Studying Relationships between Environment and Malaria Incidence in Camopi (French Guiana) through the Objective Selection of Buffer-based Landscape Characterisations

International Journal of Health GeographicsInternational Journal of Health Geographics, 2011, Volume 10, Number 1

Aurélia Stefani, Emmanuel Roux, Jean-Marie Fotsing, and Bernard Carme

“Background: Malaria remains a major health problem in French Guiana, with a mean of 3800 cases each year. A previous study in Camopi, an Amerindian village on the Oyapock River, highlighted the major contribution of environmental features to the incidence of malaria attacks. We propose a method for the objective selection of the best multivariate peridomestic landscape characterisation that maximises the chances of identifying relationships between environmental features and malaria incidence, statistically significant and meaningful from an epidemiological point of view.

“Methods: A land-cover map, the hydrological network and the geolocalised inhabited houses were used to characterise the peridomestic landscape in eleven discoid buffers with radii of 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 metres. Buffer-based landscape characterisations were first compared in terms of their capacity to discriminate between sites within the geographic space and of their effective multidimensionality in variable space. The Akaike information criterion (AIC) was then used to select the landscape model best explaining the incidences of P. vivax and P. falciparum malaria. Finally, we calculated Pearson correlation coefficients for the relationships between environmental variables and malaria incidence, by species, for the more relevant buffers.

“Results: The optimal buffers for environmental characterisation had radii of 100 m around houses for P. vivax and 400 m around houses for P. falciparum. The incidence of P. falciparum malaria seemed to be more strongly linked to environmental features than that of P. vivax malaria, within these buffers. The incidence of P. falciparum malaria in children was strongly correlated with proportions of bare soil (r = -0.69), land under high vegetation (r = 0.68) and primary forest (r = 0.54), landscape division (r = 0.48) and the number of inhabited houses (r = -0.60). The incidence of P. vivax malaria was associated only with landscape division (r = 0.49).

“Conclusions: The proposed methodology provides a simple and general framework for objective characterisation of the landscape to account for field observations. The use of this method enabled us to identify different optimal observation horizons around houses, depending on the Plasmodium species considered, and to demonstrate significant correlations between environmental features and the incidence of malaria.”

Using Geographic Information Systems (GIS) in Spatial Analysis of Mortuary Practices in the Kellis 2 Cemetery, Dakhleh Oasis, Egypt

Master’s thesis, University of Central Florida, Summer term 2011

Heba Abd Elsalam

“This thesis focuses on the use of geographic information systems (GIS) to examine mortuary practices in the Romano-Byzantine period Kellis 2 cemetery located in the Dakhleh Oasis, Egypt. The first research objective examines the relationship between age, sex and grave substructures of 701 burials in Kellis 2 cemetery. The aim of this research objective was to determine if the presence and style of grave substructures were influenced by sex or age.

Map of the Kellis 2 Cemetery

Map of the Kellis 2 Cemetery

“Although not statistically significant, GIS analysis revealed that most of the graves in the Kellis 2 cemetery have no associated substructures, but of those that did have associated substructures, adult male burials were more likely to have a substructure than adult females or juveniles. Moreover, males and females aged from 22 to 50 years were more likely to have an associated substructure than younger and older individuals. In the juvenile age categories, newborns and children aged 1 to 5 years were more likely to have an associated substructure than the other juvenile age categories. This may be related to the second research objective which focused on the spatial relationship between infant and adult burials in the Kellis 2 cemetery. The second objective was to determine if infants were more likely to be buried between two adults, perhaps representing family units. GIS and statistical analysis revealed that the infants in the Kellis 2 cemetery were more likely to be buried closer to each other or to adult females than to adult males. Of those 25 infants buried between two adults most of them were either buried between two adult females, or between an adult male and female. Only three infants were found buried between two males. Interestingly, many of the adult females buried in close proximity with an infant were of child-bearing age. GIS was a very useful tool for examining questions of mortuary practices, particularly in examining spatial relationships between variables recorded for the Kellis 2 cemetery.”