University of Nairobi
  • Nairobi, Nairobi City County, Kenya
Recent publications
The explosion of time series count data with diverse characteristics and features in recent years has led to a proliferation of new analysis models and methods. Significant efforts have been devoted to achieving flexibility capable of handling complex dependence structures, capturing multiple distributional characteristics simultaneously, and addressing nonstationary patterns such as trends, seasonality, or change points. However, it remains a challenge when considering them in the context of long-range dependence. The Lévy-based modeling framework offers a promising tool to meet the requirements of modern data analysis. It enables the modeling of both short-range and long-range serial correlation structures by selecting the kernel set accordingly and accommodates various marginal distributions within the class of infinitely divisible laws. We propose an extension of the basic stationary framework to capture additional marginal properties, such as heavy-tailedness, in both short-term and long-term dependencies, as well as overdispersion and zero inflation in simultaneous modeling. Statistical inference is based on composite pairwise likelihood. The model’s flexibility is illustrated through applications to rainfall data in Guinea from 2008 to 2023, and the number of NSF funding awarded to academic institutions. The proposed model demonstrates remarkable flexibility and versatility, capable of simultaneously capturing overdispersion, zero inflation, and heavy-tailedness in count time series data.
Maize ( Zea mays L.) is a staple food for many households in sub-Saharan Africa (SSA) and also contributes to the gross domestic product (GDP). However, the maize yields reported in most SSA countries are very low and this is mainly attributed to biotic and abiotic stresses. These stresses have been exacerbated by climate change which has led to long periods of drought or heavy flooding and the emergence of new biotic stresses. Few reports exist which compile the biotic stresses affecting maize production in SSA. Here, five major biotic stresses of maize in Kenya are presented which are attributed to high yield losses. They include Maize lethal necrosis, fall armyworm, gray leaf spot, turcicum leaf blight and desert locusts. Maize lethal necrosis and fall armyworm are new biotic stresses to the Kenyan maize farmer while gray leaf spot, and turcicum leaf blight are endemic to the region. The invasion by the desert locusts is speculated to be caused by climate change. The biotic stresses cause a reduction in maize yield of 30–100% threatening food security. Therefore, this review focuses on the cause, control measures employed to control these diseases and future prospective. There should be deliberate efforts from the government and researchers to control biotic stresses affecting maize yields as the effect of these stresses is being exacerbated by the changing climate.
Objective Evaluate effects of TB-HIV co-treatment on clinical and growth outcomes in children with HIV (CHIV). Design Longitudinal study among Kenyan hospitalized ART-naive CHIV in the PUSH trial (NCT02063880). Methods CHIV started ART within 2 weeks of enrollment; Anti-TB therapy was initiated based on clinical and TB diagnostics. Children were followed for 6 months with serial viral load, CD4%, and growth assessments (weight-for-age [WAZ], height-for-age [HAZ], and weight-for-height [WHZ]). TB-ART treated and ART-only groups were compared at 6-months post-ART for undetectable viral load [VL] (<40 c/ml), CD4% change, and growth using generalized linear models, linear regression, and linear mixed-effects models, respectively. Result Among 152 CHIV, 40.8% (62) were TB-ART treated. Pre-ART, median age was 2.0 years and growth was significantly lower, and VL significantly higher in the TB-ART vs. ART-only group. After 6 months on ART, 37.2% of CHIV had undetectable VL and median CD4% increased by 7.2% (IQR 2.0%-11.6%) with no difference between groups. The TB-ART group had lower WAZ and HAZ over 6 month follow-up (WAZ -0.81 [95% CI: -1.23, -0.38], p < 0.001; HAZ -0.15 [95% CI: -0.29, -0.01], p = 0.030) and greater rate of WAZ increase in analyses unadjusted and adjusted for baseline WAZ (unadj 0.62 [95% CI: 0.18, 1.07, p = 0.006] or adj 0.58 [95% CI: 0.12, 1.03, p = 0.013]). Conclusion TB-HIV co-treatment did not adversely affect early viral suppression and CD4 recovery post-ART. TB-ART treated CHIV had more rapid growth reconstitution, but growth deficits persisted, suggesting need for continued growth monitoring.
Heavy metal pollution is a global concern with significant ecological and health implications. However, limited studies have focused on assessing heavy metal pollution in soil resulting from heavy mineral sand (HMS) mining and processing activities, as well as its effects on ecology and human health. In this study, we assessed heavy metal concentrations in soil samples collected near an HMS mine on the south coast of Kenya using Agilent 7700s ICP-MS. Geo-accumulation index (Igeo), enrichment factor (EF), and pollution index (PI) were used to evaluate the extent of soil pollution. The non-carcinogenic (NCR) and carcinogenic (CR) health risk from metal exposure was also evaluated. The results showed moderate pollution by Ti, Mn, Zn, and Nb and high pollution by Cr and As. Mean Cr concentration exceeded the maximum allowable concentration (MAC) and trigger value (TV) by 135 and 61 times, respectively, in topsoil, while As exceeded MAC and TV by 8 and 2 times. Cr and As enrichment factors (EF) were ~ 200 and ~ 25 times higher than the EF threshold value of 1.5. The NCR assessment showed that the population was more susceptible to the effects of As, while the CR assessment indicated a higher risk from Cr and As. Notably, the CR values for both As and Cr exceeded the threshold value of 10−4. The findings of this study are essential for developing regulations to monitor, control, and mitigate soil pollution from HMS mining activities and its impact on soil and human health.
Background Cervical cancer is the leading cause of cancer death in Kenyan women. Integrating cervical cancer screening into family planning (FP) clinics is a promising strategy to improve health for reproductive-aged women. The objective of this cluster randomized trial was to test the efficacy of an implementation strategy, the Systems Analysis and Improvement Approach (SAIA), as a tool to increase cervical cancer screening in FP clinics in Mombasa County, Kenya. Methods Twenty FP clinics in Mombasa County were randomized 1:1 to SAIA versus usual procedures. SAIA has five steps: (1) cascade analysis tool to understand the cascade and identify inefficiencies, (2) sequential process flow mapping to identify bottlenecks, (3) develop and implement workflow modifications (micro-interventions) to address identified bottlenecks, (4) assess the micro-intervention in the cascade analysis tool, and (5) repeat the cycle. Prevalence ratios were calculated using Poisson regression with robust standard errors to compare the proportion of visits where women were screened for cervical cancer in SAIA clinics compared to control clinics. Results In the primary intent-to-treat analysis in the last quarter of the trial, 2.5% (37/1507) of visits with eligible FP clients at intervention facilities included cervical cancer screening compared to 3.7% (66/1793) in control clinics (prevalence ratio [PR] 0.67, 95% CI 0.45–1.00). When adjusted for having at least one provider trained to perform cervical cancer screening at baseline, there was no significant difference between screening in intervention clinics compared to control clinics (adjusted PR 1.14, 95% CI 0.74–1.75). Conclusions The primary analysis did not show an effect on cervical cancer screening. However, the COVID-19 pandemic and a healthcare worker strike likely impacted SAIA’s implementation with significant disruptions in FP care delivery during the trial. While SAIA’s data-informed decision-making and clinic-derived solutions are likely important, future work should directly study the mechanisms through which SAIA operates and the influence of contextual factors on implementation. Trial registration, NCT03514459. Registered on April 19, 2018.
Objectives The period of entry into university represents one of vulnerability to substance use for university students. The goal of this study is to document the 12-month prevalence of substance use disorders among first year university students in Kenya, and to test whether there is an association between substance use disorders and mental disorders. Methods This was a cross-sectional online survey conducted in 2019 and 2020 as part of the World Health Organization’s World Mental Health International College Student (WMH-ICS) survey initiative. A total of 334 university students completed the survey. Descriptive statistics were used to summarize the demographic characteristics of the participants. Multivariate logistic regression was used to assess the association between substance use disorder and mental disorders after adjusting for age and gender. Results The 12-month prevalence for alcohol use disorder was 3.3%, while the 12-month prevalence for other substance use disorder was 6.9%. Adjusting for age and gender, there was an association between any substance use disorder and major depression, generalized anxiety disorder, bipolar 1 disorder, intermittent explosive disorder, social anxiety disorder, suicidal ideation, suicide attempt, and non-suicidal self-injury. Conclusion These findings highlight the need to institute policies and interventions in universities in Kenya that address substance use disorders and comorbid mental disorders among first-year students.
This work presents an improved gravimetric algorithm to derive reference soil moisture, with removal of some of the hypothesis on which its original expression was based, and addition of a new corrective term that takes into account the interdependence between temperature and non-unitary water density. The temperature correction term improves reference measurements by up to 0.55% of their values in the temperature range 10–35℃. The temperature-corrected reference measurements were applied to the calibration of a hand-held soil moisture meter (Lutron PMS-714) for three soil texture types: medium, fine, and very fine. Linear regression models were used to calibrate the meter for each soil type, and the resulting calibration equations were validated with field data sampled from Sondu-Miriu watershed in Western Kenya. The validation produced errors (RMSE = 0.022, 0.010, 0.010 m3/m3) that are significantly better than the meter’s reported factory calibration errors of ± 0.05 m3/m3. While calibrations did not improve correlation statistics (R2 and RMSE), they did significantly reduce biases (+ 0.009, + 0.004, -0.001 m3/m3) compared to uncalibrated ones (-0.216, -0.181, -0.184 m3/m3). Additionally, the calibrated meter values compared well with Soil Moisture Active Passive (SMAP) surface moisture data, with errors (RMSE = 0.010, 0.007, 0.008 m3/m3) well within SMAP recommended value of ± 0.04 m3/m3. A spatial scalability test showed that the calibrations are adequately robust (with R2 = 0.81, RMSE = 0.016 m3/m3, and Bias = + 0.005 m3/m3), permitting calibration equations derived from one site to be scaled out to other sites of similar soil texture regime.
Background The effect of maternal HIV on infant Mycobacterium tuberculosis (Mtb) infection risk is not well-characterized. Methods Pregnant women with/without HIV and their infants were enrolled in a longitudinal cohort in Kenya. Mothers had interferon gamma-release assays (QFT-Plus) and tuberculin skin tests (TST) at enrollment in pregnancy; children underwent TST at 12 and 24 months of age. We estimated the incidence and correlates of infant TST-positivity using Cox proportional hazards regression. Results Among 322 infants, 170 (53%) were HIV-exposed and 152 (47%) were HIV-unexposed. Median enrollment age was 6.6 weeks [interquartile range (IQR): 6.1–10.0]; most received Bacillus Calmette-Guerin (320, 99%). Thirty-nine (12%) mothers were TST-positive; 102 (32%) were QFT-Plus-positive. Among HIV-exposed infants, 154 (95%) received antiretrovirals for HIV prevention and 141 (83%) of their mothers ever received isoniazid preventive therapy (IPT). Cumulative 24-month infant Mtb infection incidence was 3.6/100 person-years (PY) [95% confidence interval (CI): 2.4–5.5/100 PY]; 5.4/100 PY in HIV-exposed infants (10%, 17/170) versus 1.7/100 PY in HIV-unexposed infants (3.3%, 5/152) [hazard ratio (HR): 3.1 (95% CI: 1.2–8.5)]. More TST conversions occurred in the first versus second year of life [5.8 vs. 2.0/100 PY; HR: 2.9 (95% CI: 1.0–10.1)]. Infant TST-positivity was associated with maternal TST-positivity [HR: 2.9 (95% CI: 1.1–7.4)], but not QFT-Plus-positivity. Among HIV-exposed children, Mtb infection incidence was similar regardless of maternal IPT. Conclusions Mtb infection incidence (by TST) by 24 months of age was ~3-fold higher among HIV-exposed children, despite high maternal IPT uptake. Overall, more TST conversions occurred in the first 12 months compared to 12–24 months of age, similar in both HIV-exposed and HIV-unexposed children.
Objectives. We investigated the challenges faced by mothers of preterm babies practicing KMC during the Covid-19 pandemic and documented the mothers’ suggestions of possible interventions. Methods. We conducted a cross-sectional descriptive study at the New Born Unit of Kenyatta National Hospital(KNH). We interviewed 82 mothers using a researcher-administered questionnaire with closed and open-ended questions. Qualitative data generated from open-ended questions was analyzed thematically. Results. KMC was majorly affected by; fear of the baby contracting COVID-19, fear of contracting COVID-19, and social distancing restrictions. The mothers’ suggested interventions included; the need for more KMC rooms, provision of appropriate clothing, strict application of COVID-19 prevention guidelines, and greater support of practice by the family. Conclusion. The mother’s pivotal role as a partner in decision-making in regard to the improvement of KMC during pandemics and possibly other settings was demonstrated. Targeted interventions should incorporate the suggestions from the mothers.
Coding gains for arbitrarily correlated signals in a spatial diversity system with conjoint signals are presented in this study. The basic form of the proposed signal synthesizer evenly produces phase changes in the output signals. The mixer is an orthogonal transformation matrix, which is energy preserving and blind to the channel correlation matrix. The idea is to synthesize additional conjoint signal copies from the received signals that would be received if there were more antennas. However, these conjoint signals contain a level of correlation with the received signals. With the assumption of flat Rayleigh fading channels, simulation results for symbol error probability (SEP) are presented for different numbers of receive branches and varying correlation conditions. It is shown that under binary phase shift keying (BPSK), the synthesizer achieves decorrelation coding gains of about 1 dB when selection combining (SC) or equal gain combining (EGC) is used. The synthesizer’s performance across M-ary quadrature amplitude modulation (MQAM) signals is also tested. In addition, analytical frameworks are derived for BPSK and MQAM, which are tightly bound by the Monte Carlo simulation results obtained using Matlab. The correlation analysis is performed for different numbers of antennas and varied antenna spacings.
Background Many people in developing countries are struggling with chronic diseases yet traditional health services remain under-utilized in the quest for universal health care. Thousands patronize these outlets for care yet little is known about provider’s competence and how these competencies inform palliative care decisions and practices. The study documented traditional health practitioners (THPs) competencies and practices for traditional palliative cancer care service delivery in Kenya. Methods This study utilized mixed-methods design and was undertaken in major towns across Kenya. A total of 201 Traditional health practitioners were purposely sampled, and interviewed. Five in-depth interviews and 6 focus group discussions were conducted. Quantitative data were analyzed using SPSSv22 while thematic and discourse analysis was carried out for qualitative data. Results Majority (92.7%) of the THPs provided general traditional health services. Nearly half of the respondents (47.7%, n = 92) stated that they had received their knowledge and abilities through divine gifting, 71 (36.8%) lineage, 61 (31.6%) apprenticeship, and 39 (20.2%) formal study. Palliative care was determined by patient state and followed consultation with caregivers for 165 (85.5%) of respondents. For 160 respondents (83%), management practices involved a mix of patient examination, conventional medical tests, herbal medicine administration, follow-up or referral. Positive feedback consisted of symptom reduction and function recovery. Conclusion Core competencies identified include: knowledge acquisition and specialization, assessment, diagnosis and disclosure, decision making, treatment, follow-up, and referral. Traditional palliative care providers share common health-related beliefs, practices and abilities that influence how they approach and make decisions regarding the health management of their patients, despite marked ethnic diversity. The shared pathways offer a chance to develop a cogent traditional palliative care service delivery model and health policy framework to promote its integration within the health workforce. The leading unmet requirements are knowledge of intellectual property rights, disclosure frameworks, and ethical regulation principles.
Background The double burden of malnutrition (DBM) is rising globally, particularly in sub-Saharan Africa. In Sierra Leone, the incidence of overweight, obesity (OWOB), and overnutrition among women has sharply increased. This finding accompanies the high incidence of undernutrition, which has been prevalent for decades. This study aimed to determine the prevalence of different malnutrition categories (underweight, overweight, obesity, and overnutrition) and associated factors among women of reproductive age (15–49 years) in Sierra Leone using secondary data analysis of the Sierra Leone Demographic Health Survey of 2019 (SLDHS-2019). Methods We conducted secondary data analysis of the SLDHS-2019 of 7,514 women aged 15–49 years. We excluded pregnant, post-natal, lactating, and post-menopausal women. Data was collected using validated questionnaires, and respondents were selected through a multistage stratified sampling approach. A multivariable logistic regression analysis was used to determine factors associated with malnutrition among 15–49-year-old women in Sierra Leone. Results Among 15–49-year-old women in Sierra Leone, the prevalence of underweight was 6.7% (95%CI: 4.5-8.9%); overweight at 19.7% (95%CI: 17.7-21.7%); obesity was 7.4% (95% CI: 5.2-9.6%); and overnutrition, 27.1% (95%CI: 25.2-29.0%). Women aged 25–34 years were more likely to be underweight (adjusted Odds Ratios, aOR = 1.670, 95%CI: 1.254–2.224; p < 0.001) than those aged 15–24 years; women who were not married were less likely to be underweight (aOR = 0.594, 95%CI: 0.467–0.755; p < 0.001) than married women. Women from the North were less likely to be underweight (aOR = 0.734, 95%CI: 0.559–0.963; p = 0.026) than the East, and those who did not listen to the radio were less likely to be underweight (aOR = 0.673; 95%CI: 0.549–0.826; p < 0.001) than those who did. Overweight was less likely among 25–34 years (aOR = 0.609, 95%CI: 0.514–0.722; p < 0.001) and 35–49 years (aOR = 0.480, 95%CI: 0.403–0.571; p < 0.001) age-groups than 15–24 years; more likely among not married women (aOR = 1.470, 95%CI:1.249–1.730; p < 0.001) than married; less likely among working-class (aOR = 0.840, 95%CI: 0.720–0.980; p = 0.026) than not working-class; most likely in women from the North (aOR = 1.325, 95%CI:1.096–1.602; p = 0.004), and less likely among women from the South (aOR = 0.755, 95%CI: 0.631–0.903; p = 0.002) than the East; less likely among women of middle-wealth-index (aOR = 0.656, 95%CI: 0.535–0.804; p < 0.001), richer-wealth-index (aOR = 0.400, 95%CI: 0.309–0.517; p < 0.001), and richest-wealth-index (aOR = 0.317, 95%CI: 0.234–0.431; p < 0.001) than the poorest-wealth-index; and more likely among women who did not listen to radios (aOR = 1.149; 95%CI:1.002–1.317; p = 0.047) than those who did. The predictors of overweight among women 15–49 years are the same as obesity and overnutrition, except overnutrition and obesity were less likely in female-headed households (aOR = 0.717,95%CI: 0.578–0.889; p < 0.001). Conclusion The prevalence of all categories of malnutrition among women of reproductive age in Sierra Leone is high, affirming a double burden of malnutrition in this study population. Underweight was more likely among the 25–34-year age group than 15–24-year. The predictors of overweight, obesity, and overnutrition were being unmarried/single, residing in the North, and not listening to the radio. There is an urgent need for policymakers in Sierra Leone to design comprehensive educational programs for women of reproductive age on healthy lifestyles and the dangers of being underweight or over-nourished.
While the livelihoods of Somalian livestock smallholders are rely heavily on seasonal climate conditions, little is known of long-term implications of the changing climate for this nation. Here, we quantify climate change impacts on pasture productivity and profitability of livestock smallholders across a rainfall gradient in northwestern Somalia. Using the Sustainable Grazing Systems (SGS) model we explore 80 future climate realisations, with global climate models projections including low- and high-impact socio-economic pathways (SSP245 and SSP585), two climate horizons (2040 and 2080) and four case study farm regions. In general, future seasonal and annual rainfall and temperature relative to the baseline period (1981-2020) increased for most regions. Mean annual temperatures increased by 9-14%, while cumulative annual precipitation increased by 37-57% from mid to late century, respectively. Grassland production increased with later climate horizons, as higher average annual rainfall together with elevated atmospheric carbon dioxide drove up growth rates in spring and autumn. Under the low emissions scenario (SSP245), changes in farm profit were modest or positive, ranging from negative 4% in Berbera to 20% in Sheikh. Under the higher emissions scenario (SSP585), farm profits were higher, ranging from 23% to 42% above baseline profits, largely due to greater pasture production and lower requirements for supplementary feed. We conclude that future climates will benefit the productivity and profitability of smallholder farmers in Somalia, although adaptive farm management will be required to cope with increased seasonal climate variability.
Understanding the spatial dynamics of landscape use by free‐ranging herbivores is essential for species management and conservation in its natural environment. We used Ivelv’s selection index, binary logistic regression analyses and stepwise regression to understand how environmental factors shape habitat selection by the Grevy’s zebra ( Equus greyvi ). We measured biotic, abiotic and human factors that may influence presence or absence of Grevy’s zebra in Samburu‐Laikipia landscape and showed: (1) during wet periods, percentage perennial grasses, livestock density and grass quality had the greatest effect on Grevy’s zebra presence; but (2) during dry weather periods a different suite of factors determined their landscape distribution, namely, the percentage of tree and bush density, distance to water and overall grass abundance. In addition, different Grevy’s zebra demographic and reproductive classes varied in their response to environmental selective forces, thus demonstrating flexibility in their patterns of habitat selection. While we recommend more detailed studies on how abiotic and biotic interact to shape habitat selection patterns, our findings underscored the need of maintaining both dry and wet season habitats to ensure essential grazing area refugia. Our findings show that ‘soft’ development with controlled livestock stocking rates within the landscape will enhance Grevy’s zebra conservation.
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16,668 members
Peter Wachira
  • Department of Biology
Peter Muriu
  • School of Economics
Agwanda Alfred
  • Population Studies and Research Institute
Arthur Kemoli
  • Department of Paediatric Dentistry / Orthodontics
30197, 00100, Nairobi, Nairobi City County, Kenya
Head of institution
Stephen Kiama
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