A Multiscalar Analysis of Buruli Ulcer in Ghana: Environmental and Behavioral Factors in Disease Prevalence

Buruli ulcer (BU), an infectious disease caused by Mycobacterium ulcerans, is the third most common mycobacterial disease after leprosy and tuberculosis and a WHO-defined neglected tropical disease. Despite years of research, the mode of transmission of BU remains unknown. This master’s thesis provides an integrated spatial analysis of disease dynamics in Ghana, West Africa, an area of comparatively high BU incidence. Within a case/matched control study design, environmental factors associated with BU infection and spatial behaviors are investigated to uncover possible links between individual daily activity spaces and terrains of risk across disturbed landscapes. This research relies upon archival and field-collected data and analyses conducted with geographical information systems (GIS)

ASUSat1: The Development of a Low-Cost Nano-Satellite

In October 1993, the students at Arizona State University (ASU) were challenged by Orbital Sciences Corporation to develop a 4.5-kg (10-lb) satellite (ASUSat1) to be launched as a piggyback payload on a Pegasus rocket. The challenge also included the requirements for the satellite to perform meaningful science and to fit inside the Pegasus avionics section (0.033 m2 X 0.027 m). Moreover, the students were faced with the cost constraints associated with university projects. This unusual set of requirements resulted in a design and development process, which is fundamentally different from that of traditional space projects. The spacecraft capabilities and scientific mission evolved in an extremely rigid environment where cost, size and weight limits were set before the design process even started. In the ASUSat1 project, severe constraints were determined first, and then a meaningful scientific mission was chosen to fit those constraints. This design philosophy can be applied to future satellite systems. In addition, the ASUsat1 program demonstrates that universities can provide an open-minded source for the innovative nano-spacecraft technologies required for the next generation of low-cost missions, as well as an economical testbed to evaluate those technologies. At the same time, the program provides hands-on training for the space scientists and engineers of the future

Buruli Ulcer Disease and Its Association with Land Cover in Southwestern Ghana.

BACKGROUND:Buruli ulcer (BU), one of 17 neglected tropical diseases, is a debilitating skin and soft tissue infection caused by Mycobacterium ulcerans. In tropical Africa, changes in land use and proximity to water have been associated with the disease. This study presents the first analysis of BU at the village level in southwestern Ghana, where prevalence rates are among the highest globally, and explores fine and medium-scale associations with land cover by comparing patterns both within BU clusters and surrounding landscapes. METHODOLOGY/PRINCIPAL FINDINGS:We obtained 339 hospital-confirmed BU cases in southwestern Ghana between 2007 and 2010. The clusters of BU were identified using spatial scan statistics and the percentages of six land cover classes were calculated based on Landsat and Rapid Eye imagery for each of 154 villages/towns. The association between BU prevalence and each land cover class was calculated using negative binomial regression models. We found that older people had a significantly higher risk for BU after considering population age structure. BU cases were positively associated with the higher percentage of water and grassland surrounding each village, but negatively associated with the percent of urban. The results also showed that BU was clustered in areas with high percentage of mining activity, suggesting that water and mining play an important and potentially interactive role in BU occurrence. CONCLUSIONS/SIGNIFICANCE:Our study highlights the importance of multiple land use changes along the Offin River, particularly mining and agriculture, which might be associated with BU disease in southwestern Ghana. Our study is the first to use both medium- and high-resolution imagery to assess these changes. We also show that older populations (≥ 60 y) appear to be at higher risk of BU disease than children, once BU data were weighted by population age structures

Early Pleistocene stratigraphy, sedimentary environments, and formation contexts at Dmanisi in the Georgian Caucasus

International audienc

Iron Regulatory Proteins Mediate Host Resistance to Salmonella Infection

SummaryMacrophages are essential for systemic iron recycling, and also control iron availability to pathogens. Iron metabolism in mammalian cells is orchestrated posttranscriptionally by iron-regulatory proteins (IRP)-1 and -2. Here, we generated mice with selective and combined ablation of both IRPs in macrophages to investigate the role of IRPs in controlling iron availability. These animals are hyperferritinemic but otherwise display normal clinical iron parameters. However, mutant mice rapidly succumb to systemic infection with Salmonella Typhimurium, a pathogenic bacterium that multiplies within macrophages, with increased bacterial burdens in liver and spleen. Ex vivo infection experiments indicate that IRP function restricts bacterial access to iron via the EntC and Feo bacterial iron-acquisition systems. Further, IRPs contain Salmonella by promoting the induction of lipocalin 2, a host antimicrobial factor that inhibits bacterial uptake of iron-laden siderophores, and by suppressing the ferritin iron pool. This work reveals the importance of the IRPs in innate immunity

The association of BU prevalence and land cover classes in different spatial extents using spatial lag regression models.

<p>The two models with smaller AIC values from the negative binomial regression analysis were selected for spatial lag regression analysis. The dependent variable is the natural logarithm -transformed number of BU cases in each village. The covariates are the percentages of land cover classes in a buffer in different distances.</p

Land cover map of the primary BU cluster based on the classification of the Rapid Eye image.

<p>Bottom inset shows extent of satellite imagery within the cluster. The area has a few villages/towns with a high number of BU cases, e.g. Ayanfuri and Pokukrom.</p

Spatial distribution and spatial cluster of BU cases and prevalence.

<p>The map to the left shows the spatial distribution of BU cases in each village/town. The large yellow circle is the primary cluster of BU disease, which is located at 5.930°N and 1.861°W with a radius of 22.94 km. It includes 33 villages and 174 BU cases. The map to the right is the spatial distribution of BU prevalence in each village/town. The prevalence is calculated using the number of BU cases divided by the population in each village.</p

The study extent used to assess the relationship between Buruli Ulcer and land use in southwest Ghana.

<p>The study extent was determined by the Landsat images, which covered ~95% of the villages/towns with BU cases in the clinical dataset.</p

The association of BU prevalence and land cover classes at different spatial extents using negative binomial regression models.

<p>The dependent variable is the natural logarithm-transformed number of BU cases in each village with the natural logarithm-transformed population in each village as an offset. The covariates are the percentages of land cover classes in a buffer in different distances. For each buffer distance, the results of the model with a smaller AIC value were presented.</p