Mycobacterium ulcerans, the causative agent of Buruli ulcer, is an emerging environmental bacterium in Australia and West Africa. The primary risk factor associated with Buruli ulcer is proximity to slow moving water. Environmental constraints for disease are shown by the absence of infection in arid regions of infected countries. A particularly mysterious aspect of Buruli ulcer is the fact that endemic and non-endemic villages may be only a few kilometers apart within the same watershed. Recent studies suggest that aquatic invertebrate species may serve as reservoirs for M. ulcerans, although transmission pathways remain unknown. Systematic studies of the distribution of M. ulcerans in the environment using standard ecological methods have not been reported. Here we present results from the first study based on random sampling of endemic and non-endemic sites. In this study PCR-based methods, along with biofilm collections, have been used to map the presence of M. ulcerans within 26 aquatic sites in Ghana. Results suggest that M. ulcerans is present in both endemic and non-endemic sites and that variable number tandem repeat (VNTR) profiling can be used to follow chains of transmission from the environment to humans. Our results suggesting that the distribution of M. ulcerans is far broader than the distribution of human disease is characteristic of environmental pathogens. These findings imply that focal demography, along with patterns of human water contact, may play a major role in transmission of Buruli ulcer.

The continual demand for freshwater by industry (e.g. tourism) and agriculture, a growing population, and increasing development over the past 100 years has resulted in the construction of diversions within many streams of Hawaii. The main objective of this study was to evaluate the impact of stream diversions on riffle macroinvertebrate communities. Benthic macroinvertebrate larval populations were compared above and below a diversion in Iao Stream, Maui, Hawaii, from April to August 2000. During this summer approximately 92-97% of daily stream flow was diverted from Iao Stream. Three taxa, Procanace sp. (Diptera: Canacidae), Atyoida bisulcata (Crustacea: Decapoda), and Amphipoda (Crustacea), were only collected above the diversion. However, the most numerous taxa, Chironomidae (63-64% of the total macroinvertebrate community), Hydroptila arctia (Trichoptera: Hydroptilidae; 15%), and Cheumatopsyche pettiti (Trichoptera: Hydropsychidae; 8%), were found both above and below the diversion. The relative percentage abundance of these dominant taxa remained relatively consistent above and below the diversion over the study period. However, the mean total density of individual dominant taxa was greater above the diversion. The mean total macroinvertebrate density above the diversion was 46% greater than below the diversion (Student t-test: df = 30, t = −3.22, p > 0.01). No correlation was found between temperature and density. A positive correlation was detected between Froude number and mean total macroinvertebrate density. Overall, the reduction in macroinvertebrate diversity and in individual and total density below the diversion suggest that trophic interactions, and thus energy flow, could be affected by reduced flow in Hawaiian streams. The information gained from this study will contribute to knowledge on Hawaiian stream ecosystems, help to create minimum instream flow standards for stream restoration, and will provide information for future freshwater management issues on the Hawaiian islands.

Buruli ulcer is a necrotizing skin disease caused by Mycobacterium ulcerans and associated with exposure to aquatic habitats. To assess possible transmission of M. ulcerans by aquatic biting insects, we conducted a fi eld examination of biting water bugs (Hemiptera: Naucoridae, Belostomatidae, Nepidae) in 15 disease-endemic and 12 non-disease-endemic areas of Ghana, Africa. From collections of 22,832 invertebrates, we compared composition, abundance, and associated M. ulcerans positivity among sites. Biting hemipterans were rare and represented a small percentage (usually <2%) of invertebrate communities. No signifi cant differences were found in hemipteran abundance or pathogen positivity between disease-endemic and nondisease-endemic sites, and between abundance of biting hemipterans and M. ulcerans positivity. Therefore, although infection through insect bites is possible, little fi eld evidence supports the assumption that biting hemipterans are primary vectors of M. ulcerans. M ycobacterium ulcerans infection is an emerging skin disease often called Buruli ulcer (BU). Infection results in illness and lasting negative socioeconomic effects in rural areas of the tropics and subtropics (1). The pathologic changes, clinical signs and symptoms, and treatment have been reviewed elsewhere (2-5). In this article we evaluate fi eld evidence for the potential of aquatic invertebrates to be vectors of M. ulcerans.The exact mode of BU transmission remains unknown; however, past epidemiologic studies have associated BU with human activity near, or within, slow-fl owing or standing water bodies that have been created or disturbed by humans (2-4). Although several water-related risk factors have been recognized, none has been consistently reported, making it diffi cult to identify specifi c water-related risk activities (6-8). Most studies suggest that infection occurs through inoculation of M. ulcerans into skin lesions or insect bites (2,4,9-11). Portaels et al. (11) were the fi rst to propose that aquatic insects might serve as vectors of M. ulcerans. This hypothesis maintains that M. ulcerans is found in biofi lms of aquatic habitats and concentrated by grazing or fi lter-feeding invertebrates that are then consumed by predators known to bite humans (11). Initial evidence for this hypothesis used PCR detection of the insertion sequence IS2404 to document M. ulcerans' association with biting water bugs (Hemiptera), fi ltered concentrates of water, detritus, and aquatic plants (4,(12)(13)(14). These studies were important for understanding the possible environmental reservoirs of M. ulcerans. However, IS2404 is now understood to be not specifi c for M. ulcerans because this insertion sequence has been found in a number of other aquatic mycobacterial species, including M. marinum (15)(16)(17). When more discriminatory methods based on detection of variable number tandem repeats were used, many IS2404-positive environmental samples were reported to lack M. ulcerans (18). In light of these recent fi ndings, the relative fr...

1. We examined whether the anthropogenic degradation of wetlands leads to homogenization of the biota at local and ⁄ or landscape scales and, if so, what specific factors account for such an effect. We compared 16 isolated wetlands (Michigan, U.S.A.) that varied in surrounding land use: half had developed, and half undeveloped, riparian zones. Samples of macrophytes, epiphytic diatoms, zooplankton, macroinvertebrates and water chemistry were collected along three transects in each wetland. 2. Developed wetlands were more nutrient-rich with higher Cl concentrations. The plant community at developed sites was dominated by Lemnaceae (duckweed), while undeveloped wetlands were dominated by rooted, floating-leaved vegetation and sensitive plant species. Undeveloped wetlands contained heterogeneous and species-rich plant communities, greater species richness of zooplankton and diatoms, and heterogeneous zooplankton distributions as compared to developed sites. 3. A comparison among wetlands showed that diatom and zooplankton assemblages in developed wetlands were nested subsets of richer biota found in less developed wetlands. Conversely, plant communities were more heterogeneously distributed among developed wetlands at the landscape level. This may be attributable to patchy invasions by exotic species, which were a feature of the degraded wetlands within developed landscapes. 4. Our results indicate that several taxonomic groups showed similar, probably interdependent, responses to wetland degradation and habitat homogenization at both the local and landscape scales. This change in community structure from a species-rich and heterogeneous community dominated by floating-leaved plants in undeveloped wetlands, to nutrient-rich wetlands dominated by duckweed may represent a shift to an alternate stable state.