Investigation of potential environmental reservoirs of mycobacterium ulcerans in North Queensland

Mycobacterium ulcerans is the causative agent of Buruli ulcer (BU). It is a geographically restricted neglected tropical disease characterized by extensive and painless necrosis of the skin and soft tissue with formation of large ulcers, usually on the extremities. This disease has been reported in 33 countries worldwide including Australia. In Australia, BU has been reported in coastal Victoria and the Mossman-Daintree area of north Queensland. The mode of transmission and potential environmental reservoir of the organism causing this disease is not well understood. It appears likely that these factors vary in different geographical locations and epidemiological settings. This dissertation aims to investigate the potential reservoirs of M. ulcerans in the BU endemic area of north Queensland, Australia. In Chapter 2, a systematic review is presented to describe what is known of potential animal reservoirs of M. ulcerans in regions throughout the world. The review was conducted using MEDLINE and INFORMIT databases to aggregate published data on this topic. Non-human cases of BU were found only in Australia and small native mammals were identified as potential reservoirs of the infection. Chapter 3 describes the geospatial analysis of cases of BU reported between 2009 and 2018, in an endemic area of North Queensland, Australia, using ArcMap 10.4.1 software. Hot-spot analysis did not find any statistically significant cluster of cases within the endemic areas. Additionally, an association between the amount of rainfall and month of diagnosis of BU cases was described, supporting other observations about the average incubation period of this disease. Chapter 4 and 5 detail the survey of local fauna from the same endemic area of north Queensland, Australia, for the presence of M. ulcerans. Mosquito and animal traps were set up at endemic sites throughout the study period and mosquitoes and animal faecal samples were collected and tested for the presence of M. ulcerans DNA. DNA from M. ulcerans was detected from two bandicoot scat samples and one mosquito pool. These samples were collected from sites in close proximity to human cases of BU. Chapter 6 describes a blood feeding experiment to investigate the role of mosquitoes in transmission of M. ulcerans. Batches of mosquitoes were fed with defibrinated sheep blood containing heat-killed M. ulcerans. DNA extracted from heads, abdomen and legs of mosquitoes was tested for the presence of M. ulcerans DNA. DNA from M. ulcerans was detected from heads of mosquitoes and pools of whole mosquitoes, providing supportive evidence for the role of mosquitoes as a mechanical vector in the transmission of M. ulcerans

Flesh, Blood, Sex and Consumption: Applied Epidemiology in Victoria

In this thesis I present the key projects and activities that I completed as part of the Australian National University's Master of Philosophy in Applied Epidemiology (MAE) program during 2018-2019. During this time I was based in the Communicable Disease Epidemiology and Surveillance (CDES) unit at the Victorian Department of Health and Human Services (DHHS), and the Surveillance and Evaluation section of the Burnet Institute in Melbourne, Victoria. I completed four major projects across these two organisations, as well as being involved with a range of other infectious disease surveillance and research activities. At DHHS, I investigated a cluster of tuberculosis cases in a cultural community. This three-year investigation was one of the largest tuberculosis cluster investigations ever undertaken by the Department of Health and Human Services and the Victorian Tuberculosis Program. The epidemiological side of the investigation in which I was involved utilised epidemiological, social-location and genomic data to better understand transmission within the cluster. I also conducted an epidemiological study of delays in patient presentation and diagnosis for Buruli ulcer in Victoria. Given the current lack of effective interventions to reduce disease transmission in Victoria, prompt diagnosis and treatment are critical to minimise the impact of the disease. The study aimed to characterise and identify factors influencing presentation and diagnosis delays in patients notified to DHHS between 2011 and 2017 to better inform public health messaging for the public and medical practitioners. The study was published in the Tropical Medicine and Infectious Diseases journal in July 2019. At the Burnet Institute I completed a program evaluation of the ACCESS project, a sentinel surveillance system for STIs and BBVs that was funded by the Australian Government Department of Health to expand nationally during 2016-2019. Based on the outcomes of the evaluation, I made several recommendations to improve the operation of the ACCESS project during the next potential funding period. My data analysis project at the Burnet Institute examined the epidemiology and subtype diversity of HIV-1 in newly-arrived Asian-born and Australian-born men who have sex with men (MSM) populations using routinely-collected surveillance and subtyping data. Understanding and addressing HIV transmission in the newly-arrived Asian-born MSM population is increasingly important in Victoria, with both the population and the proportion of HIV notifications from the population increasing in recent years. The appendices to the thesis include summaries of other program requirements outside these four main projects. I developed public health communications materials for a non-scientific audience in the form of participant information for the NHMRC-funded Beating Buruli in Victoria case-control study. I completed three teaching activities; a lecture on data visualisation, a session on the basics of social network analysis for infectious diseases, and a "lesson from the field" on tuberculosis cluster and outbreak investigations. Finally, I present a short summary of my involvement as a team leader in the SaMELFS Samoa mosquito survey and molecular xenomonitoring study, for which I travelled to Samoa in June 2019. Through the completion of these projects and activities I have clearly demonstrated the core field epidemiology training program competencies and accumulated knowledge and experience that will no doubt serve me well in the future

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

A major objective of this open access book is to summarize the current status of Buruli Ulcer (BU) research for the first time. It will identify gaps in our knowledge, stimulate research and support control of the disease by providing insight into approaches for surveillance, diagnosis, and treatment of Buruli Ulcer. Book chapters will cover the history, epidemiology diagnosis, treatment and disease burden of BU and provide insight into the microbiology, genomics, transmission and virulence of Mycobacterium ulcerans. ; Supports further investigation by summarizing state of the art in the field of Buruli ulcer research Enriches understanding of epidemiology of Buruli ulcer in different geographic regions Reviews exhaustively the characteristics of Mycobacterium ulcerans diseas

Global and local environmental changes as drivers of Buruli ulcer emergence

International audienceMany emerging infectious diseases are caused by generalist pathogens that infect and transmit via multiple host species with multiple dissemination routes, thus confounding the understanding of pathogen transmission pathways from wildlife reservoirs to humans. The emergence of these pathogens in human populations has frequently been associated with global changes, such as socio-economic, climate or biodiversity modifications, by allowing generalist pathogens to invade and persist in new ecological niches, infect new host species, and thus change the nature of transmission pathways. Using the case of Buruli ulcer disease, we review how land-use changes, climatic patterns and biodiversity alterations contribute to disease emergence in many parts of the world. Here we clearly show that Mycobacterium ulcerans is an environmental pathogen characterized by multi-host transmission dynamics and that its infectious pathways to humans rely on the local effects of global environmental changes. We show that the interplay between habitat changes (for example, deforestation and agricultural land-use changes) and climatic patterns (for example, rainfall events), applied in a local context, can lead to abiotic environmental changes and functional changes in local biodiversity that favor the pathogen’s prevalence in the environment and may explain disease emergence

Rifampicin and clarithromycin (extended release) versus rifampicin and streptomycin for limited Buruli ulcer lesions: a randomised, open-label, non-inferiority phase 3 trial.

BACKGROUND: Buruli ulcer is a neglected tropical disease caused by Mycobacterium ulcerans infection that damages the skin and subcutis. It is most prevalent in western and central Africa and Australia. Standard antimicrobial treatment with oral rifampicin 10 mg/kg plus intramuscular streptomycin 15 mg/kg once daily for 8 weeks (RS8) is highly effective, but streptomycin injections are painful and potentially harmful. We aimed to compare the efficacy and tolerability of fully oral rifampicin 10 mg/kg plus clarithromycin 15 mg/kg extended release once daily for 8 weeks (RC8) with that of RS8 for treatment of early Buruli ulcer lesions. METHODS: We did an open-label, non-inferiority, randomised (1:1 with blocks of six), multicentre, phase 3 clinical trial comparing fully oral RC8 with RS8 in patients with early, limited Buruli ulcer lesions. There were four trial sites in hospitals in Ghana (Agogo, Tepa, Nkawie, Dunkwa) and one in Benin (Pobè). Participants were included if they were aged 5 years or older and had typical Buruli ulcer with no more than one lesion (caterories I and II) no larger than 10 cm in diameter. The trial was open label, and neither the investigators who took measurements of the lesions nor the attending doctors were masked to treatment assignment. The primary clinical endpoint was lesion healing (ie, full epithelialisation or stable scar) without recurrence at 52 weeks after start of antimicrobial therapy. The primary endpoint and safety were assessed in the intention-to-treat population. A sample size of 332 participants was calculated to detect inferiority of RC8 by a margin of 12%. This study was registered with ClinicalTrials.gov, NCT01659437. FINDINGS: Between Jan 1, 2013, and Dec 31, 2017, participants were recruited to the trial. We stopped recruitment after 310 participants. Median age of participants was 14 years (IQR 10-29) and 153 (52%) were female. 297 patients had PCR-confirmed Buruli ulcer; 151 (51%) were assigned to RS8 treatment, and 146 (49%) received oral RC8 treatment. In the RS8 group, lesions healed in 144 (95%, 95% CI 91 to 98) of 151 patients, whereas lesions healed in 140 (96%, 91 to 99) of 146 patients in the RC8 group. The difference in proportion, -0·5% (-5·2 to 4·2), was not significantly greater than zero (p=0·59), showing that RC8 treatment is non-inferior to RS8 treatment for lesion healing at 52 weeks. Treatment-related adverse events were recorded in 20 (13%) patients receiving RS8 and in nine (7%) patients receiving RC8. Most adverse events were grade 1-2, but one (1%) patient receiving RS8 developed serious ototoxicity and ended treatment after 6 weeks. No patients needed surgical resection. Four patients (two in each study group) had skin grafts. INTERPRETATION: Fully oral RC8 regimen was non-inferior to RS8 for treatment of early, limited Buruli ulcer and was associated with fewer adverse events. Therefore, we propose that fully oral RC8 should be the preferred therapy for early, limited lesions of Buruli ulcer. FUNDING: WHO with additional support from MAP International, American Leprosy Missions, Fondation Raoul Follereau France, Buruli ulcer Groningen Foundation, Sanofi-Pasteur, and BuruliVac

Potential animal reservoir of Mycobacterium ulcerans: a systematic review

Mycobacterium ulcerans is the causative agent of Buruli ulcer, also known in Australia as Daintree ulcer or Bairnsdale ulcer. This destructive skin disease is characterized by extensive and painless necrosis of the skin and soft tissue with the formation of large ulcers, commonly on the leg or arm. To date, 33 countries with tropical, subtropical and temperate climates in Africa, the Americas, Asia and the Western Pacific have reported cases of Buruli ulcer. The disease is rarely fatal, although it may lead to permanent disability and/or disfigurement if not treated appropriately or in time. It is the third most common mycobacterial infection in the world after tuberculosis and leprosy. The precise mode of transmission of M. ulcerans is yet to be elucidated. Nevertheless, it is possible that the mode of transmission varies with different geographical areas and epidemiological settings. The knowledge about the possible routes of transmission and potential animal reservoirs of M. ulcerans is poorly understood and still remains patchy. Infectious diseases arise from the interaction of agent, host and environment. The majority of emerging or remerging infectious disease in human populations is spread by animals: either wildlife, livestock or pets. Animals may act as hosts or reservoirs and subsequently spread the organism to the environment or directly to the human population. The reservoirs may or may not be the direct source of infection for the hosts; however, they play a major role in maintenance of the organism in the environment, and in the mode of transmission. This remains valid for M. ulcerans. Possums have been suggested as one of the reservoir of M. ulcerans in south-eastern Australia, where possums ingest M. ulcerans from the environment, amplify them and shed the organism through their faeces. We conducted a systematic review with selected key words on PubMed and INFORMIT databases to aggregate available published data on animal reservoirs of M. ulcerans around the world. After certain inclusion and exclusion criteria were implemented, a total of 17 studies was included in the review. A variety of animals around the world e.g., rodents, shrews, possums (ringtail and brushtail), horses, dogs, alpacas, koalas and Indian flap-shelled turtles have been recorded as being infected with M. ulcerans. The majority of studies included in this review identified animal reservoirs as predisposing to the emergence and reemergence of M. ulcerans infection. Taken together, from the selected studies in this systematic review, it is clear that exotic wildlife and native mammals play a significant role as reservoirs for M. ulceran

Improving Buruli ulcer control:steps towards decentralized care

The studies presented in this thesis were conducted in Benin, one of the countries in West Africa most affected by Buruli ulcer. We contributed in various ways to improve detection and management of Buruli ulcer, and describe the evolution of the epidemiology and pathogenicity of Buruli ulcer in Benin. We present the results of the evaluation of a novel diagnostic confirmation test for Buruli ulcer, as well as the effectiveness of a pilot project of decentralization of care as a strategy for the control of Buruli ulcer. We discuss the role of surgery in the treatment of Buruli ulcer through a randomized clinical trial to assess the effect of postponing the decision to include surgical treatment in the management of Buruli ulcer, and through a survey on surgical practice in different hospitals providing care for Buruli ulcer patients

Hosts and transmission of Mycobacterium ulcerans: a systematic review

The control of Buruli ulcer (BU), a debilitating neglected tropical disease, is hampered by the inadequate understanding of the mode of transmission of its causative agent, Mycobacterium ulcerans (M. ulcerans). The DNA of M. ulcerans has been detected in some living organisms and non-living environmental samples of both aquatic and terrestrial sources. However, it is unclear whether the identified organisms support in vivo multiplication of the bacterium or play any role in its transmission. This paper identifies hosts of M. ulcerans, reviews progress made in unravelling the exact mode of transmission of M. ulcerans and identifies research gaps in this aspect of BU epidemiology. Using the search terms, ‘niche, Mycobacterium ulcerans’ and ‘mode of transmission, Mycobacterium ulcerans’ as well as defined inclusion criteria, information was obtained from the PubMed database and reviewed to assess their importance to the research question. Aquatic bugs of the genera Appasus and Diplonychus as well as Naucoris cimicoides and possums were identified to support in vivo multiplication of the bacterium. Bite of M. ulcerans contaminated Aedes notoscriptus, bite of aquatic bugs harboring or contaminated with M. ulcerans, and M. ulcerans contaminated skin-puncturing materials present in nature create opportunity for its transmission and infection. Appropriate protective measures may be useful to reduce the risk of exposure to M. ulcerans in BU endemic areas, and incorporation of trophic interactions of aquatic organisms known to support in vivo multiplication of M. ulcerans is needed in future research for better understanding of the spread of M. ulcerans in nature. French title: Hôtes et transmission de Mycobacterium ulcerans: une revue systématique   Le contrôle de l'ulcère de Buruli (UB), une maladie tropicale négligée débilitante, est entravé par la compréhension insuffisante du mode de transmission de son agent causal, Mycobacterium ulcerans (M. ulcerans). L'ADN de M. ulcerans a été détecté dans certains organismes vivants et des échantillons environnementaux non vivants de sources aquatiques et terrestres. Cependant, il n'est pas clair si les organismes identifiés favorisent la multiplication in vivo de la bactérie ou jouent un rôle dans sa transmission. Cet article identifie les hôtes de M. ulcerans, passe en revue les progrès réalisés pour démêler le mode exact de transmission de M. ulcerans et identifie les lacunes de la recherche dans cet aspect de l'épidémiologie de l'UB. À l'aide des termes de recherche « niche, Mycobacterium ulcerans » et « mode de transmission, Mycobacterium ulcerans » ainsi que des critères d'inclusion définis, des informations ont été obtenues à partir de la base de données PubMed et examinées pour évaluer leur importance pour la question de recherche. Des punaises aquatiques des genres Appasus et Diplonychus ainsi que Naucoris cimicoides et possums ont été identifiées pour soutenir la multiplication in vivo de la bactérie. La piqûre d'Aedes notoscriptus contaminé par M. ulcerans, la piqûre d'insectes aquatiques hébergeant ou contaminés par M. ulcerans et les matériaux de perforation de la peau contaminés par M. ulcerans présents dans la nature créent une opportunité de transmission et d'infection. Des mesures de protection appropriées peuvent être utiles pour réduire le risque d'exposition à M. ulcerans dans les zones d'endémie UB, et l'incorporation d'interactions trophiques d'organismes aquatiques connus pour favoriser la multiplication in vivo de M. ulcerans est nécessaire dans les recherches futures pour une meilleure compréhension de la propagation de M. ulcerans dans la nature. &nbsp

Laboratory diagnosis of Buruli ulcer : challenges and future perspectives

Current options to control Buruli ulcer (BU) are limited, as no effective vaccine is available and knowledge on transmission mechanisms of the causative agent, Mycobacterium ulcerans, is incomplete. Early case detection and rapid initiation of treatment are key elements to prevent the development of large, disfiguring ulcers often associated with permanent physical disability and stigma. BU has been reported from 34 countries, with the greatest disease burden in West Africa and steadily increasing case numbers in south-eastern Australia. The disease can present in a variety of clinical manifestations, including relatively unspecific, painless nodules, plaques, and edema, which may eventually progress to chronic, ulcerative lesions. The clinical diagnosis of BU is therefore complicated by a broad differential diagnosis, particularly in tropical areas, where the prevalence of other skin conditions with a similar appearance is high. With the introduction of combination antibiotic therapy, replacing excision surgery as the standard treatment for BU, pre-treatment confirmation of the clinical diagnosis has further gained in importance to avoid the redundant use of anti-mycobacterial drugs. At present, available confirmatory diagnostic tests either lack sufficient sensitivity/specificity or are centralized and thus often not accessible to patients living in remote, rural areas of Africa. In recognition of this disparity, WHO and other stakeholders have called for new diagnostic tools for BU that can be applied at district hospitals or primary healthcare facilities. This chapter highlights challenges, advances and future prospects for the necessary decentralization of the diagnosis of BU