Mycobacterium ulcerans Ecological Dynamics and Its Association with Freshwater Ecosystems and Aquatic Communities: Results from a 12-Month Environmental Survey in Cameroon

Abstract

Background Mycobacterium ulcerans (MU) is the agent responsible for Buruli Ulcer (BU), an emerging skin disease with dramatic socioeconomic and health outcomes, especially in rural settings. BU emergence and distribution is linked to aquatic ecosystems in tropical and subtropical countries, especially to swampy and flooded areas. Aquatic animal organisms are likely to play a role either as host reservoirs or vectors of the bacilli. However, information on MU ecological dynamics, both in space and time, is dramatically lacking. As a result, the ecology of the disease agent, and consequently its mode of transmission, remains largely unknown, which jeopardizes public health attempts for its control. The objective of this study was to gain insight on MU environmental distribution and colonization of aquatic organisms through time.Methodology/Principal FindingsLongitudinal sampling of 32 communities of aquatic macro-invertebrates and vertebrates was conducted from different environments in two BU endemic regions in Cameroon during 12 months. As a result, 238,496 individuals were classified and MU presence was assessed by qPCR in 3,084 sample-pools containing these aquatic organisms. Our study showed a broad distribution of MU in all ecosystems and taxonomic groups, with important regional differences in its occurrence. Colonization dynamics fluctuated along the year, with the highest peaks in August and October. The large variations observed in the colonization dynamics of different taxonomic groups and aquatic ecosystems suggest that the trends shown here are the result of complex ecological processes that need further investigation.Conclusion/PerspectivesThis is the largest field study on MU ecology to date, providing the first detailed description of its spatio-temporal dynamics in different aquatic ecosystems within BU endemic regions. We argue that coupling this data with fine-scale epidemiological data through statistical and mathematical models will provide a major step forward in the understanding of MU ecology and mode of transmission.

Experimental Survival of Mycobacterium ulcerans in Watery Soil, a Potential Source of Buruli Ulcer

“…1 Epidemiological studies conducted in West Africa traced to stagnant freshwater points. 2 Several studies have reported the detection of M. ulcerans DNA in stagnant freshwater 3,4 and aquatic environments. 5,6 Moreover, the only environmental M. ulcerans isolate was recovered from a water strider in Benin.…”

Seasonal Patterns of Buruli Ulcer Incidence, Central Africa, 2002–2012

“…B) M. ulcerans prevalencein the aquatic environment (percentage of M. ulcerans– positive samples) ( 14 ). C) Estimated abundance of M. ulcerans –positive hemipterans (expressed as % of maximum abundance) ( 14 ). D) Monthly median number of BU cases detected in the Akonolinga district, 2002–2012 (this study).…”

“…Variations in BU incidence result from variations in population exposure ( 13 ) combined with variations in environmental presence of M. ulcerans ( 14 ). We hypothesize that one of the main drivers of these variations is the seasonal flooding of the Nyong River, which rises 3–5 m from April through November, creating temporary bodies of water and swamps on a vast surface, deeply affecting the ecosystem.…”

Chemistry of natural waters and its relation to Buruli ulcer in Ghana

“…One might expect M. ulcerans, a slow-growing mycobacterium, to thrive in similar environments to those bacteria studied by Iivanainen et al (1993). Previous work has shown that the optimal pH growth range of M. ulcerans varies between 5.4 and 7.4 (Portaels and Pattyn, 1982), and that unlike many other mycobacteria, M. ulcerans has a preference for low oxygen conditions (Palomino et al, 1998;Garchitorena et al, 2014).…”

“…Garchitorena et al (2014) explored the spatial and temporal variation of M. ulcerans in a variety of aquatic ecosystems. They found that while low oxygen, high temperature swamps were a preferred location for M. ulcerans, colonization dynamics in aquatic systems varied throughout the year and were correlated to rainfall.…”