buruli ulcer is not randomly distributed. M. ulcerans prefers an in vitro temperature of 30–33°C and growth is inhibited at higher temperatures. This study investigated whether variations in skin surface temperature distribution in healthy volunteers could partly account for Buruli ulcer lesion distribution.

Methodology/Principal findings

In this observational study, a thermal camera (FLIR E8) was used to measure skin surface temperature at the sternal notch and at 44 predetermined locations on the limbs of 18 human participants. Body locations of high, middle and low Buruli ulcer incidence were identified from existing density maps of lesion distribution. Skin temperature of the three incidence location groups were compared, and differences in age and sex groups were also analysed.

We found an inverse relationship between skin temperature and lesion distribution, where high incidence locations were significantly cooler and low incidence locations significantly warmer (Kruskal-Wallis test p<0.0001). Linear mixed effects regression analysis estimated that skin surface temperature accounts for 22.0% of the variance in Buruli ulcer lesion distribution (marginal R-squared = 0.219) in the anterior location group, and 0.6% in the posterior group (marginal R-squared 0.006). Men had warmer upper and lower limbs than females (Mann-Whitney U test p = 0.0003 and p<0.0001 respectively).

Conclusions/Significance

We have found an inverse relationship between skin temperature and Buruli ulcer lesion distribution, however this association is weak. Additional unknown factors are likely to be involved that explain the majority of the variation in Buruli lesion distribution.

Individual and clinical variables associated with the risk of Buruli ulcer acquisition: A systematic review and meta-analysis

BACKGROUND

Buruli ulcer (BU) is a necrotizing skin disease, caused by Mycobacterium ulcerans, with poorly understood acquisition risk factors. This review aims at evaluating the importance of individual-sex, age, family ties with history of BU, gene variants-and clinical-Bacillus Calmette-Guérin (BCG) immunization, Human Immunodeficiency Virus (HIV) infection-variables in this process.

METHODS

A systematic review was performed considering the following databases: ClinicalTrials.gov, Cochrane Controlled Register of Trials (CENTRAL), Current Contents Connect, Embase, MEDLINE, SciELO, Scopus and Web of Science. Eligible studies were critically appraised with The Joanna Briggs Institute checklists and heterogeneity was assessed with Cochran Q-test and I2 statistic. Published demographic data was descriptively analysed and clinical data pooled within random-effects modelling for meta-analysis.

RESULTS

A total of 29 studies were included in the systematic review. Two randomized controlled trials (RCTs) and 21 case-control studies were selected for meta-analysis. Studies show that BU mainly affects age extremes, more preponderately males among children. Data pooled from RCTs do not reveal BCG to be protective against BU (odds ratio (OR) = 0.63; 95% CI = 0.38-1.05; I2 = 56%), a finding case-control studies appear to corroborate. HIV infection (OR = 6.80; 95% CI = 2.33-19.85; I2 = 0%) and SLC11A1 rs17235409 A allele (OR = 1.86; 95% CI = 1.25-2.77; I2 = 0%) are associated with increased prevalence of the disease. No definite conclusions can be drawn regarding the influence of previous family history of BU.

DISCUSSION

While available evidence warrants further robustness, these results have direct implications on current interventions and future research programs, and foster the development of more cost-effective preventive and screening measures.

REGISTRATION

The study was registered at PROSPERO with number CRD42019123611.

Mapping the global distribution of Buruli ulcer: a systematic review with evidence consensus

BACKGROUND

Buruli ulcer can cause disfigurement and long-term loss of function. It is underdiagnosed and under-reported, and its current distribution is unclear. We aimed to synthesise and evaluate data on Buruli ulcer prevalence and distribution.

METHODS

We did a systematic review of Buruli ulcer prevalence and used an evidence consensus framework to describe and evaluate evidence for Buruli ulcer distribution worldwide. We searched PubMed and Web of Science databases from inception to Aug 6, 2018, for records of Buruli ulcer and Mycobacterium ulcerans detection, with no limits on study type, publication date, participant population, or location. English, French, and Spanish language publications were included. We included population-based surveys presenting Buruli ulcer prevalence estimates, or data that allowed prevalence to be estimated, in the systematic review. We extracted geographical data on the occurrence of Buruli ulcer cases and M ulcerans detection from studies of any type for the evidence consensus framework; articles that did not report original data were excluded. For the main analysis, we extracted prevalence estimates from included surveys and calculated 95% CIs using Byar's method. We included occurrence records, reports to WHO and the Global Infectious Diseases and Epidemiology Network, and surveillance data from Buruli ulcer control programmes in the evidence consensus framework to grade the strength of evidence for Buruli ulcer endemicity. This study is registered with PROSPERO, number CRD42018116260.

FINDINGS

2763 titles met the search criteria. We extracted prevalence estimates from ten studies and occurrence data from 208 studies and five unpublished surveillance datasets. Prevalence estimates within study areas ranged from 3·2 (95% CI 3·1-3·3) cases per 10 000 population in Côte d'Ivoire to 26·9 (23·5-30·7) cases per 10 000 population in Benin. There was evidence of Buruli ulcer in 32 countries and consensus on presence in 12.

INTERPRETATION

The global distribution of Buruli ulcer is uncertain and potentially wider than currently recognised. Our findings represent the strongest available evidence on Buruli ulcer distribution so far and have many potential applications, from directing surveillance activities to informing burden estimates.

FUNDING

AIM Initiative.

The gendered impact of Buruli ulcer on the household production of health and social support networks: Why decentralization favors women

Background

Buruli ulcer [BU] is a chronic and debilitating neglected tropical skin disease caused by Mycobacterium ulcerans. The treatment of moderate to severe BU affects the well-being of entire households and places a strain on both gender relations within households and social relations with kin asked for various types of support. In this paper, we employ the conceptual lenses provided by the Household Production of Health approach to understanding the impact of illness on the household as a unit of analysis, gender studies, and social support related research to better understand BU health care decision making and the psychosocial experience of BU hospitalization.

Methods

An ethnography attentive to circumstance and the nested contexts within which stakeholders respond to BU was conducted employing semi-structured interviews, illness narratives, and case studies. An iterative process of data collection with preliminary analyses and reflection shaped subsequent interviews. Interviews were conducted with 45 women in households having a member afflicted with BU in two communes of Benin with high prevalence rates for BU. The first commune [ZE] has a well-established decentralized BU treatment program and a well-functioning referral network linked to the Allada reference hospital specializing in the care of BU and other chronic ulcers. The second commune [Ouinhi] is one of the last regions of the country to introduce a decentralized BU treatment program. A maximum variation purposeful sample was selected to identify information-rich health care decision cases for in-depth study.

Principal findings

Study results demonstrated that although men are the primary decision makers for healthcare decisions outside the home, women are largely responsible for arranging care for the afflicted in hospital in addition to managing their own households. A woman’s agency and ability to influence the decision-making process is largely based on whatever social support and substitute labor she can mobilize from her own network of kin relations. When support wanes, women are placed in a vulnerable position and often end up destitute. Decentralized BU treatment is preferred because it enables a woman to remain in her own household as a patient or caretaker of an ill family member while engaging in child care and petty revenue earing activities. Remaining in the hospital (a liminal space) as either patient or caretaker also renders a woman vulnerable to rumor and innuendo about sexual liaisons and constitutes a form of social risk. Social risk in some cases eclipses the physical risk of the disease in what we would describe as a hierarchy of risks.

Conclusion

This study illustrates the importance of decentralized treatment programs for NTDs such as BU. Such programs enable patients to remain in their homes while being treated, and do not displace women responsible for the welfare of the entire household. When women are displaced the well-being of the entire household is placed in jeopardy.

In this gender-focused study of the neglected tropical disease Buruli ulcer (BU) in Benin, West Africa, we document how seeking care for BU is influenced by broad-based concerns about the household production of health and the availability of resources women can mobilize from their social support networks. Women and girls shoulder a disproportionate share of the burdens incurred by BU treatment and prefer decentralized treatment from local health stations to free hospital care. Long term and often-indeterminate residence in hospital threatens the integrity of households and results in marital stress, economic vulnerability, school and vocational training dropout, and loss of essential income-generating activities. The case study of BU clearly demonstrates the necessity of recognizing the household, and not just the patient, as a unit of analysis in public health and the need to consider the ripple effect of serious illness beyond the household to one’s social network. We draw attention to the fact that while men are the decision makers about health care in patrilineal Beninese society, a women’s agency in influencing decision making is tied to her accumulation of social capital, capital that is taxed by long term medical treatment weakening her safety net in the future.

Knowledge and practices of health practitioners on treatment of Buruli ulcer in the Mbonge, Ekondo Titi and Muyuka Health Districts, South West Region, Cameroon

INTRODUCTION

After tuberculosis and leprosy, Buruli ulcer (BU) is the third most common mycobacterial infection. Buruli ulcer begins as a localized skin lesion that progresses to extensive ulceration thus leading to functional disability, loss of economic productivity and social stigma. This study is aimed at assessing the knowledge and practices among health practitioners on the treatment of BU in the Mbonge, Ekondo Titi and Muyuka Health Districts of the South West Region of Cameroon.

METHODS

This is a cross-sectional study that investigates participants' knowledge and practices on the treatment of BU. The study uses a qualitative method of structured questionnaires in the process of data collection.

RESULTS

Seventy percent (70%) of the participants acknowledged they encounter cases of BU in their respective Hospitals or Health centers. Among these, 48% agreed they managed BU in their facilities and up to 91.7% noted that their community members are aware that BU is managed in their facility while seventy percent of the medical practitioners indicated they cannot identify the various stages of BU. Eighty-one percent of the practitioners from Muyuka HD indicated they could not identify the various stages of BU. More than 63% of the practitioners regarded BU patients as normal people in their communities however, practitioners that practiced for less than 5 years were likely not to admit BU patients in the same room with other patients. Beliefs such as being cursed (47.06%) and being possessed (29.41%) were reported by practitioners that acknowledged the existence of traditional beliefs in the community.

CONCLUSION

Despite the fact that a majority of the health practitioners knew what BU is, most of them demonstrated lack of knowledge on the identification of the various stages and management of the illness. Practitioners demonstrated positive attitude towards patients although they would not admit them in the same room with other patients. Considering the poor knowledge on identification and management demonstrated by most of the practitioners, management of the disease would be inadequate and may even aggravate the patient's situation. Training and onsite mentorship on screening, identification and management of BU is therefore highly recommended amongst health personnel practicing in endemic areas.

PCR detection of Mycobacterium ulcerans-significance for clinical practice and epidemiology

Introduction: Buruli ulcer (BU) is a neglected disease which has been reported from mostly impoverished, remote rural areas from 35 countries worldwide. BU affects skin, subcutaneous tissue, and bones, and may cause massive tissue destruction and life-long disabilities if not diagnosed and treated early. Without laboratory confirmation diagnostic and treatment errors may occur. This review describes the application of IS2404 PCR, the preferred diagnostic test, in the area of individual patient management and clinico-epidemiological studies. Areas covered: A Medline search included publications on clinical sample collection, DNA extraction, and PCR detection formats of the past and present, potential and limitations of clinical application, as well as clinico-epidemiological studies. Expert commentary: A global network of reference laboratories basically provides the possibility for PCR confirmation of 70% of all BU cases worldwide as requested by the WHO. Keeping laboratory confirmation on a constant level requires continuous outreach activities. Among the potential measures to maintain sustainability of laboratory confirmation and outreach activities are decentralized or mobile diagnostics available at point of care, such as IS2404-based LAMP, which complement the standard IS2404-based diagnostic tools available at central level.

The changing epidemiology worldwide of Mycobacterium ulcerans

Mycobacterium ulcerans is recognised as the third most common mycobacterial infection worldwide. It causes necrotising infections of skin and soft tissue and is classified as a neglected tropical disease by the World Health Organization (WHO). However, despite extensive research, the environmental reservoir of the organism and mode of transmission of the infection to humans remain unknown. This limits the ability to design and implement public health interventions to effectively and consistently prevent the spread and reduce the incidence of this disease. In recent years, the epidemiology of the disease has changed. In most endemic regions of the world, the number of cases reported to the WHO are reducing, with a 64% reduction in cases reported worldwide in the last 9 years. Conversely, in a smaller number of countries including Australia and Nigeria, reported cases are increasing at a rapid rate, new endemic areas continue to appear, and in Australia cases are becoming more severe. The reasons for this changing epidemiology are unknown. We review the epidemiology of M. ulcerans disease worldwide, and document recent changes. We also outline and discuss the current state of knowledge on the ecology of M. ulcerans, possible transmission mechanisms to humans and what may be enabling the spread of M. ulcerans into new endemic areas.

Transmission of Hepatitis B and D Viruses in an African Rural Community

According to the World Health Organization (WHO), an estimated 257 million people worldwide are chronically infected with hepatitis B virus (HBV), with approximately 15 million of them being coinfected with hepatitis D virus (HDV). To investigate the prevalence and transmission of HBV and HDV within the general population of a rural village in Cameroon, we analyzed serum samples from most (401/448) of the villagers. HBV surface antigen (HBsAg) was detected in 54 (13.5%) of the 401 samples, with 15% of them also containing anti-HDV antibodies. Although Cameroon has integrated HBV vaccination into their Expanded Program on Immunization for newborns in 2005, an HBsAg carriage rate of 5% was found in children below the age of 5 years. Of the 54 HBsAg-positive samples, 49 HBV pre-S/S sequences (7 genotype A and 42 genotype E sequences) could be amplified by PCR. In spite of the extreme geographical restriction in the recruitment of study participants, a remarkable genetic diversity within HBV genotypes was observed. Phylogenetic analysis of the sequences obtained from PCR products combined with demographic information revealed that the presence of some genetic variants was restricted to members of one household, indicative of intrafamilial transmission, which appears to take place at least in part perinatally from mother to child. Other genetic variants were more widely distributed, reflecting horizontal interhousehold transmission. Data for two households with more than one HBV-HDV-coinfected individual indicate that the two viruses are not necessarily transmitted together, as family members with identical HBV sequences had different HDV statuses. IMPORTANCE This study revealed that the prevalence of HBV and HDV in a rural area of Cameroon is extremely high, underlining the pressing need for the improvement of control strategies. Systematic serological and phylogenetic analyses of HBV sequences turned out to be useful tools to identify networks of virus transmission within and between households. The high HBsAg carriage rate found among children demonstrates that implementation of the HBV birth dose vaccine and improvement of vaccine coverage will be key elements in preventing both HBV and HDV infections. In addition, the high HBsAg carriage rate in adolescents and adults emphasizes the need for identification of chronically infected individuals and linkage to WHO-recommended treatment to prevent progression to liver cirrhosis and hepatocellular carcinoma.

The association of rainfall and Buruli ulcer in southeastern Australia

Background

Buruli ulcer has been increasing in incidence in southeastern Australia with unclear transmission mechanisms. We aimed to investigate the link between rainfall and case numbers in two endemic areas of the state of Victoria; the Bellarine and Mornington Peninsulas.

Methodology

We created yearly and monthly graphs comparing rainfall with local Buruli ulcer incidence for the period 2004–2016 by endemic region and then considered a range of time lag intervals of 0–24 months to investigate patterns of correlation.

Conclusions

Optimal positive correlation for the Bellarine Peninsula occurred with a 12-month prior rainfall lag, however, no significant correlation was observed on the Mornington Peninsula for any time lag. These results provide an update in evidence to further explore transmission mechanisms which may differ between these geographically proximate endemic regions.

Buruli ulcer, a mycobacterial infection resulting in destructive soft tissue lesions, has been increasing in incidence in southeastern Australia over recent years. Exact transmission mechanisms and therefore preventative measures remain unclear. We aimed to investigate a possible link between Buruli ulcer and rainfall for two major endemic areas of the state of Victoria; the Bellarine and Mornington Peninsulas. Our results demonstrate a positive correlation with rainfall on the Bellarine Peninsula with a prior rainfall lag of 12 months but no correlation on the Mornington Peninsula. Established time-frames such as the incubation period and average delay to diagnosis (due to slow and often asymptomatic progression of the disease) make up a total of at least 5–6 months. On the Bellarine Peninsula, there appears to be another 5–6 months of unaccounted time from rainfall to transmission of the pathogen. This provides a basis to explore previously proposed transmission mechanisms which, based on the discrepancy noted with rainfall correlation, may differ between endemic regions.

Improving clinical and epidemiological predictors of Buruli ulcer

Background

Buruli ulcer (BU) is a chronic necrotizing infectious skin disease caused by Mycobacterium ulcerans. The treatment with BU-specific antibiotics is initiated after clinical suspicion based on the WHO clinical and epidemiological criteria. This study aimed to estimate the predictive values of these criteria and how they could be improved.

Methodology/Principal findings

A total of 224 consecutive patients presenting with skin and soft tissue lesions that could be compatible with BU, including those recognized as unlikely BU by experienced clinicians, were recruited in two BU treatment centers in southern Benin between March 2012 and March 2015. For each participant, the WHO and four additional epidemiological and clinical diagnostic criteria were recorded. For microbiological confirmation, direct smear examination and IS2404 PCR were performed. We fitted a logistic regression model with PCR positivity for BU confirmation as outcome variable. On univariate analysis, most of the clinical and epidemiological WHO criteria were associated with a positive PCR result. However, lesions on the lower limbs and WHO category 3 lesions were rather associated with a negative PCR result (respectively OR: 0.4, 95%CI: 0.3–0.8; OR: 0.5, 95%IC: 0.3–0.9). Among the additional characteristics studied, the characteristic smell of BU was strongest associated with a positive PCR result (OR = 16.4; 95%CI = 7.5–35.6).

Conclusion/Significance

The WHO diagnostic criteria could be improved upon by differentiating between lesions on the upper and lower limbs and by including lesion size and the characteristic smell recognized by experienced clinicians.

Buruli ulcer (BU) is a neglected necrotizing skin disease caused by Mycobacterium ulcerans. The treatment with BU-specific antibiotics is initiated after clinical suspicion based on WHO diagnostic criteria. In this study we evaluated the WHO diagnostic guidelines for BU and how these criteria could be improved. A total of 224 patients presenting with skin lesions were recruited in two BU treatment centers in southern Benin between March 2012 and March 2015. Most of the clinical and epidemiological WHO criteria were associated with a confirmed BU diagnosis although lesions on the lower limbs were rather associated with a negative PCR result. Among the additional characteristics studied, the characteristic smell of BU was most strongly associated with a positive PCR result. The WHO diagnostic criteria could therefore be improved upon by discriminating between lesions on the upper and lower limbs and by including lesion size and the characteristic smell recognized by experienced clinicians. The volatiles responsible for this smell could serve as a Point-of-Care diagnostic test, useful for non-invasive confirmation during active case-finding activities, and for training of clinicians.

Developing a Buruli ulcer community of practice in Bankim, Cameroon: A model for Buruli ulcer outreach in Africa

Background

In the Cameroon, previous efforts to identify Buruli ulcer (BU) through the mobilization of community health workers (CHWs) yielded poor results. In this paper, we describe the successful creation of a BU community of practice (BUCOP) in Bankim, Cameroon composed of hospital staff, former patients, CHWs, and traditional healers.

Methods and principle findings

All seven stages of a well-defined formative research process were conducted during three phases of research carried out by a team of social scientists working closely with Bankim hospital staff. Phase one ethnographic research generated interventions tested in a phase two proof of concept study followed by a three- year pilot project. In phase three the pilot project was evaluated. An outcome evaluation documented a significant rise in BU detection, especially category I cases, and a shift in case referral. Trained CHW and traditional healers initially referred most suspected cases of BU to Bankim hospital. Over time, household members exposed to an innovative and culturally sensitive outreach education program referred the greatest number of suspected cases. Laboratory confirmation of suspected BU cases referred by community stakeholders was above 30%. An impact and process evaluation found that sustained collaboration between health staff, CHWs, and traditional healers had been achieved. CHWs came to play a more active role in organizing BU outreach activities, which increased their social status. Traditional healers found they gained more from collaboration than they lost from referral.

Conclusion/ Significance

Setting up lines of communication, and promoting collaboration and trust between community stakeholders and health staff is essential to the control of neglected tropical diseases. It is also essential to health system strengthening and emerging disease preparedness. The BUCOP model described in this paper holds great promise for bringing communities together to solve pressing health problems in a culturally sensitive manner.

Buruli ulcer (BU) is a neglected tropical disease primarily found in West Africa largely effecting the rural poor. BU has a known cause and cure, but an unknown route of transmission and a poorly understood incubation period. If not treated early and in a timely manner, BU often progresses to an advanced state requiring surgery and prolonged wound care. In the Cameroon, previous efforts to mobilize community health workers and educate community members to identify cases of BU yielded poor results. In this paper, we describe steps undertaken to create a successful BU community of practice (BUCOP) composed of community stakeholders working in concert with clinic staff. The success of the BUCOP was measured in terms of numbers of suspected BU cases referred and confirmed, a decline in treatment drop out, and sustained collaboration among stakeholders both during and following the pilot project. Pilot project success is attributed to an innovative and culturally sensitive approach to BU outreach education, increased levels of patient assistance, and mutual respect among BUCOP members for what each stakeholder contributed to BU detection, treatment, psychosocial support, and spiritual protection.

Community knowledge, perceptions and attitudes regarding leprosy in rural Cameroon: The case of Ekondotiti and Mbonge health districts in the South-west Region

BACKGROUND

Although leprosy is one of the oldest diseases known to humanity, it remains largely misunderstood. Misconceptions about leprosy lead to stigma towards people with the disease. This study aimed at exploring the knowledge, perceptions and attitudes regarding leprosy in rural Cameroon.

METHODS

We carried out a cross-sectional community survey of 233 respondents aged 15-75 years, free from leprosy, and living in two rural health districts of the South-west Region of Cameroon. A questionnaire designed to evaluate knowledge, perceptions and attitudes about leprosy was used. Binary logistic regression was used to determine independent predictors of negative attitudes.

RESULTS

About 82% of respondents had heard about, and 64.4% knew someone with leprosy. Information on leprosy was mainly from community volunteers (40.6%), friends (38.0%), and the media (24%). Only 19.7% of respondents knew the cause of leprosy, and a considerable proportion linked it to a spell (25.3%), unclean blood (15.5%) and heredity (14.6%). About 72% knew that leprosy is curable and 86.3% would advise medical treatment. Attitudes towards leprosy patients were generally negative. Only 42% would shake hands, 32.6% would share the same plate, and 28.3% and 27% respectively, would allow their child to play or marry a person with leprosy. Furthermore, only 33.9% approved of participation of leprosy patients, and 42.9% of their employment. Independent predictors of negative attitudes were: the belief that leprosy is a curse; is caused by a germ; and having seen a leprosy patient. The negative attitudes were dampened by: the beliefs that leprosy is a punishment, is hereditary and is due to poor personal hygiene.

CONCLUSION

An awareness intervention using community volunteers and the media, with information on the cause of leprosy, its clinical manifestations and curability, and sensitization messages correcting the misconceptions and beliefs regarding leprosy, could improve the community knowledge and attitudes towards leprosy. This would ultimately contribute to the reduction of leprosy burden in the community.

Characteristics and epidemiological profile of Buruli ulcer in the district of Tiassalé, south Côte d'Ivoire

Buruli ulcer (BU) is a cutaneous infectious disease caused by Mycobacterium ulcerans. It is the third most common mycobacterial disease in the world in the immunocompetent patient and second in Côte d'Ivoire after tuberculosis. This study aimed to assess the characteristics and epidemiological profile of BU in the district of Tiassalé, an important focus of the disease in south Côte d'Ivoire, in order to better direct actions for prevention and control. Retrospective clinical data of BU cases in the period 2005-2010 from all 19 district health centres were collected and linked with geographical and environmental survey data. A total of 1145 cases of BU were recorded between 2005 and 2010 in the district of Tiassalé. Children under the age of 15 years were the most affected (53.0%) with a higher prevalence among males compared to females (54.7% versus 45.3%). Among individuals aged 15-49 years, females had a higher prevalence than males (54.2% versus 45.8%). The villages of Ahondo, Léléblé and Taabo, located in close proximity to the man-made Lake Taabo that was constructed in the late 1970s by damming the Bandama River, and the village of Sokrogbo located downstream of the dam, showed the highest BU rates in the sub-prefecture of Taabo. In the sub-prefecture of Tiassalé, the villages of Affikro, Morokro and N'Zianouan, located near N'Zi River, a tributary of the Bandama River, were the most affected. The distribution of BU is associated with environmental patterns (i.e. distance between village and Lake Taabo or Bandama River and its tributary N'Zi River). Awareness campaigns, coupled with early diagnosis and improved clinical management of BU, have been implemented in the district of Tiassalé and the incidence of BU has declined.

Susceptibility to Mycobacterium ulcerans Disease (Buruli ulcer) Is Associated with IFNG and iNOS Gene Polymorphisms

Buruli ulcer (BU) is a chronic necrotizing disease of the skin and subcutaneous fat tissue. The causative agent, Mycobacterium ulcerans, produces mycolactone, a macrolide toxin, which causes apoptosis of mammalian cells. Only a small proportion of individuals exposed to M. ulcerans develop clinical disease, as surrounding macrophages may control the infection by bacterial killing at an early stage, while mycolactone concentration is still low. Otherwise, bacterial multiplication leads to in higher concentrations of mycolactone, with formation of necrotizing lesions that are no more accessible to immune cells. By typing a cohort of 96 Ghanaian BU patients and 384 endemic controls without BU, we show an association between BU and single nucleotide polymorphisms (SNPs) in iNOS (rs9282799) and IFNG (rs2069705). Both polymorphisms influence promoter activity in vitro. A previously reported SNP in SLC11A1 (NRAMP, rs17235409) tended to be associated with BU. Altogether, these data reflect the importance of IFNG signaling in early defense against M. ulcerans infection.

The location of Australian Buruli ulcer lesions-Implications for unravelling disease transmission

Background

Buruli ulcer (BU), caused by Mycobacterium ulcerans, is increasing in incidence in Victoria, Australia. To improve understanding of disease transmission, we aimed to map the location of BU lesions on the human body.

Methods

Using notification data and clinical records review, we conducted a retrospective observational study of patients diagnosed with BU in Victoria from 1998–2015. We created electronic density maps of lesion locations using spatial analysis software and compared lesion distribution by age, gender, presence of multiple lesions and month of infection.

Findings

We examined 579 patients with 649 lesions; 32 (5.5%) patients had multiple lesions. Lesions were predominantly located on lower (70.0%) and upper (27.1%) limbs, and showed a non-random distribution with strong predilection for the ankles, elbows and calves. When stratified by gender, upper limb lesions were more common (OR 1·97, 95% CI 1·38–2·82, p<0·001) while lower limb lesions were less common in men than in women (OR 0·48, 95% CI 0·34–0·68, p<0·001). Patients aged ≥ 65 years (OR 3·13, 95% CI 1·52–6·43, p = 0·001) and those with a lesion on the ankle (OR 2·49, 95% CI 1·14–5·43, p = 0·02) were more likely to have multiple lesions. Most infections (71.3%) were likely acquired in the warmer 6 months of the year.

Interpretation

Comparison with published work in Cameroon, Africa, showed similar lesion distribution and suggests the mode of M. ulcerans transmission may be the same across the globe. Our findings also aid clinical diagnosis and provide quantitative background information for further research investigating disease transmission.

Buruli ulcer is an emerging tropical disease that is also increasingly common in the temperate Australian state of Victoria. The mode of transmission of this geographically restricted infection remains elusive. We have accurately mapped the location of 649 PCR-confirmed Buruli lesions affecting 579 patients and displayed their position on front and back human body diagrams. Lesion distribution density was assessed with computer-generated heat-maps. Buruli lesion distribution was most common on exposed parts of the body (distal limbs). However, even on exposed areas, lesion distribution was highly unevenly distributed and focused towards ankles, backs of calves and elbows. The palmar and plantar surfaces of hands and feet were rarely affected. We propose that targeting behavior by biting insects rather than direct contact with a contaminated environment best explains the lesion distribution we observed.

The Macrolide Toxin Mycolactone Promotes Bim-Dependent Apoptosis in Buruli Ulcer through Inhibition of mTOR

Mycolactone, the macrolide exotoxin produced by Mycobacterium ulcerans, is central to the pathogenesis of the chronic necrotizing skin disease Buruli ulcer (BU). Here we show that mycolactone acts as an inhibitor of the mechanistic Target of Rapamycin (mTOR) signaling pathway by interfering with the assembly of the two distinct mTOR protein complexes mTORC1 and mTORC2, which regulate different cellular processes. Inhibition of the assembly of the rictor containing mTORC2 complex by mycolactone prevents phosphorylation of the serine/threonine protein kinase Akt. The associated inactivation of Akt leads to the dephosphorylation and activation of the Akt-targeted transcription factor FoxO3. Subsequent up-regulation of the FoxO3 target gene BCL2L11 (Bim) increases expression of the pro-apoptotic regulator Bim, driving mycolactone treated mammalian cells into apoptosis. The central role of Bim-dependent apoptosis in BU pathogenesis deduced from our experiments with cultured mammalian cells was further verified in an experimental M. ulcerans infection model. As predicted by the model, M. ulcerans infected Bim knockout mice did not develop necrotic BU lesions with large clusters of extracellular bacteria, but were able to contain the mycobacterial multiplication. Our findings provide a new coherent and comprehensive concept of BU pathogenesis.

Yaws resurgence in Bankim, Cameroon: The relative effectiveness of different means of detection in rural communities

Background

Yaws is an infectious, debilitating and disfiguring disease of poverty that mainly affects children in rural communities in tropical areas. In Cameroon, mass-treatment campaigns carried out in the 1950s reduced yaws to such low levels that it was presumed the disease was eradicated. In 2010, an epidemiological study in Bankim Health District detected 29 cases of yaws. Five different means of detecting yaws in clinical and community settings were initiated in Bankim over the following five years.

Methodology

This observational study reviews data on the number of cases of yaws identified by each of the five yaws detection approaches: 1) passive yaws detection at local clinics after staff attended Neglected Tropical Disease awareness workshops, 2) community-based case detection carried out in remote communities by hospital staff who relied on community health workers to identify cases, 3) yaws screening following mass Buruli Ulcer outreach programs being piloted in the district, 4) school-based screening programs conducted as stand-alone and follow-up activities to mass outreach events, and 5) house to house active surveillance activities conducted in thirty-eight communities. Implementation of each of the four community-based approaches was observed by a team of health social scientists tasked with assessing the strengths and limitations of each detection method.

Findings

Eight hundred and fifteen cases of yaws were detected between 2012 and 2015. Only 7% were detected at local clinics. Small outreach programs and household surveys detected yaws in a broad spectrum of communities. The most successful means of yaws detection, accounting for over 70% of cases identified, were mass outreach programs and school based screenings in communities where yaws was detected.

Conclusion

The five interventions for detecting yaws had a synergistic effect and proved to be valuable components of a yaws eradication program. Well planned, culturally sensitive mass outreach educational programs accompanied by school-based programs proved to be particularly effective in Bankim. Including yaws detection in a Buruli Ulcer outreach program constituted a win-win situation, as the demonstration effect of yaws treatment (rapid cure) increased confidence in early Buruli ulcer treatment. Mass outreach programs functioned as magnets for both diseases as well as other kinds of chronic wounds that future outreach programs need to address.

Yaws is an infectious and disfiguring disease of poverty primarily affecting children in rural communities in tropical areas. Yaws is easily treated by a single dose of antibiotics and is on the World Health Organization’s eradication list. Yaws was thought eradicated in the Cameroon in the 1950s following aggressive mass-treatment campaigns. In 2010, epidemiological research revealed a resurgence of the disease. This paper discusses the relative success of five different means of detecting yaws in rural areas of Bankim District between 2012 and 2015. While few cases of yaws were detected at local clinics during this time, many cases were detected in the community. The most successful means of detecting yaws were mass outreach programs designed to educate the public about neglected tropical diseases found in the region, and follow up school-based screening programs. These programs were supported by local chiefs and traditional healers and found to be the best way of increasing community awareness about yaws, motivating community health workers to participate in outreach, and fostering trust in the free medical treatment being provided.

Mycobacterium ulcerans infection (Buruli ulcer) in French Guiana, South America, 1969-2013: an epidemiological study

BACKGROUND

Mycobacterium ulcerans infection is the third most common mycobacterial disease in the world after tuberculosis and leprosy. To date, transmission pathways from its environmental reservoir to humans are still unknown. In South America, French Guiana has the highest reported number of M ulcerans infections across the continent. This empirical study aimed to characterise the epidemiology of M ulcerans infection in French Guiana between 1969 and 2013.

METHODS

Data were collected prospectively mainly by two dermatologists at Cayenne Hospital's dermatology department between Jan 1, 1969, and Dec 31, 2013, for age, date of diagnosis, sex, residence, location of the lesion, type of lesion, associated symptoms, and diagnostic method (smear, culture, PCR, or histology) for all confirmed and suspected cases of M ulcerans. We obtained population data from censuses. We calculated mean M ulcerans infection incidences, presented as the number of cases per 100 000 person-years.

FINDINGS

245 patients with M ulcerans infections were reported at Cayenne Hospital's dermatology department during the study period. M ulcerans infection incidence decreased over time, from 6·07 infections per 100 000 person-years (95% CI 4·46-7·67) in 1969-83 to 4·77 infections per 100 000 person-years (3·75-5·79) in 1984-98 and to 3·49 infections per 100 000 person-years (2·83-4·16) in 1999-2013. The proportion of children with infections also declined with time, from 42 (76%) of 55 patients in 1969-83 to 26 (31%) of 84 in 1984-98 and to 22 (21%) of 106 in 1999-2013. Most cases occurred in coastal areas surrounded by marshy savannah (incidence of 21·08 per 100 000 person-years in Sinnamary and 21·18 per 100 000 person-years in Mana). Lesions mainly affected limbs (lower limbs 161 [66%] patients; upper limbs 60 [24%] patients). We diagnosed no bone infections.

INTERPRETATION

The decrease of M ulcerans infection incidence and the proportion of children with infections over a 45 year period in this ultra-peripheral French territory might have been mostly driven by improving living conditions, prophylactic recommendations, and access to health care.

FUNDING

Agence Nationale de la Recherche.

Experimental demonstration of the possible role of Acanthamoeba polyphaga in the infection and disease progression in Buruli Ulcer (BU) using ICR mice

The transmission of Buruli ulcer (BU), caused by Mycobacterium ulcerans (MU), remains puzzling although a number of hypothesis including through bites of infected aquatic insects have been proposed. We report the results of experiments using ICR mice that give credence to our hypothesis that Acanthamoeba species may play a role in BU transmission. We cocultured MU N2 and MU 1615 which expresses red fluorescent protein (RFP) and Acanthamoeba polyphaga (AP), and confirmed infected AP by Ziehl-Neelsen (ZN) staining. We tested for viability of MU inside AP and observed strong RFP signals inside both trophozoites and cysts after 3 and 42 days of coculturing respectively. ICR mice were topically treated, either on shaved intact or shaved pinpricked rumps, with one of the following; MU N2 only (2.25 x 106 colony forming units [CFU] / ml), MU N2:AP coculture (2.96 x 104 CFU: 1.6 x 106 cells/ml), AP only (1.6 x 106 cells/ml), PYG medium and sterile distilled water. Both MU N2 only and MU N2:AP elicited reddening on day (D) 31; edema on D 45 and D 44 respectively, and ulcers on D 49 at pinpricked sites only. To ascertain infectivity and pathogenicity of MU N2 only and MU N2:AP, and compare their virulence, the standard mouse footpad inoculation method was used. MU N2:AP elicited reddening in footpads by D 3 compared to D 14 with MU N2 only of the same dose of MU N2 (2.96 x 104 CFU). ZN-stained MU were observed in both thin sectioned and homogenized lesions, and aspirates from infected sites. Viable MU N2 were recovered from cultures of the homogenates and aspirates. This study demonstrates in ICR mice MU transmission via passive infection, and shows that punctures in the skin are prerequisite for infection, and that coculturing of MU with AP enhances pathogenesis.

Mycobacterium ulcerans Mouse Model Refinement for Pre-Clinical Profiling of Vaccine Candidates

Buruli Ulcer is a neglected tropical disease leading to extensive disabilities and morbidity in West Africa. In this paper we sought to characterize various strains of Mycobacterium ulcerans (M.ulcerans) with different origins and laboratory passage records while refining a mouse model for Buruli ulcer. We described, compared and followed the kinetics of the histo-pathological outcome of infection of a collection of strains at various anatomical sites of infection in order to find a suitable model for further immunization studies. Moreover we compared the outcome of infection in C57Bl/6 and Balbc/J mice. Specifically we described thoroughly one M. ulcerans strain characterized by slow growth rate and limited tissue necrosis, which presents close ressemblance with the infection kinetics in humans. This strain caused macrophages as well as T and B cells infiltration, correlating with mycobacterial proliferation at the site of infection as well as in the draining lymph nodes, making it a suitable strain to screen vaccine candidates efficacy.

Mycobacterium ulcerans in the Daintree 2009-2015 and the mini-epidemic of 2011

BACKGROUND

Mycobacterium ulcerans infection (Buruli ulcer) is the third most common mycobacterial disease in humans, with presentations ranging from self-limiting skin nodules and ulcers to aggressive infiltrative infections with extensive oedema, fat and skin necrosis. The two foci in Australia are in Victoria and Far North Queensland. We present the 2009-2015 case series for the Queensland focus with special reference to the 2011 spike of 64 cases.

METHODS

This case series is based on a combination of prospectively and retrospectively collected data on 95 confirmed cases of M. ulcerans between 2009 and 2015 from the endemic area, consisting of 88 Category 1 lesions (single lesion less than 5 cm), three Category 2 (5-15 cm plaques) and four Category 3 (one multiple lesions, three oedematous infection).

RESULTS

Eighty-nine patients underwent surgery. Thirty-two patients received antibiotics. Management details for three patients were unavailable. Recurrent disease was identified in six patients (6%).

CONCLUSION

Mycobacterium ulcerans infection (Buruli ulcer) is an endemic but uncommon infection in Far North Queensland with usually fewer than 10 cases per year. Small ulcers predominate. Most were excised and antibiotic treatment was frequently adjuvant rather than therapeutic. The 64 cases in 2011 was unexpected, not duplicated subsequently, and may relate to local climatic variations. Local awareness of the disease facilitated early presentation and diagnosis in most cases, enabling timely treatment while lesions were small and easily managed.

Economic inequality caused by feedbacks between poverty and the dynamics of a rare tropical disease: the case of Buruli ulcer in sub-Saharan Africa

Neglected tropical diseases (NTDs) have received increasing attention in recent years by the global heath community, as they cumulatively constitute substantial burdens of disease as well as barriers for economic development. A number of common tropical diseases such as malaria, hookworm or schistosomiasis have well-documented economic impacts. However, much less is known about the population-level impacts of diseases that are rare but associated with high disability burden, which represent a great number of tropical diseases. Using an individual-based model of Buruli ulcer (BU), we demonstrate that, through feedbacks between health and economic status, such NTDs can have a significant impact on the economic structure of human populations even at low incidence levels. While average wealth is only marginally affected by BU, the economic conditions of certain subpopulations are impacted sufficiently to create changes in measurable population-level inequality. A reduction of the disability burden caused by BU can thus maximize the economic growth of the poorest subpopulations and reduce significantly the economic inequalities introduced by the disease in endemic regions.

A Community Based Study on the Mode of Transmission, Prevention and Treatment of Buruli Ulcers in Southwest Cameroon: Knowledge, Attitude and Practices

Background

Buruli ulcer (BU) is a neglected tropical disease affecting the skin, tissues and in some cases the bones, caused by the environmental pathogen Mycobacterium ulcerans (M. ulcerans). Its mode of transmission is still elusive. Delayed treatment may cause irreversible disabilities with consequent social and economic impacts on the victim. Socio-cultural beliefs, practices and attitudes in endemic communities have been shown to influence timely treatment causing disease management, prevention and control a great challenge. An assessment of these factors in endemic localities is important in designing successful intervention strategies. Considering this, we assessed the knowledge, attitude and practices regarding BU in three endemic localities in the South West region, Cameroon to highlight existing misconceptions that need to be addressed to enhance prompt treatment and facilitate effective prevention and control.

Methods and Findings

A cross-sectional study was executed in three BU endemic health districts. Using qualitative and quantitative approaches we surveyed 320 randomly selected household heads, interviewed BU patients and conducted three focus group discussions (FGDs) to obtain information on awareness, beliefs, treatment, and attitudes towards victims. The influence of socio-demographic factors on these variables was investigated.

Results

Respondents (84.4%) had a good knowledge of BU though only 65% considered it a health problem while 49.4% believed it is contagious. Socio-demographic factors significantly (P<0.05) influenced awareness of BU, knowledge and practice on treatment and attitudes towards victims. Although the majority of respondents stated the hospital as the place for appropriate treatment, FGDs and some BU victims preferred witchdoctors/herbalists and prayers, and considered the hospital as the last option. We documented beliefs about the disease which could delay treatment.

Conclusion

Though we are reporting a high level of knowledge of BU, there exist fallacies about BU and negative attitudes towards victims in communities studied. Efforts towards disease eradication must first of all target these misconceptions.

Local Cellular Immune Responses and Pathogenesis of Buruli Ulcer Lesions in the Experimental Mycobacterium Ulcerans Pig Infection Model

Background

Buruli ulcer is a neglected tropical disease of the skin that is caused by infection with Mycobacterium ulcerans. We recently established an experimental pig (Sus scrofa) infection model for Buruli ulcer to investigate host-pathogen interactions, the efficacy of candidate vaccines and of new treatment options.

Methodology/Principal Findings

Here we have used the model to study pathogenesis and early host-pathogen interactions in the affected porcine skin upon infection with mycolactone-producing and non-producing M. ulcerans strains. Histopathological analyses of nodular lesions in the porcine skin revealed that six weeks after infection with wild-type M. ulcerans bacteria extracellular acid fast bacilli were surrounded by distinct layers of neutrophils, macrophages and lymphocytes. Upon ulceration, the necrotic tissue containing the major bacterial burden was sloughing off, leading to the loss of most of the mycobacteria. Compared to wild-type M. ulcerans bacteria, toxin-deficient mutants caused an increased granulomatous cellular infiltration without massive tissue necrosis, and only smaller clusters of acid fast bacilli.

Conclusions/Significance

In summary, the present study shows that the pathogenesis and early immune response to M. ulcerans infection in the pig is very well reflecting BU disease in humans, making the pig infection model an excellent tool for the profiling of new therapeutic and prophylactic interventions.

Buruli ulcer is a necrotizing ulcerative disease of the skin and underlying tissue caused by infection with Mycobacterium ulcerans. Because patients often present late to health facilities, early stages of Buruli ulcer are only insufficiently described by histopathology. To study early host-pathogen interactions, we recently established an experimental pig infection model for Buruli ulcer. Here we used the model to study the pathogenesis and the local cellular immune responses upon infection with mycolactone-producing and non-producing M. ulcerans strains. Infection with toxin-producing bacteria led to the development of nodular lesions six weeks after infection, in which extracellular clumps of acid fast bacilli were surrounded by distinct layers of leukocytes. Ulceration of the nodular lesions subsequently led to the loss of most of the bacterial burden. In contrast, after infection with toxin-deficient M. ulcerans bacteria increased granulomatous cellular infiltration was observed, and massive tissue necrosis was absent. Pathogenesis as well as early immune responses to M. ulcerans infection in the pig is very well reflecting the human disease, making it a good model for the evaluation of the efficacy of new treatment options and candidate vaccines.

Buruli ulcer in Nigeria: results of a pilot case study in three rural districts

Background

Buruli ulcer (BU), also known as Mycobacterium ulcerans disease, is the third most common mycobacterial disease worldwide. Although BU disease has been diagnosed among Nigerians in neighbouring West African countries, data on the burden of the disease in Nigeria itself are scanty. This study aimed to assess the magnitude and epidemiology of BU in the South South region of Nigeria.

Methods

We conducted a cross-sectional survey in the Ogoja territory (comprising 31 communities). We undertook sensitisation programmes centred on BU in 10 of the communities. Participants were asked to identify community members with long-standing ulcers, who were then invited for evaluation. We also contacted traditional healers to refer their clients who had non-healing ulcers. All suspected cases had a full clinical evaluation and laboratory testing. Confirmed cases were given treatment in a referral hospital in the territory.

Results

We diagnosed 41 clinical BU cases; 36 (87.8 %) of which were confirmed by quantitative polymerase chain reaction (qPCR). These 36 PCR-confirmed cases were diagnosed in a total population of 192,169 inhabitants. Therefore, the estimated crude prevalence of BU was 18.7 per 100,000 population, varying from 6.0 to 41.4 per 100,000 in the districts surveyed. The majority (66.7 %) of the cases were females. About 92 % of the BU lesions were located on the patients’ extremities. No differences were observed between the sexes in terms of the location of the lesions. The age of the patients ranged from four to 60 years, with a median age of 17 years. All 35 (100 %) patients who consented to treatment completed chemotherapy as prescribed. Of the treated cases, 29 (82.9 %) needed and received surgery. All cases healed, but 29 (82.9 %) had some limitations in movement. Healing with limitations in movement occurred in 18/19 (94.7 %) and 8/10 (80.0 %) of patients with lesions >15 cm (Category III) and 6–15 cm in diameter (Category II), respectively. The median duration of treatment was 130 (87–164) days for children and 98 (56–134) days for adults (p = 0.15).

Conclusions

In Nigeria, BU is endemic but its severity is underestimated—at least in the study setting. There is a need to identify and map BU endemic regions in Nigeria. A comprehensive BU control programme is also urgently needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0119-8) contains supplementary material, which is available to authorized users.

Burden and Historical Trend of Buruli Ulcer Prevalence in Selected Communities along the Offin River of Ghana

Buruli ulcer (BU) is a neglected tropical skin disease caused by Mycobacterium ulcerans with more than two thirds of the global cases reported in West Africa. A nationwide active BU case search conducted in 1999 identified two health districts along the Offin River as two of the three most endemic districts in Ghana. Based on recent anecdotal accounts that transmission is unstable along the Offin River, we conducted from March to June 2013 an exhaustive household survey and active case search in 13 selected communities within a five-kilometer radius along the Offin River. The overall prevalence of BU was 2.3% among the surveyed population of 20,390 inhabitants and 477 of the total 480 cases detected (99.4%) were historical (healed) cases. By estimating the year of occurrence for each case per community and taking into account available passive surveillance records of health facilities and the District Health Directorate, we observed a general trend of continuous emergence of cases in communities located midstream the Offin River whereas downstream communities showed more sporadic patterns. We monitored the incidence of cases after the survey and recorded a cumulative incidence rate of 0.04% for the 13 communities over a 17-month active surveillance period from August 2013 to December 2014. Our data reveal an overall decline in BU incidence along the Offin River similar to the general decline in BU incidence in recent years reported by the World Health Organization for West Africa.

Buruli ulcer (BU) is a tropical skin disease caused by Mycobacterium ulcerans and more than two thirds of the global cases reported in West Africa. The Offin has been considered the most endemic river valley in Ghana following a nationwide active case search conducted in 1999. Here, we present findings of an exhaustive household survey and case search of 13 selected communities along the Offin river aimed at addressing recent anecdotal accounts of unstable transmission of M. ulcerans within the river basin. We observed among the surveyed population of 20,390 inhabitants, an overall 2.3% prevalence of BU with 99.4% of the total cases detected being historical cases. We also observed a general trend of continuous and sporadic emergence of cases in mid and downstream communities, respectively. Subsequently, we detected a total of eight cases (0.04% cumulative incidence rate) in a prospective 17-month active surveillance of all 13 communities. These data confirm the recent decline in BU incidence in historically endemic communities along the Offin river basin, analogous to the observation made in recent years by the World Health Organization for West Africa.

Interferon-γ Is a Crucial Activator of Early Host Immune Defense against Mycobacterium ulcerans Infection in Mice

Buruli ulcer (BU), caused by infection with Mycobacterium ulcerans, is a chronic necrotizing human skin disease associated with the production of the cytotoxic macrolide exotoxin mycolactone. Despite extensive research, the type of immune responses elicited against this pathogen and the effector functions conferring protection against BU are not yet fully understood. While histopathological analyses of advanced BU lesions have demonstrated a mainly extracellular localization of the toxin producing acid fast bacilli, there is growing evidence for an early intra-macrophage growth phase of M. ulcerans. This has led us to investigate whether interferon-γ might play an important role in containing M. ulcerans infections. In an experimental Buruli ulcer mouse model we found that interferon-γ is indeed a critical regulator of early host immune defense against M. ulcerans infections. Interferon-γ knockout mice displayed a faster progression of the infection compared to wild-type mice. This accelerated progression was reflected in faster and more extensive tissue necrosis and oedema formation, as well as in a significantly higher bacterial burden after five weeks of infection, indicating that mice lacking interferon-γ have a reduced capacity to kill intracellular bacilli during the early intra-macrophage growth phase of M. ulcerans. This data demonstrates a prominent role of interferon-γ in early defense against M. ulcerans infection and supports the view that concepts for vaccine development against tuberculosis may also be valid for BU.

Mycobacterium ulcerans is the causative agent of Buruli ulcer (BU), a slow progressing ulcerative skin disease. The mode of transmission of M. ulcerans remains unknown and only little is known about the early stages of the disease and the nature of protective immune responses against this pathogen. Given the increasing evidence for an early intracellular growth phase of M. ulcerans, we aimed at evaluating the impact of cell-mediated immunity for immunological defense against M. ulcerans infections. By comparing wild-type and interferon-γ-deficient mice in a BU mouse model, we could demonstrate that interferon-γ is a critical regulator of early host immune defense against M. ulcerans infections, indicative for an important role of early intracellular multiplication of the pathogen. In mice lacking interferon-γ the bacterial burden increased faster, resulting in accelerated pathogenesis. The observed differences between the two mouse strains were most likely due to differences in the capacity of macrophages to kill intracellular bacilli during the early stages of infection.

Vaccination with the Surface Proteins MUL_2232 and MUL_3720 of Mycobacterium ulcerans Induces Antibodies but Fails to Provide Protection against Buruli Ulcer

Background

Buruli ulcer, caused by infection with Mycobacterium ulcerans, is a chronic ulcerative neglected tropical disease of the skin and subcutaneous tissue that is most prevalent in West African countries. M. ulcerans produces a cytotoxic macrolide exotoxin called mycolactone, which causes extensive necrosis of infected subcutaneous tissue and the development of characteristic ulcerative lesions with undermined edges. While cellular immune responses are expected to play a key role against early intracellular stages of M. ulcerans in macrophages, antibody mediated protection might be of major relevance against advanced stages, where bacilli are predominantly found as extracellular clusters.

Methodology/Principal Findings

To assess whether vaccine induced antibodies against surface antigens of M. ulcerans can protect against Buruli ulcer we formulated two surface vaccine candidate antigens, MUL_2232 and MUL_3720, as recombinant proteins with the synthetic Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant-stable emulsion. The candidate vaccines elicited strong antibody responses without a strong bias towards a T_H1 type cellular response, as indicated by the IgG2a to IgG1 ratio. Despite the cross-reactivity of the induced antibodies with the native antigens, no significant protection was observed against progression of an experimental M. ulcerans infection in a mouse footpad challenge model.

Conclusions

Even though vaccine-induced antibodies have the potential to opsonise the extracellular bacilli they do not have a protective effect since infiltrating phagocytes might be killed by mycolactone before reaching the bacteria, as indicated by lack of viable infiltrates in the necrotic infection foci.

Buruli ulcer is a slow progressing ulcerative disease of the skin and subcutaneous tissue that is most prevalent in West African rural communities. Mycobacterium ulcerans, the causative agent of the disease, produces a toxin called mycolactone, which is held responsible for the extensive tissue damage seen in advanced Buruli ulcer lesions. To date, no effective vaccine against the disease exists and it is unclear to what extent antibodies against cell surface antigens of M. ulcerans play a role in protection. To assess whether vaccine induced antibodies against cell surface proteins can protect against Buruli ulcer, we formulated two surface vaccine candidate antigens, MUL_2232 and MUL_3720, as adjuvanted recombinant proteins and investigated their protective potential in a mouse model of M. ulcerans infection. Despite the induction of strong antibody responses against the surface molecules and cross-reactivity of the induced antibodies with the antigens in their native context, we did not observe protection against the disease. While the vaccine-induced antibodies could opsonize the extracellular bacilli, infiltrating phagocytes might be killed early by mycolactone.

A Sero-epidemiological Approach to Explore Transmission of Mycobacterium ulcerans

The debilitating skin disease Buruli ulcer (BU) is caused by infection with Mycobacterium ulcerans. While various hypotheses on potential reservoirs and vectors of M. ulcerans exist, the mode of transmission has remained unclear. Epidemiological studies have indicated that children below the age of four are less exposed to the pathogen and at lower risk of developing BU than older children. In the present study we compared the age at which children begin to develop antibody responses against M. ulcerans with the age pattern of responses to other pathogens transmitted by various mechanisms. A total of 1,352 sera from individuals living in the BU endemic Offin river valley of Ghana were included in the study. While first serological responses to the mosquito transmitted malaria parasite Plasmodium falciparum and to soil transmitted Strongyloides helminths emerged around the age of one and two years, sero-conversion for M. ulcerans and for the water transmitted trematode Schistosoma mansoni occurred at around four and five years, respectively. Our data suggest that exposure to M. ulcerans intensifies strongly at the age when children start to have more intense contact with the environment, outside the small movement range of young children. Further results from our serological investigations in the Offin river valley also indicate ongoing transmission of Treponema pallidum, the causative agent of yaws.

Buruli Ulcer in Cameroon: The Development and Impact of the National Control Programme

BACKGROUND

Cameroon is endemic for Buruli ulcer (BU) and organised institutional BU control began in 2002. The objective was to describe the evolution, achievements and challenges of the national BU control programme (NBUCP) and to make suggestions for scaling up the programme.

METHODS

We analysed collated data on BU from 2001 to 2014 and reviewed activity reports NBUCP in Cameroon. Case-detection rates and key BU control indicators were calculated and plotted on a time scale to determine trends in performance. A linear regression analysis of BU detection rate from 2005-2014 was done. The regression coefficient was tested statistically for the significance in variation of BU detection rate.

PRINCIPAL FINDINGS

In 14 years of BU control, 3700 cases were notified. The BU detection rate dropped significantly from 3.89 to 1.45 per 100 000 inhabitants. The number of BU endemic health districts rose from two to 64. Five BU diagnostic and treatment centres are functional and two more are planned for 2015. The health system has been strengthened and BU research and education has gained more interest in Cameroon.

CONCLUSION/SIGNIFICANCE

Although institutional BU control Cameroon only began 30 years after the first cases were reported in 1969, a number of milestones have been attained. These would serve as stepping stones for charting the way forward and improving upon control activities in the country if the major challenge of resource allocation is dealt with.

Socio-Environmental Factors Associated with the Risk of Contracting Buruli Ulcer in Tiassalé, South Côte d'Ivoire: A Case-Control Study

BACKGROUND

Buruli ulcer (BU) is a cutaneous infectious disease caused by Mycobacterium ulcerans. The exact mode of transmission remains elusive; yet, some studies identified environmental, socio-sanitary, and behavioral risk factors. The purpose of this study was to assess the association of such factors to contracting BU in Tiassalé, south Côte d'Ivoire.

METHODOLOGY

A case-control study was conducted in 2012. Cases were BU patients diagnosed according to clinical definition put forth by the World Health Organization, readily confirmed by IS2404 polymerase chain reaction (PCR) analysis prior to our study and recruited at one of the health centers of the district. Two controls were matched for each control, by age group (to the nearest 5 years), sex, and living community. Participants were interviewed after providing oral witnessed consent, assessing behavioral, environmental, and socio-sanitary factors.

PRINCIPAL FINDINGS

A total of 51 incident and prevalent cases and 102 controls were enrolled. Sex ratio (male:female) was 0.9. Median age was 25 years (range: 5-70 years). Regular contact with unprotected surface water (adjusted odds ratio (aOR) = 6.5; 95% confidence interval (CI) = 2.1-19.7) and absence of protective equipment during agricultural activities (aOR = 18.5, 95% CI = 5.2-66.7) were identified as the main factors associated with the risk of contracting BU. Etiologic fractions among exposed to both factors were 84.9% and 94.6%, respectively. Good knowledge about the risks that may result in BU (aOR = 0.3, 95% CI = 0.1-0.8) and perception about the disease causes (aOR = 0.1, 95% CI = 0.02-0.3) showed protection against BU with a respective preventive fraction of 70% and 90%.

CONCLUSIONS/SIGNIFICANCE

Main risk factors identified in this study were the contact with unprotected water bodies through daily activities and the absence of protective equipment during agricultural activities. An effective strategy to reduce the incidence of BU should involve compliance with protective equipment during agricultural activities and avoidance of contact with surface water and community capacity building through training and sensitization.

Environmental transmission of Mycobacterium ulcerans drives dynamics of Buruli ulcer in endemic regions of Cameroon

Buruli Ulcer is a devastating skin disease caused by the pathogen Mycobacterium ulcerans. Emergence and distribution of Buruli ulcer cases is clearly linked to aquatic ecosystems, but the specific route of transmission of M. ulcerans to humans remains unclear. Relying on the most detailed field data in space and time on M. ulcerans and Buruli ulcer available today, we assess the relative contribution of two potential transmission routes--environmental and water bug transmission--to the dynamics of Buruli ulcer in two endemic regions of Cameroon. The temporal dynamics of Buruli ulcer incidence are explained by estimating rates of different routes of transmission in mathematical models. Independently, we also estimate statistical models of the different transmission pathways on the spatial distribution of Buruli ulcer. The results of these two independent approaches are corroborative and suggest that environmental transmission pathways explain the temporal and spatial patterns of Buruli ulcer in our endemic areas better than the water bug transmission.

Local Heat Application for the Treatment of Buruli Ulcer: Results of a Phase II Open Label Single Center Non Comparative Clinical Trial

Buruli ulcer (BU) is a necrotizing skin disease. Local thermotherapy is a highly effective, simple, cheap and safe treatment. It has in particular potential as home-based remedy for BU suspicious lesions at community level where laboratory confirmation is not available.

Background. Buruli ulcer (BU) is a necrotizing skin disease most prevalent among West African children. The causative organism, Mycobacterium ulcerans, is sensitive to temperatures above 37°C. We investigated the safety and efficacy of a local heat application device based on phase change material.

Methods. In a phase II open label single center noncomparative clinical trial (ISRCTN 72102977) under GCP standards in Cameroon, laboratory confirmed BU patients received up to 8 weeks of heat treatment. We assessed efficacy based on the endpoints ‘absence of clinical BU specific features’ or ‘wound closure’ within 6 months (“primary cure”), and ‘absence of clinical recurrence within 24 month’ (“definite cure”).

Results. Of 53 patients 51 (96%) had ulcerative disease. 62% were classified as World Health Organization category II, 19% each as category I and III. The average lesion size was 45 cm². Within 6 months after completion of heat treatment 92.4% (49 of 53, 95% confidence interval [CI], 81.8% to 98.0%) achieved cure of their primary lesion. At 24 months follow-up 83.7% (41 of 49, 95% CI, 70.3% to 92.7%) of patients with primary cure remained free of recurrence. Heat treatment was well tolerated; adverse effects were occasional mild local skin reactions.

Conclusions. Local thermotherapy is a highly effective, simple, cheap and safe treatment for M. ulcerans disease. It has in particular potential as home-based remedy for BU suspicious lesions at community level where laboratory confirmation is not available.

Clinical Trials Registration. ISRCT 72102977.

Use of Recombinant Virus Replicon Particles for Vaccination against Mycobacterium ulcerans Disease

Buruli ulcer, caused by infection with Mycobacterium ulcerans, is a necrotizing disease of the skin and subcutaneous tissue, which is most prevalent in rural regions of West African countries. The majority of clinical presentations seen in patients are ulcers on limbs that can be treated by eight weeks of antibiotic therapy. Nevertheless, scarring and permanent disabilities occur frequently and Buruli ulcer still causes high morbidity. A vaccine against the disease is so far not available but would be of great benefit if used for prophylaxis as well as therapy. In the present study, vesicular stomatitis virus-based RNA replicon particles encoding the M. ulcerans proteins MUL2232 and MUL3720 were generated and the expression of the recombinant antigens characterized in vitro. Immunisation of mice with the recombinant replicon particles elicited antibodies that reacted with the endogenous antigens of M. ulcerans cells. A prime-boost immunization regimen with MUL2232-recombinant replicon particles and recombinant MUL2232 protein induced a strong immune response but only slightly reduced bacterial multiplication in a mouse model of M. ulcerans infection. We conclude that a monovalent vaccine based on the MUL2232 antigen will probably not sufficiently control M. ulcerans infection in humans.

Infection with Mycobacterium ulcerans can lead to a slow progressing, ulcerative disease of the skin and underlying soft tissue called Buruli ulcer. The disease is most prevalent in rural African communities with limited access to health care facilities. The most efficient means to prevent the disease, a vaccine against Buruli ulcer is not available to date. In the present study we investigated the immunogenicity and protective potential of a single cycle virus system expressing the two M. ulcerans antigens MUL2232 and MUL3720. Immunization of mice with those vesicular stomatitis virus replicon particles led to the induction of humoral as well as cellular immune responses in the immunized animals. Subsequent challenge experiments in a mouse model of M. ulcerans infection demonstrated only a limited reduction of bacterial burden in mice immunized with a prime-boost approach with MUL2232. Most probably, a vaccine formulation with only one antigen will not be able to provide protection against Buruli ulcer in humans.

Locally Confined Clonal Complexes of Mycobacterium ulcerans in Two Buruli Ulcer Endemic Regions of Cameroon

Background

Mycobacterium ulcerans is the causative agent of the necrotizing skin disease Buruli ulcer (BU), which has been reported from over 30 countries worldwide. The majority of notified patients come from West African countries, such as Côte d’Ivoire, Ghana, Benin and Cameroon. All clinical isolates of M. ulcerans from these countries are closely related and their genomes differ only in a limited number of single nucleotide polymorphisms (SNPs).

Methodology/Principal Findings

We performed a molecular epidemiological study with clinical isolates from patients from two distinct BU endemic regions of Cameroon, the Nyong and the Mapé river basins. Whole genome sequencing of the M. ulcerans strains from these two BU endemic areas revealed the presence of two phylogenetically distinct clonal complexes. The strains from the Nyong river basin were genetically more diverse and less closely related to the M. ulcerans strain circulating in Ghana and Benin than the strains causing BU in the Mapé river basin.

Conclusions

Our comparative genomic analysis revealed that M. ulcerans clones diversify locally by the accumulation of SNPs. Case isolates coming from more recently emerging BU endemic areas, such as the Mapé river basin, may be less diverse than populations from longer standing disease foci, such as the Nyong river basin. Exchange of strains between distinct endemic areas seems to be rare and local clonal complexes can be easily distinguished by whole genome sequencing.

Buruli ulcer (BU) is a progressively necrotizing disease of the skin, caused by infection with Mycobacterium ulcerans. BU occurs very focally with highest incidence in West Africa. The mode of transmission and the nature and role of potential environmental reservoirs are currently not entirely understood. In this study we sequenced whole genomes of sets of M. ulcerans case isolates from two BU endemic regions in Cameroon. We identified two distinct phylogenetic lineages, which directly correlated with the two endemic regions. Furthermore, we showed that the genetic diversity of M. ulcerans is higher in the older endemic region of Cameroon (Nyong river basin) compared to the more recently emerged infection focus in the same country (Mapé river basin). Together, our results demonstrate that M. ulcerans is developing local clonal complexes by the accumulation of single nucleotide polymorphisms (SNPs) and that these complexes often remain confined to individual endemic foci. The gene encoding for rpoB, which is known to harbour drug resistance mutations against rifampicin in M. tuberculosis, was not affected by SNPs in any of the analysed M. ulcerans strains.

Buruli Ulcer Disease and Its Association with Land Cover in Southwestern Ghana

BACKGROUND

Buruli ulcer (BU), one of 17 neglected tropical diseases, is a debilitating skin and soft tissue infection caused by Mycobacterium ulcerans. In tropical Africa, changes in land use and proximity to water have been associated with the disease. This study presents the first analysis of BU at the village level in southwestern Ghana, where prevalence rates are among the highest globally, and explores fine and medium-scale associations with land cover by comparing patterns both within BU clusters and surrounding landscapes.

METHODOLOGY/PRINCIPAL FINDINGS

We obtained 339 hospital-confirmed BU cases in southwestern Ghana between 2007 and 2010. The clusters of BU were identified using spatial scan statistics and the percentages of six land cover classes were calculated based on Landsat and Rapid Eye imagery for each of 154 villages/towns. The association between BU prevalence and each land cover class was calculated using negative binomial regression models. We found that older people had a significantly higher risk for BU after considering population age structure. BU cases were positively associated with the higher percentage of water and grassland surrounding each village, but negatively associated with the percent of urban. The results also showed that BU was clustered in areas with high percentage of mining activity, suggesting that water and mining play an important and potentially interactive role in BU occurrence.

CONCLUSIONS/SIGNIFICANCE

Our study highlights the importance of multiple land use changes along the Offin River, particularly mining and agriculture, which might be associated with BU disease in southwestern Ghana. Our study is the first to use both medium- and high-resolution imagery to assess these changes. We also show that older populations (≥ 60 y) appear to be at higher risk of BU disease than children, once BU data were weighted by population age structures.

Whole genome comparisons suggest random distribution of Mycobacterium ulcerans genotypes in a Buruli ulcer endemic region of Ghana

Efforts to control the spread of Buruli ulcer – an emerging ulcerative skin infection caused by Mycobacterium ulcerans - have been hampered by our poor understanding of reservoirs and transmission. To help address this issue, we compared whole genomes from 18 clinical M. ulcerans isolates from a 30km² region within the Asante Akim North District, Ashanti region, Ghana, with 15 other M. ulcerans isolates from elsewhere in Ghana and the surrounding countries of Ivory Coast, Togo, Benin and Nigeria. Contrary to our expectations of finding minor DNA sequence variations among isolates representing a single M. ulcerans circulating genotype, we found instead two distinct genotypes. One genotype was closely related to isolates from neighbouring regions of Amansie West and Densu, consistent with the predicted local endemic clone, but the second genotype (separated by 138 single nucleotide polymorphisms [SNPs] from other Ghanaian strains) most closely matched M. ulcerans from Nigeria, suggesting another introduction of M. ulcerans to Ghana, perhaps from that country. Both the exotic genotype and the local Ghanaian genotype displayed highly restricted intra-strain genetic variation, with less than 50 SNP differences across a 5.2Mbp core genome within each genotype. Interestingly, there was no discernible spatial clustering of genotypes at the local village scale. Interviews revealed no obvious epidemiological links among BU patients who had been infected with identical M. ulcerans genotypes but lived in geographically separate villages. We conclude that M. ulcerans is spread widely across the region, with multiple genotypes present in any one area. These data give us new perspectives on the behaviour of possible reservoirs and subsequent transmission mechanisms of M. ulcerans. These observations also show for the first time that M. ulcerans can be mobilized, introduced to a new area and then spread within a population. Potential reservoirs of M. ulcerans thus might include humans, or perhaps M. ulcerans-infected animals such as livestock that move regularly between countries.

In this study we use the power of whole genome sequence comparisons to track the spread of Mycobacterium ulcerans, the causative agent of Buruli ulcer, through several villages in the Ashanti region of Ghana, providing new insights on the behaviour of this enigmatic and emerging pathogen.

Epidemiology and management of Buruli ulcer

Buruli ulcer (Mycobacterium ulcerans infection) is a neglected tropical disease of skin and subcutaneous tissue that can result in long-term cosmetic and functional disability. It is a geographically restricted infection but transmission has been reported in endemic areas in more than 30 countries worldwide. The heaviest burden of disease lies in West and Sub-Saharan Africa where it affects children and adults in subsistence agricultural communities. Mycobacterium ulcerans infection is probably acquired via inoculation of the skin either directly from the environment or indirectly via insect bites. The environmental reservoir and exact route of transmission are not completely understood. It may be that the mode of acquisition varies in different parts of the world. Because of this uncertainty it has been nicknamed the 'mysterious disease'. The therapeutic approach has evolved in the past decade from aggressive surgical resection alone, to a greater focus on antibiotic therapy combined with adjunctive surgery.