School-wide publications

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Start date: 2000

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Now showing 1 - 10 of 26
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    Stratified Sampling of Neighborhood Sections for Population Estimation: A Case Study of Bo City, Sierra Leone
    (Public Library of Science, 2015-07-15) Hillson, Roger
    There is a need for better estimators of population size in places that have undergone rapid growth and where collection of census data is difficult. We explored simulated estimates of urban population based on survey data from Bo, Sierra Leone, using two approaches: (1) stratified sampling from across 20 neighborhoods and (2) stratified single-stage cluster sampling of only four randomly-sampled neighborhoods. The stratification variables evaluated were (a) occupants per individual residence, (b) occupants per neighborhood, and (c) residential structures per neighborhood. For method (1), stratification variable (a) yielded the most accurate re-estimate of the current total population. Stratification variable (c), which can be estimated from aerial photography and zoning type verification, and variable (b), which could be ascertained by surveying a limited number of households, increased the accuracy of method (2). Small household-level surveys with appropriate sampling methods can yield reasonably accurate estimations of urban populations.
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    Reevaluating HLA-A2-restricted Lassa epitopes in human Lassa fever survivors
    (American Association of Immunologists, 2020-05-01) Sullivan, Brian Martin
    Many factors contribute to the selection of epitope-specific T cells. Often, candidate epitopes are generated through in silico prediction of various biological processes, mainly peptide generation and MHC binding, that are then tested in relevant biological assays. This is especially true of epitopes derived from BSL-4 pathogens or where relevant patient samples are difficult to obtain. Two previous studies identified CD8+ T cell epitopes from the Lassa virus glycoprotein through in silico prediction, experimental MHC binding assays, and epitope generation in HLA-A2 transgenic mice. Using samples from ten HLA-A\*02:01 Lassa fever survivors, we tested whether these previously described epitope-specific CD8+ T cells were present and their relation to the broader Lassa virus-specific T cell response. Using overnight stimulation assays, we detected robust LASV-specific responses to the glycoprotein and nucleoprotein, but only one of the three epitopes (GP60–68)shown to be present and protective in mice made a substantial contribution to the overall LASV-specific response. Using a more sensitive proliferation assay, we detected the remaining two epitopes in some individuals at a very low frequency. Overall, this study shows the limitations of epitope discovery through in silico prediction, MHC binding and transgenic mouse models and highlights the complex nature of T cell selection during natural infection of humans.
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    A synoptic revision of Inversodicraea (Podostemaceae)
    (National Herbarium of the Netherlands, 2017-09-14) Cheek, Martin
    Six new species of Inversodicraea (I. feika from Sierra Leone, I. liberia from Liberia, and I. ebo, I. eladii, I. tchoutoi, and I. xanderi from Cameroon) are described as new to science in the context of a synoptic revision of this African genus, now comprising 30 species, including I. cussetiana comb. nov., newly transferred from Macropodiella. Inversodicraea is now equal in number of species to Ledermanniella (as redefined), as the largest genus of the family in Africa. Terete or slightly dorsiventrally flattened leaf petioles (not sheathing and/or stipulate) are newly discovered to distinguish the genus from Ledermanniella, in addition to the presence of scale-leaves. Inversodicraea boumiensis, I. annithomae, and I. bosii are redelimited in this paper. Examples of species hybrids are discussed. Eighteen species are point endemics. A key and IUCN 2012 standard conservation assessments for all species are included. 28 of the 30 species have been assessed as Threatened or Near Threatened. Hydroelectric projects are the biggest source of extinction risk to species of the genus, threatening 19 of the 30 species.
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    Surveillance of COVID-19 in Cameroon: Implications for policymakers and the healthcare system
    (AOSIS, 2021-01-29) Bonnechère, Bruno
    At first less impacted than the rest of the world, African countries, including Cameroon, are also facing the spread of COVID-19. This study aimed to analyze the spread of the COVID-19 in Cameroon, one of the most affected countries in sub- Saharan Africa. We used the data from the Africa Centre for Disease Control and Prevention, reporting the number of confirmed cases and deaths, and analyzed the regularity of tests and confirmed cases and compared those numbers with neighboring countries. We tested different phenomenological models to model the early phase of the outbreak. Since the first reported cases on the 7th of March, 18,662 people have been diagnosed with COVID-19 as of the 24th of August, 186,243 tests have been performed, and 408 deaths have been recorded. New cases have been recorded only in 50% of the days since the first reported cases. There are considerable disparities in the reporting of daily cases, making it difficult to interpret these numbers and to model the evolution of the pandemic with the phenomenological models. Currently, following the finding from this study, it is challenging to predict the evolution of the pandemic and to make comparisons between countries as screening measures are so sparse. Monitoring should be performed regularly to provide a more accurate estimate of the situation and allocate healthcare resources more efficiently.
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    Identification of Common CD8+T Cell Epitopes from Lassa Fever Survivors in Nigeria and Sierra Leone
    (American Society for Microbiology, 2020-04-06) Sakabe, Saori
    The high morbidity and mortality associated with clinical cases of Lassa fever, together with the lack of licensed vaccines and limited and partially effective interventions, make Lassa virus (LASV) an important health concern in its regions of endemicity in West Africa. Previous infection with LASV protects from disease after subsequent exposure, providing a framework for designing vaccines to elicit similar protective immunity. Multiple major lineages of LASV circulate in West Africa, and therefore, ideal vaccine candidates should elicit immunity to all lineages. We therefore sought to identify common T cell epitopes between Lassa fever survivors from Sierra Leone and Nigeria, where distinct lineages circulate. We identified three such epitopes derived from highly conserved regions within LASV proteins. In this process, we also identified nine other T cell epitopes. These data should help in the design of an effective pan-LASV vaccine.
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    High prevalence of multidrug resistant Enterobacteriaceae isolated from outpatient urine samples but not the hospital environment in Bo, Sierra Leone
    (BioMed Central, 2016-04-18) Łęski, Tomasz A.
    BACKGROUND: The rising level of antimicrobial resistance among bacterial pathogens is one of the most significant public health problems globally. While the antibiotic resistance of clinically important bacteria is closely tracked in many developed countries, the types and levels of resistance and multidrug resistance (MDR) among pathogens currently circulating in most countries of sub-Saharan Africa are virtually unknown. METHODS: From December 2013 to April 2014, we collected 93 urine specimens from all outpatients showing symptoms of urinary tract infection (UTI) and 189 fomite swabs from a small hospital in Bo, Sierra Leone. Culture on chromogenic agar combined with biochemical and DNA sequence-based assays was used to detect and identify the bacterial isolates. Their antimicrobial susceptibilities were determined using a panel of 11 antibiotics or antibiotic combinations. RESULTS: The 70 Enterobacteriaceae urine isolates were identified as Citrobacter freundii (n = 22), Klebsiella pneumoniae (n = 15), Enterobacter cloacae (n = 15), Escherichia coli (n = 13), Enterobacter sp./Leclercia sp. (n = 4) and Escherichia hermannii (n = 1). Antimicrobial susceptibility testing demonstrated that 85.7 % of these isolates were MDR while 64.3 % produced an extended-spectrum ß-lactamase (ESBL). The most notable observations included widespread resistance to sulphonamides (91.4 %), chloramphenicol (72.9 %), gentamycin (72.9 %), ampicillin with sulbactam (51.4 %) and ciprofloxacin (47.1 %) with C. freundii exhibiting the highest and E. coli the lowest prevalence of multidrug resistance. The environmental cultures resulted in only five Enterobacteriaceae isolates out of 189 collected with lower overall antibiotic resistance. CONCLUSIONS: The surprisingly high proportion of C. freundii found in urine of patients with suspected UTI supports earlier findings of the growing role of this pathogen in UTIs in low-resource countries. The isolates of all analyzed species showed worryingly high levels of resistance to both first- and second-line antibiotics as well as a high frequency of MDR and ESBL phenotypes, which likely resulted from the lack of consistent antibiotic stewardship policies in Sierra Leone. Analysis of hospital environmental isolates however suggested that fomites in this naturally ventilated hospital were not a major reservoir for Enterobacteriaceae or antibiotic resistance determinants.
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    Cercospora leaf spot on cowpea-Sierra Leone
    (CAB International Publishing, 2013-09-01) Kanteh, S. M.
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    The Recharge Potential of Groundwater in the Mokonde Community in Southern Sierra Leone
    (Scientific Research Publishing, 2015) Mansaray, Abubakarr Sidique
    Understanding the hydrologic budget is crucial in planning for community based water supply. The water budget includes rainfall intensity, groundwater recharge, interception, evapotranspiration, and surface runoff. The percentage of rain going to recharge groundwater, rivers, and lakes is very important from the standpoint of human water consumption and ecosystems service. The objective of this work is to determine the recharge potential of groundwater in the Mokonde Community, Southern Sierra Leone. The community is dependent on wells as the main source of domestic water supply. This research need was born out of the absence of available data to show the relationship between rainfall amounts and groundwater recharge in the study area. In this study we monitored groundwater in a well at the United Methodist Church (UMC) compound at Ngegba Street. Automatic water logging devices were deployed to take readings in water level fluctuations every 15 minutes. Monitoring continued throughout the hydrological year of Sierra Leone. A rain gauge was deployed at neighboring UMC Primary School, and daily rainfall records taken at 9:00 a.m. Our team members also deployed at the well on a daily basis to collect data on abstraction of water. The results revealed, through a 29-year rainfall data and the Specific Yield, that 1170 mm of rainfall (48%) was the maximum potential of rainfall that would make groundwater a convenient source of water supply in the area. This demand was higher with the recent 1-year rainfall data. Increase in settlement had likely led to reduction in pervious area, and hence more and more rainfall needed for recharge. The time it took for maximum recharge (4 weeks) was shorter than that for maximum discharge (28 - 30 weeks). Groundwater flowed southwards towards the Gbengitay stream, which drained into the Tia River. These results would inform first step in delineating the water balance in the study area. Future studies could include the quality aspect, stream/river flow, interception and evapotranspiration. These pieces of information are required to help informed decision for water security.
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    Massively multiplexed microbial identification using resequencing DNA microarrays for outbreak investigation
    (SPIE, 2011-05-13) Łęski, Tomasz A.
    Multiplexed microbial diagnostic assays are a promising method for detection and identification of pathogens causing syndromes characterized by nonspecific symptoms in which traditional differential diagnosis is difficult. Also such assays can play an important role in outbreak investigations and environmental screening for intentional or accidental release of biothreat agents, which requires simultaneous testing for hundreds of potential pathogens. The resequencing pathogen microarray (RPM) is an emerging technological platform, relying on a combination of massively multiplex PCR and high-density DNA microarrays for rapid detection and high-resolution identification of hundreds of infectious agents simultaneously. The RPM diagnostic system was deployed in Sierra Leone, West Africa in collaboration with Njala University and Mercy Hospital Research Laboratory located in Bo. We used the RPM-Flu microarray designed for broad-range detection of human respiratory pathogens, to investigate a suspected outbreak of avian influenza in a number of poultry farms in which significant mortality of chickens was observed. The microarray results were additionally confirmed by influenza specific real-time PCR. The results of the study excluded the possibility that the outbreak was caused by influenza, but implicated Klebsiella pneumoniae as a possible pathogen. The outcome of this feasibility study confirms that application of broad-spectrum detection platforms for outbreak investigation in low-resource locations is possible and allows for rapid discovery of the responsible agents, even in cases when different agents are suspected. This strategy enables quick and cost effective detection of low probability events such as outbreak of a rare disease or intentional release of a biothreat agent.