Soils And Human Health
: The Investigation Of Soil Variables Associated With Podoconiosis In North West Cameroon, And Their Detection By Hyperspectral Remote Sensing

  • Harriet Gislam

Student thesis: Doctoral Thesis


Podoconiosis is a neglected tropical disease, which results in lower leg lymphoedema. The inflammatory disease is caused by long-term contact with irritant particles in the soil. Identifying podoconiosis risk at a national level has been achieved in several studies using environmental factors associated with podoconiosis such as elevation and precipitation. However, from those studies it has been acknowledged that podoconiosis occurrence is variable among areas predicted as high risk. The genetic aspect of the disease may account for some of the local variation; however, it is also likely that the occurrence or abundance of irritant particles could be impacting local variation. There has been no conclusive agreement on the irritant particle which causes podoconiosis. The present study investigates potential podoconiosis associated soil variables in North West Cameroon and assesses the ability to predict the abundance of these soil variables using remote sensing techniques.

The study utilises two approaches to identify podoconiosis associated soil variables. The first approach uses North West Cameroon podoconiosis disease data and ground-sampled mineralogical and chemical soil point samples. Geospatial and statistical analysis is carried out on these datasets.

The second approach uses macrophage cell lines to measure the inflammatory response of cells treated with mineral and soil sample stimuli. The pathogenesis of podoconiosis is not fully understood, however, the NLRP3 inflammasome is key to many other sterile inflammatory diseases. Therefore, the NLRP3 inflammasome response of podoconiosis-associated minerals and podoconiosis endemic soil samples was investigated.

Lastly, the study assesses the capability of using advanced hyperspectral remote sensing techniques to predict the abundances of the potential podoconiosis associated soil properties, which were identified in the previous analysis chapters. The study utilises synthetic data based on PRISMA hyperspectral band characteristics and real mineral proportion values collected at the North West Cameroon study site.

The study identified several soil variables which are potentially associated with podoconiosis in North West Cameroon, which included quartz, mica, potassium feldspar, Ba, Be, K, Na, Rb, Sr, and Tl. However, the strength of these associations was acknowledged as weak to moderate. The macrophage analysis identified kaolinite and smectite as potential activators of the NLRP3 pathway. Finally, the study develops a hyperspectral remote sensing methodology to detect potential podoconiosis soil covariates. A new method was introduced to overcome the absence of pure endmembers, by using mixed signatures as inputs into linear unmixing models. The new method predicts the abundance of minerals with distinct diagnostic absorption features captured by the hyperspectral data.
Date of AwardOct 2022
Original languageEnglish
SupervisorNiall Burnside (Supervisor), Matthew Brolly (Supervisor), Gail Davey (Supervisor) & Kebede Deribe (Supervisor)

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