Aquatic macroinvertebrate assemblages of Ghana, West Africa: understanding the ecology of a neglected tropical disease.

Buruli ulcer (BU) is an emerging, but neglected tropical disease, where there has been a reported association with disturbed aquatic habitats and proposed aquatic macroinvertebrate vectors such as biting Hemiptera. An initial step in understanding the potential role of macroinvertebrates in the ecology of BU is to better understand the entire community, not just one or two taxa, in relation to the pathogen, Mycobacterium ulcerans, at a large spatial scale. For the first time at a country-wide scale this research documents that M. ulcerans was frequently detected from environmental samples taken from BU endemic regions, but was not present in 30 waterbodies of a non-endemic region. There were significant differences in macroinvertebrate community structure and identified potential indicator taxa in relation to pathogen presence. These results suggest that specific macroinvertebrate taxa or functional metrics may potentially be used as aquatic biological indicators of M. ulcerans. Developing ecological indicators of this pathogen is a first step for understanding the disease ecology of BU and should assist future studies of transmission.

Effectiveness of wound cleansing treatments on maggot (Diptera, Calliphoridae) mortality.

Myiasis is defined as an infestation of the organs and/or tissues of human and other animals by fly maggots. Fly species that normally breed in meat or carrion (Diptera: Calliphoridae, Sarcophagidae) may become involved in cutaneous myiasis by colonizing preexisting wounds. Reports of human wound myiasis contracted in hospitals and nursing homes, especially when patients are chronically ill or bed-ridden, are not uncommon across North America and often result in cases of neglect and civil litigation. Based on a case history dealing with this latter situation and circumstances surrounding the treatment of maggot infestation, we designed an experiment to assess the effectiveness of wound cleansing solutions on maggot mortality. Treatments, consisting of four commonly used cleaning solutions (isopropyl alcohol, Dakin's solution, iodine, and hydrogen peroxide) and a control (deionized water), were applied to experimental units (n=5), with each unit consisting of groups of actively feeding Lucilia sericata maggots (Diptera: Calliphoridae). Every 24h, treatments were applied and mortality was assessed for the duration of the study (14 days). Total mean mortality increased over the duration of the experiment, with an initial large increase (10-25%) after the first treatment application, followed by a gradual increase over the remainder of the study. General differences among treatments indicated greatest mean total mortality for Dakin's solution (sodium hypochlorite) (46%), followed by isopropyl alcohol (42%), Betadine (37%), hydrogen peroxide (33%) and lowest mortality for the control (25%); however, no statistically significant differences were observed among treatments and no treatment resulted in 100% maggot mortality. Traditional wound cleansing solutions may not be sufficient for maggot infestations of pre-existing wounds and supplemental treatments may be necessary to effectively treat cases of wound myiasis.

Aquatic invertebrates as unlikely vectors of Buruli ulcer disease.

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 field 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 significant differences were found in hemipteran abundance or pathogen positivity between disease-endemic and non-disease-endemic sites, and between abundance of biting hemipterans and M. ulcerans positivity. Therefore, although infection through insect bites is possible, little field evidence supports the assumption that biting hemipterans are primary vectors of M. ulcerans.

Distribution of Mycobacterium ulcerans in buruli ulcer endemic and non-endemic aquatic sites in Ghana.

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.