River Njoro Research Articles

Impact of Weirs on Decomposition Rates of Dombeya goetzenii (K. Schum) Leaf Litter in the River Njoro, Kenya

Water storage impoundments have deleterious effects on the structure and functioning of running water ecosystems. Many studies have been undertaken on the impacts of large impoundments on river ecosystems. However, comparatively few researches have determined the impact of small weirs on the functioning and structure of running water ecosystems. The main objective of the current study was to determine the impact of weirs on the decomposition rates of Dombeya goetzenii leaf litter in the Njoro River. The study was undertaken at five study sites located along the middle reaches of the Njoro River, near Egerton University, between November 2021 and January 2022. Four study sites were situated at upstream and downstream areas (i.e., approximately 10 m) of two weirs (i.e., Treetops and Canning weirs). A reference site was situated approximately 100 m upstream from the impoundment of the first weir. Physicochemical factors such as temperature, conductivity and nutrients (e.g., nitrates, ammonium) were determined at each study site. Additionally, decomposition rates of one of the most common tree species (i.e., Dombeya goetzenii) found growing along the Njoro River were determined. Leaf litter decomposition was determined using fine (100 µm) and coarse (500 µm) mesh litter bags and the negative exponential decay model was used to estimate decomposition rates (-k per day). The mean leaf litter decomposition rate was highest at the reference site (-k/day = 0.04) and lowest (-k/day = 0.02) at the upstream side of the first weir (i.e., Treetops weir).Leaf litter decomposition rates differed significantly (p = 0.002) between the aforementioned sites. Weirs had a significant local effect on the decomposition rates of Dombeya goetzenii leaf litter. The study provides crucial information to managers of riverine ecosystems about the impact of water storage weirs on an ecosystem function. The concerned government agencies should take action to prevent negative effects of weirs on riverine ecosystems.

Seasonal Variations in Surface Water Quality in River Njoro and Lake Nakuru, Kenya

Water pollution from rivers and lakes has resulted in serious environmental issues on a global scale. The public's growing concern over the decline in river and lake water quality makes it more important than ever to assess the water quality of these bodies of water over a prolonged period of time. During the rainy and dry seasons of 2022, 120 water samples were collected from 5 monitoring stations located within River Njoro and Lake Nakuru. The samples underwent physicochemical analysis of selected water parameters, which included salinity, temperature, pH, turbidity, total nitrogen (TN), total phosphorus (TP), electric conductivity (EC), and total dissolved solids (TDS). The results were compared using the National Environmental Management Authority (NEMA) of Kenya's guidelines and the results showed that the water quality of the Njoro river and Lake Nakuru fluctuated with the seasons, particularly in the lower water column of river Njoro. The quality parameters had the following values; EC values range between 73.33 ± 0.55 μs/cm - 533.33 ± 0.64 - μs/cm, respectively for both seasons; Salinity values range from 0.085 ± 0.02 ppt - 2.59 ± 0.03 ppt; pH values were between 8.8 – 9.3; Temperature was 23.69 ± 0.07 °C – 14.22± 0.07°C; Turbidity varied significantly – 13.95 ± 0.27 NTU - 36.03 ± 0.35 NTU; TDS between 46.67 ± 0.11 ppm- 243.33 ± 0.04 ppm; TN ranges between 5.97 ± 3.24 mg/L - 8.57 ± 3.18 mg/L and TP 7.49 ± 1.7-9.41 ± 1.84 mg/L in the dry and rainy seasons, for River Njoro and Lake Nakuru respectively. This study showed that the degree to which human activity affects water quality varies with the season. Therefore, most of these factors should be considered while controlling rivers downstream in order to ensure the health of aquatic life, also it is essential to increase lake water quality monitoring and regulate human activity. Additionally, the results revealed that water pollution resulted primarily from domestic wastewater, agricultural runoff and industrial effluents.

Settlement Schemes and their Implication on Eastern Mau Water Catchment, Kenya

Settlement schemes are aimed at settling landless people and those displaced by disasters to support socio-economic and environmental development of a country. Eastern Mau Forest Reserve is an important water catchment that has settlement schemes established, which has led to encroachments and degradation of the catchment. This paper, therefore, assesses the implications of human settlements on Eastern Mau water catchment by examining the trends in land use/cover change and river flows for four decades. Primary data was collected from key informant interviews based on purposive sampling whereas secondary data was derived from Landsat satellite images over a 10-year period and analysed using Maximum Likelihood Function from ArcGIS. Data on river flows from River Njoro was obtained from Water Resources Authority Office in Nakuru. Rainfall and temperature data were obtained from Kenya Meteorological Station in Nakuru. Time series analysis is used to understand the trend in river flows over time while Pearson correlation is used to determine relationship between farmlands and river flows. The results indicate a sharp decline in forest cover by 42.7% and an increase in farmlands by 41%. Dense vegetation and farmlands have an inverse relationship as an increase in farmlands lead to a decrease in forest cover. People have settled beyond the established settlement schemes boundaries leading to encroachment and drying up of some rivers. There is also an increase in rainfall and river flows over the years, with monthly river flows increasing in peak flows and declining during low seasons. There is a positive correlation between farmlands and river flows between 1989 and 2020. There is need for regeneration of encroached areas and defining boundary of Eastern Mau to allow initiatives and interventions that help with sustainable management of the catchment area.

Assessment of performance of wastewater stabilization ponds using faecal indicator bacteria reduction efficiency in a tropical environment

Egerton University (EU) uses Wastewater Stabilization Ponds (WSPs) for wastewater treatment. An adjoining wetland with gravel bed substrate and freesurface flow meant to polish discharge before releasing into River Njoro is currently non-operational. The current study aimed at establishing the performance of WSPs in terms of concentration and reduction efficiencies of Faecal Indicator Bacteria (FIB); Total Coliforms (TC) and Escherichia coli (E. coli). Wastewater samples were collected weekly for one month from mid- November to mid-December 2017. Total Coliforms and E. coli were isolated using selective and differential media following Membrane Filtration (MF) method. Colonies were cultured on Chromocult Coliform Agar (CCA) and enumerated using standard procedures for examination of water and wastewater. The results were expressed as Colony Forming Units (CFUs) per 100 ml of the original sample. The inlet showed highest concentration of FIB which reduced along the treatment pathway. Total Coliforms and E. coli ranged between 2.5 × 108 - 2.9 × 1011 and 5.9 × 105 - 1.8 × 1010 CFUs/100 ml respectively with cumulative reduction efficiencies between 2 to 4 log units for E. coli and 2 to 3 log units for TC in the two maturation ponds. Although concentration of FIB in EU WSPs reduces along the treatment pathway, the effluent quality is above recommended international standards for discharge into surface waters. The trend is attributed to lack of frequent monitoring, insufficient maintenance, together with short- circuiting effect due to by-passing of wastewater in the design of the new pond system.

Assessing the Impact of land-use types on the groundwater quality: a case study of Mid River Njoro Catchment, Kenya

The study assessed the impact of land-use types on the groundwater quality of the mid River Njoro catchment, Kenya. Groundwater samples were collected from eight boreholes between the period of October 2017 to February 2018 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen, nitrate, ammonium, and total phosphorus. These parameters were used to calculate the Groundwater Quality Index (GQI) value of the study area. The concentration maps (“primary maps I”) were constructed using Kriging interpolation of ArcGIS software from the seven groundwater quality parameters. The “primary maps I” were standardized with the KEBS and WHO standards to the “primary maps II” for ease of integration into a GIS environment. The “primary maps II” were then rated and weighted using a polynomial function to generate “rank maps” before calculating the GQI using spatial analyst tools of ArcGIS software. The land use map was prepared from a high-resolution Google earth satellite imagery of 2015. The mean GQI values for the different land use polygons were calculated and compared using GIS techniques. The GQI ranged from 68.38 to 70.92, indicating a high groundwater quality of mid River Njoro catchment. The major land-use types identified include settlement area, forest cover, agricultural land and mixed area. The agricultural land dominated the study area, followed by settlement area, forest cover and finally mixed area. The mean GQI value in each land use type varied minimally and this could be because of the diffuse nature of the land use types of the study area. Settlement area had low GQI, followed by agricultural land, mixed area and the forest cover had the highest mean GQI value, which corresponds to good quality of groundwater. Even though the variation is insignificant in this particular study, it somehow indicates the adverse effects of different land use on the quality of groundwater.

Stratigraphy and Fluoride Levels Variation in Borehole Water: A Case of River Njoro Catchment

Boreholes are main sources of water for human use in the Rift Valley. However these boreholes have fluoride levels higher than the World Health Organization (WHO) recommended levels of 1.5 mg/l and consequently have raised serious health issues. This study sought to determine the relationship between borehole stratigraphy and fluoride levels in ground water in river Njoro catchment. This study adopted purposive longitudinal survey. The study adopted descriptive analysis of the borehole stratigraphy characteristics and fluoride levels recorded. The sources of data included; field surveys which were used to collect data on the borehole fluoride levels data and qualitative analysis of the stratigraphy data. From the results of the study, it was observed that the fluoride levels in boreholes in river Njoro catchment were dependent on the stratigraphy matrix of the boreholes. Therefore lithological formations have an influence on fluoride level River Njoro catchment. This study will form a pool of knowledge to other researchers who have an interest in the study of fluoride occurrence in ground water in the Rift Valley. Further the study will help in assisting the drillers in decision making after geological surveys of where to locate the boreholes.

Impact of Human Settlement on Land Use/Land Cover Changes in the Middle River Njoro Sub Watershed in Kenya

This study investigated the use of remote sensing and GIS in evaluating the impacts of human settlement on land use /Land cover changes. The study also investigated the drivers behind the change in the middle of River Njoro sub watershed for a period of 27 years. Drivers of land use change were captured by the use of DPSIR model where Drivers (D) represented human needs, Pressures (P), human activities, State (S), the ecosystem, Impact (I) services from the ecosystem and Response (R), the decisions taken by land users. Land sat MSS and Land sat ETM+ (path 185, row 31) were used in this study. The Land sat ETM+ image (June 1987, May, 2000 and July, 2014) was downloaded from USGS Earth Resources Observation Systems data website. Remote sensing image processing was performed by using ERDAS Imagine 9.1. Three land use/land cover (LULC) classes were established as Human settlement, forest and shrub land. Severe land cover changes was found to have occurred from 1987-2000, where human settlement increased by 52%, shrub land reduced by 19%, and forestry reduced by 72%. In the year 2000 – 2014, human settlement increased by 121%, shrub land reduced by 45%, and forestry reduced by 64%. Forestry and shrub land were found to be consistently reducing while human settlement was increasing. It was evident from the images that the LULC changes with corresponding soil quality deterioration mostly occurred in the upper and middle parts of the Middle river Njoro sub watershed which were initially under forest. To minimize the risk of vegetation destruction and soil degradation, it will be necessary to identify socioeconomic safety nets and initiate restoration of the environment to original pre- catastrophe status.

Heterogeneity in Event-Based Soil Hydrologic Response to Different Land Use Types in Upper River Njoro Catchment, Kenya

Soil hydrologic response depends on the soil characteristics such as infiltration capacity, porosity, organic matter content and bulk density. Knowledge on the dynamics of these soil parameters and soil hydrologic response as a result of different land use types is crucial for formulation and adoption of proper soil and water conservation techniques for increased agricultural production. In this research, soil hydrologic response to different land use types is evaluated. Four land use types were purposely selected. These included natural forest, deforested land, fallow agricultural land and grassland. Soil samples were collected and soil hydraulic and hydrological properties that included soil texture, bulk density, saturated hydraulic conductivity, porosity and organic matter content were determined in the soil laboratory. The evaluated soil hydrological response parameters included runoff coefficients, infiltration rate, water repellency and ponding time. The findings showed that the highest and lowest mean bulk density of 1.36 and 0.96 g/cm3 was recorded for deforested and natural forest land respectively. The highest mean saturated hydraulic conductivity (170.21cm/day), porosity (0.62) and organic matter content (4.63%) were observed in the natural forest while the lowest values (24.78cm/day, 0.47 and 0.75%) respectively were found in the deforested land. High water repellency (100.34 cm/hr) and runoff coefficient (0.0077) was recorded in the deforested areas. The findings of this indicate how different land use types affect on-site hydrologic response and generation of stream flow in the catchment hence providing baseline data for future soil and water relations research.

Effect of Magnetic Flux Density on the Population of Salmonella Species in River Njoro Water

In this study, the experimental results of the concentration of Salmonella species in water exposed to magnetic flux density are presented. Water samples were collected from River Njoro, Nakuru County, Kenya. The initial Salmonella species counts for the samples were obtained using Membrane Filtration techniques. The samples were then exposed to different magnetic flux densities (2mT, 6mT and 10mT) at time intervals of 6 hours and 18 hours for each magnetic flux. Membrane filtration was also done after magnetic treatment of the samples. The data obtained was photographed and presented in tables and bar graphs. The maximum disinfection efficiency was 77 % for bacteria exposed to a magnetic flux of 10 mT for 6 hours. This study proved that magnetic field can be used as inhibitory factor against the Salmonella species.

Effects of Magnetic Flux Density on the Population of Escherichia coli in River Njoro Water

In this study, the experimental results of the concentration of Escherichia coli in water exposed to magnetic flux density are presented. Water samples were collected from River Njoro, Nakuru County, Kenya. The initial Escherichia coli (E.coli) counts for the samples were obtained using Membrane Filtration techniques. The samples were then exposed to different magnetic flux densities (2mT, 6mT and 10mT) at time intervals of 6 hours and 18 hours for each magnetic flux. Membrane filtration was also done after magnetic treatment of the samples. The data obtained was photographed and presented in tables and bar graphs. The maximum disinfection efficiency was 82.2% for bacteria exposed to a magnetic flux of 10 mT for 6 hours. This study proved that magnetic field can be used as inhibitory factor against the E.coli.

Linking landforms and land use to land degradation in the Middle River Njoro Watershed

Land degradation is the decline in the productive capacity of an ecosystem. This mainly occurs due to processes induced by human activities, such as deforestation, poor farming practices, or enhanced industrial growth leading to various land degradation processes such as, flooding, drought and accelerated erosion. The objective of the study was to link landforms and land uses to land degradation. Soils in the catchments were distinguished on the basis of Physiographic, parent material/ geology and soil characteristics. Eight soil mapping units were identified in the area. The validity of the identified soil mapping units were checked in the field using auger hole, mini pits, road and erosion cut observations. Representative profile pits were sighted in the major mapping units. The profile pits were described according to FAO (1977) and Kenya Soil Survey (1987). Soil classification was done according to FAO/UNESCO (1997). Soil mapping units were found to follow soil physiographic units/ land forms. Soils on mountains and hills were found to be somewhat excessively drained, shallow to moderately deep. Those from uplands and plateaus were well drained, deep to very deep. Soils on plains fell on two extremes; those that were well drained, deep to very deep and those that were imperfectly drained to poorly drained, moderately deep to very deep. Physical, chemical and biological land degradation was found to take place in the different physiographic units/ land forms at varying degrees. Soil erosion, nutrient depletion and vegetation depletion were found to be the most important degradation processes. Soil, physiographic units, soil susceptibility and hazard maps were drawn and their classes in the different landforms established.

Effects of land use and management on aggregate stability and hydraulic conductivity of soils within River Njoro Watershed in Kenya

There has been tremendous changes in land use and management in the River Njoro Watershed during the last three decades. Formerly large scale farms have been converted into smallholder farms and plantation forests have gradually been lost. These changes in land use and management have brought in different approaches that have triggered soil erosion and other forms of land degradation. The objective of this study was to trace the changes in land use and determine their effects on aggregate stability and hydraulic conductivity. A semi detailed soil survey of the watershed was undertaken following a three-tier approach comprising image interpretation, field surveys and laboratory analysis. The measured variables in the soil were analysed using ANOVA and correlation analysis. The major land uses were found to be forestland, agricultural land, grassland, and wetland. A strong soil type _ landscape relationship was observed within the watershed. Soils of slopes were moderately to severely eroded, shallow and less developed whereas those on summits, pen plains, uplands, plateaus and valleys were deep and well developed. Aggregate stability was the highest in forestland and decreased in the order of grassland, agricultural land and wetland respectively. The mean weight diameter under the various land use conditions was 0.68, 0.64, 0.58, and 0 41 respectively. Hydraulic conductivity was the highest in forest-land and decreased in the order of agricultural land, grassland and wetland respectively. There was significant negative correlation between hydraulic conductivity and the bulk density and clay content of the soils. Reduced aggregate stability and lowered hydraulic conductivity is likely to be responsible for some of the severe soil erosion and other forms of land degradation observed in the River Njoro Watershed.

Using the Soil and Water Assessment Tool (SWAT) to assess land use impact on water resources in an East African watershed

Summary Land cover and land use changes in Kenya’s Rift Valley have altered the hydrologic response of the River Njoro watershed by changing the partitioning of excess rainfall into surface discharge and groundwater recharge. The watershed contributes a significant amount of water to Lake Nakuru National Park, an internationally recognized Ramsar site, as well as groundwater supplies for local communities and the city of Nakuru. Three land use maps representing a 17-year period when the region underwent significant transitions served as inputs for hydrologic modeling using the Automated Geospatial Watershed Assessment (AGWA) tool, a GIS-based hydrologic modeling system. AGWA was used to parameterize the Soil and Water Assessment Tool (SWAT), a hydrologic model suitable for assessing the relative impact of land cover change on hydrologic response. The SWAT model was calibrated using observation data taken during the 1990s with high annual concordance. Simulation results showed that land use changes have resulted in corresponding increases in surface runoff and decreases in groundwater recharge. Hydrologic changes were highly variable both spatially and temporally, and the uppermost reaches of the forested highlands were most significantly affected. These changes have negative implications for the ecological health of the river system as well as Lake Nakuru and local communities.

Coupling agricultural non-point source (AgNPS) model and geographic information system (GIS) tools to predict peak runoff and sediment generation in the upper River Njoro catchment in Kenya

Human interference in the upper River Njoro catchment has led to the increased exposure of the land to accelerated erosion. An application that combined the capabilities of remote sensing, geographic information system (GIS) and agricultural non-point source (AgNPS) model was used to estimate peak runoff rate and sediment yield from the upper River Njoro catchment. Remotely sensed Landsat Thematic Mapper (TM) images were used to obtain land cover and associated AgNPS model input parameters. Other input parameters for the model were extracted from GIS layers using the agricultural non-point source-integrated land and water information system (AgNPS-ILWIS) interface. Surface water quantity and quality data including peak runoff and sediment yield of selected storm events were obtained from two gauging stations, within the catchment. Base flow separation was done so that measured direct peak runoff rate and sediment yield generated by direct runoff could be determined and compared directly with the model simulated results. Simulated peak runoff rates in Upstream (Treetop) station were satisfactory with an EFF of 0.78 and a percent error of 4.1%. The sediment yield was also reasonably estimated with an EFF of 0.88 and a 2% error. The downstream (Egerton) station results were also satisfactorily predicted with peak runoff rate having an EFF of 0.69 and a 5.5% error of estimates, while the estimated sediment yield had an EFF of 0.86 and a 2.5% error. Key words: Peak runoff, sediment, agricultural non-point source (AgNPS), geographic information system (GIS), integrated land and water information system (ILWIS), soil loss.

English

The purpose of this study was to investigate the presence of Aeromonas hydrophila at commonly used water collection points on the River Njoro and to determine the in-vitro antimicrobial susceptibility and plasmid profiles of isolates. In total, 126 samples were collected and 36.5% of them were positive for A. hydrophila. The A. hydrophila were recovered on membrane filters, cultured on Trypticase Soy agar, Bile aesculin agar and Aeromonas Medium agar. They were further characterized using cytochrome oxidase and API 20E tests. Detection of drug susceptibility was determined using modified disc diffusion method to ampicillin (25 μg), cefaclor (30 μg), ceftizoxime (30 μg), cefixime (5 μg), cefazidime (30 μg), gentamicin (200 μg), streptomycin (25 μg), chloramphenicol (50 μg), nalidixic acid (30 μg) and ciprofloxacin (1 μg). Most of the isolates showed multi-drug resistance to two or more antibiotics. Chloramphenicol, nalidixic acid, ciprofloxacin, cefazidime and cefixime were the most sensitive drugs with 100% efficacy whereas ampicillin, cefaclor and streptomycin were the most resistant drugs having 100, 67 and 50 resistance, respectively. There was low resistance against ceftizoxime (16.7%) and gentamicin (23.3%). These results indicates that all A. hydrophila isolated from River Njoro had complete resistance to ampicillin and showed variable resistance to cefaclor, streptomycin, gentamycin and ceftizoxime. R-plasmids were extracted from multi-drug resistance strains and separated by agarose gel (0.8%) electrophoresis for profiling. Plasmid profiling revealed that most of the multi-drug resistant isolates contained one plasmid of 21.0 kb. Although some strains exhibited different antimicrobial resistance patterns, all of their plasmids were of the same size (21.0 kb). However, there were no plasmids in the antimicrobial sensitive isolates. This study also indicates that plasmid 21.0 kb is common in A. hydrophila and is important for antimicrobial resistance and virulence. Further studies are required to ascertain the role of this plasmid as a virulence marker.

Disaggregating human population for improved land use management in Kenya

Understanding the spatial distribution of population across a landscape is important in land use planning. In developing nations, where resources are limited, such information can facilitate more efficient decision-making for resource allocations. This article examines three methods for characterizing the distribution of human population within a natural boundary that overlaps but is substantially different from the geography of the corresponding census data. Using land cover information in conjunction with available census data, simple areal weighting, binary dasymetric mapping, and global regression methods are tested. Strengths and weaknesses of each technique are discussed. Our findings offer a new population estimate for the River Njoro watershed in Kenya and suggest that census data alone are inadequate for many resource management decisions. At the same time, however, care must be taken to account for the spatial characteristics of the environment when developing a model for improved estimates of population distribution.

New Common Ground in Pastoral and Settled Agricultural Communities in Kenya: Renegotiated Institutions and the Gender Implications

Against the backdrop of climate change, population increase and changing economic and social structures, this article analyzes dynamic interactions between Maasai pastoralists and settled agricultural communities in River Njoro Watershed, Kenya. Here, policy changes led to transition of land ownership from communal to private ownership, creating a new institutional environment and abetting modification of institutions governing sharing of resources. Primary data used in the study were collected from settled farmers and pastoralists. Changing property rights from communal to individual holdings have forced communities to modify their indigenous communal institutional arrangements and renegotiate gender roles to cope with the changing property rights. As a result, women's workload has increased and their traditional control of resources has slipped; hence, they have sought new alternatives to meet traditional obligations. Therefore, they have negotiated new identities within family and community institutions. Men, on the other hand, are gaining from the private property rights regime.

Observing Changes in Riparian Buffer Strip Soil Properties Related to Land Use Activities in the River Njoro Watershed, Kenya

Riparian buffer strip guidelines are under scrutiny in the River Njoro Watershed in Kenya. This study investigated soil properties (bulk density, carbon, nitrogen, and phosphorus) in different land use types (small scale agriculture in recent settlements, mixed agriculture in established peri-urban settlements, large- scale commercial agriculture, and the gazetted forest reference condition) and their adjacent buffer strips. Bulk density, carbon, nitrogen, and phosphorus within 30-m riparian buffer strips adjacent to recent settlement landuseareasweresimilar tothoseofthegazettedforest reference condition, but only bulk density of the buffer strips adjacent to peri-urban and commercial agriculture land use areas were similar to the gazetted forest reference condition. Phosphorus is a sensitive indicator of the impacts of human activity, as increased concen- trations were observed with increasing scale of land use activity. For riparian buffers adjacent to recent settle- ments, soil phosphorus was significantly higher in buffers narrower than 30 m (5.01 mg P kg −1 )t han gazetted forest (3.40 mg P kg −1 )b ut not significantly different for riparian buffers wider than 30 m (3.81 mg P kg −1 ) compared to gazetted forest. Based on the research, it is recommended that policies governing riparian buffer strips become (1) stricter, with the current "maximum" of 30 m considered a minimum; and (2) adaptive, with 30 m used in small- scale agricultural areas, and wider riparian buffer strips used in medium- and large-scale agricultural areas.

Intermittent slow sand filtration for preventing diarrhoea among children in Kenyan households using unimproved water sources: randomized controlled trial

Measure effectiveness of intermittent slow sand filtration for reducing child diarrhoea among households using unimproved water sources in rural Kenya. A randomized controlled trail was conducted among populations meeting a high-risk profile for child diarrhoea from drinking river water in the River Njoro watershed. Intervention households (30) were provided the concrete BioSand Filter and instructed on filter use and maintenance. Control households (29) continued normal practices. Longitudinal monthly monitoring of diarrhoea (seven-day daily prevalence recall) and of influent, effluent, and drinking water quality for fecal coliform was conducted for 6 months. Intervention households had better drinking water quality than control households (fecal coliform geometric mean, 30.0 CFU vs. 89.0 CFU/100 ml, P < 0.001) and reported significantly fewer diarrhoea days (86 days over 626 child-weeks) compared to controls (203 days over 558 child-weeks) among children up to 15 (age-adjusted RR 0.46; 95 % CI = 0.22, 0.96). Greater child diarrhoea reduction due to the intervention (age-adjusted RR 0.23, 95 % CI = 0.10, 0.51) was observed among the sub-group using unimproved water sources all of the time. Intermittent slow sand filtration, a non-commercial technology, produces similar observed effects on child diarrhoea as commercial POU products, adding to the range of effective options for poor populations (chlorination, ceramic filtration, solar disinfection, flocculation/disinfection).

Identifying human and livestock sources of fecal contamination in Kenya with host-specific Bacteroidales assays

Microbial source tracking to distinguish between human, livestock and wildlife fecal pollution using molecular techniques is a rapidly evolving approach in many developed countries, but has not previously been applied on the African continent. DNA extracts from cow, donkey, and human fecal specimens and raw domestic sewage samples collected in Kenya were tested against five existing quantitative PCR assays designed to detect universal (2), human-specific (2), and cow-specific (1) fecal Bacteroidales genetic markers. Water samples from the River Njoro in Kenya were evaluated using the five tested Bacteroidales markers and a multi-species assay for Cryptosporidium in a preliminary exploration of fecal pollution sources and health risks in this watershed. Diagnostic sensitivity on the validation set varied from 18 to 100% for the five assays while diagnostic specificity was 100%. Of the 2 universal assays, Total Bacteroidales [Dick, L.K, Field, K.G., 2004. Rapid estimation of numbers of fecal Bacteroidetes by use of a quantitative PCR assay for 16S rRNA genes. Appl. Environ. Microbiol. 70, 5695–5697] showed lower generic fecal diagnostic sensitivity, at 55%, than BacUni-UCD, at 100%, in detecting fecal markers on the 42-sample validation set. Human-specific assay HF183 demonstrated 65% sensitivity overall, and 80% on the human sewage samples, compared to 18% overall and 0% sewage for human-specific assay BacHum-UCD. Cow-specific assay BacCow-UCD had 94% sensitivity. Testing of 18 water samples indicates cows are a likely predominant source of fecal contamination in the Njoro Watershed (78% prevailing rate). Probabilistic assessment of human assay results indicates at most three of the river water samples contained human Bacteroidales. Cryptosporidium spp. markers were detected in samples from nine of the 12 sampling locations. Evidence suggesting widespread contamination by cow feces and Cryptosporidium in the Njoro watershed raises serious concerns for human and animal health.