Vaccination efforts for Buruli Ulcer

BACKGROUND

Buruli ulcer is one of the most common mycobacterial diseases usually affecting poorer populations in tropical and subtropical environments. This disease, caused by M. ulcerans infection, has devastating effects for patients, with significant health and economic burden. Antibiotics are often used to treat affected individuals, but in most cases, surgery is necessary.

AREA COVERED

We present progress on Buruli ulcer vaccines and identify knowledge gaps in this neglected tropical disease.

EXPERT OPINION

The lack of appropriate infrastructure in endemic areas, as well as the severity of symptoms and lack of non-invasive treatment options, highlights the need for an effective vaccine to combat this disease. In terms of humoral immunity, it is vital to consider its significance and the magnitude to which it inhibits or slowdowns the progression of the disease. Only by answering these key questions will it be possible to tailor more appropriate vaccination and preventative provisions.

Epidemiology of Buruli Ulcer Infections, Victoria, Australia, 2011-2016

Buruli ulcer (BU) is a destructive soft-tissue infection caused by the environmental pathogen Mycobacterium ulcerans. In response to rising BU notifications in the state of Victoria, Australia, we reviewed all cases that occurred during 2011–2016 to precisely map the time and likely place of M. ulcerans acquisition. We found that 600 cases of BU had been notified; just over half were in residents and the remainder in visitors to defined BU-endemic areas. During the study period, notifications increased almost 3-fold, from 66 in 2013 to 182 in 2016. We identified 4 BU-endemic areas: Bellarine Peninsula, Mornington Peninsula, Frankston region, and the southeastern Bayside suburbs of Melbourne. We observed a decline in cases on the Bellarine Peninsula but a progressive increase elsewhere. Acquisitions peaked in late summer. The appearance of new BU-endemic areas and the decline in established areas probably correlate with changes in the level of local environmental contamination with M. ulcerans.

Decrease in Mycobacterium ulcerans disease (Buruli ulcer) in the Lalo District of Bénin (West Africa)

BACKGROUND

Buruli ulcer (BU) is a chronic, necrotizing infectious skin disease caused by Mycobacterium ulcerans. In recent years, there has been a decrease in the number of new cases detected. This study aimed to show the evolution of its distribution in the Lalo District in Bénin from 2006 to 2017.

METHODS

The database of the BU Detection and Treatment Center of Lalo allowed us to identify 1017 new cases in the Lalo District from 2006 to 2017. The annual prevalence was calculated with subdistricts and villages. The trends of the demographic variables and those related to the clinical and treatment features were analysed using Microsoft Excel® 2007 and Epi Info® 7. Arc View version® 3.4 was used for mapping.

RESULTS

From 2006 to 2017, the case prevalence of BU in the Lalo District decreased by 95%. The spatial distribution of BU cases confirmed the foci of the distribution, as described in the literature. The most endemic subdistricts were Ahomadégbé, Adoukandji, Gnizounmè and Tchito, with a cumulative prevalence of 315, 225, 215 and 213 cases per 10,000 inhabitants, respectively. The least endemic subdistricts were Zalli, Banigbé, Lalo-Centre and Lokogba, with 16, 16, 10, and 5 cases per 10,000 inhabitants, respectively. A significant decrease in the number of patients with ulcerative lesions (p = 0.002), as well as those with category 3 lesions (p < 0.001) and those treated surgically (p < 0.001), was observed. The patients confirmed by PCR increased (from 40.42% in 2006 to 84.62% in 2017), and joint limitation decreased (from 13.41% in 2006 to 0.0% in 2017).

CONCLUSION

This study confirmed the general decrease in BU prevalence rates in Lalo District at the subdistrict and village levels, as also observed at the country level. This decrease is a result of the success of the BU control strategies implemented in Bénin, especially in the Lalo District.

A survey on Mycobacterium ulcerans in Mosquitoes and March flies captured from endemic areas of Northern Queensland, Australia

Mycobacterium ulcerans is the causative agent of Buruli ulcer (BU). This nontuberculous mycobacterial infection has been reported in 34 countries worldwide. In Australia, the majority of cases of BU have been recorded in coastal Victoria and the Mossman-Daintree areas of north Queensland. Mosquitoes have been postulated as a vector of M. ulcerans in Victoria, however the specific mode of transmission of this disease is still far from being well understood. In the current study, we trapped and analysed 16,900 (allocated to 845 pools) mosquitoes and 296 March flies from the endemic areas of north Queensland to examine for the presence of M. ulcerans DNA by polymerase chain reaction. Seven of 845 pools of mosquitoes were positive on screening using the IS2404 PCR target (maximum likelihood estimate 0.4/1,000). M. ulcerans DNA was detected from one pool of mosquitoes from which all three PCR targets: IS2404, IS2606 and the ketoreductase B domain of mycolactone polyketide synthase gene were detected. None of the March fly samples were positive for the presence of M. ulcerans DNA.

The causative agent of Buruli ulcer is Mycobacterium ulcerans. This destructive skin disease is characterized by extensive and painless necrosis of skin and underlying tissues usually on extremities of body due to production of toxin named mycolactone. The disease is prevalent in Africa and coastal Australia. The exact mode of transmission and potential environmental reservoir for the pathogen still remain obscure. Aquatic and biting insects have been identified as potential niche in transmission and maintenance of pathogen in the environment. In this study we screened mosquitoes and march flies captured from endemic areas of northern Queensland for the presence of M. ulcerans DNA. We found seven pools of mosquito out of 845 pools positive for IS2404. In only one of the seven samples were the additional targets IS2606 and KR detected. None of the March fly samples were positive. The results could indicate a low burden of the bacteria in the environment coinciding with a comparatively low number of human cases of M. ulcerans infection seen during the trapping period of the study.

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.

Mycobacterium ulcerans disease management in Australian patients: the re-emergence of surgery as an important treatment modality

With the demonstration of the effectiveness of antibiotic treatment, the management of Mycobacterium ulcerans disease has changed from a predominantly surgically to a predominantly medically treated disease. However, research among Australian patients has revealed that antibiotic treatment alone is associated with prolonged wound healing times, high rates of treatment toxicity, and the potential for significant tissue destruction associated with severe paradoxical reactions. We present the current state of M. ulcerans management in Barwon Health, Australia, where a close working relationship exists between the Plastic Surgical and Infectious Diseases units. Here treatment has evolved based on nearly 20 years of experience gained from managing more around 600 patients from a M. ulcerans epidemic on the nearby Bellarine and Mornington Peninsulas. In our experience, surgery has re-emerged to play an important role in the treatment of M. ulcerans in improving the rate of wound healing, minimizing antibiotic associated toxicity and preventing further tissue loss associated with severe paradoxical reactions. For selected small lesions surgery without antibiotics may also be an effective treatment option, however aggressive surgical resection of lesions with wide margins through uninvolved tissue should no longer be performed. Furthermore, extensive excisional surgery that will require the use of split skin grafts and vascularized tissue flaps to repair skin defects should be avoided if possible.

Mycobacterium ulcerans DNA in Bandicoot Excreta in Buruli Ulcer-Endemic Area, Northern Queensland, Australia

To identify potential reservoirs/vectors of Mycobacterium ulcerans in northern Queensland, Australia, we analyzed environmental samples collected from the Daintree River catchment area, to which Buruli ulcer is endemic, and adjacent coastal lowlands by species-specific PCR. We detected M. ulcerans DNA in soil, mosquitoes, and excreta of bandicoots, which are small terrestrial marsupials.

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. ulcerans.

Comparative Genomics Shows That Mycobacterium ulcerans Migration and Expansion Preceded the Rise of Buruli Ulcer in Southeastern Australia

Since 2000, cases of the neglected tropical disease Buruli ulcer, caused by infection with Mycobacterium ulcerans, have increased 100-fold around Melbourne (population 4.4 million), the capital of Victoria, in temperate southeastern Australia. The reasons for this increase are unclear. Here, we used whole-genome sequence comparisons of 178 M. ulcerans isolates obtained primarily from human clinical specimens, spanning 70 years, to model the population dynamics of this pathogen from this region. Using phylogeographic and advanced Bayesian phylogenetic approaches, we found that there has been a migration of the pathogen from the east end of the state, beginning in the 1980s, 300 km west to the major human population center around Melbourne. This move was then followed by a significant increase in M. ulcerans population size. These analyses inform our thinking around Buruli ulcer transmission and control, indicating that M. ulcerans is introduced to a new environment and then expands, rather than it being from the awakening of a quiescent pathogen reservoir.IMPORTANCE Buruli ulcer is a destructive skin and soft tissue infection caused by Mycobacterium ulcerans and is characterized by progressive skin ulceration, which can lead to permanent disfigurement and long-term disability. Despite the majority of disease burden occurring in regions of West and central Africa, Buruli ulcer is also becoming increasingly common in southeastern Australia. Major impediments to controlling disease spread are incomplete understandings of the environmental reservoirs and modes of transmission of M. ulcerans The significance of our research is that we used genomics to assess the population structure of this pathogen at the Australian continental scale. We have then reconstructed a historical bacterial spread and modeled demographic dynamics to reveal bacterial population expansion across southeastern Australia. These findings provide explanations for the observed epidemiological trends with Buruli ulcer and suggest possible management to control disease spread.

The incubation period of Buruli ulcer (Mycobacterium ulcerans infection) in Victoria, Australia - Remains similar despite changing geographic distribution of disease

BACKGROUND

Buruli ulcer (BU) is a geographically-restricted infection caused by Mycobacterium ulcerans; contact with an endemic region is the primary risk factor for disease acquisition. Globally, efforts to estimate the incubation period of BU are often hindered as most patients reside permanently in endemic areas. However, in the south-eastern Australian state of Victoria, a significant proportion of people who acquire BU are visitors to endemic regions. During a sustained outbreak of BU on the Bellarine peninsula we estimated a mean incubation period of 4.5 months. Since then cases on the Bellarine peninsula have declined but a new endemic area has developed centred on the Mornington peninsula.

METHOD

Retrospective review of 443 cases of BU notified in Victoria between 2013 and 2016. Telephone interviews were performed to identify all cases with a single visit to an endemic region, or multiple visits within a one month period. The incubation period was defined as the time between exposure to an endemic region and symptom onset. Data were subsequently combined with those from our earlier study incorporating cases from 2002 to 2012.

RESULTS

Among the 20 new cases identified in short-term visitors, the mean incubation period was 143 days (4.8 months), very similar to the previous estimate of 135 days (4.5 months). This was despite the predominant exposure location shifting from the Bellarine peninsula to the Mornington peninsula. We found no association between incubation period and age, sex, location of exposure, duration of exposure to an endemic region or location of BU lesion.

CONCLUSIONS

Our study confirms the mean incubation period of BU in Victoria to be between 4 and 5 months. This knowledge can guide clinicians and suggests that the mode of transmission of BU is similar in different geographic regions in Victoria.

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.

Mycobacterium ulcerans in the Elderly: More Severe Disease and Suboptimal Outcomes

Background

The clinical presentation of M. ulcerans disease and the safety and effectiveness of treatment may differ in elderly compared with younger populations related to relative immune defficiencies, co-morbidities and drug interactions. However, elderly populations with M. ulcerans disease have not been comprehensively studied.

Methodology/Principal Findings

A retrospective analysis was performed on an observational cohort of all confirmed M. ulcerans cases managed at Barwon Health from 1/1/1998-31/12/2014. The cohort included 327 patients; 131(40.0%) ≥65 years and 196(60.0%) <65 years of age. Patients ≥65 years had a shorter median duration of symptoms prior to diagnosis (p<0.01), a higher proportion with diabetes (p<0.001) and immune suppression (p<0.001), and were more likely to have lesions that were multiple (OR 4.67, 95% CI 1.78–12.31, p<0.001) and WHO category 3 (OR 4.59, 95% CI 1.98–10.59, p<0.001). Antibiotic complications occurred in 69(24.3%) treatment episodes at an increased incidence in those aged ≥65 years (OR 5.29, 95% CI 2.81–9.98, p<0.001). There were 4(1.2%) deaths, with significantly more in the age-group ≥65 years (4 compared with 0 deaths, p = 0.01). The overall treatment success rate was 92.2%. For the age-group ≥65 years there was a reduced rate of treatment success overall (OR 0.34, 95% CI 0.14–0.80, p = <0.01) and when surgery was used alone (OR 0.21, 95% CI 0.06–0.76, p<0.01). Patients ≥65 years were more likely to have a paradoxical reaction (OR 2.06, 95% CI 1.17–3.62, p = 0.01).

Conclusions/Significance

Elderly patients comprise a significant proportion of M. ulcerans disease patients in Australian populations and present with more severe and advanced disease forms. Currently recommended treatments are associated with increased toxicity and reduced effectiveness in elderly populations. Increased efforts are required to diagnose M. ulcerans earlier in elderly populations, and research is urgently required to develop more effective and less toxic treatments for this age-group.

Mycobacterium ulcerans is an infection that can affect all age-groups. It causes necrosis of skin and soft-tissue often resulting in severe outcomes and long-term disability. However, due to the majority of infections worldwide occurring in children and young adults, there is a paucity of information available in elderly patients. It is important that elderly patients are not neglected as the clinical presentation and treatment outcomes may differ significantly from younger patients related to relative immune defficiencies, co-morbidities and increased potential for drug interactions. We specifically examined patients with M. ulcerans disease aged ≥ 65 years and showed that they comprise a significant proportion of patients affected in Australian populations. They present with more severe and advanced disease forms, and suffer from increased toxicity and reduced effectiveness of the currently recommended treatments. Therefore, our study demonstrates that increased efforts are required to diagnose M. ulcerans disease earlier in elderly populations, and that research is urgently required to develop more effective and less toxic treatments for this age-group.

The Buruli Ulcer

Buruli ulcer (BU) is caused by Mycobacterium ulcerans and can manifest as a simple nodule or as aggressive skin ulcers leading to debilitating osteoarthritis or limb deformity. The disease is more prevalent in those living in remote rural areas, especially in children younger than 15 years. The exact mode of transmission is possibly through traumatic skin lesions contaminated by M ulcerans. IS2404 polymerase chain reaction from ulcer swabs or biopsies is a rapid method for confirmation of BU. In coendemic countries, HIV infection complicates the progression of BU, leading to rapidly spreading osteomyelitis. Treatment is principally medical, with antitubercular drugs, and surgery is utilized for complicated disease. Because of ineffective vaccination, primary prevention is the best option for control of the disease.

Mycobacterium ulcerans infection imported from Australia to Missouri, USA, 2012

Buruli ulcer, the third most common mycobacterial disease worldwide, rarely affects travelers and is uncommon in the United States. We report a travel-associated case imported from Australia and review 3 previous cases diagnosed and treated in the United States. The differential diagnoses for unusual chronic cutaneous ulcers and those nonresponsive to conventional therapy should include Mycobacterium ulcerans infection.

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.

Clinical features and risk factors of oedematous Mycobacterium ulcerans lesions in an Australian population: beware cellulitis in an endemic area

INTRODUCTION

Oedematous lesions are a less common but more severe form of Mycobacterium ulcerans disease. Misdiagnosis as bacterial cellulitis can lead to delays in treatment. We report the first comprehensive descriptions of the clinical features and risk factors of patients with oedematous disease from the Bellarine Peninsula of south-eastern Victoria, Australia.

METHODS

Data on all confirmed Mycobacterium ulcerans cases managed at Barwon Health, Victoria, were collected from 1/1/1998-31/12/2012. A multivariate logistic regression model was used to assess associations with oedematous forms of Mycobacterium ulcerans disease.

RESULTS

Seventeen of 238 (7%) patients had oedematous Mycobacterium ulcerans lesions. Their median age was 70 years (IQR 17-82 years) and 71% were male. Twenty-one percent of lesions were WHO category one, 35% category two and 41% category three. 16 (94%) patients were initially diagnosed with cellulitis and received a median 14 days (IQR 9-17 days) of antibiotics and 65% required hospitalization prior to Mycobacterium ulcerans diagnosis. Fever was present in 50% and pain in 87% of patients. The WCC, neutrophil count and CRP were elevated in 54%, 62% and 75% of cases respectively. The median duration of antibiotic treatment was 84 days (IQR 67-96) and 94% of cases required surgical intervention. On multivariable analysis, there was an increased likelihood of a lesion being oedematous if on the hand (OR 85.62, 95% CI 13.69-535.70; P<0.001), elbow (OR 7.83, 95% CI 1.39-43.96; p<0.001) or ankle (OR 7.92, 95% CI 1.28-49.16; p<0.001), or if the patient had diabetes mellitus (OR 9.42, 95% CI 1.62-54.74; p = 0.02).

CONCLUSIONS

In an Australian population, oedematous Mycobacterium ulcerans lesions present with similar symptoms, signs and investigation results to, and are commonly mistakenly diagnosed for, bacterial limb cellulitis. There is an increased likelihood of oedematous lesions affecting the hand, elbow or ankle, and in patients with diabetes.

Treatment costs of Mycobacterium ulcerans in the antibiotic era

Mycobacterium ulcerans infection results in significant disfiguring morbidity, and treatment is expensive. To estimate the cost of treatment in the antibiotic era, a retrospective study of 71 patients diagnosed and treated for M. ulcerans in the Bellarine Peninsula (Victoria, Australia) between 1998 and 2006 was performed. Patients were categorised into minor single episode infection, major single episode infection and recurrent disease. Data were collected on each treatment cost component. To determine the change from costs in the pre-antibiotic era, mean direct costs were compared with those from a study in a nearby region between 1991 and 1998. All costs were in Australian dollars in 2006-2007 prices. The mean overall cost was $6181 per episode, with the highest cost components being hospitalisation (mean $3977; 63%) and surgeon fees ($949; 12%). Treatment costs per episode increased significantly from minor infection ($2235) to major infection ($6338) to recurrent disease ($13 372). Compared with the pre-antibiotic era, costs have significantly decreased, with a 52% reduction in overall cost per episode, driven mainly by a reduction in hospitalisation costs. Therefore, earlier diagnosis and treatment of M. ulcerans, including the use of outpatient-based oral antibiotic regimens, has the potential to reduce the cost of treatment.

The incubation period of Buruli ulcer (Mycobacterium ulcerans infection)

INTRODUCTION

Buruli Ulcer (BU) is caused by the environmental microbe Mycobacterium ulcerans. Despite unclear transmission, contact with a BU endemic region is the key known risk factor. In Victoria, Australia, where endemic areas have been carefully mapped, we aimed to estimate the Incubation Period (IP) of BU by interviewing patients who reported defined periods of contact with an endemic area prior to BU diagnosis.

METHOD

A retrospective review was undertaken of 408 notifications of BU in Victoria from 2002 to 2012. Telephone interviews using a structured questionnaire and review of notification records were performed. Patients with a single visit exposure to a defined endemic area were included and the period from exposure to disease onset determined (IP).

RESULTS

We identified 111 of 408 notified patients (27%) who had a residential address outside a known endemic area, of whom 23 (6%) reported a single visit exposure within the previous 24 months. The median age of included patients was 30 years (range: 6 to 73) and 65% were male. 61% had visited the Bellarine Peninsula, currently the most active endemic area. The median time from symptom onset to diagnosis was 71 days (range: 34-204 days). The midpoint of the reported IP range was utilized to calculate a point estimate of the IP for each case. Subsequently, the mean IP for the cohort was calculated at 135 days (IQR: 109-160; CI 95%: 113.9-156), corresponding to 4.5 months or 19.2 weeks. The shortest IP recorded was 32 days and longest 264 days (Figure 1 & 2). IP did not vary for variables investigated.

CONCLUSIONS

The estimated mean IP of BU in Victoria is 135 days (IQR: 109-160 days), 4.5 months. The shortest recorded was IP 34 days and longest 264 days. A greater understanding of BU IP will aid clinical risk assessment and future research.

Buruli ulcer disease in travelers and differentiation of Mycobacterium ulcerans strains from northern Australia

Buruli ulcer (BU) is a necrotizing infection of skin and soft tissue caused by Mycobacterium ulcerans. In Australia, most cases of BU are linked to temperate, coastal Victoria and tropical, northern Queensland, and strains from these regions are distinguishable by variable-number tandem repeat (VNTR) typing. We present an epidemiological investigation of five patients found to have been infected during interstate travel and describe two nucleotide polymorphisms that differentiate M. ulcerans strains from northern Australia.

Risk of Buruli ulcer and detection of Mycobacterium ulcerans in mosquitoes in southeastern Australia

BACKGROUND

Buruli ulcer (BU) is a destructive skin condition caused by infection with the environmental bacterium, Mycobacterium ulcerans. The mode of transmission of M. ulcerans is not completely understood, but several studies have explored the role of biting insects. In this study, we tested for an association between the detection of M. ulcerans in mosquitoes and the risk of BU disease in humans in an endemic area of southeastern Australia.

METHODOLOGY/PRINCIPAL FINDINGS

Adult mosquitoes were trapped in seven towns on the Bellarine Peninsula in Victoria, Australia, from December 2004 to December 2009 and screened for M. ulcerans by real-time PCR. The number of laboratory-confirmed cases of BU in permanent residents of these towns diagnosed during the same period was tallied to determine the average cumulative incidence of BU in each location. Pearson's correlation coefficient (r) was calculated for the proportion of M. ulcerans-positive mosquitoes per town correlated with the incidence of BU per town. We found a strong dose-response relationship between the detection of M. ulcerans in mosquitoes and the risk of human disease (r, 0.99; 95% CI, 0.92-0.99; p < 0.001).

CONCLUSIONS/SIGNIFICANCE

The results of this study strengthen the hypothesis that mosquitoes are involved in the transmission of M. ulcerans in southeastern Australia. This has implications for the development of intervention strategies to control and prevent BU.