Small mammals particularly rodents, are considered the primary natural hosts of plague. Literature suggests that plague persistence in natural foci has a root cause in soils. The objective of this study was to investigate the relationship between on the one hand landforms and associated soil properties, and on the other hand small mammals and fleas in West Usambara Mountains in Tanzania, a plague endemic area. Standard field survey methods coupled with Geographical Information System (GIS) technique were used to examine landform and soils characteristics. Soil samples were analysed in the laboratory for physico-chemical properties. Small mammals were trapped on pre-established landform positions and identified to genus/species level. Fleas were removed from the trapped small mammals and counted. Exploration of landform and soil data was done using ArcGIS Toolbox functions and descriptive statistical analysis. The relationships between landforms, soils, small mammals and fleas were established by generalised linear regression model (GLM) operated in R statistics software. Results show that landforms and soils influence the abundance of small mammals and fleas and their spatial distribution. The abundance of small mammals and fleas increased with increase in elevation. Small mammal species richness also increases with elevation. A landform-soil model shows that available phosphorus, slope aspect and elevation were statistically significant predictors explaining richness and abundance of small mammals. Fleas' abundance and spatial distribution were influenced by hill-shade, available phosphorus and base saturation. The study suggests that landforms and soils have a strong influence on the richness and evenness of small mammals and their fleas' abundance hence could be used to explain plague dynamics in the area. _________________________________________________________________________________________

Previous studies suggest that rodent burrows, a proxy for rodent population are important for predicting plague risk areas. However, studies that link landform, surface attributes and rodent burrows in the Western Usambara Mountains in Tanzania are scanty. Therefore, this study was conducted in plague endemic area of the Western Usambara Mountains in northern, Tanzania, to explore the relationship between rodent burrows, and landform and surface attributes. The study was carried out in three areas corresponding to high (Lokome), medium (Lukozi) and low (Mwangoi) frequency of reported plague cases. Data were collected from 117, 200 and 170 observation sites for Lokome, Lukozi and Mwangoi, respectively using 100 m x 200 m quadrats. Remote sensing and field surveys were used to collect data on landform and surface attributes. Rodent burrows were surveyed and quantified by counting the number of burrows in 20m x 20m grids demarcated on the main 100m x 200m quadrats. The collected data were analysed in R software using boosted regression trees (BRT) technique. Rodent burrows were found at an elevation of above 1600m in the high and medium plague frequency landscapes. No burrows were found in the low plague frequency landscape situated below 1500m. BRT analysis shows a significant relationship between landform characteristics and rodent burrows in both high and medium plague frequency landscapes. Overall, elevation and hillshade are the most important determinants of rodent burrow distribution in the studied landscapes. It is concluded that in high altitudes, specific landform attributes (hill-shade, slope, elevation) and vegetation cover-favour rodent burrowing.

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Literature suggests that higher resolution remote sensing data integrated in Geographic Information System (GIS) can provide greater possibility to refine the analysis of land cover and terrain characteristics for explanation of abundance and distribution of plague hosts and vectors and hence of health risk hazards to humans. These technologies are not widely used in East Africa for studies on diseases including plague. The objective of this study was to refine the analysis of single and combined land cover and terrain characteristics in order to gain an insight into localized plague infection risks in the West Usambara Mountains in north-eastern Tanzania. The study used a geospatial approach to assess the influence of land cover and terrain factors on the abundance and spatial distribution of plague hosts (small mammals) and plague vectors (fleas). It considered different levels of scale and resolution. Boosted Regression Tree (BRT) statistical method was used to clarify the relationships between land cover and terrain variables with small mammals and fleas. Results indicate that elevation positively influenced the presence of small mammals. The presence of fleas was clearly influenced by land management features such as miraba. Medium to high resolution remotely sensed data integrated in a GIS have been found to be quite useful in this type of analysis. These findings contribute to efforts on plague surveillance and awareness creation among communities on the probable risks associated with various landscape factors during epidemics. ________________________________________________________________________________________

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Heterogeneity in the landscapes of West Usambara Mountains on land use and human activities has been reported. However, the interface of land use patterns and human modified soils with small mammal and flea abundance for possible explanation of plague has not been explored. This study was carried out to determine the link between anthropogenic soils and land use patterns on small mammal and flea abundance and the occurrence of reported plague in the Western Usambara Mountains in Tanzania. Standard soil survey methods were used to identify and describe soils and land use patterns on lower slopes and valley bottoms on which the surrounding villages are reported to have high and medium plague frequencies. The identified soils were characterised in terms of their morphological and physico-chemical properties and classified according to FAO-World Reference Base for Soil Resources. Small mammals were trapped on the same landscape positions and identified to genus/species level. Fleas were removed from the trapped small mammals, counted and identified to species level. In total 57 small mammals were captured from which 32 fleas were collected. Results show that human settlements and mixed cultivation on lower slopes and continuous vegetable cropping in the valley bottoms are dominant land use types. Intensive use of forest soils, manuring and irrigation on farms in the studied landscapes have contributed to the development of uniquely human modified soils namely Hortic Anthrosols in the lower slopes and Plaggic Irragric Hortic Anthrosols in valley bottoms. The identified anthropogenic soils and land use patterns are associated with high abundance of small mammals (Mastomys natalensis) and flea species (Xenopsylla brasiliensis and Dinopsyllus lypusus). This phenomenon is vividly apparent in the villages with medium to high plague frequencies. The study suggests that plague surveillance programmes should consider the existing relationship between anthropogenic soils, land use patterns, small mammal and flea abundance. _____________________________________________________________________________________

Indigenous soil and water conservation (SWC) technologies such as miraba (rectangular grass strip bounds that do not necessarily follow contours) and micro ridges have been used widely in the Usambara Mountains, Tanzania. However, their strengths and limitations to crop productivity have not been investigated. This study aimed to determine soil fertility and crop yield variability under

A study was carried out to examine distribution of salt affected soils by types and extent in the Ndungu Agricultural Development Project (NADP) area of Tanzania. The objective was to generate information to guide salt-affected soil management for sustainable rice production. Conventional methods including use of mini-pits and profile pits, coupled with farmers’ experiences were used to characterise soil. A total of seven randomly selected soil profile pits located in major soils were dug and described. Soil was sampled from natural horizons for laboratory analysis. In addition a total of 158 topsoil (0 – 20 cm depth) composites soil samples were randomly collected from 90 sites of NADP project area for laboratory analysis. Results showed that a few blocks (block is a piece of farm of 6 to 12 acres) had high exchangeable sodium percentage and high levels of bicarbonates, indicating salt-affected soils. Soil pH, exchangeable sodium percentage (ESP), and electrical conductivity of soil paste extract (ECe) values as high as 9.06, 28.7 cmol(+)Nakg-1, and 14dSm-1 were measured. Out of 90 blocks, 10 blocks (11%) showed slight to strong salt effects. Two blocks (2%) has been abandoned, and in some cultivated blocks zero yields were recorded due to salt content. The different levels of salinity development in the project area suggest site-specific remediation and appropriate management options be developed to improve crop production. These include rehabilitation of the irrigation infrastructure, use of farmyard manure as a soil amendment and growing salt-tolerant rice varieties. Furthermore, it is important to create awareness among farmers of the problem of salt-affected soil on rice productivity.