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Ren, Hang, Wei Guo, Zhenke Zhang, Leonard Musyoka Kisovi, and Priyanko Das. "Population Density and Spatial Patterns of Informal Settlements in Nairobi, Kenya." Sustainability 12, no. 18 (September 18, 2020): 7717. http://dx.doi.org/10.3390/su12187717.
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The widespread informal settlements in Nairobi have interested many researchers and urban policymakers. Reasonable planning of urban density is the key to sustainable development. By using the spatial population data of 2000, 2010, and 2020, this study aims to explore the changes in population density and spatial patterns of informal settlements in Nairobi. The result of spatial correlation analysis shows that the informal settlements are the centers of population growth and agglomeration and are mostly distributed in the belts of 4 and 8 km from Nairobi’s central business district (CBD). A series of population density models in Nairobi were examined; it showed that the correlation between population density and distance to CBD was positive within a 4 km area, while for areas outside 8 km, they were negatively related. The factors determining population density distribution are also discussed. We argue that where people choose to settle is a decision process between the expected benefits and the cost of living; the informal settlements around the 4-km belt in Nairobi has become the choice for most poor people. This paper ends with suggestions for urban planning and upgrading informal settlements. The findings will increase our understanding of urban population distribution in underdeveloped countries.
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Muyanga, Milu, and T. S. Jayne. "Effects of rising rural population density on smallholder agriculture in Kenya." Food Policy 48 (October 2014): 98–113. http://dx.doi.org/10.1016/j.foodpol.2014.03.001.
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Califf, Katy J., David S. Green, Aaron P. Wagner, Kim T. Scribner, Karen Beatty, Meredith E. Wagner, and Kay E. Holekamp. "Genetic relatedness and space use in two populations of striped hyenas (Hyaena hyaena)." Journal of Mammalogy 101, no. 2 (November 27, 2019): 361–72. http://dx.doi.org/10.1093/jmammal/gyz165.
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Abstract Surprising social complexity and variability have recently been documented in several mammalian species once believed to be strictly solitary, and variation in resource abundance may drive this variation in sociality. Wagner et al. (Wagner, A. P., S. Creel, L. G. Frank, and S. T. Kalinowski. 2007. Patterns of relatedness and parentage in an asocial, polyandrous striped hyena population. Molecular Ecology 16:4356–4369) reported unusual space-use patterns among female striped hyenas (Hyaena hyaena) in central Kenya, where pairwise relatedness among females increased with the geographic distance separating them. The authors suggested that this pattern, very rare among mammals, might reflect attempts by females to avoid competition with close relatives for scarce resources in areas of range overlap. Here, we compare those data to new data, documenting genetic relatedness and space use in a previously unstudied wild population of striped hyenas in southern Kenya. We tested hypotheses suggesting that resource abundance and population density affect patterns of genetic relatedness and geographic distance in this species. Our results suggest that higher per capita prey density results in relaxed competition for food, and greater social tolerance among female striped hyenas. A hypothesis suggesting lower population density in the southern population was not supported. Relaxed resource competition also may lead to female–female cooperation in the southern population; we documented for the first time behavioral evidence of den sharing by adult female striped hyenas. Our data indicate that different populations of this little-studied species exhibit behavioral plasticity; in this case, markedly different space-use patterns and patterns of spatial relatedness under different ecological conditions.
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Off, Eileen C., Lynne A. Isbell, and Truman P. Young. "Population Density and Habitat Preferences Of the Kenya Lesser Galago (Galago senegalensis braccatus) Along The Ewaso Nyiro River, Laikipia, Kenya." Journal of East African Natural History 97, no. 1 (January 2008): 109–16. http://dx.doi.org/10.2982/0012-8317(2008)97[109:pdahpo]2.0.co;2.
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Iyer, Hari S., John Flanigan, Nicholas G. Wolf, Lee Frederick Schroeder, Susan Horton, Marcia C. Castro, and Timothy R. Rebbeck. "Geospatial evaluation of trade-offs between equity in physical access to healthcare and health systems efficiency." BMJ Global Health 5, no. 10 (October 2020): e003493. http://dx.doi.org/10.1136/bmjgh-2020-003493.
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IntroductionDecisions regarding the geographical placement of healthcare services require consideration of trade-offs between equity and efficiency, but few empirical assessments are available. We applied a novel geospatial framework to study these trade-offs in four African countries.MethodsGeolocation data on population density (a surrogate for efficiency), health centres and cancer referral centres in Kenya, Malawi, Tanzania and Rwanda were obtained from online databases. Travel time to the closest facility (a surrogate for equity) was estimated with 1 km resolution using the Access Mod 5 least cost distance algorithm. We studied associations between district-level average population density and travel time to closest facility for each country using Pearson’s correlation, and spatial autocorrelation using the Global Moran’s I statistic. Geographical clusters of districts with inefficient resource allocation were identified using the bivariate local indicator of spatial autocorrelation.ResultsPopulation density was inversely associated with travel time for all countries and levels of the health system (Pearson’s correlation range, health centres: −0.89 to −0.71; cancer referral centres: −0.92 to −0.43), favouring efficiency. For health centres, negative spatial autocorrelation (geographical clustering of dissimilar values of population density and travel time) was weaker in Rwanda (−0.310) and Tanzania (−0.292), countries with explicit policies supporting equitable access to rural healthcare, relative to Kenya (−0.579) and Malawi (−0.543). Stronger spatial autocorrelation was observed for cancer referral centres (Rwanda: −0.341; Tanzania: −0.259; Kenya: −0.595; Malawi: −0.666). Significant geographical clusters of sparsely populated districts with long travel times to care were identified across countries.ConclusionNegative spatial correlations suggested that the geographical distribution of health services favoured efficiency over equity, but spatial autocorrelation measures revealed more equitable geographical distribution of facilities in certain countries. These findings suggest that even when prioritising efficiency, thoughtful decisions regarding geographical allocation could increase equitable physical access to services.
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Njuguna, Catherine Waithira, Hellen Wangechi Kamiri, John Robert Okalebo, Wilson Ngetich, and Syphilline Kebeney. "Evaluating the effect of plant population densities and nitrogen application on the leaf area index of maize in a reclaimed wetland in Kenya." Acta Universitatis Sapientiae, Agriculture and Environment 8, no. 1 (December 1, 2016): 139–48. http://dx.doi.org/10.1515/ausae-2016-0013.
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Abstract Maize is the main staple food in Kenya with over 90% of Kenyans relying on it. While the annual national consumption is increasing, the production of this crop has been on the decline in the last two decades. Maize production in Kenya fell by 33.4% in 2013 with Nyeri among the counties said to be grappling with the production of this crop. Land pressure is one of the major causes of decreased availability of food as well as soil depletion and encroachment upon fragile ecosystems such as wetlands. Nitrogen is a key nutrient in the production of maize, and its deficiency is a major factor limiting its production. This study investigated the effect of N application at 120 kg N/ha and maize density on the Leaf Area Index in reclaimed wetland soils in an experimental set-up comprising a randomized complete block design with three replications. The research was carried out in Nyeri County, Kenya. Leaf Area Index (LAI) was determined using the given SunScan formula. Measurements were done continuously until crop physiological maturity. Results indicated that the leaf area index increased with nitrogen application and reduced with spacing for most treatments. There were no significant differences between the two methods (Copy Method and SunScan). Leaf Area Index (LAI) was high in treatments containing nitrogen and high plant density. It was concluded that high plant density gives high LAI. 50 cm * 12.5 cm (-N) and 50 cm * 12.5 cm (+N) are the recommended plant densities for the site.
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Dominic, Kimani, Muchane Muchai, Johnstone Kimanzi, Joseph Mwangi, Wanyoike Wamiti, Samuel Bakari, Bernhard Walter, and Peter Njoroge. "Habitat structure determines the abundance of the Endangered Sharpe’s Longclaw Macronyx sharpei (Aves: Passeriformes: Motacillidae) at Timau montane grasslands in central Kenya." Journal of Threatened Taxa 12, no. 5 (April 26, 2020): 15565–71. http://dx.doi.org/10.11609/jott.5366.12.5.15565-15571.
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Understanding the habitat selection and structure of a species is critical for developing evidence-centered conservation actions. Sharpe’s Longclaw Macronyx sharpei, a passerine bird endemic to Kenya, is threatened by reductions in habitat size and quality that have left it inhabiting a small and highly fragmented range. From January to June 2016 we investigated the abundance and density of Sharpe’s Longclaw in Marania farm located in Meru county in the northern sector of Mt. Kenya, where no previous study had been done. Population abundance and density were determined using the flush and count method. We observed that these birds were exclusively found in grasslands, being most abundant in habitats of short grass with tussocks, and less so in areas with tall grass. This habitat specificity indicates a key requirement for survival of Sharpe’s Longclaw populations in this area. We recommend surveys in and around Marania farm to determine the distribution of suitable habitats for this species, and that the farm be designated an Important Bird Area. Further studies should also focus on determining the intensity of grazing that is compatible with conservation of Sharpe’s Longclaw populations.
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O'Keeffe, J. H. "Population Biology of the Freshwater Snail Bulinus globosus on the Kenya Coast. II. Feeding and Density Effects on Population Parameters." Journal of Applied Ecology 22, no. 1 (April 1985): 85. http://dx.doi.org/10.2307/2403329.
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Perry, B. D., T. M. Kyendo, S. W. Mbugua, I. E. Price, and S. Varma. "Increasing rabies vaccination coverage in urban dog populations of high human population density suburbs: a case study in Nairobi, Kenya." Preventive Veterinary Medicine 22, no. 1-2 (February 1995): 137–42. http://dx.doi.org/10.1016/0167-5877(94)00407-a.
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Haugerud, Angelique. "Land tenure and agrarian change in Kenya." Africa 59, no. 1 (January 1989): 61–90. http://dx.doi.org/10.2307/1160764.
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Opening ParagraphThis article examines the relationship of formal and informal land-tenure systems to processes of agrarian change. Although it is often assumed that formal legal recognition of private rights in land can help to transform agriculture, causal links between particular tenure systems and agrarian processes are not easily demonstrated. It is difficult to separate the effects of land tenure from those of a host of other influences on agriculture. A number of studies have pointed to causal relationships among high population density, agricultural intensity, and individualisation of land rights (Podolefsky, 1987). Nevertheless, formal privatisation per se may have relatively little effect on processes of agrarian change, even in an economy where land is productive and scarce and where its distribution is relatively unequal.
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Kiruki, Harun, and Joseph Njung'e. "Population density, structure and early growth characteristics of Tarchonanthus camphoratus in a woodland at Naivasha, Kenya." African Journal of Ecology 45, no. 1 (March 2007): 31–40. http://dx.doi.org/10.1111/j.1365-2028.2006.00672.x.
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Delany, M. J., and R. H. Monro. "Movement and spatial distribution of the Nile rat (Arvicanthis niloticus) in Kenya." Journal of Tropical Ecology 1, no. 2 (May 1985): 111–30. http://dx.doi.org/10.1017/s0266467400000183.
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ABSTRACTThe movement and spatial distribution of marked Nile rats, Arvicanthis niloticus, was traced through phases of a low density population from January to August 1981, a rapidly growing population from September to January 1982, and a high and declining post-reproductive population from February to April 1982. Apart from late in the population cycle there was considerable movement, interchange and establishment of new ranges. As the population increased individual ranges became smaller. The rats apparently preferred field edges and did not favour the fields themselves. Females frequently established themselves at certain sites where they produced their litters; some of the offspring remained with the mother in the warren. There is also evidence that ousiders of both sexes joined these warrens. Males were generally more wide-ranging than females. Agricultural practices, e.g. mowing and trampling by cattle, influenced the rats preparedness to remain within a particular location. Exploitation of all the available habitat took several months to achieve.
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RANDOLPH, S. E., and D. J. ROGERS. "A generic population model for the African tick Rhipicephalus appendiculatus." Parasitology 115, no. 3 (September 1997): 265–79. http://dx.doi.org/10.1017/s0031182097001315.
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We present a simulation population model for the African tick Rhipicephalus appendiculatus, based on previous analyses of the mortality factors most closely correlated with observed population changes at 11 sites in equatorial and South Africa. The model incorporates temperature-dependent rates of egg production and development, climate-driven density-independent mortality rates, particularly during the adult-larval stage, and density-dependent regulation of both nymphs and adults. Diapause is also included for tick populations in southern Africa. The model successfully describes both the seasonality and annual range of variation in numbers of each tick stage observed at each of 4 test sites in Uganda, Burundi and South Africa. Sensitivity analysis showed that the final version of the model is robust to 4-fold variation in most parameter values (that were per force based on informed guesses), but is more sensitive to the regression coefficients determining density-dependent interstadial mortality (that were derived from analysis of field data). The model is able to predict the seasonality of ticks from a site in Kenya where a full prior population analysis was not possible because only adults and nymphs had been counted. The model is potentially applicable to other species of ticks, both tropical and temperate, to predict tick abundance and seasonality as risk factors for tick-borne diseases.
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Wesolowski, Amy, C. J. E. Metcalf, Nathan Eagle, Janeth Kombich, Bryan T. Grenfell, Ottar N. Bjørnstad, Justin Lessler, Andrew J. Tatem, and Caroline O. Buckee. "Quantifying seasonal population fluxes driving rubella transmission dynamics using mobile phone data." Proceedings of the National Academy of Sciences 112, no. 35 (August 17, 2015): 11114–19. http://dx.doi.org/10.1073/pnas.1423542112.
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Changing patterns of human aggregation are thought to drive annual and multiannual outbreaks of infectious diseases, but the paucity of data about travel behavior and population flux over time has made this idea difficult to test quantitatively. Current measures of human mobility, especially in low-income settings, are often static, relying on approximate travel times, road networks, or cross-sectional surveys. Mobile phone data provide a unique source of information about human travel, but the power of these data to describe epidemiologically relevant changes in population density remains unclear. Here we quantify seasonal travel patterns using mobile phone data from nearly 15 million anonymous subscribers in Kenya. Using a rich data source of rubella incidence, we show that patterns of population travel (fluxes) inferred from mobile phone data are predictive of disease transmission and improve significantly on standard school term time and weather covariates. Further, combining seasonal and spatial data on travel from mobile phone data allows us to characterize seasonal fluctuations in risk across Kenya and produce dynamic importation risk maps for rubella. Mobile phone data therefore offer a valuable previously unidentified source of data for measuring key drivers of seasonal epidemics.
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Barber, G. M., and W. J. Milne. "Modelling Internal Migration in Kenya: An Econometric Analysis with Limited Data." Environment and Planning A: Economy and Space 20, no. 9 (September 1988): 1185–96. http://dx.doi.org/10.1068/a201185.
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In this paper the determinants of internal migration in Kenya are analyzed on the basis of a human capital model. Explanatory variables included in the specification are both economic (wage rates and employment rates) and noneconomic (for example, population density and educational attainment). Also incorporated are variables which reflect intervening opportunities. These variables are defined as distance-weighted averages of the variables in all of the districts in Kenya except the origin and destination districts. The econometric results show that destination variables are important determinants of internal migration, as is distance between the districts. Further, the variables for the intervening opportunities add significantly to the explanatory power of the model.
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Swinkels, R. A., S. Franzel, K. D. Shepherd, E. Ohlsson, and J. K. Ndufa. "The economics of short rotation improved fallows: evidence from areas of high population density in Western Kenya." Agricultural Systems 55, no. 1 (September 1997): 99–121. http://dx.doi.org/10.1016/s0308-521x(96)00098-4.
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Kanga, Erustus M., Joseph O. Ogutu, Han Olff, and Peter Santema. "Population trend and distribution of the Vulnerable common hippopotamus Hippopotamus amphibius in the Mara Region of Kenya." Oryx 45, no. 1 (January 2011): 20–27. http://dx.doi.org/10.1017/s0030605310000931.
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AbstractThe common hippopotamus Hippopotamus amphibius can significantly influence the dynamics of ecosystems and engender serious conflicts with people but, in Kenya, one of the species strongholds, it has been little studied or monitored. We surveyed the hippopotamus population in the Masai Mara National Reserve and the adjoining pastoral ranches in 2006 using foot counts along 155.3 km of the main rivers. We counted 4,170 hippopotamuses in 171 schools. Comparisons with earlier surveys suggest that this population increased by 169.6% between 1971 and 1980 within the reserve and, although it did not increase within the reserve during 1980–2006, it increased by 359.4% outside the reserve during this period against a background of deteriorating habitat conditions. The overall density in 2006 was 26.9 hippopotamuses km-1 of river, equivalent to a biomass of 26,677 kg km-1 of river. The ratio of calves to 100 adults was 9:100 inside the reserve, 10:100 outside the reserve and 6:100 along tributaries of the Mara River, implying that the population is either increasing or that its spatial distribution is being compressed because of range contraction. The apparent increase in the hippopotamus population contrasts with marked contemporaneous declines in the populations of most other large mammalian herbivore species in the Reserve. We discuss possible reasons underlying the increase in the hippopotamus population.
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KEESING, FELICIA, and TARA CRAWFORD. "Impacts of density and large mammals on space use by the pouched mouse (Saccostomus mearnsi) in central Kenya." Journal of Tropical Ecology 17, no. 3 (April 26, 2001): 465–72. http://dx.doi.org/10.1017/s0266467401001328.
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Rodents in tropical Africa have been recognized for decades both as important pests of agriculture and as reservoirs of numerous diseases that affect humans and livestock (Keesing 2000). Despite this recognition, however, little is known about the ecology and behaviour of these abundant and widespread animals. Because the impacts of small mammals as pests are expected to be some function of their population density, most ecological research on African rodents has focused on their population dynamics (Delany 1972, 1986; Leirs et al. 1994, 1996a).
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Ogello, EO, H.-J. Kim, K. Suga, and A. Hagiwara. "Lifetable demography and population growth of the rotifer Brachionus angularis in Kenya: influence of temperature and food density." African Journal of Aquatic Science 41, no. 3 (August 16, 2016): 329–36. http://dx.doi.org/10.2989/16085914.2016.1186590.
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Kefa, Christopher Amutabi, Mark Lung, Anton Espira, and Andrew J. Gregory. "Quantifying the rate of subsistence wood harvesting from a tropical rainforest in Kenya." Oryx 52, no. 2 (April 17, 2017): 369–73. http://dx.doi.org/10.1017/s003060531600106x.
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AbstractOne of the major threats to tropical forests throughout the world is the frequency and intensity with which local people use forests for subsistence. Kakamega Forest in Kenya is one such forest, in which fuelwood harvest is a primary use. The Kenya Forest Service and Kenya Wildlife Service have tried to regulate subsistence harvesting in this forest. However, high human population density (c. 542 people per km2) and extreme poverty leave local people little choice but to use forest resources to survive. We investigated patterns of wood use by people across Kakamega Forest. Our results indicate that wood harvesters prefer indigenous as opposed to non-indigenous wood, as the former sells for a premium price. Harungana madagascariensis and Psidium guajava were the most harvested indigenous and non-indigenous woods, respectively. Our data suggest that because market economies seem to drive forest use, perhaps they can be used to incentivize forest conservation. Proper integration of economic forest conservation interventions, economic diversification, and effective forest management are needed to protect Kakamega Forest.
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Martin, Lynn B., Courtney A. C. Coon, Andrea L. Liebl, and Aaron W. Schrey. "Surveillance for microbes and range expansion in house sparrows." Proceedings of the Royal Society B: Biological Sciences 281, no. 1774 (January 7, 2014): 20132690. http://dx.doi.org/10.1098/rspb.2013.2690.
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Interactions between hosts and parasites influence the success of host introductions and range expansions post-introduction. However, the physiological mechanisms mediating these outcomes are little known. In some vertebrates, variation in the regulation of inflammation has been implicated, perhaps because inflammation imparts excessive costs, including high resource demands and collateral damage upon encounter with novel parasites. Here, we tested the hypothesis that variation in the regulation of inflammation contributed to the spread of house sparrows ( Passer domesticus ) across Kenya, one of the world's most recent invasions of this species. Specifically, we asked whether inflammatory gene expression declines with population age (i.e. distance from Mombasa (dfM), the site of introduction around 1950). We compared expression of two microbe surveillance molecules (Toll-like receptors, TLRs-2 and 4) and a proinflammatory cytokine (interleukin-6, IL-6) before and after an injection of an immunogenic component of Gram-negative bacteria (lipopolysaccharide, LPS) among six sparrow populations. We then used a best-subset model selection approach to determine whether population age (dfM) or other factors (e.g. malaria or coccidian infection, sparrow density or genetic group membership) best-explained gene expression. For baseline expression of TLR-2 and TLR-4 , population age tended to be the best predictor with expression decreasing with population age, although other factors were also important. Induced expression of TLRs was affected by LPS treatment alone. For induced IL-6 , only LPS treatment reliably predicted expression; baseline expression was not explained by any factor. These data suggest that changes in microbe surveillance, more so than downstream control of inflammation via cytokines, might have been important to the house sparrow invasion of Kenya.
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Nyberg, G., A. Bargués Tobella, J. Kinyangi, and U. Ilstedt. "Soil property changes over a 120-yr chronosequence from forest to agriculture in western Kenya." Hydrology and Earth System Sciences 16, no. 7 (July 13, 2012): 2085–94. http://dx.doi.org/10.5194/hess-16-2085-2012.
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Abstract. Much of the native forest in the highlands of western Kenya has been converted to agricultural land in order to feed the growing population, and more land is being cleared. In tropical Africa, this land use change results in progressive soil degradation, as the period of cultivation increases. Both rates and variation in infiltration, soil carbon concentration and other soil parameters are influenced by management within agricultural systems, but they have rarely been well documented in East Africa. We constructed a chronosequence for an area of western Kenya, using two native forest sites and six fields that had been converted to agriculture for up to 119 yr. We assessed changes in infiltrability (the steady-state infiltration rate), bulk density, proportion of macro- and microaggregates in soil, soil C and N concentrations, as well as the isotopic signature of soil C (δ13C), along the 119-yr chronosequence of conversion from natural forest to agriculture. Infiltration, soil C and N decreased within 40 yr after conversion, while bulk density increased. Median infiltration rates fell to about 15% of the initial values in the forest, and C and N concentrations dropped to around 60%, whilst the bulk density increased by 50%. Despite high spatial variability, these parameters have correlated well with time since conversion and with each other.
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Toukem, Nadia K., Abdullahi A. Yusuf, Thomas Dubois, Elfatih M. Abdel-Rahman, Marian Salim Adan, and Samira A. Mohamed. "Landscape Vegetation Productivity Influences Population Dynamics of Key Pests in Small Avocado Farms in Kenya." Insects 11, no. 7 (July 9, 2020): 424. http://dx.doi.org/10.3390/insects11070424.
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Avocado (Persea americana Mill.) production contributes to the economic growth of East Africa. However, poor fruit quality caused by infestations of tephritid fruit flies (Tephritidae) and the false codling moth, Thaumatotibia leucotreta (Meyrick), hampers access to lucrative export markets. Remote sensing and spatial analysis are increasingly applied to crop pest studies to develop sustainable and cost-effective control strategies. In this study, we assessed pest abundance in Muranga, Kenya, across three vegetation productivity classes, viz., low, medium and high, which were estimated using the normalised difference vegetation index at a landscape scale. Population densities of the oriental fruit fly, Bactrocera dorsalis (Hendel) and T. leucotreta in avocado farms were estimated through specific baited traps and fruit rearing. The population density of T. leucotreta varied across the vegetation productivity classes throughout the study period, although not significantly. Meanwhile, B. dorsalis showed a clear trend of decrease over time and was significantly lower in high vegetation productivity class compared to low and medium classes. Ceratitis cosyra (Walker) was the most abundant pest reared from fruit with few associated parasitoids, Pachycrepoideus vindemmiae (Rondani) and Toxeumorpha nigricola (Ferriere).
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Okello, Moses Makonjio, Lekishon Kenana, Hanori Maliti, John Warui Kiringe, Erastus Kanga, Fiesta Warinwa, Samwel Bakari, et al. "Population density of elephants and other key large herbivores in the Amboseli ecosystem of Kenya in relation to droughts." Journal of Arid Environments 135 (December 2016): 64–74. http://dx.doi.org/10.1016/j.jaridenv.2016.08.012.
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Costa, Newton de Lucena, Liana Jank, João Avelar Magalhães, Amaury Burlamaqui Bendahan, Braz Henrique Nunes Rodrigues, and Francisco José de Seixas Santos. "Forage yield and morphogenesis of Megathyrsus maximus cultivars in Roraimas’s savannas." Research, Society and Development 9, no. 8 (July 24, 2020): e652986054. http://dx.doi.org/10.33448/rsd-v9i8.6054.
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In order to evaluate the forage productivity and the morphogenic and structural characteristics of Megathyrsus maximus cultivars (Massai, Mombasa, Kenya, Tamani, Tanzania and Zuri), an experiment was conduct under natural environmental conditions in the savannahs of Roraima. The highest yields of green dry matter (GDM) were found with cultivars Zuri (4,317 kg ha-1) and Mombasa (4,115 kg ha-1), followed by Kenya (3,868 kg ha-1) and Tamani (3,755 kg ha-1), while Massai (3,341 kg ha-1) and Tanzania (3,225 kg ha-1) were the least productive. GDM yield was directly correlated with LAI and inversely proportional to tiller population density (TPD). The cultivars Tanzania and Kenya had the highest number of tiller leaves and leaf appearance rates, while the highest leaf expansion rates were estimate in cultivars Zuri and Kenya. The highest average length of tiller leaves was estimate in the cultivars Zuri and Mombasa. Leaf senescence rates were inversely proportional to TPD and the highest recorded with the cultivars Mombasa and Tamani. The six cultivars of M. maximus showed satisfactory forage yields and can be recommend for cultivation in the edaphoclimatic conditions of the of Roraima’s savannas. The determination of morphogenic and structural characteristics can contribute to the establishment of appropriate and specific management practices for each cultivar, aiming to optimize its productivity and reduce losses due to leaf senescence.
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BORGHESIO, LUCA, DAINA SAMBA, MWANGI GITHIRU, LEON BENNUN, and KEN NORRIS. "Population estimates and habitat use by the Critically Endangered Taita Apalis Apalis fuscigularis in south-eastern Kenya." Bird Conservation International 20, no. 4 (April 26, 2010): 440–55. http://dx.doi.org/10.1017/s0959270910000298.
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SummaryThe Taita Apalis Apalis fuscigularis (IUCN category: Critically Endangered) is a species endemic to south-eastern Kenya. We assessed population size and habitat use in the three forest sites in which it is known to occur (Ngangao, Chawia and Vuria, totalling 257 ha). The estimate of total population size, derived from distance sampling at 412 sample points, ranged from 310 to 654 individuals, with the northern section of Ngangao fragment having 10-fold higher densities than Chawia (2.47–4.93 versus 0.22–0.41 birds ha−1). Ngangao north alone hosted 50% of the global population of the species. The highly degraded Vuria fragment also had moderately high densities (1.63–3.72 birds ha−1) suggesting that the species tolerates some human disturbance. Taita Apalis prefers vegetation with abundant climbers, but the predictive power of habitat use models was low, suggesting that habitat structure is not a primary cause for the low density of the species in Chawia. Protecting the subpopulation in the northern section of Ngangao is a priority, as is identifying factors responsible of the low abundance in Chawia, because ameliorating conditions in this large fragment could substantially increase the population of Taita Apalis.
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Mulwa, Ronald K., Leon A. Bennun, Callistus K. P. O. Ogol, and Luc Lens. "Population status and distribution of Taita White-eye Zosterops silvanus in the fragmented forests of Taita Hills and Mount Kasigau, Kenya." Bird Conservation International 17, no. 2 (May 29, 2007): 141–50. http://dx.doi.org/10.1017/s0959270907000664.
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AbstractOur study focused on the Taita White-eye Zosterops silvanus, one of three bird species endemic to the Taita Hill forests, south-east Kenya. Formerly considered Critically Endangered, Taita White-eye has been down-listed to Endangered following the findings of this study. Between November 1998 and September 1999 we counted this species along line transects to establish their current population status and distribution in its entire range. White-eye censuses were conducted in nine forest fragments of the Taita Hills and the virtually undisturbed Mt Kasigau forest. The total global population of Taita White-eyes was estimated to be c. 7,100 birds. Mt Kasigau was shown to be the species' main stronghold, maintaining a very high density (26 birds ha−1) and holding 80% (5,600 individuals) of the entire population. In the Taita Hills forests, densities were consistently higher in the small isolated fragments than in the large ones, though the former held only a small population (3% of total). At Mt Sagala, a large isolated block where indigenous trees have been largely replaced with exotic plantation, this species was not encountered. We found no evidence of interchange between the White-eye populations on Mt Kasigau and the Taita Hills forests, probably because of the separation by a low-altitude, dry woodland habitat barrier. While prioritization for conservation action should focus more on the Taita Hills forest fragments, Mt Kasigau should be treated as fragile ecosystem which holds a huge, apparently insular population of Taita White-eyes.
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Kwoba, Emmah N., Philip Kitala, Linus Ochieng, Elkanah Otiang, Robert Ndung’u, Gati Wambura, Katie Hampson, and S. M. Thumbi. "Dog health and demographic surveillance survey in Western Kenya: Demography and management practices relevant for rabies transmission and control." AAS Open Research 2 (February 7, 2019): 5. http://dx.doi.org/10.12688/aasopenres.12902.1.
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Background: Domestic dogs transmit 99% of the estimated 59,000 human rabies deaths occurring globally annually. To achieve the global target of zero human deaths from rabies by 2030, effective mass dog vaccination campaigns that break rabies transmission cycles in dog populations are required. This study describes the design of a dog health and demographic surveillance study established within a human health and demographic surveillance study in Western Kenya. Using baseline data from the dog cohort study, we quantify demographic parameters and describe management practices relevant for rabies transmission. Methods: All dogs in 1213 households participating in a linked human and animal health syndromic surveillance study were recruited. Data on household demographics, dog ownership, dog age and sex ratios, reproductive indices, rabies vaccination, management practices, dog movement and health status were collected at least monthly. Results: 460 of 1213 (38%) of the study households owned dogs (mean 2 dogs/household), and 526 (70%) of those without dogs had owned dogs previously. 802 dogs were recruited into the study, more than half (52%) of those with known ages were ≤ 1 year old. The dog:human ratio in the study population was 1:7, the dog density 54 dogs/km2, and the female: male dog sex ratio was 1:1.3. Rabies vaccination was low (5% coverage), and only 48 (12%) male dogs and 13 (5%) female dogs were castrated and spayed, respectively. Dogs were predominantly local breed (99%), mainly kept for security purposes, almost always (97%) left to scavenge for leftovers and 61% roamed freely. Conclusion: Low vaccination coverage, unrestricted dog movement, and high dog population turnover with a large proportion of dogs below one-year-old support endemic rabies circulation in this population. These gaps present opportunities for the design of effective dog rabies control plans to break rabies transmission cycles in this part of Kenya.
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O’Meara, Wendy Prudhomme, Ryan Simmons, Paige Bullins, Betsy Freedman, Lucy Abel, Judith Mangeni, Steve M. Taylor, and Andrew A. Obala. "Mosquito Exposure and Malaria Morbidity: A Microlevel Analysis of Household Mosquito Populations and Malaria in a Population-Based Longitudinal Cohort in Western Kenya." Journal of Infectious Diseases 221, no. 7 (October 30, 2019): 1176–84. http://dx.doi.org/10.1093/infdis/jiz561.
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Abstract Background Malaria morbidity is highly overdispersed in the population. Fine-scale differences in mosquito exposure may partially explain this heterogeneity in individual malaria outcomes. Methods In 38 households we explored the effect of household-level mosquito exposure and individual insecticide-treated net (ITN) use on relative risk (RR) of confirmed malaria. We conducted monthly active surveillance (n = 254; 2624 person-months) and weekly mosquito collection (2092 household-days of collection), and used molecular techniques to confirm human blood feeding and exposure to infectious mosquitoes. Results Of 1494 female Anopheles (89.8% Anopheles gambiae sensu lato), 88.3% were fed, 51.9% had a human blood meal, and 9.2% were sporozoite infected. In total, 168 laboratory-confirmed malaria episodes were reported (incidence rate 0.064 episodes per person-month at risk; 95% confidence interval [CI], .055–.074). Malaria risk was directly associated with exposure to sporozoite-infected mosquitoes (RR, 1.24; 95% CI, 1.11–1.38). No direct effect was measured between ITN use and malaria morbidity; however, ITN use did moderate the effect of mosquito exposure on morbidity. Conclusions Malaria risk increases linearly with vector density and feeding success for persons with low ITN use. In contrast, malaria risk among high ITN users is consistently low and insensitive to variation in mosquito exposure.
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Kagezi, G. H., M. Kaib, P. Nyeko, C. Bakuneeta, M. Schädler, J. Stadler, and R. Brandl. "Impacts of land-use intensification on litter decomposition in western Kenya." Web Ecology 16, no. 1 (February 11, 2016): 51–58. http://dx.doi.org/10.5194/we-16-51-2016.
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Abstract. Tropical forests are faced with a substantial loss of forest cover due to human activities. The various forms of land use influence habitat structure, microclimate, and co-occurring species, with possible effects on ecosystem processes. The forests of western Kenya are the most eastern parts of the Congolian rainforests. Due to the high human population density only few remnants of these rainforests remained. Even protected areas are influenced by human disturbances, with unknown effects on ecosystem processes. Therefore, we quantified the mass loss of leaf litter with and without access of soil invertebrates within forest fragments and sites affected by increasing levels of agricultural land-use intensity in the Kakamega area (western Kenya; 1500 m a.s.l.). Mass loss of litter as an estimate of decomposition rate increased with rainfall during the annual cycle. Furthermore, mass loss increased with the area of forest fragments and decreased with land-use intensification. We found that soil invertebrates had only small effects on mass loss (< 10 %), and this effect decreased with land-use intensification. Our data showed that forest fragmentation has negative effects on litter decomposition. However, the magnitude of this negative effect was not as large as expected.
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Onyango, Dancan O., Christopher O. Ikporukpo, John O. Taiwo, and Stephen B. Opiyo. "Monitoring the extent and impacts of watershed urban development in the Lake Victoria Basin, Kenya, using a combination of population dynamics, remote sensing and GIS techniques." Environmental & Socio-economic Studies 9, no. 2 (June 1, 2021): 11–25. http://dx.doi.org/10.2478/environ-2021-0007.
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Abstract Several urban centres of different sizes have developed over time, and continue to grow, within the basin of Lake Victoria. Uncontrolled urban development, especially along the lake shore, puts environmental pressure on Lake Victoria and its local ecosystem. This study sought to monitor the extent and impacts of urban development (as measured by population growth and built-up land use/land cover) in the Lake Victoria basin, Kenya, between 1978 and 2018. Remote sensing and GIS-based land use/land cover classification was conducted to extract change in built-up areas from Landsat 3, 4, 5 and 8 satellite imagery obtained for the month of January at intervals of ten years. Change in population distribution and density was analysed based on decadal census data from the Kenya National Bureau of Statistics between 1979 and 2019. A statistical regression model was then estimated to relate population growth to built-up area expansion. Results indicate that the basin’s built-up area has expanded by 97% between 1978 and 2018 while the population increased by 140% between 1979 and 2019. Urban development was attributed to the rapidly increasing population in the area as seen in a positive statistical correlation (R2=0.5744) between increase in built-up area and population growth. The resulting environmental pressure on the local ecosystem has been documented mainly in terms of degradation of lake water quality, eutrophication and aquatic biodiversity loss. The study recommends the enactment and implementation of appropriate eco-sensitive local legislation and policies for sustainable urban and rural land use planning in the area. This should aim to control and regulate urban expansion especially in the immediate shoreline areas of the lake and associated riparian zones.
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Gopal, Sucharita, Yaxiong Ma, Chen Xin, Joshua Pitts, and Lawrence Were. "Characterizing the Spatial Determinants and Prevention of Malaria in Kenya." International Journal of Environmental Research and Public Health 16, no. 24 (December 12, 2019): 5078. http://dx.doi.org/10.3390/ijerph16245078.
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The United Nations’ Sustainable Development Goal 3 is to ensure health and well-being for all at all ages with a specific target to end malaria by 2030. Aligned with this goal, the primary objective of this study is to determine the effectiveness of utilizing local spatial variations to uncover the statistical relationships between malaria incidence rate and environmental and behavioral factors across the counties of Kenya. Two data sources are used—Kenya Demographic and Health Surveys of 2000, 2005, 2010, and 2015, and the national Malaria Indicator Survey of 2015. The spatial analysis shows clustering of counties with high malaria incidence rate, or hot spots, in the Lake Victoria region and the east coastal area around Mombasa; there are significant clusters of counties with low incidence rate, or cold spot areas in Nairobi. We apply an analysis technique, geographically weighted regression, that helps to better model how environmental and social determinants are related to malaria incidence rate while accounting for the confounding effects of spatial non-stationarity. Some general patterns persist over the four years of observation. We establish that variables including rainfall, proximity to water, vegetation, and population density, show differential impacts on the incidence of malaria in Kenya. The El-Nino–southern oscillation (ENSO) event in 2015 was significant in driving up malaria in the southern region of Lake Victoria compared with prior time-periods. The applied spatial multivariate clustering analysis indicates the significance of social and behavioral survey responses. This study can help build a better spatially explicit predictive model for malaria in Kenya capturing the role and spatial distribution of environmental, social, behavioral, and other characteristics of the households.
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Opiyo, Judith Siambe, and Paul Shetler Fast. "Adapting Care Groups to Urban Slums: A Case Study of a Church-Based Effort to Improve Maternal and Child Health Outcomes in Mathare, Nairobi, Kenya." Christian Journal for Global Health 6, no. 2 (December 23, 2019): 33–43. http://dx.doi.org/10.15566/cjgh.v6i2.317.
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In many places in Africa, progress on maternal and child health has been slow and uneven, with widening geographic and socio-economic disparities, despite economic growth and continued investments in health systems. In Kenya, modest national-level gains mask wide disparities in progress, with near stagnation among the very poor, those with the least education, and those living in either extremely rural contexts or dense informal urban slums. Progress toward Kenya’s maternal and child health Sustainable Development Goals (SDGs) will depend on finding new ways to work effectively in dense urban slums, where poverty and ill-health are increasingly concentrated, and older program models have failed to deliver. Effective approaches will require addressing significant knowledge, behavior, and trust gaps, especially with the poorest and most vulnerable residents of slum communities like Nairobi’s Mathare. Care Groups were designed to address these specific types of gaps but have only been effectively tested and scaled in rural and peri-urban environments. The Kenya Mennonite Church’s Center for Peacebuilding and Nationhood’s maternal and child health Care Group project in Mathare, Nairobi, one of the largest informal settlements in Kenya, is the first to adapt the Care Group model to an urban slum environment. However, significant adaptation of the model was required by the uniquely challenging nature of a context characterized by high population density, crowding, extremely transient and unstable populations, low social trust, lack of traditional social structures, high vulnerability to crime, political disruption, and frequent rapid onset disasters. This case study explores the contextual complexity of adapting a model like Care Groups to the realities of a dense African urban slum, the innovative strategies the project has used, its successes, challenges, and the unique benefits of doing this work on a small scale rooted in a local church organization.
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Levy, Emily J., Matthew N. Zipple, Emily McLean, Fernando A. Campos, Mauna Dasari, Arielle S. Fogel, Mathias Franz, et al. "A comparison of dominance rank metrics reveals multiple competitive landscapes in an animal society." Proceedings of the Royal Society B: Biological Sciences 287, no. 1934 (September 9, 2020): 20201013. http://dx.doi.org/10.1098/rspb.2020.1013.
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Across group-living animals, linear dominance hierarchies lead to disparities in access to resources, health outcomes and reproductive performance. Studies of how dominance rank predicts these traits typically employ one of several dominance rank metrics without examining the assumptions each metric makes about its underlying competitive processes. Here, we compare the ability of two dominance rank metrics—simple ordinal rank and proportional or ‘standardized’ rank—to predict 20 traits in a wild baboon population in Amboseli, Kenya. We propose that simple ordinal rank best predicts traits when competition is density-dependent, whereas proportional rank best predicts traits when competition is density-independent. We found that for 75% of traits (15/20), one rank metric performed better than the other. Strikingly, all male traits were best predicted by simple ordinal rank, whereas female traits were evenly split between proportional and simple ordinal rank. Hence, male and female traits are shaped by different competitive processes: males are largely driven by density-dependent resource access (e.g. access to oestrous females), whereas females are shaped by both density-independent (e.g. distributed food resources) and density-dependent resource access. This method of comparing how different rank metrics predict traits can be used to distinguish between different competitive processes operating in animal societies.
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V. M., Kega,, Kasina, M, Olubayo F, and Nderitu, J. H. "A Study of the African White Rice Stem Borer (Maliarpha separatella Rag.) Population Density Fluctuations at Mwea Irrigation Scheme in Central Kenya." Universal Journal of Agricultural Research 5, no. 1 (January 2017): 52–56. http://dx.doi.org/10.13189/ujar.2017.050108.
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Borghesio, Luca, and Paola Laiolo. "Seasonal foraging ecology in a forest avifauna of northern Kenya." Journal of Tropical Ecology 20, no. 2 (March 2004): 145–55. http://dx.doi.org/10.1017/s0266467403001159.
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We studied the avian foraging ecology in a single montane forest of northern Kenya, analysing the pattern of seasonal variation (wet vs. dry period) and its relationship with habitat structure. The foraging behaviour of 28 species was described in terms of four major dimensions (i.e. foraging technique, food substrate, perching site and perching height). Seasonal rainfall produced an increase in vegetation growth in the lower vegetation layers, while fruiting and flowering peaked in the dry season. We did not find much seasonal variation in foraging ecology when we analysed our data at the species or at the community levels. At the guild level, however, we found some seasonal shifts in perching height, food substrate and foraging technique. Some of these shifts seemed to be determined by food availability and distribution, as omnivores increased fruit consumption when this resource was more abundant, and nectarivores tracked the vertical distribution of flowers. The vertical biomass distribution of this avian community seemed to be largely determined by food. However, seasonal variation in the total biomass of some guilds was probably related to factors not considered in this study, such as breeding, or intra-African migratory movements. Altogether, despite marked seasonal variation in vegetation structure and food resources, the bird assemblage showed little change in its feeding ecology and micro-habitat use. Hence, we suggest that changes in habitat structure and resource levels were coped with primarily by adjusting population density and food requirements through seasonal breeding or migration.
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Iraboneye, Norbert, Miriam K. Charimbu, and Nancy W. Mungai. "Effect of Canola and Compound Fertilizer on Potato (Solanum Tuberosum L.) Bacterial Wilt Management." European Journal of Agriculture and Food Sciences 3, no. 1 (January 14, 2021): 28–38. http://dx.doi.org/10.24018/ejfood.2021.3.1.130.
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Bacterial wilt is a problematic disease affecting potato production in Kenya and the available management methods are not efficient. Field, semi-field and laboratory experiments were conducted to evaluate the effect of canola green manure and compound fertilizer on bacterial wilt management. Laboratory experiment was conducted at Egerton university biological laboratory to evaluate the effect of canola extract on R. solanacearum population density in-vitro. Four levels of canola extract quantities were used; 0, 100, 200, 300microlitres, and enrich immunomodulator (Di-bromo Di-nitro propane 1-3-diol) (DDD) was used as a positive control. Inoculum was prepared from infested soil and Selective Medium South Africa (SMSA) (Casamino acids, Bacto-Peptone, Glycerol, and Bacto-Agar) was used as growth medium in a completely randomized design. Field experiment was carried out in two sites (Elburgon site is in Upper high land zone two (UH2) and Mau-Narok is in Upper high land zone one UH1). Two levels of canola green manure (with and without green manure application), four levels of fertilizer (NPK+Ca+Mg+ micronutrients) applied at 0(F1), 250(F2), 575(F3), 900 (F4) kg ha-1 and diammonium phosphate (DAP500 kg ha-1) +Calcium ammonium nitrate (CAN300 kg ha-1) (F5) as a positive control. The experiment was carried out in randomized complete block design (RCBD) spilt plot replicated three times, canola green manure as main plot and fertilizer and varieties combination as sub plots. Semi-field experiment (in pots) was conducted at Egerton university farm, five levels of canola green manure (100, 75, 50 and 0 g kg-1 soil) and four levels of the compound fertilizer as used in the field experiment were used in a completely randomized design (CRD) with three replicates. The data shows that canola extract did not have a significant (Pr <0.05) effect on bacterial population density (CFU), where chemical treatment (DDD) restricted the growth of R. solanacearum under laboratory experiment. Under field and semi-filed experiments, canola green manure and fertilizer treatments had no significant (Pr <0.05) effect on bacterial population density in the soil nor bacterial wilt incidence. Kenya karibu variety it did not show any wilting symptoms of bacterial wilt across the sites and semi-field experiment. Canola did not suppress the growth of R. solanacearum; further investigation should be done on other brassica family plants.
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Nyberg, G., A. Bargués Tobella, J. Kinyangi, and U. Ilstedt. "Patterns of water infiltration and soil degradation over a 120-yr chronosequence from forest to agriculture in western Kenya." Hydrology and Earth System Sciences Discussions 8, no. 4 (July 20, 2011): 6993–7015. http://dx.doi.org/10.5194/hessd-8-6993-2011.
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Abstract. Soil degradation is commonly reported in the tropics where forest is converted to agriculture. Much of the native forest in the highlands of western Kenya has been converted to agricultural land in order to feed the growing population, and more land is being cleared. In tropical Africa, this land use change results in progressive soil degradation, as the period of cultivation increases. Sites that were converted to agriculture at different times can be evaluated as a chronosequence; this can aid in our understanding of the processes at work, particularly those in the soil. Both levels and variation of infiltration, soil carbon and other parameters are influenced by management within agricultural systems, but they have rarely been well documented in East Africa. We constructed a chronosequence for an area of western Kenya, using two native forest sites and six fields that had been converted to agriculture for varying lengths of time. We assessed changes in infiltrability (the steady-state infiltration rate), soil C and N, bulk density, δ13C, and the proportion of macro- and microaggregates in soil along a 119 yr chronosequence of conversion from natural forest to agriculture. Infiltration, soil C and N, decreased rapidly after conversion, while bulk density increased. Median infiltration rates fell to about 15 % of the initial values in the forest and C and N values dropped to around 60 %, whilst the bulk density increased by 50 %. Despite high spatial variability in infiltrability, these parameters correlated well with time since conversion and with each other. Our results indicate that landscape planners should include wooded elements in the landscape in sufficient quantity to ensure water infiltration at rates that prevent runoff and erosion. This should be the case for restoring degraded landscapes, as well as for the development of new agricultural areas.
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Zhou, Guofa, Daibin Zhong, Ming-Chieh Lee, Xiaoming Wang, Harrysone E. Atieli, John I. Githure, Andrew K. Githeko, James Kazura, and Guiyun Yan. "Multi-Indicator and Multistep Assessment of Malaria Transmission Risks in Western Kenya." American Journal of Tropical Medicine and Hygiene 104, no. 4 (April 7, 2021): 1359–70. http://dx.doi.org/10.4269/ajtmh.20-1211.
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ABSTRACTMalaria risk factor assessment is a critical step in determining cost-effective intervention strategies and operational plans in a regional setting. We develop a multi-indicator multistep approach to model the malaria risks at the population level in western Kenya. We used a combination of cross-sectional seasonal malaria infection prevalence, vector density, and cohort surveillance of malaria incidence at the village level to classify villages into malaria risk groups through unsupervised classification. Generalized boosted multinomial logistics regression analysis was performed to determine village-level risk factors using environmental, biological, socioeconomic, and climatic features. Thirty-six villages in western Kenya were first classified into two to five operational groups based on different combinations of malaria risk indicators. Risk assessment indicated that altitude accounted for 45–65% of all importance value relative to all other factors; all other variable importance values were < 6% in all models. After adjusting by altitude, villages were classified into three groups within distinct geographic areas regardless of the combination of risk indicators. Risk analysis based on altitude-adjusted classification indicated that factors related to larval habitat abundance accounted for 63% of all importance value, followed by geographic features related to the ponding effect (17%), vegetation cover or greenness (15%), and the number of bed nets combined with February temperature (5%). These results suggest that altitude is the intrinsic factor in determining malaria transmission risk in western Kenya. Malaria vector larval habitat management, such as habitat reduction and larviciding, may be an important supplement to the current first-line vector control tools in the study area.
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Stave, J., G. Oba, and N. C. Stenseth. "Temporal changes in woody-plant use and the ekwar indigenous tree management system along the Turkwel River, Kenya." Environmental Conservation 28, no. 2 (June 2001): 150–59. http://dx.doi.org/10.1017/s0376892901000157.
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Indigenous systems of management for regulating extraction of non-timber forest products (NTFP) have not been well documented in arid zone grazing lands. Conservation projects have therefore lacked information on customary rights to trees, while they have enforced systems of tree resource management that often conflicted with the indigenous system. This study focused on the indigenous tree tenure system of the Turkana pastoralists called ekwar (plural ngikwarin). The indigenous tree management system in 15.4 km2 of the Turkwel River floodplain woodlands near Lodwar, Kenya was investigated. The study began in 1990 after impoundment of the Turkwel Gorge Dam. In 1990 and 1998, Turkana pastoralists were interviewed about the ekwar. In individual ngikwarin woody cover, wood volume and woody-plant density were measured, and wood extraction assessed in terms of stems and twigs removed by the pastoralists and the urban population of Lodwar. Intensity of charcoal burning was assessed in terms of the density of earthen kilns, and livestock impact in terms of browsing frequency on woody plants. Potential Acacia tortilis litter production was estimated and an ekwar quality index developed to describe woodland productivity conditions. Tree produce was shared with and leased to friends and relatives. Woody cover showed no significant changes, while woody-plant density and volume declined, over the 8-year period. The Turkana usually do not cut live trees, but use dead trees and dry tree-parts for making charcoal. Increased kiln density and increased extraction of tree-parts were considered to be indicative of increased pressure on the riverine woodlands. Livestock browsing did not seem to contribute to woodland degradation. However, decline in woody-plant density and volume might have contributed to the reduction of litter production of A. tortilis. Trends in woodlands in the floodplain might be associated with damming of the Turkwel River and local anthropogenic pressures. Also, the ekwar system of tree tenure seemed to be threatened by the official forestry policy that it be ignored. Incorporating the ekwar system into the forestry conservation policy may achieve sustainable use and improve conservation of the Turkwel River floodplain woodlands.
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Muriuki, Caroline, Mary Guantai, Namikoye Samita, Joseph Mulwa, Matolo Nyamai, and Muo Kasina. "Abundance and Diversity of Frugivorous Fruit Flies in Kandara, Murang’a County, Kenya." African Phytosanitary Journal 2, no. 1 (November 1, 2020): 41–50. http://dx.doi.org/10.52855/slmz8250.
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Fruits and vegetables are important source of livelihood to farmers and major horticulture sub sector with high contribution to agricultural GDP in Kenya. This study was conducted to determine diversity and abundance of frugivorous fruit flies in Kandara sub county, Murang’a County in 2018, at a place where first area of low pest population was created in Kenya for Bactrocera dorsalis. Three sets of pheromone traps (Methyl-Eugenol, Cuelure and Trimedlure) were set in six trap stations within farmers’ orchards in four agro-ecological zones (LH1 (Lower Highland Zone), UM1 (Upper Mid-land Zone), UM2, and UM3). The trap catch data was collected fortnightly and data analyzed. Six fruit flies species namely; Bactrocera dorsalis, Ceratitis cosyra, Ceratitis capitata, Zeugodacus cucurbitae, Dacus bivittatus and Perilampsis sp were identified. Bactrocera dorsalis population was significantly (P<.001) different across the four agro-ecologies with lowest densities at LH1 and highest at UM3. Likewise, C. capitata recorded significant (P=0.042) difference densities across the agro-ecological zones, but no significant (P=0.386) difference was recorded for C. cosyra across the agro-ecological zones. Further, there was significant (P=0.012) difference in the number of Perilampsis sp across the agro-ecologies with the highest number recorded in UM1. Both Z. cucurbitae (P=0.061) and D. bivittatus (P=0.056) had low abundance across the agro-ecologies. The peak infestation period differed across the various fruit fly species, whereby B. dorsalis peaked in May, C. capitata in February and C. cosyra in January. The study shows that abundance for the fruit flies is probably related to their preferred hostplant and the weather patterns. We recommend continuous monitoring and intensifying trapping activities during peak periods in order to control the pest and protect fruits from damage. Farmers should be trained on the use of pheromone traps to reduce over-reliance on pesticides. Key words: Agro-ecologies, Bactrocera dorsalis, Ceratitis sp, fruit fly density, Pheromone
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IBOI, ENAHORO A., ABBA B. GUMEL, and JESSE E. TAYLOR. "MATHEMATICAL MODELING OF THE IMPACT OF PERIODIC RELEASE OF STERILE MALE MOSQUITOES AND SEASONALITY ON THE POPULATION ABUNDANCE OF MALARIA MOSQUITOES." Journal of Biological Systems 28, no. 02 (April 18, 2020): 277–310. http://dx.doi.org/10.1142/s0218339020400033.
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This study presents a new mathematical model for assessing the impact of sterile insect technology (SIT) and seasonal variation in local temperature on the population abundance of malaria mosquitoes in an endemic setting. Simulations of the model, using temperature data from Kipsamoite area of Kenya, show that a peak abundance of the mosquito population is attained in the Kipsamoite area when the mean monthly temperature reaches [Formula: see text]. Furthermore, in the absence of seasonal variation in local temperature, our results show that releasing more sterile male mosquitoes (e.g., 100,000) over a one year period with relatively short duration between releases (e.g., weekly, bi-weekly or even monthly) is more effective than releasing smaller numbers of the sterile male mosquitoes (e.g., 10,000) over the same implementation period and frequency of release. It is also shown that density-dependent larval mortality plays an important role in determining the threshold number of sterile male mosquitoes that need to be released in order to achieve effective control (or elimination) of the mosquito population in the community. In particular, low(high) density-dependent mortality requires high(low) numbers of sterile male mosquitoes to be released to achieve such control. In the presence of seasonal variation in local temperature, effective control of the mosquito population using SIT is only feasible if a large number of the sterile male mosquitoes (e.g., 100,000) is periodically released within a very short time interval (at most weekly). In other words, seasonal variation in temperature necessitates more frequent releases (of a large number) of sterile male mosquitoes to ensure the effectiveness of the SIT intervention in curtailing the targeted mosquito population.
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Turner, D. A., and R. Brightwell. "An evaluation of a sequential aerial spraying operation against Glossina pallidipes Austen (Diptera: Glossinidae) in the Lambwe Valley of Kenya: aspects of post-spray recovery and evidence of natural population regulation." Bulletin of Entomological Research 76, no. 2 (June 1986): 331–49. http://dx.doi.org/10.1017/s0007485300014802.
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AbstractAn attempt to eradicate Glossina pallidipes Austen from the Lambwe Valley of western Kenya by sequential aerial application of endosulfan aerosol spray is described. The operation was ultimately unsuccessful, even after nine sprays of relatively heavy dosages of insecticide. Survivors were present throughout after each spray, and females mated and bred between sprays. The population was reduced by over 99·9% in main habitats of thicket and woodland and by about 90% in conifer plantation. The outcome of a model of spray effectiveness suggested, however, that the final reduction in population size was the cumulative effect of only about a 90% kill per spray application. Post-spray monitoring showed that the tsetse population in thicket returned to its pre-spray level in little more than 12 months and became stabilized thereafter. Elsewhere, recovery was much slower and more variable. Evidence was found for population regulation by density-dependent emigration of flies. Calculations of population growth rate gave an instantaneous rate of increase of 0·0148/day, equivalent to a finite rate of increase of 1·568/month or a doubling time of 47 days. This permitted a 90-fold increase in population size over a ten-month period of unrestricted growth. The failure to achieve eradication is discussed in terms of certain operational shortcomings and environmental constraints which exist in the Lambwe Valley.
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Odhiambo, H. O., J. O. Nyabundi, and J. Chweya. "Effects of Soil Moisture and Vapour Pressure Deficits on Shoot Growth and the Yield of Tea in the Kenya Highlands." Experimental Agriculture 29, no. 3 (July 1993): 341–50. http://dx.doi.org/10.1017/s0014479700020901.
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SUMMARYProlonged moisture stress and high vapour pressure deficits reduced the shoot water potential, shoot population density, rate of shoot extension and yield of clonal tea. The more drought susceptible Clone 6/8 had a lower shoot water potential, rate of shoot extension, number of shoots per unit area, rate of shoot regeneration and yield than the more tolerant Clones 31/8, 57/15 and 15/10 during the periods of low soil moisture, which coincided with high vapour pressure deficits. The changes in the shoot growth components could be used as an index of the suitability of different clones for different regimes of soil moisture and vapour pressure deficits.Factores ambientales que afectan el rendimiento del té
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Touray, Abdoulie O., Victor A. Mobegi, Fred Wamunyokoli, Hellen Butungi, and Jeremy K. Herren. "Prevalence of asymptomatic P. falciparum gametocyte carriage in schoolchildren and assessment of the association between gametocyte density, multiplicity of infection and mosquito infection prevalence." Wellcome Open Research 5 (October 29, 2020): 259. http://dx.doi.org/10.12688/wellcomeopenres.16299.1.
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Background: Malaria is a major public health threat in sub-Saharan Africa. Asymptomatic Plasmodium falciparum gametocyte carriers are potential infectious reservoirs for sustaining transmission in many malaria endemic regions. The aim of the study was to assess the prevalence of gametocyte carriage and some of its associated risk factors among asymptomatic schoolchildren in Western Kenya and further analyse the association between gametocyte density, multiplicity of infection (MOI) and mosquito infection prevalence. Methods: Rapid diagnostic tests were used to screen for P. falciparum parasite infection among schoolchildren (5-15 years old) and the results were verified using microscopy. Microscopy positive gametocyte carriers were selected to feed laboratory reared An. gambiae s.l. mosquitoes using membrane feeding method. Genomic DNA was extracted from dry blood spot samples and P. falciparum populations were genotyped using 10 polymorphic microsatellite markers. Assessment of the association between MOI and gametocyte density and mosquito infection prevalence was conducted. Results: A significantly higher prevalence of P. falciparum infection was found in males 31.54% (764/2422) (p-value < 0.001) compared to females 26.72% (657/2459). The microscopy gametocyte prevalence among the study population was 2% (84/4881). Children aged 5-9 years have a higher prevalence of gametocyte carriage (odds ratios = 2.1 [95% CI = 1.3–3.4], P = 0.002) as compared to children aged 10-15 years. After challenging An. gambiae s.l. by membrane feeding assay on gametocyte positive patient blood, our results indicate that 68.1% of the variation in mosquito infection prevalence is accounted for by gametocyte density and MOI (R-SQR. = 0.681, p < 0.001). Conclusions: Age was a significant risk factor for gametocyte carriage, as indicated by the higher risk of gametocyte carriage among the younger children (5-9 years). Gametocyte density and MOI statistically significantly predicted mosquito infection prevalence. Both of the variables added significantly to the prediction (p < 0.05).
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Green, David S., Matthew T. Farr, Kay E. Holekamp, Eli D. Strauss, and Elise F. Zipkin. "Can hyena behaviour provide information on population trends of sympatric carnivores?" Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1781 (July 29, 2019): 20180052. http://dx.doi.org/10.1098/rstb.2018.0052.
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Mammalian carnivores are declining worldwide owing to human activities. Behavioural indicators have the potential to help identify population trends and inform conservation actions, although this area of research is understudied. We investigate whether behaviour is linked to abundance in a community of carnivores in the Masai Mara National Reserve, Kenya. Anthropogenic disturbance increased exponentially in parts of the Reserve between 1988 and 2017, mainly owing to daily incursions by large numbers of livestock and tourists. Previous research showed that hyena behaviour changed markedly during this period. Through a series of vignettes, we inquire whether hyena behaviours correlate with changes in abundance of hyenas themselves, or those of other carnivore species in the region. We find that changes in spotted hyena behaviour in disturbed areas, but not in undisturbed areas, can be linked to changes in their demography (vignette 1). We also find that declines in observed lion–hyena interactions, as well as increases in spotted hyena abundance, are probably caused by competitive release of hyenas from declining lion abundance (vignette 2). Finally, we demonstrate that in some cases, hyena behaviour and demography is linked to the density and distribution of sympatric carnivores, and that behavioural changes in hyenas can provide information on shifts within the carnivore community (vignettes 3 and 4). Our vignettes reveal intriguing relationships between behaviour and demography that should be explored in future research. Pairing behavioural studies with more traditional monitoring efforts can yield useful insights regarding population and community trends, and aid wildlife conservation and management. This article is part of the theme issue ‘Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation'.
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WAMBUI, MBOTE BETH, ALFRED OPERE, JOHN M. GITHAIGA, and FREDRICK K. KARANJA. "Assessing the impacts of climate variability and climate change on biodiversity in Lake Nakuru, Kenya." Bonorowo Wetlands 8, no. 1 (June 1, 2018): 13–24. http://dx.doi.org/10.13057/bonorowo/w080102.
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Wambui MB, Opere A, Githaiga MJ, Karanja FK. 2017. Assessing the impacts of climate variability and climate change on biodiversity in Lake Nakuru, Kenya. Bonorowo Wetlands 1: 13-24. This study evaluates the impacts of the raised water levels and the flooding of Lake Nakuru and its surrounding areas on biodiversity, specifically, the phytoplankton and lesser flamingo communities, due to climate change and climate variability. The study was to review and analyze noticed climatic records from 2000 to 2014. Several methods were used to ascertain the past and current trends of climatic parameters (temperature, rainfall and evaporation), and also the physicochemical characteristics of Lake Nakuru (conductivity, phytoplankton, lesser flamingos and the lake depth). These included time series analysis, and trend analysis, so the Pearson’s correlation analysis was used to show a relationship between the alterations in lake conductivity to alterations in population estimates of the lesser flamingos and the phytoplankton. Data set extracted from the Coupled Model Intercomparison Project Phase 5 (CMIP5) (IPCC Fifth Assessment Report (AR5) Atlas subset) models were subjected to time series analysis method where the future climate scenarios of near surface temperature, rainfall and evaporation were plotted for the period 2017 to 2100 (projection) for RCP2.6 and RCP8.5 relative to the baseline period 1971 to 2000 in Lake Nakuru were analysed. The results were used to evaluate the impact of climate change on the lesser flamingos and phytoplankton abundance. It was noticed that there was a raise in the mean annual rainfall during the study period (2009 to 2014) which brought the increment in the lake’s surface area from a low area of 31.8 km² in January 2010 to a high of 54.7 km² in Sept 2013, indicating an increment of 22.9 km² (71.92% surface area increment). Mean conductivity of the lake also lessened leading to the loss of phytoplankton on which flamingos feed making them to migrate. A strong positive correlation between conductivity and the lesser flamingo population was noticed signifying that low conductivity affects the growth of phytoplankton and since the lesser flamingos depend on the phytoplankton for their feed, this subsequently revealed that the phytoplankton density could be a notable predictor of the lesser flamingo occurrence in Lake Nakuru. There was also a strong positive correlation noticed between phytoplankton and the lesser flamingo population which confirms that feed availability is a key determining factor of the lesser flamingo distribution in the lake. It is projected that there would be an increment in temperatures, rainfall and evaporation for the period 2017 to 2100 under RCP2.6 and RCP8.5 relative to the baseline period 1971 to 2000 obtained from the Coupled Model Intercomparison Project phase 5 (CMIP5) multi-model ensemble. As a result, it is expected that the lake will further increment in surface area and depth by the year 2100 due to increased rainfall thereby affecting the populations of the lesser flamingos and phytoplankton, as the physicochemical factors of the lake will alter as well during the projected period.
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Darlington, J. P. E. C., P. R. Zimmerman, J. Greenberg, C. Westberg, and P. Bakwin. "Production of metabolic gases by nests of the termite Macrotermes jeanneli in Kenya." Journal of Tropical Ecology 13, no. 4 (July 1997): 491–510. http://dx.doi.org/10.1017/s0266467400010671.
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ABSTRACTNests of a fungus-growing termite Macrotermes jeanneli discharge all their metabolic gases through a single outlet to the atmosphere. This made it possible to measure the production of metabolic gases, and the rates of water loss, for intact nests in the field. Rates of production of carbon dioxide and methane from isolated nest components (different termite castes and intact fungus combs) were measured. Using previously published nest population data and fungus comb weights in relation to nest size, the expected gas production rates for intact nests were calculated. These estimates were compared with direct observations of the gaseous outflow from intact nests. The rates were in reasonable agreement, but some nests emitted excess carbon dioxide, probably produced by respiration of tree roots and non-termite soil organisms. Large nests may have a total gas outflow of 100,000 to 400,000 1 d–1 including 800 to 1500 1 d–1 of CO2 and 0.5 to 1.3 1 d–1 of CH4. Nests lose water at the rate of up, to 13 1 d–1 gross, but allowing for ambient humidity the net water loss was up to about 5 1 d–1. Some of this is metabolic water, but the larger proportion comes from the soil. Area-based estimates of gas production were made for this and two other species of Macrotermes, but they are not accurate because the field distribution and mound density are not adequately known.
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Agyemang, Elfriede, Clement Zeh, Irene Mukui, David Maman, and Andrea Kim. "HIV Transmission Rates and Factors Associated with Recent HIV Infection: Results from the Ndhiwa HIV Impact Assessment, South Nyanza, Kenya, 2012." Open Forum Infectious Diseases 4, suppl_1 (2017): S15. http://dx.doi.org/10.1093/ofid/ofx162.037.
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Abstract Background Identifying populations with high HIV transmission rates is important for prevention and treatment strategies. Persons with recently acquired HIV infection are drivers of HIV transmission due to high levels of HIV viral load (VL). We assessed annual HIV transmission rates and factors associated with recent infection to inform targeted interventions in a hyperendemic region in Kenya. Methods The Ndhiwa HIV impact assessment was a population-based survey among persons aged 15–59 years living in South Nyanza, Kenya in 2012. Respondents were tested for HIV using rapid tests per national guidelines and provided blood for centralized testing. Specimens from HIV+ persons were tested for VL and recent infection. Recent infection was defined as normalized optical density value <1.5 on the Limiting Antigen Enzyme Immunoassay, VL >1,000 copies/mL, and no report of HIV treatment. The annual HIV transmission rate per 100 persons living with HIV (PLHIV) was calculated as HIV incidence divided by HIV prevalence, multiplied by 100. Annualized HIV incidence was estimated, assuming a mean duration of recent infection of 141 days (confidence interval [CI] 123–160). Multivariate analysis identified independent factors associated with recent infection. Estimates were adjusted for survey design. Results Of 6,076 persons tested, 1,457 were HIV+, and 28 were recently infected. HIV incidence and prevalence were 1.7% (CI 1.5–2.0) and 24.1% (CI 22.6–25.5), respectively. Per 100 PLHIV, the annual HIV transmission rate was 7.0 and varied by sex (4.6 male vs. 8.3 female), age (5.2 aged 30+ vs. 10.4 aged <30), and residence (1.4 Kobama vs. 12.0 Riana vs. 12.1 Pala divisions). After controlling for age, sex, and residence, recently infected persons were significantly more likely to reside in Pala division (AOR 8.3, CI 1.1–62.9) than HIV-uninfected persons. Conclusion Approximately 7 in 100 PLHIV transmitted to HIV-uninfected persons in South Nyanza in 2012, similar to national rates observed in the 2012 Kenya AIDS Indicator Survey. HIV transmission rates were higher in females than males, younger than older, and Riana and Pala than other divisions. Residence in Pala was a risk factor for recent infection. These findings could guide prioritization of interventions to interrupt HIV transmission in this hyperendemic setting. Disclosures All authors: No reported disclosures.
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Marshall, Michael, Michael Norton-Griffiths, Harvey Herr, Richard Lamprey, Justin Sheffield, Tor Vagen, and Joseph Okotto-Okotto. "Continuous and consistent land use/cover change estimates using socio-ecological data." Earth System Dynamics 8, no. 1 (February 8, 2017): 55–73. http://dx.doi.org/10.5194/esd-8-55-2017.
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Abstract. A growing body of research shows the importance of land use/cover change (LULCC) on modifying the Earth system. Land surface models are used to stimulate land–atmosphere dynamics at the macroscale, but model bias and uncertainty remain that need to be addressed before the importance of LULCC is fully realized. In this study, we propose a method of improving LULCC estimates for land surface modeling exercises. The method is driven by projectable socio-ecological geospatial predictors available seamlessly across sub-Saharan Africa and yielded continuous (annual) estimates of LULCC at 5 km × 5 km spatial resolution. The method was developed with 2252 sample area frames of 5 km × 5 km consisting of the proportion of several land cover types in Kenya over multiple years. Forty-three socio-ecological predictors were evaluated for model development. Machine learning was used for data reduction, and simple (functional) relationships defined by generalized additive models were constructed on a subset of the highest-ranked predictors (p ≤ 10) to estimate LULCC. The predictors explained 62 and 65 % of the variance in the proportion of agriculture and natural vegetation, respectively, but were less successful at estimating more descriptive land cover types. In each case, population density on an annual basis was the highest-ranked predictor. The approach was compared to a commonly used remote sensing classification procedure, given the wide use of such techniques for macroscale LULCC detection, and outperformed it for each land cover type. The approach was used to demonstrate significant trends in expanding (declining) agricultural (natural vegetation) land cover in Kenya from 1983 to 2012, with the largest increases (declines) occurring in densely populated high agricultural production zones. Future work should address the improvement (development) of existing (new) geospatial predictors and issues of model scalability and transferability.