Abstract
BackgroundBuruli ulcer (BU), caused by Mycobacterium ulcerans (M. ulcerans), is a necrotizing skin disease found in more than 30 countries worldwide. BU incidence is highest in West Africa; however, cases have substantially increased in coastal regions of southern Australia over the past 30 years. Although the mode of transmission remains uncertain, the spatial pattern of BU emergence in recent years seems to suggest that there is an environmental niche for M. ulcerans and BU prevalence.Methodology/Principal FindingsNetwork analysis was applied to BU cases in Victoria, Australia, from 1981–2008. Results revealed a non-random spatio-temporal pattern at the regional scale as well as a stable and efficient BU disease network, indicating that deterministic factors influence the occurrence of this disease. Monthly BU incidence reported by locality was analyzed with landscape and climate data using a multilevel Poisson regression approach. The results suggest the highest BU risk areas occur at low elevations with forested land cover, similar to previous studies of BU risk in West Africa. Additionally, climate conditions as far as 1.5 years in advance appear to impact disease incidence. Warmer and wetter conditions 18–19 months prior to case emergence, followed by a dry period approximately 5 months prior to case emergence seem to favor the occurrence of BU.Conclusions/SignificanceThe BU network structure in Victoria, Australia, suggests external environmental factors favor M. ulcerans transmission and, therefore, BU incidence. A unique combination of environmental conditions, including land cover type, temperature and a wet-dry sequence, may produce habitat characteristics that support M. ulcerans transmission and BU prevalence. These findings imply that future BU research efforts on transmission mechanisms should focus on potential vectors/reservoirs found in those environmental niches. Further, this study is the first to quantitatively estimate environmental lag times associated with BU outbreaks, providing insights for future transmission investigations.
Highlights
Buruli Ulcer Disease Buruli ulcer disease (BU), reported within the top three most frequent human mycobacterial diseases [1], is a rapidly emerging yet neglected tropical disease
The null hypothesis ‘Ho = the actual BU network is random’ was rejected at a significance level of 99%. These findings indicate that the BU network structure was not random, i.e., stable, and due to the presence of supernodes, the network was efficient for disease transfer
The efficient and stable properties of the BU network in Victoria indicate that BU incidence will not likely diminish on its own and is readily transmitted throughout the region
Summary
Buruli Ulcer Disease Buruli ulcer disease (BU), reported within the top three most frequent human mycobacterial diseases [1], is a rapidly emerging yet neglected tropical disease. BU is endemic in at least 32 tropical and subtropical countries around the world, but most severely impacts areas of sub-Saharan Africa [1,2]. The disease is caused by infection with the environmental pathogen Mycobacterium ulcerans (M. ulcerans) and primarily affects the skin, often progressing without pain or fever to the patient [3]. Symptoms can range from a painless, mobile nodule underneath the skin to, if left untreated, large skin ulcerations and sometimes osteomyelitis, a severe bone infection [3]. Buruli ulcer (BU), caused by Mycobacterium ulcerans (M. ulcerans), is a necrotizing skin disease found in more than 30 countries worldwide. The mode of transmission remains uncertain, the spatial pattern of BU emergence in recent years seems to suggest that there is an environmental niche for M. ulcerans and BU prevalence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
