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1
Du, Plessis Gerda. "Actinobacterial diversity of the Ethiopian Rift Valley lakes." University of the Western Cape, 2011. http://hdl.handle.net/11394/5385.
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>Magister Scientiae - MScThe class Actinobacteria consists of a heterogeneous group of filamentous, Gram-positive bacteria that colonise most terrestrial and aquatic environments. The industrial and biotechnological importance of the secondary metabolites produced by members of this class has propelled it into the forefront of metagenomics studies. The Ethiopian Rift Valley lakes are characterized by several physical extremes, making it a polyextremophilic environment and a possible untapped source of novel actinobacterial species. The aims of the current study were to identify and compare the eubacterial diversity between three geographically divided soda lakes within the ERV focusing on the actinobacterial subpopulation. This was done by means of a culture-dependent (classical culturing) and culture-independent (DGGE and ARDRA) approach. The results indicate that the eubacterial 16S rRNA gene libraries were similar in composition with a predominance of α-Proteobacteria and Firmicutes in all three lakes. Conversely, the actinobacterial 16S rRNA gene libraries were significantly different and could be used to distinguish between sites. The actinobacterial OTUs detected belonged to both the Rubrobacterales and Actinomycetales orders with members of the genus Arthrobacter being found in all three lakes. Geochemical properties were significantly different between the lakes, although more than one property attributed to the variance between community compositions. The diversity detected in the culture-based study differed significantly and all isolates belonged to the genus Streptomyces. Two novel strains were characterized by means of phylogenetic (16S rRNA gene sequence), physiological, morphological and biochemical analyses. Both novel isolates were capable of growing under "extreme" conditions- pH 12, 10% NaCl and 45°C. Partial enzyme characterization revealed that both strains produced xylanase enzymes that were active at pH 6.5 and 8.5 with an increase in activity up to 45°C. The results obtained revealed a previously undetected diversity of actinobacteria in the Ethiopian Rift Valley with a potentially novel subpopulation adapted to haloalkaline conditions. The low 16S rRNA sequence similarity of a substantial proportion of the libraries suggests that culture-based isolation may play a vital role in deciphering the community fingerprint.
The National Research Foundation and the Norwegian Research Council
2
Woldemariam, Desalegn Lidetu. "Nematode prevalence, helminth management practices and anthelmintic resistance in small ruminants in the Mid-Rift Valley of Ethiopia." Thesis, University of Pretoria, 2005. http://upetd.up.ac.za/thesis/available/etd-03022006-144251/.
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Gabaldon, Moreno Andrea. "Förnybar energi-driven membrandestillering för rening av dricksvatten: Main Ethiopian Rift Valley fallstudie." Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244403.
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Fluoride is present in all type of water sources, but levels beyond the current World Health Organization guideline of 1.5 mg/L can be very harmful for people’s health. Due to the volcanic nature of rocks in the Ethiopian Rift Valley, groundwater is contaminated with fluoride, and studies have even recorded levels up to 26 mg/L. These excessive levels are affecting more than 14 million women and children in Ethiopia. Providing population with safe and clean water could help to achieve the Sustainable Development Goal 6 (i.e. Ensure availability and sustainable management of water and sanitation for all) from the United Nations. Membrane distillation systems have been extensively tested in literature, proving to be effective in removing fluoride, even at higher concentration levels (500 mg/L). Membrane distillation is a heat driven system that works under feed water temperatures below 100 ºC. Renewable energy sources such as geothermal, solar or biomass can be used to provide that heat. This report evaluates techno-economically different technologies using TRNSYS: flat plate solar collectors, evacuated tube solar collectors and biogas from animal dung, as heat source for the membrane distillation unit. The size of the hypothetical installations was optimized to cover the demand of 30 households. Several indicators were calculated to compare the different technologies: specific energy demand, water production, and efficiency of the systems. Investment costs and operation and management costs were considered to calculate total costs and payback period of the different installations. The results show that the best techno-economic option to be installed is a hybrid model that includes a combined heat and power unit powered by biogas and evacuated tube collectors, as can meet the demand with one membrane distillation unit and also supplies electricity and biogas for cooking. However, depending on the specific location, the availability of solar radiation and manure can vary, and consequently the best option will change. In case the existence of livestock is limited, three membrane distillation units coupled with 85 m2 of evacuated tube collectors can cover the demand. If the availability of sun is limited one membrane unit coupled with a standalone biogas unit can be considered. Flat plate collectors are never the best option, as they require the biggest investment cost. Nevertheless, the existence of local manufacturers can decrease the costs.Fluor finns i alla typer av vattenkällor, men koncentrationer som ligger över nuvarande Världshälsoorganisationens riktlinjer (max 1.5 mg/L) kan vara skadlig för hälsan. Grundvatten vid Ethiopian Rift Valley innehåller höga fluorhalter på grund av geologiska orsaker, och studier har visat nivåer upp till 26 mg/L. Sådana höga halter påverkar över 14 millioner Etiopiska kvinnor och barn negativt. Att tillgodose befolkningen med säkert och rent dricksvatten skulle bidra till uppfyllelsen av FN:s Hållbarhetsmål nr 6 (Säkerställa tillgång till och hållbar vatten- och sanitetsförvaltning för alla). Membrandestillering har testats grundligt och har visat sig att vara en effektiv teknik för fluorseparering även vid höga halter (över 500 mg/L). Membrandestillering ar en värmedriven process som utnyttjar källor under 100 ºC. Värmen kan fås från förnybara energikällor som geotermisk energi, solenergi och biobränsle. Denna rapport presenterar en tekno-ekonomisk utvärdering av olika teknik med TRNSYS: plan solfångare, vakuumrörsolfångare och biogas från boskapsgödsel. Storleken hos de undersökta systemen optimerades för att täcka behovet av 30 hushåll. Flera indikatorer beräknades för att jämföra de olika teknikerna: specifika energibehov, vattenproduktion och systemens verkningsgrader. Investeringskostnaderna och drift- och underhållskostnaderna låg som grund för att bestämma bruttokostnaderna och återbetalningstiderna av de olika systemen. Resultaten visar att den mest fördelaktiga konfigurationen består av en hybrid av biogas och vakuumrörsolfångare. Detta system tillgodoser vattenbehovet och dessutom levererar el och gas för matlagning. Tillgången till solenergi och gödsel spelar en viktig roll när det gäller systemvalet. Om tillgång till gödsel är begränsad kan efterfrågan täcks genom tre membrandestilleringsenheter kopplade till 85 m2 vakuumrörsolfångare. Däremot om solenergin är begränsad kan ett system med en membrandestilleringsenhet kopplade till en biogasanläggning tillgodose vattenbehovet. Plan solfångare är aldrig ett bra alternativ eftersom de kräver höga investeringskostnader. Tillgång till lokal tillverkning kan dock minska sådana kostnader.
4
Garedew, Efrem. "Land-use and land-cover dynamics and rural livelihood perspectives, in the semi-arid areas of Central Rift Valley of Ethiopia." Umeå : Dept.of Forest Resource Management, Swedish University of Agricultural Sciences, 2010. http://epsilon.slu.se/201007.pdf.
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Gabaldon, Moreno Andrea. "Renewables-driven membrane distillation for drinking water purification: Main Ethiopian Rift Valley case study." Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-246101.
Full textAbstract:
Fluoride is present in all type of water sources, but levels beyond the current World Health Organization guideline of 1.5 mg/L can be very harmful for people’s health. Due to the volcanic nature of rocks in the Ethiopian Rift Valley, groundwater is contaminated with fluoride, and studies have even recorded levels up to 26 mg/L. These excessive levels are affecting more than 14 million women and children in Ethiopia. Providing population with safe and clean water could help to achieve the Sustainable Development Goal 6 (i.e. Ensure availability and sustainable management of water and sanitation for all) from the United Nations. Membrane distillation systems have been extensively tested in literature, proving to be effective in removing fluoride, even at higher concentration levels (500 mg/L). Membrane distillation is a heat driven system that works under feed water temperatures below 100 ºC. Renewable energy sources such as geothermal, solar or biomass can be used to provide that heat. This report evaluates techno-economically different technologies using TRNSYS: flat plate solar collectors, evacuated tube solar collectors and biogas from animal dung, as heat source for the membrane distillation unit. The size of the hypothetical installations was optimized to cover the demand of 30 households. Several indicators were calculated to compare the different technologies: specific energy demand, water production, and efficiency of the systems. Investment costs and operation and management costs were considered to calculate total costs and payback period of the different installations. The results show that the best techno-economic option to be installed is a hybrid model that includes a combined heat and power unit powered by biogas and evacuated tube collectors, as can meet the demand with one membrane distillation unit and also supplies electricity and biogas for cooking. However, depending on the specific location, the availability of solar radiation and manure can vary, and consequently the best option will change. In case the existence of livestock is limited, three membrane distillation units coupled with 85 m2 of evacuated tube collectors can cover the demand. If the availability of sun is limited one membrane unit coupled with a standalone biogas unit can be considered. Flat plate collectors are never the best option, as they require the biggest investment cost. Nevertheless, the existence of local manufacturers can decrease the costs.Fluor finns i alla typer av vattenkällor, men koncentrationer som ligger över nuvarande Världshälsoorganisationens riktlinjer (max 1.5 mg/L) kan vara skadlig för hälsan. Grundvatten vid Ethiopian Rift Valley innehåller höga fluorhalter på grund av geologiska orsaker, och studier har visat nivåer upp till 26 mg/L. Sådana höga halter påverkar över 14 millioner Etiopiska kvinnor och barn negativt. Att tillgodose befolkningen med säkert och rent dricksvatten skulle bidra till uppfyllelsen av FN:s Hållbarhetsmål nr 6 (Säkerställa tillgång till och hållbar vatten- och sanitetsförvaltning för alla). Membrandestillering har testats grundligt och har visat sig att vara en effektiv teknik för fluorseparering även vid höga halter (över 500 mg/L). Membrandestillering ar en värmedriven process som utnyttjar källor under 100 ºC. Värmen kan fås från förnybara energikällor som geotermisk energi, solenergi och biobränsle. Denna rapport presenterar en tekno-ekonomisk utvärdering av olika teknik med TRNSYS: plan solfångare, vakuumrörsolfångare och biogas från boskapsgödsel. Storleken hos de undersökta systemen optimerades för att täcka behovet av 30 hushåll. Flera indikatorer beräknades för att jämföra de olika teknikerna: specifika energibehov, vattenproduktion och systemens verkningsgrader. Investeringskostnaderna och drift- och underhållskostnaderna låg som grund för att bestämma bruttokostnaderna och återbetalningstiderna av de olika systemen. Resultaten visar att den mest fördelaktiga konfigurationen består av en hybrid av biogas och vakuumrörsolfångare. Detta system tillgodoser vattenbehovet och dessutom levererar el och gas för matlagning. Tillgången till solenergi och gödsel spelar en viktig roll när det gäller systemvalet. Om tillgång till gödsel är begränsad kan efterfrågan täcks genom tre membrandestilleringsenheter kopplade till 85 m2 vakuumrörsolfångare. Däremot om solenergin är begränsad kan ett system med en membrandestilleringsenhet kopplade till en biogasanläggning tillgodose vattenbehovet. Plan solfångare är aldrig ett bra alternativ eftersom de kräver höga investeringskostnader. Tillgång till lokal tillverkning kan dock minska sådana kostnader.
6
Eshete, Getachew. "Assessment of fuelwood resources in acacia woodlands in the Rift Valley of Ethiopia : towards the development of planning tools for sustainable management /." Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5638-X.pdf.
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Konchi, Wakgari Furi. "Hydrogeology of complex volcanic systems in continental rifted zone : integrated geochimical, geophysical and hydrodynamic approach : Middle Awash basin, Main Ethiopian Rift, Ethiopia." Poitiers, 2010. http://theses.edel.univ-poitiers.fr/theses/2010/Konchi-Wakgari-Furi/2010-Konchi-Wakgari-Furi-These.pdf.
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Middle Awash basin, located in the complex volcanic centre of the Ethiopian Rift valley, is one of the drought prone areas marked by considerable water supply problems. Due to lack of surface waters, groundwater remains the sole resource supplying water for domestic and livestock. However, its effective use has been hampered due to the complex aquifer system of this basin. In this study, multidisciplinary method has been applied to characterize the hydrogeological system of this complex volcanic basin. The combined results from datasets show two distinct aquifer systems linked to geology and physiographic location. The Ca-alkaline rocks like basalt, ignimbrite, and trachybasalt form aquifers in the mountain regions whereas the Na-alkalne rocks which include scoria, pumice, tuff, and volcanoclastics are main aquifers in rift floor. Ground waters circulating in the highland areas are slightly mineralized and are Ca-Na-HCO3 type. On the other hand, ground waters in the rift floor are Na-HCO3-Cl types and are highly mineralized as well as contain high load of fluoride much higher than the permitted standard. Rivers hydrograph, hydrochemistry, environmental isotope, and 2D tomography are in good agreement showing fast percolation of rainfall and strong interaction between surface waters and ground waters. Result from numerical groundwater flow modeling further indicates the strong interaction between groundwater and surface waters in the form of losing and gainingLe bassin central d'Awash, situé dans le centre volcanique complexe de la Vallée du Rift éthiopien, est un des secteurs les plus touchés par la sécheresse et par des problèmes considérables d'approvisionnement en eau. En raison du manque d'eau de surface, l'eau souterraine reste la ressource unique fournissant l'eau potable. Cependant, l'exploitation effective de l'eau souterraine s'est heurtée à la méconnaissance du système hydrogéologique complexe de ce bassin. Dans cette étude, une approche pluridisciplinaire a été mise en oeuvre pour caractériser l'hydrogéologie de ce bassin volcanique complexe. Les résultats couplés de l'ensemble des données montrent deux systèmes aquifères distincts liés à la géologie et à la localisation physiographique. Les roches Ca-alcalines comme le basalte, l'ignimbrite et le trachybasalte forment des aquifères dans les régions de montagne tandis que les roches Na-alcalines qui incluent les scories, la pierre ponce, les tufs et les volcanoclastiques constituent les principaux aquifères au niveau du plancher du rift. Les eaux souterraines circulant dans les secteurs montagneux sont légèrement minéralisées et sont de type Ca-Na-HCO3. Par contre, les eaux souterraines du plancher du rift sont de type Na-HCO3-Cl, sont fortement minéralisées et contiennent une charge en fluorure beaucoup plus élevée que les normes permises. Les résultats de diverses approches (hydrogrammes des fleuves, hydrochimie, isotopes environnementaux et tomographie 2D) sont concordants et montrent une percolation rapide des eaux de pluie et une forte interaction entre les eaux de surface et les eaux souterraines. Les résultats de modélisation numérique confirment la forte interaction eau souterraine - eaux de surface
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Tesfaye, Chekol Gashaw [Verfasser], Matthias [Akademischer Betreuer] [Gutachter] Wolff, and Hauke [Gutachter] Reuter. "Population and Ecosystem-based Fisheries Assessment of the Rift Valley Lake Koka, Ethiopia / Gashaw Tesfaye Chekol ; Gutachter: Matthias Wolff, Hauke Reuter ; Betreuer: Matthias Wolff." Bremen : Staats- und Universitätsbibliothek Bremen, 2016. http://d-nb.info/1113718870/34.
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Gebremariam, Bogale [Verfasser]. "Basin scale sedimentary and water quality responses to external forcing in Lake Abaya, southern Ethiopian Rift Valley / Bogale Gebremariam." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/102349745X/34.
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Mesfin, Melaku. "COMPARATIVE STUDY OF CYANOBACTERIA OF DESERT AND SEMI-DESERT CRUSTS OF TWO DIFFERENT CONTINENTS: AFRICA (ETHIOPIA) AND NORTH AMERICA (USA)." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1245854204.
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Sherefa, Muzein Bedru. "Remote Sensing & GIS for Land Cover/ Land Use Change Detection and Analysis in the Semi-Natural Ecosystems and Agriculture Landscapes of the Central Ethiopian Rift Valley." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1173870635741-98410.
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Technical complexities and the high cost of satellite images have hindered the adoption of remote sensing technology and tools for nature conservation works in Ethiopia as in many developing countries. The terrestrial and aquatic ecosystems in Abijjata Shala Lakes National Park (ASLNP) and the Important Bird Areas (IBAs) around the park are considered to be one of the most important home ranges for birds. However, little is known about the effect of land use/land cover (LULC) dynamics, due to lack of technical know how and logistical problems. However, it has been shown in this study that sophisticated image management works are not always relevant. Instead a simple method of utilizing the thermal band has been demonstrated. A new approach of long-term dynamics analysis method has also been suggested. A successful classification of images was achieved after such simple enhancement tests. It has been discovered that, there were more active LULC change processes in the area in the first study period (1973 to 1986) than during the second study period (1986-2000). In the first period nearly half of the landscape underwent land cover change processes with more than 26% of the entire landscape experiencing forest or land degradation. In the second period the extent of the change process was limited to only 1/3 of the total area with a smaller amount of degradation processes than before. During the entire study period, agriculture was responsible for the loss of more than 4/5 of the total terrestrial productive ecosystem. More than 37.6% of the total park area has been experiencing this loss for the past 3 decades. Only 1/5 of this area has a chance to revive, the remaining has undergone a permanent degradation. Lake Abijjata lost half of its size during the past 30 years. In the Zeway-Awassa basin 750 km², 2428km² and 3575km² of terrestrial lands and water bodies are within a distance of 10km, 20km and 30km from IBAs respectively. There are ecologically important areas where two or more IBAs overlap. In areas where more than two to five IBAs overlap, up to 85km² of areas have been recently degraded. High livestock density is one of the reasons for degradation. Using a monthly MODIS data from 2000-2005 and a series of interpolation techniques, the productivity of the area as well as the standing biomass were estimated. Moreover, a new method of spatially accurate livestock density assessment was developed in this study. Only 0.3% of the park area is found to be suitable for productive livestock development but nearly all inhabitants think the area is suitable. Feed availability in ASLNP is scarce even during rainy seasons. Especially the open woodlands are subject to overgrazing. Such shortage forces the inhabitants to cut trees for charcoal making to buy animal feed and non-food consumables. While more than 95% of the inhabitants in the park expanded their agriculture lands, only 13.3% of the farmers managed to produce cereals for market. The application of low cost remote sensing and GIS methods provided ample information that enables to conclude that low productivity and household food insecurity are the main driving forces behind land cover changes that are negatively affecting the natural and semi-natural ecosystems in the central and southern Rift Valley of Ethiopia. The restoration of natural ecosystems or conservation of biodiversity can be achieved only if those driving forces are tackled sustainably.
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Sherefa, Muzein Bedru. "Remote Sensing & GIS for Land Cover/ Land Use Change Detection and Analysis in the Semi-Natural Ecosystems and Agriculture Landscapes of the Central Ethiopian Rift Valley." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1173870635741-98410.
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Muzein, Bedru Sherefa. "Remote sensing & GIS for land cover, land use change detection and analysis in the semi-natural ecosystems and agriculture landscapes of the Central Ethiopian Rift Valley." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983727910.
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Lumley, Sarah. "Survival strategies of Rift Valley fever virus." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/847025/.
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Rift Valley fever phlebovirus (RVFV) is an arbovirus of medical and veterinary importance causing severe disease and mortality in humans and ruminants in endemic regions in Africa and the Arabian Peninsula. Understanding the capability, and limiting factors, of temperate British mosquitoes to support replication and transmission of RVFV is critical in order to understand the potential for RVFV establishment were it introduced to the UK. Using in vitro cell culture the effect of temperature on viral replication kinetics independently of the mosquito was investigated; demonstrating temperatures below 20 ̊C negatively affect RVFV replication. The full replication cycle was supported at 20 ̊C in vitro, and this was confirmed within in vivo mosquito experiments with wild-caught Aedes detritus demonstrating a transmission potential for RVFV at 20 ̊C and 25 ̊C. Experiments with two colonised lines of Cx. pipiens further demonstrated the transmission potential for RVFV by mosquitoes present in the UK. A novel RNA in situ hybridisation technique substantiated this result showing widespread dissemination of virus from the primary site of infection and evidence of secondary sites of replication within a single mosquito. Characterisation of the consensus sequence of RVFV propagated within these British mosquitoes in comparison to an in vivo mouse model showed potential for virus adaptation when switching between disparate hosts. Reproducible changes at the consensus level within each host had not previously been shown in early passages of RVFV in studies utilising in vitro models of replication. This suggests that RVFV replication generates genomic variation that may lead to adaptations that could promote potential survival in temperate regions. Taken together these findings indicate that transmission of RVFV within the UK by indigenous mosquitoes is possible. However, factors affecting mosquito survival including temperatures greater than 20 ̊C and ingestion of the higher virus dose (10^7 PFU/mL) will limit the likelihood of such events occurring.
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Näslund, Jonas. "Rift Valley fever : development of diagnostics and vaccines." Doctoral thesis, Umeå universitet, Klinisk mikrobiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30676.
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Rift Valley Fever virus (RVFV) causes an infection with severe impact on animal and human health. The disease is endemic throughout almost the entire African continent and large regions of the Arabian Peninsula. During epidemics, high mortality is observed in animals, especially among cattle, goats, and sheep. In humans, the symptoms vary from a benign influenza-like disease to a life-threatening hemorrhagic fever. Due to the devastating effect on communities in endemic regions and the possibility of further spread of this virus, there is an imperative need to improve and develop control measurements against this emerging disease. Therefore, this thesis focuses on diagnostics and vaccines against RVFV. RVFV infection kinetics was studied in a mouse model system by detection and quantification of viral genomes, using a developed quantitative real-time PCR (QRT-PCR) method. This novel QRT-PCR method proved to be reliable and serves as a supplement to standard diagnostics, direct virus isolation and serological methods. High levels of viral RNA were found in blood and liver samples from experimentally infected mice during the first days post infection. Thereafter the levels declined rapidly and dropped below detection limit approximately seven days post infection. The QRT-PCR technique was also used in a study aimed to improve diagnosis of RVFV from field samples collected on filter strips. Today, the available RVFV vaccines are only approved for animal use and these vaccines have several shortcomings. Since RVFV is a highly pathogenic organism requiring bio-safety level 3 laboratories, two different none-replicating vaccine approaches have been applied and evaluated using a mouse model. A DNA based vaccine, administered via gene-gun, and the use of virus-like particles (VLP), by the intra-peritoneal route. RVFV specific and neutralising antibodies were raised with both vaccine approaches. However, VLP vaccination against Rift valley Fever proved to be more promising as a future vaccine, since higher titres of neutralising antibodies and improved survival rate were found upon a lethal RVFV challenge in mice. In conclusion, a sensitive and specific method for quantifying RVFV infection and a promising vaccine candidate against RVFV were developed.
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Henry, William John. "A seismic investigation of the Kenya Rift Valley." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/35038.
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In August of 1985 the crustal structure underlying the Kenya rift valley was investigated by long range explosion seismology. The experiment (KRISP85) consisted of two seismic lines in the central sector of the rift, one along the axis (140 km) and the other across it (50 km). Interpretation of the data, including time-term analysis and ray tracing has yielded the following information. The thickness of rift infill varies from about 6 km below Lake Naivasha to about 2 km and 1.5 km below Lake Magadi and Lake Bogoria respectively. The underlying material has a P-wave velocity of 6.05 +/- 0.03 km/s which suggests the rift is underlain by Precambrian metamorphic basement. A localised high velocity zone identified to the east of Nakuru may be associated with basic intrusive material. The P-wave velocity increases discontinuously to 6.45 +/- 0.05 km/s at a depth of 12.5 +/- 1-0 km. This depth is similar to that inferred for the brittle-ductile transition zone from a study of local seismicity in the Lake Bogoria region. A high P-wave velocity layer (7.1 +/- 0.15 km/s) occurs at 22 +/- 2 km depth which might be associated with a sill-like basic intrusion in the lower crust. An upper mantle velocity of 7.5 +/- 0.2 km/s (unreversed) is reached at a depth of 34.0 +/- 2.0 km. This implies that only moderate crustal attenuation has occurred beneath the central sector of the rift. No evidence was obtained for the existence of an "axial intrusion" reaching to shallow levels below the rift and causing crustal separation as suggested by previous studies. Relative residuals determined for 46 teleseismic events recorded by a 15 station, small aperture seismic array in the vicinity of Lake Bogoria indicate considerable lateral heterogeneity in the upper crust. An Aki inversion of the relative residuals has revealed the existence of two distinct low velocity zones which may be associated with magma chambers.
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Näslund, Jonas. "Rift Valley fever development of diagnostics and vaccines /." Umeå : Department of Clinical Microbiology, Umeå university, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30676.
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Baudin, Maria. "Rift Valley fever : consequences of virus-host interactions." Doctoral thesis, Umeå universitet, Virologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-126602.
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Rift Valley fever virus (RVFV) is a mosquito-borne virus which has the ability to infect a large variety of animals including humans in Africa and Arabian Peninsula. The abortion rate among these animals are close to 100%, and young animals develop severe disease which often are lethal. In humans, Rift Valley fever (RVF) presents in most cases as a mild illness with influenza-like symptoms. However, in about 8% of the cases it progresses into a more severe disease with a high case fatality rate. Since there is such a high abortion rate among infected animals, a link between human miscarriage and RVFV has been suggested, but never proven. We could in paper I for the first time show an association between acute RVFV infection and miscarriage in humans. We observed an increase in pregnant women arriving at the Port Sudan Hospital with fever of unknown origin, and several of the patients experienced miscarriage. When we analysed their blood samples for several viral diseases we found that many had an acute RVFV infection and of these, 54% experienced a miscarriage. The odds of having a miscarriage was 7 times higher for RVFV patients compared to the RVFV negative women of which only 12% miscarried. These results indicated that RVFV infection could be a contributing factor to miscarriage. RVFV is an enveloped virus containing the viral glycoproteins n and c (Gn and Gc respectively), where Gn most likely is responsible for the initial cellular contact. The protein DC-SIGN on dendritic cells and the glycosaminoglycan heparan sulfate has been suggested as cellular receptors for RVFV, however other mechanisms are probably also involved in binding and entry. Charge is a driving force for molecular interaction and has been shown to be important for cellular attachment of several viruses, and in paper II we could show that when the charge around the cells was altered, the infection was affected. We also showed that Gn most likely has a positive charge at a physiological pH. When we added negatively charged molecules to the viral particles before infection, we observed a decreased infection efficiency, which we also observed after removal of carbohydrate structures from the cell surface. Our results suggested that the cellular interaction partner for initial attachment is a negatively charged carbohydrate. Further investigations into the mechanisms of RVFV cellular interactions has to be undertaken in order to understand, and ultimately prevent, infection and disease. There is currently no vaccine approved for human use and no specific treatments for RVF, so there is a great need for developing safe effective drugs targeting this virus. We designed a whole-cell based high-throughput screen (HTS) assay which we used to screen libraries of small molecular compounds for anti-RVFV properties. After dose-response and toxicity analysis of the initial hits, we identified six safe and effective inhibitors of RVFV infection that with further testing could become drug candidates for treatment of RVF. This study demonstrated the application of HTS using a whole-cell virus replication reporter gene assay as an effective method to identify novel compounds with potential antiviral activity against RVFV.
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Ballot, Andreas. "Cyanobacteria in Kenyan Rift Valley lakes a biological and toxicological study /." [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/116/index.html.
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Lang, Yuekun. "Identification and evaluation of antivirals for Rift Valley fever virus." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38195.
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Doctor of PhilosophyDepartment of Diagnostic Medicine/Pathobiology
Wenjun Ma
Rift Valley fever virus (RVFV) is an enveloped, negative-sense, ssRNA virus with a tripartite genome that causes morbidity and mortality in both livestock and humans. Although RVFV is mainly circulating in mainland Africa, this arthropod-borne virus is a potential threat to the other parts of the world. No fully licensed vaccines for human or animal use in the U.S., and effective antiviral drugs have not been identified. As virulent RVFV strains are only handled in biosafety level (BSL) 3 or higher level facilities in the U.S., few laboratories have access to RVFV which limits antiviral development. However, it is crucial to develop effective antivirals to protect public and animal health. Animal models that reproduce Rift Valley fever are vital to identifying and developing antiviral compounds. The currently available attenuated RVFV strain, MP12, provides a BSL-2 challenge model virus for preliminary investigations of RVFV prior to using the virulent RVFV strains. All strains of RVFV have a highly conserved genome, indicating that antivirals or vaccines effective against any RVFV strain will most likely be effective for all RVFV strains. Therefore, we hypothesize that the MP12 is a suitable model virus that can be used for identification and evaluation of effective RVF antivirals. The first objective of this project was to establish a mouse model susceptible to MP12 infection. Based on the literature, we selected and screened six different strains of mice to test their susceptibilities to MP12. We found the STAT-1 knockout mice are the most susceptible to MP12 infection based on clinical symptoms, mortality, viremia, virus replication, histopathological, and immunochemical analyses. Importantly, these mice displayed acute-onset hepatitis and delayed-onset encephalitis similar to severe cases of human RVFV infection. Our second objective was to identify potential antiviral drugs in vitro. We developed and employed a cell-based assay using the recombinant MP12 virus expressing Renilla luciferase to screen a library of 727 small compounds purchased from National Institutes of Health. Of the compounds, 23 were identified and further tested for their inhibitory activities on the recombinant MP12 virus expressing green fluorescent protein. Further plaque reduction assays confirmed that two compounds inhibited replication of parental RVFV MP12 strain with limited cytotoxic effects. The 50% inhibitory concentrations using an MP12 multiplicity of infection (MOI) of 2 were 211.4 µM and 139.5 µM, respectively. Our third objective was to evaluate these two candidates, 6-azauridine and mitoxantrone, in vivo using our mouse model. After one-hour post MP12 infection via an intranasal route, treatment was given intranasally twice daily. Mice treated with placebo and 6-azauridine displayed severe weight loss and reached the threshold for euthanasia with obvious neurological signs, while mice treated with ribavirin (a known antiviral drug) or mitoxantrone showed delayed onset of disease. This result indicates that the mitoxantrone can improve the outcome of RVFV infection in our mouse model. The underlying mechanism of mitoxantrone to inhibit RVFV replication remains to be investigated. Our studies build the foundation for identification and development of antivirals against RVFV in a BSL-2 environment.
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Wara, George Fordam Otieno. "State Recognition of Customary Land Rights in the Kenyan Rift Valley." Thesis, University of Pretoria, 2021. http://hdl.handle.net/2263/78592.
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This thesis is about the struggles of communities inhabiting the Kenyan Rift Valley to assert their customary land rights. I focus on the Rift Valley because its interface of dominance by the state statutory system over the community systems continues to pose an existential threat to the Kenyan state. I chose the Maasai, Kikuyu, Nandi and Kipsigis because the Maasai lost the largest amount of land to European settlement in the Rift Valley, the Kikuyu represent the latest community migrants to the region while the Nandi and Kipsigis claim the Rift Valley to be their ancestral land. I use theoretical concepts of systems theory, social dominance and legal pluralism to test whether the new interface model of recognition by the state of communal tenure will be effective in redressing the unhealthy competition for land resources, instabilities and conflict in the region. The struggles of these Rift Valley communities against the state system date back to 1895 when the British established a protectorate over East Africa and implemented policies that disrupted the equilibrium between the communities and their environments. The colonial state and the neo-colonial state disrupted the customary practices of the Rift Valley communities by dispossessing them of their lands. As a result of this disruption, these communities, as systems, have been pushed to the fringes of the Kenyan socio-economic system. The communities remained resilient and continued to resist the state’s disruption by asserting their customary land rights. They organized local protests that grew so widespread and complex as to pose an existential threat to the state. The colonial state then decided to increase African participation in the integrated Kenyan socio-economic system through an assimilationist policy known as the Swynnerton Plan. The Swynnerton Plan failed to adequately address the disruption because it favoured a progression in the direction of individual tenure and away from communal tenure. The first Kenyan Constitution of 1963 continued the trend toward individual tenure rights as it also failed to recognize communal tenure rights. Shortly after Kenyan independence, the state attempted to confer tenure rights to pastoral communities through the creation of group ranches. However, this effort also failed mainly because of a disconnect between the communities and the individuals that they entrusted with the management of their land. State intervention concerning community land rights in South Africa, Australia, Tanzania and Canada have shown that effective recognition and enforcement of such rights is possible where there is political goodwill. Recent legal developments in Kenya are also encouraging steps in the effort to create a stable interface between the state and community systems. Kenya promulgated a new Constitution in 2010 that finally recognizes communal tenure. It subsequently enacted legislation in 2012 to initiate investigations into historical land injustices and to recommend appropriate redress. Significantly for customary land rights, Kenya enacted legislation in 2016 that defines community land to include customary land. I conclude with suggestions on remodelling and implementation of this new communal tenure framework to effectively recognize the customary land rights of communities inhabiting the Rift Valley.Thesis (LLD)--University of Pretoria, 2021.
Public Law
LLD
Unrestricted
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Black, Stuart. "U-Th disequilibria systematics of the Olkaria complex Gregory Rift Valley, Kenya." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358148.
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Masotti, Roberta. "Seismic structure across the Kenya Rift Valley : data analysis and geodynamic implications." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/35064.
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During the 1990 Kenya Rift International Seismic Project (KRISP 90) a 450 km E-W crustal refraction profile was undertaken across the Kenya Rift, a late Tertiary to Recent extensional feature associated with extensive volcanic activity. The P-wave data have been analysed using 2-D ray-tracing, finite difference and reflectivity dynamic modelling. A simultaneous velocity and travel time inversion has been applied to the forward model to test its uniqueness and resolution. The analyses show an asymmetric sedimentary basin which is thickest against the rift's major western boundary fault. The crustal velocities vary from 6.2 km/s in the Archaean craton to the west of the rift to about 6.0 km/s in the Proterozoic orogenic belt along the remainder of the profile. The crustal thickness outside the rift varies from 38 3 km adjacent to the rift's western margin and 34 2 km to the east. Beneath the rift itself the thickness is only 30 2 km. The upper mantle velocity is generally about 8.0 km/s except beneath the rift where it is consistently low at 7.6 - 7.8 km/s. This anomalously low velocity suggests a 5 - 6% partial melt. The combined seismic and gravity model supports the contention that convective processes in the mantle are dynamically supporting the uplifted East African Plateau. Kinematic and dynamic modelling of the S-wave field show that upper crustal phases have been recorded only outside the rift. Mid and lower crustal S arrivals do not seem to have been attenuated underneath the rift axis, precluding an extensive hot regime at lower crustal depth. A reflected phase is observed from an interface within the mantle beneath the western flank of the rift. Detailed analyses of this phase confirm the presence of a high velocity layer (8.4 km/s) below 60 km: compositional anomalies as well as crystal orientation have been suggested as an explanation for the observed velocity structure. This evidence may delimit the lateral extent of the upper mantle low velocity zone underneath the graben itself. A model of extension via simple shear in the upper crust and pure shear in the lower crust and upper mantle is suggested. The presence of a small diapir under the Kenya Rift, radiating from a 'weak' plume seated under the East African Plateau, is envisaged; the diapir appears to have spread asymmetrically towards the Proterozoic lithosphere to the east of the rift.
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Thurnherr, Andreas M. "Hydrography and flow in the rift valley of the Mid-Atlantic Ridge." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42174/.
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Slow-spreading mid-ocean ridges such as the Mid-Atlantic Ridge are characterized by deep axial rift valleys which are isolated from the water on the ridge flanks. Topographic effects therefore have a significant impact on the rift-valley hydrography and dynamics but little is known about the details. Known processes of global importance acting near the axes of midocean ridges include high rates of diapycnal mixing associated with the rough topography and high-temperature hydrothermal circulation, a major source for a number of chemical constituents of the ocean. Physical data sets from the rift valley of two connected segments of the Mid-Atlantic Ridge, which include the largest known hydrothermal vent field of the Atlantic, were analyzed to investigate the segment-scale hydrography, dynamics and geothermal fluxes. The data include two quasi-synoptic hydrographic and particle plume surveys (one year apart) and one-year-long records from an array of moored current meters. The hydrographic properties of the rift-valley water were similar during the two surveys, suggesting a stable state characterized by inflow from the eastern ridge flank, unidirectional along-segment flow (directly observed during an entire year), and monotonic along-valley hydrographic gradients consistent with high rates of diapycnal mixing. Geothermal processes do not appear to contribute significantly to these patterns. The data contain signatures of a range of dynamical processes consistent with high rates of diapycnal mixing, including hydraulically controlled sill flows, topographic lee waves and high-energy tidal flows. The spatial distribution of the light-scattering anomalies associated with the dispersing hydrothermal particle plume are consistent with the dynamical observations. Close to the vent field the particle distribution is highly inhomogeneous but density-averaged profiles in¬ dicate that the mean plume is Gaussian in depth. To quantify the fluxes associated with the hydrothermal plume the corresponding hydrographic anomalies were determined. The ABSTRACT ii complexity of the hydrography within the rift valley precludes the application of "standard" methods ho that a new method had to be developed resulting in the first quantitative hydrographic anomaly measurements of an Atlantic hydrothermal plume. The hydrographic and particle anomalies of this plume are linearly correlated, indicating that the particles behave conservatively in the near field. Estimates for the heat flux associated with the hydrothermal plume were derived using two established methods, one based on plume-rise modeling and the other on the advection of heat anomalies away from the vent field. Height-of-rise modeling yields values which are an order of magnitude too low because the plume model relies on a point-source assumption which is violated by the geometry of the vent field. The uncertainties associated with the advection method are particularly small at the site studied because of the uni-directionality of the flow field, the small uncertainties of the hydrographic anomaly measurements, and the Gaussian shape of the averaged near-field plume. The resulting estimate for the heat flux associated with the particle plume is 2.5 GW. Mass and heat budgets of the rift valley indicate that high diapycnal diffusivities are required to account for the hydrographic observations and suggest that a portion of the water flowing along the rift valley may be lost to the overlying water column. Inspired by the observations a simple analytical and numerical model for the flow within the rift valley was developed. The results indicate that the rift valley acts as an efficient low-pass filter with characteristic time scales of weeks to months, providing a plausible explanation for the persistence of the along-segment flow.
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Chun, Elizabeth M. "Developing a Recombinant Plant Virus Nanoparticle Vaccine for Rift Valley Fever Virus." Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/scripps_theses/1345.
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Rift Valley Fever (RVF) is an emerging infectious disease found in both livestock and humans. RVF is associated with high abortion and mortality rates in livestock and can be fatal in humans. As such, RVF is economically and socially significant to affected smallholder and subsistence farmers, those infected, and national livestock industries. However, Rift Valley Fever virus (RVFV) vaccines are not commercially available outside of endemic areas or for humans, and current vaccines are limited in their safety and efficacy. A plant-based, viral nanoparticle vaccine offers a more affordable alternative to conventional vaccines that is safe, rapidly producible, and easily scalable, better meeting the needs of impacted communities. This project focuses on assessing the potential of using a Nicotiana benthamiana plant expression system to generate recombinant tobacco mosaic virus (TMV) nanoparticles displaying RVFV glycoprotein epitopes. Eight TMV-RVFV glycoprotein constructs were designed. Five TMV-RVFV constructs were successfully cloned, and four recombinant TMV constructs were successfully expressed in planta. The antigenicity of these constructs was examined for their possible use in RVFV vaccine development.
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LaBeaud, Angelle Desiree. "New Understanding of the Epidemiology of Rift Valley Fever Virus in Kenya." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1237579750.
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Sakkas, Vassilis A. "Combined transient electromagnetic and magnetotelluric study of the southern Kenya Rift Valley." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30437.
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The transient electromagnetic (TEM) method and the magnetotelluric (MT) technique have been applied to determine the electrical resistivity structure across the southern Kenya Rift Valley. The main profile extends from the shores of Lake Victoria, west of the Rift Valley, to the north of the Chyulu Hills volcanic chain, 150 km SE of the rift. A second profile runs parallel to the Chyulu Hills volcanic trend. Data from 19 stations along the two profiles have been processed using classical techniques and in the case of MT, analysed with modern tensor decomposition methods. The TEM data have facilitated the removal of static shift effects from the MT data and recovery of the near-surface (<300 m) geoelectric structure. One-dimensional joint inversion of TEM and MT data yielded an approximate geoelectric structure for the region. Subsequent two-dimensional modelling has revealed a more realistic resistivity distribution for the complex environment of the Kenya Rift. A resistive (>2000 .m) Archaean crust 30 km thick, with a 10-12 km mid-crustal conductive (100 .m) zone, resting on a moderately resistive (100 .m) mantle appears at the west end of the main profile. A conductive fault-like zone extending to mantle depths in the area of the Oloololo Escarpment coincides with the exposed boundary between the Archaean Nyanza Craton and the Proterozoic Mozambique Belt. A poorly constrained highly resistive (>10000 .m) (Proterozoic ?) crust is found at the western flank of the rift. Low resistivities (<50 .m) are found down to the base of the crust in the rift zone and are possibly due to the presence of sedimentary fill deposits at shallow depths, and the presence of magmatism and partial melt at deeper levels. East of the rift a less sharply defined geoelectric margin, offset from the accepted topographic and geologic boundary of the rift, marks the transition to a more resistive (1000 .m.) Proterozoic crust. Significantly enhanced conductivities (<100 .m) are implied in the complex 3-D region of the Chyulu Hills.
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Marshall, A. Saskia. "High-silical peralkaline magmatism of the Greater Olkaria Volcanic Complex, Kenya Rift Valley." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310585.
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Métras, Raphaëlle. "A spatial statistical approach towards understanding Rift Valley fever epidemics in South Africa." Thesis, Royal Veterinary College (University of London), 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618293.
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Mwangi, John Gowland. "Factors related to the motivation of extension agents in Kenya's Rift Valley Province /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848531362887.
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Hansson, Ebba. "Characterizing Subsurface Structure of Two Contrasting Sites in the Main Ethiopian Rift." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-396851.
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The Main Ethiopian Rift is a part of the East African Rift, from where the African plate is being teared apart and separated from the Indian and the Arabian plate. Even though earthquakes in this area are relatively less frequent, the subsurface structure is a subject of big research interest, since information about the subsurface layers has considerable relevance when it comes to site amplication related to earthquakes. The aim of this project is to map and compare the subsurface structures of two sites located in the Ethiopian Rift, using seismic refraction technique. By looking at the first arrivals of artificial seismic waves on a designated site, the velocities as well as the thicknessof the subsurface layers can be obtained. The result showed that the both sites contained a low velocity structure which contained weathered material.
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Mendenhall, Michelle. "Punta Toro Virus Infection in Mice: Strain Differences in Pathogenesis and Regulation of Interferon Response Pathways." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/425.
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The Adames strain of Punta Toro virus (PTV-A) causes acute hepatic disease in hamsters and mice similar to that seen in natural Rift Valley fever virus (RVFV) infection, while the Balliet strain (PTV-B) is apathogenic. The ability of PTV-A to suppress the interferon (IFN) response has been demonstrated in hamsters and is thought to be a contributing factor to PTV-A's pathogenicity in hamsters. PTV-B is not assumed to exhibit this IFN-antagonistic activity, as it stimulates production of significantly higher IFN-β levels. To elucidate the role of IFN in resistance of mice to PTV-B infection, we utilized mice deficient in a critical IFN signaling protein, STAT-1. We found that these mice were drastically more susceptible to PTV-B, which caused 100% lethality compared to 0% in their wild-type counterparts. STAT-1 deficient mice were also more susceptible to PTV-A, as these mice succumbed to infection significantly earlier than wild-type mice (p=0.0058). We sought to determine whether PTV-A's IFN-antagonistic mechanism is functional in mice by examining expression of IFN-β in primary macrophages infected with either strain. We found that IFN-β protein concentration is higher in samples taken from PTV-B-infected cells. We employed quantitative PCR arrays specific to IFN signaling and response pathways to evaluate changes in gene expression throughout the course of infection with either virus strain. We found several genes with differentially regulated expression between PTV-A- and PTV-B-infected macrophages, including Ifnβ1 and multiple Ifnα subtypes. Also, several genes coding for inflammatory and chemotactic molecules, Cxcl11, Cxcl10, Cxcl9, Vcam1, and Il6, demonstrated increased expression in PTV-B samples compared to PTV-A. Of particular interest, Isg20, a 3'-5' exonuclease with specificity for single-stranded RNA, was stimulated ~2-fold higher by PTV-B, and Iigp1, from the family of GTPases associated with host defense against intracellular pathogens, was stimulated ~2.7-fold higher by PTV-B. The individual functions of each of these genes in mouse resistance to PTV-B could be a focus of future studies to better understand essential host defense mechanisms to phleboviral infection.
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Bicknell, Joshua. "The meaning of violence : a journey of understanding through the Rift Valley of Kenya." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30399.
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On the 30th December 2007, following the disputed presidential election fought between Raila Odinga of the ODM Party and Mwai Kibaki of the PNU Party, violence erupted in the Rift Valley of Kenya. Focusing on the Kalenjin and Kikuyu ethnicities this paper takes a hermeneutical approach and argues that explanations of violence will always be incomplete without a prior understanding of what violence means for the different communities involved. It argues that this understanding comes from the dominant traditions of violence that people grow up in, which are constructed and held in narrative form. From this theoretical approach and building on five weeks of fieldwork conducted in the Rift Valley of Kenya in the September and October of 2010, the argument proceeds that in both the Kikuyu and Kalenjin communities storylines were constructed by the elites and opinion makers, building on existing narratives and framing events and experiences. These storylines were then reproduced at a local level and constructed violence as legitimate, necessary and directly led to fighting. From this conclusion, the final part of this paper suggests that by comprehending the compelling narratives leading to violence, persuasive counter-narratives can be introduced and strengthened, which might deconstruct violence as legitimate and make communities want peace. Overall, it is suggested that a hermeneutical approach to violence is valuable and must be pursued where the overriding goal is peace and human dignity.
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Núñez, García Ana Isabel. "Influence of mosquito-virus interaction on Zika virus and Rift Valley fever phlebovirus transmission." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670697.
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Les malalties transmeses per vectors representen un alt percentatge de les malalties infeccioses en el món. Concretament, les malalties causades per arbovirus (arthropod-born viruses), que circulen en la naturalesa entre artròpodes (els seus vectors), i els hostes vertebrats (els seus reservorios), poden causar malalties greus en els hostes vertebrats, però no causen una patologia significativa en els vectors. Durant dècades les malalties causades per arbovirus van ser oblidades, ja que en la seva gran majoria estaven localitzades en zones en vies de desenvolupament. En l'actualitat, factors ambientals, ecològics i socioeconòmics, com el canvi climàtic i la globalització, han contribuït a l'emergència i reemergencia de les malalties arbovirales. El constant moviment de persones i mercaderies ha donat lloc a la colonització i establiment d'espècies d'exòtiques al nostre país, com el mosquit tigre (Aedes albopictus), el qual és transmissor de molts arbovirus (e.g. el virus del dengue, el virus Zika (ZIKV) o el virus chikungunya). El desenvolupament d'aquesta tesi es va centrar en realitzar estudis de competència vectorial per al ZIKV i en un estudi del transcriptoma de Culex pipiens després de ser exposat al phlebovirus de la febre de la Vall del Rift (RVFV) per a comprendre les interaccions el virus i els mosquits locals.
Els capítols I i II es van focalitzar a estimar la competència vectorial per a ZIKV de diferents espècies de mosquits de camp presents al nostre país: Aedes albopictus, Aedes caspius i Culex pipiens. A més, es van desenvolupar experiments de transmissió vertical per a determinar si la generació de mosquits provinents de femelles infectades amb el ZIKV és capaç de disseminar-ho. Durant el desenvolupament d'aquests estudis, s'ha demostrat que els mosquits locals de l'espècie Ae. albopictus són vectors competents per al ZIKV. No obstant això, les espècies Cx. pipiens i Ae. caspius són refractàries per a aquest arbovirus. Respecte a l'experiment de transmissió vertical, es va demostrar que la progènie de les femelles inoculades amb el virus de manera intratoràcica va ser susceptible a la infecció del virus, però no van ser capaços de disseminar-lo.
D'altra banda, el capítol III es va centrar en l'estudi de les interaccions a nivell molecular entre l'espècie de mosquit Cx. pipiens i RVFV, amb l'objectiu caracteritzar les alteracions a nivell molecular de l'expressió dels gens corresponents al sistema immune del mosquit durant la infecció per RVFV mitjançant una anàlisi del transcriptoma de novo. Com a resultat, es van obtenir 48 gens diferencialment expressats en els mosquits davant la presència del virus que servir de diana per a controlar la infecció, ja sigui per a desequilibrar la tolerància dels mosquits al virus com per a inhibir la infecció en els mosquits. Els resultats obtinguts de l'estudi de les alteracions del transcriptoma de mosquits de l'espècie Cx. pipiens exposats a RVFV estableixen les bases per a la realització de futurs estudis funcionals dels gens involucrats a controlar/permetre la infecció per RVFV.
En el seu conjunt, el desenvolupament d'aquesta tesi incrementa el coneixement per a millorar el disseny d'estratègies eficients per a la vigilància de vectors transmissors del ZIKV i del RVFV.Las enfermedades transmitidas por vectores representan un alto porcentaje de las enfermedades infecciosas en el mundo. Concretamente, las enfermedades causadas por arbovirus (arthropod-borne viruses), que circulan en la naturaleza entre artrópodos (sus vectores), y los hospedadores vertebrados (sus reservorios), pueden causar enfermedades graves en los hospedadores vertebrados, pero no causan una patología significativa en los vectores. Durante décadas las enfermedades causadas por arbovirus fueron olvidadas, ya que en su gran mayoría estaban localizadas en zonas en vías de desarrollo. En la actualidad, factores ambientales, ecológicos y socioeconómicos, como el cambio climático y la globalización, han contribuido a la emergencia y reemergencia de las enfermedades arbovirales. El constante movimiento de personas y mercancías ha dado lugar a la colonización y establecimiento de especies de exóticas en nuestro país, como el mosquito tigre (Aedes albopictus), el cual es transmisor de muchos arbovirus (e.g. el virus del dengue, el virus Zika (ZIKV) o el virus chikungunya). El desarrollo de esta tesis se centró en realizar estudios de competencia vectorial para el ZIKV y en un estudio del transcriptoma de Culex pipiens después de ser expuesto al phlebovirus de la fiebre del Valle del Rift (RVFV) para comprender las interacciones el virus y los mosquitos locales. Los capítulos I y II se focalizaron en estimar la competencia vectorial para ZIKV de diferentes especies de mosquitos de campo presentes en nuestro país: Aedes albopictus, Aedes caspius y Culex pipiens. Además, se desarrollaron experimentos de transmisión vertical para determinar si la generación de mosquitos provenientes de hembras infectadas con el ZIKV es capaz de diseminarlo. Durante el desarrollo de estos estudios, se ha demostrado que los mosquitos locales de la especie Ae. albopictus son vectores competentes para el ZIKV. Sin embargo, las especies Cx. pipiens y Ae. caspius son refractarias para este arbovirus. Con respecto al experimento de transmisión vertical, se demostró que la progenie de las hembras inoculadas con el virus de forma intratorácica fue susceptible a la infección del virus, pero no fueron capaces de diseminarlo. Por otro lado, el capítulo III se centró en el estudio de las interacciones a nivel molecular entre la especie de mosquito Cx. pipiens y RVFV, con el objetivo caracterizar las alteraciones a nivel molecular de la expresión de los genes correspondientes al sistema inmune del mosquito durante la infección por RVFV mediante un análisis del transcriptoma de novo. Como resultado, se obtuvieron 48 genes diferencialmente expresados en los mosquitos ante la presencia del virus que servir de diana para controlar la infección, ya sea para desequilibrar la tolerancia de los mosquitos al virus como para inhibir la infección en los mosquitos. Los resultados obtenidos del estudio de las alteraciones del transcriptoma de mosquitos de la especie Cx. pipiens expuestos a RVFV sientan las bases para la realización de futuros estudios funcionales de los genes involucrados en controlar/permitir la infección por RVFV. En conjunto, el desarrollo de esta tesis incrementa el conocimiento para mejorar el diseño de estrategias eficientes para la vigilancia de vectores transmisores del ZIKV y del RVFV.
Vector-borne diseases represent a 17 % of infectious diseases in the world. Among them, those diseases caused by arboviruses (arthropod-borne viruses), which circulate in the nature between arthropods (their vectors) and vertebrate hosts (their reservoirs), are currently provoking serious diseases in humans and animals. For decades, the arboviral diseases were neglected, since most of them were located in developing areas. Nowadays, environmental, ecological and socioeconomic factors (e.g., globalization and climate change) have contributed to the emergence and re-emergence of arboviral diseases. The constant movement of people and merchandise has allowed the colonization and establishment of exotic mosquito species in our country such as the tiger mosquito (Aedes albopictus), which is a potential vector of many arboviruses (e.g., dengue virus, Zika virus or chikungunya virus). This thesis focused on conducting vector competence and transmission studies in local mosquito species for Zika virus (ZIKV) and on the study of the Culex pipiens transcriptome alteration after being exposed to the Rift Valley fever phlebovirus (RVFV) in order to better understand how virus-vector interaction influences on ZIKV and RVFV transmission. Chapters I and II focused on estimating the vector competence for ZIKV of different field-collected mosquito species present in our country: Aedes albopictus, Aedes caspius and Culex pipiens. In addition, vertical transmission studies were performed to determine if the progeny of females infected with ZIKV were able to disseminate the virus. The results of these studies showed that local populations of Ae. albopictus were competent vectors for ZIKV and Cx. pipiens and Ae. caspius species were refractory for this arbovirus. Moreover, it was demonstrated that ZIKV was able to be transmitted to the progeny but the later could not disseminate the virus. Chapter III focused on the study of interactions between the Cx. pipiens mosquito species and RVFV at molecular level, with the aim to characterize the alterations in the expression of the mosquito genes related to the immune system during RVFV infection by analyzing de novo transcriptome. As a result, 48 immune differentially expressed genes in mosquitoes exposed to RVFV were altered, which could serve as potential targets to control the infection, either by unbalancing the mosquito tolerance to RVFV or by inhibiting the infection in mosquitoes. The results obtained on the Cx. pipiens transcriptome alterations due to exposure to RVFV pave the way for future functional studies about genes involved in the control/tolerance of RVFV infection. Overall, this thesis increased the knowledge to better design efficient strategies for ZIKV and RVFV surveillance and control.
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Rolon, Luisa F. "Structural geometry of the Jura-Cretaceous rift of the Middle Magdalena Valley basin--Colombia." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=23.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vi, 63 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 29-37).
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Mottram, Timothy James. "The interactome of Rift Valley fever phlebovirus : towards the identification of new intervention strategies." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/41034/.
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Rift Valley fever phlebovirus (RVFV) is an ongoing threat to both humans and animals across the continent of Africa. RVFV is a member of the Phlebovirus genus and Phenuviridae family, within the Bunyavirales order. Members of the Phlebovirus genus are characterised by a negative sense tripartite RNA genome. The large (L) segment encodes the RNA-dependent RNA polymerase (L), the medium (M) segment encodes the two glycoproteins Gn and Gc, and the small segment (S) encodes the nucleocapsid (N) protein and the non-structural protein NSs. The N protein performs a number of important functions, including encapsidation of the viral genome allowing viral RNA replication and transcription. Research into N protein-protein interactions has been limited. The work presented in this thesis characterises previously unidentified functional residues of RVFV N protein and describes new insights into virus-host protein-protein interactions. Two previously uncharacterized N protein residues, F11 and F149, when substituted for alanine, performed all its known functions; Encapsidation of the viral genome, N-N multimerisation and L protein interaction. However, utilising a minigenome assay still showed these mutants lack replication capacity. This indicates that currently unknown interactions with these residues are disrupted. Furthermore, a proteomics study on N protein immunoprecipitated from lung epithelial A549 cell infections was performed to identify RVFV N interaction partners, revealing 23 potential candidates. A subsequent siRNA knockdown of candidates identified β-catenin, Polyadenylate binding protein 1 and 4, Annexin 1 and 2, and Scaffold attachment factor B as important for functional viral replication. Previous research indicated β-catenin, the effector molecule of the WNT pathway, was involved with RVFV replication. Utilising a TOPFlash reporter assay, it was determined that the WNT pathway, of which β-catenin is the effector molecule, was inhibited by RVFV infection. The generation of a CRISPR-Cas9 β-catenin knockout cell line provided a useful tool for further study into N protein-protein and RVFV-β-catenin interactions. The knockout of β-catenin significantly reduced RVFV replication, similarly to siRNA-mediated knock down. Additionally, it was observed through the use of confocal microscopy that upon infection with RVFV, β-catenin relocalised from the plasma membrane to a diffuse pattern across the cytoplasm. Furthermore, during the course of this study, it was investigated whether RVFV N protein can affect mosquito antiviral pathway(s), similarly to yellow fever virus (genus flavivirus) capsid protein. Using alphavirus Semliki Forest virus (SFV) as a model, allowing work to be carried out in a CL-2 lab setting, it was found that N protein does not possess such properties. However, Zika virus (genus flavivirus) capsid protein (ZIKV C) showed significant proviral properties, however, this effect did not occur via disruption of the siRNA pathway, the most efficient mosquito antiviral mechanism, as evidenced by ZIKV C having no effect within our siRNA assay. To summarise, the data in this thesis reveals new interactions between RVFV nucleocapsid protein and mammalian host proteins that are important for RVFV replication. It provides a basis for future research on RVFV (or phleboviruses, in general) nucleocapsid research. The disruption of RVFV N-host protein interactions or direct disruption of N function could lead to new therapeutic strategies against this important emerging virus.
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Mbewana, Sandiswa. "Development of Rift Valley fever virus candidate vaccines and reagents produced in Nicotiana benthamiana." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25446.
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Rift Valley fever (RVF) is a haemorrhagic fever agent caused by an infection with an enveloped negative-stranded RNA Rift Valley fever virus (RVFV). It belongs to the genus Phlebovirus in the family Bunyaviridae. The virus is spread by infected mosquitoes and affects ruminants and humans, causing high numbers of neonatal fatalities in animals and occasional fatalities in humans. It is endemic to parts of Africa and the Arabian Peninsula, but is described as an emerging virus due to the wide range of mosquitoes that could spread the disease into non-endemic areas, posing serious health and agricultural problems. The disease can be prevented by vaccination, but there is currently no Food and Drug Administration-approved RVFV vaccine that can be used outside endemic areas, while there are two live attenuated vaccines available for use in endemic areas. These vaccines have the potential for reversion, and are therefore not recommended for use in countries where RVFV is not endemic. This indicates the need for more RVFV vaccine research and development. This work focused on the development of a RVFV vaccine candidate that would allow for differentiation between infected and vaccinated animals as well as humans.
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Hoare, Sally. "A multi-proxy approach to reconstructing palaeoenvironmental change at Kilombe, Central Rift Valley, Kenya." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2037599/.
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Linking climate and evolutionary change within the hominin lineage relies on the production of higher resolution records from sites which preserve hominin fossil and/or archaeological occurrences. The Acheulean site of Kilombe in the Central Rift Valley, Kenya is one of the largest handaxe sites in Eastern Africa; its immediate area is now shown to preserve a continuous sedimentary record from the early Pleistocene through to the Holocene. The main Acheulean occurrences at Kilombe date to about one million years, and are preserved in less than one metre of sedimentation. However, renewed research since 2008 has identified a recurring human presence with handaxes found in other parts of the sequence, along with Middle and Later Stone Age materials from late Pleistocene and potentially Holocene deposits. This thesis presents a record of palaeoenvironmental change extending from 1.07 to 0.487 Ma and coeval with the Acheulean occurrences at Kilombe. A multi-proxy approach was taken here to investigate the nature and impact of both long-term trends of environmental change and those occurring on shorter timescales over a 500,000 year period. The techniques of environmental magnetism and desktop-based major and trace element geochemistry were adopted as a rapid, non-destructive approach which require only small amounts of sample for analyses making them ideal proxies from which to examine environmental change over a long time period with little expense incurred. A long-term record of environmental change is revealed from the Kilombe sedimentary sequences based on geochemical and magnetic proxies sensitive to chemical weathering intensity and pedogenesis. Overall, results reveal a long-term increasing trend in aridification/cooling at Kilombe throughout the Pleistocene with substantial variability superimposed upon this trend linked to a range of environmental processes including dissolution and volcanic activity. This research now provides a general environmental setting for the major Acheulean occurrences at Kilombe.
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Huhndorf, Michael H. Loew Sabine Susanne. "Phylogeography and molecular phylogenetics of East African rodents assessing the role of vicariance /." Normal, Ill. : Illinois State University, 2007. http://proquest.umi.com/pqdweb?index=0&did=1432808091&SrchMode=2&sid=7&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1216229896&clientId=43838.
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Thesis (Ph. D.)--Illinois State University, 2007.Title from title page screen, viewed on July 16, 2008. Dissertation Committee: Sabine S. Loew (chair), Angelo P. Capparella, William L. Perry, John M. Bates, Julian C. Kerbis Peterhans. Includes bibliographical references (leaves 89-99) and abstract. Also available in print.
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Teka, Girma. "NaCl, Heparin, and Heparan Sulphate Affects Binding of Rift Valley Fever Virus to Human Cells." Thesis, Umeå universitet, Biomedicinsk laboratorievetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-58534.
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Scharton, Dionna. "Antiviral Activity of Favipiravir (T-705) Against Lethal Rift Valley Fever Virus Infection in Hamsters." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2323.
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Rift Valley Fever is a zoonotic, arthropod-borne disease that adversely affects ungulates and people. The etiologic agent, Rift Valley fever virus (RVFV; Bunyaviridae, Phlebovirus), is primarily transmitted through mosquito bites, yet can be transmitted by exposure to infectious aerosols. Presently, there are no licensed vaccines or therapeutics to prevent or treat severe RVFV infection in humans. We have previously reported on the activity of favipiravir (T-705) against the MP-12 vaccine strain of RVFV and other bunyaviruses in cell culture. Additionally, efficacy has been documented in mouse and hamster models of infection with the related Punta Toro virus. Here, we characterize a hamster RVFV challenge model and use it to evaluate the activity of favipiravir against the highly pathogenic ZH501 strain of the virus. Subcutaneous RVFV challenge resulted in substantial serum and tissue viral loads and caused severe disease and mortality within 2-3 days after infection. Oral favipiravir (200 mg/kg/day) prevented mortality in 60% or greater in hamsters challenged with RVFV when administered within 6 h post-exposure and reduced RVFV titers in serum and tissues relative to the time of treatment initiation. In contrast, although ribavirin (75 mg/kg/day) was effective at protecting animals from the peracute RVFV disease, most ultimately succumbed from a delayed-onset neurologic disease associated with high RVFV burden in the brain observed in moribund animals. When combined, T-705 and ribavirin treatment started 24 h post-infection significantly improved survival outcome and reduced serum and tissue virus titers compared to monotherapy. Our findings demonstrate significant post-RVFV exposure efficacy with favipiravir against both peracute disease and delayed-onset neuroinvasion, and suggest added benefit when combined with ribavirin.
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Brown, Geoffrey James. "The effect of Rift Valley fever virus clone 13 vaccine on semen quality in rams." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/46103.
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Rift Valley fever (RVF) is an arthropod-borne viral disease of significant importance in both livestock and humans. Epidemics occur periodically in domestic ruminants, typically after heavy rains, which encourage rapid multiplication of mosquito vectors. Clinical symptoms in livestock vary from inapparent infection to abortions and peracute deaths.
The disease has significant zoonotic potential. People in contact with infected livestock may develop disease that varies from mild flu-like symptoms to severe neurological and haemorrhagic disorders and death.
An important way of controlling the disease is through vaccination of susceptible livestock. Rift Valley fever virus (RVFV) clone 13 is a relatively new livestock vaccine against RVF that is derived from an avirulent natural mutant strain of RVFV. This vaccine has been shown in previous studies to confer protective immunity against infection with live virus.
The effect of this vaccine on semen quality in male animals has never been tested.
The purpose of the current trial was to determine whether RVFV clone 13 vaccine had any effect on semen quality in rams. The hypothesis tested was that animals vaccinated with RVFV clone 13 vaccine would not experience a reduction in semen quality (measured by evaluating the percentage progressively motile and percentage morphologically normal spermatozoa in successive ejaculates) relative to unvaccinated control animals.
A test/control model was used to evaluate the effect of this vaccine on semen quality.
A group of peripubertal ram lambs were tested for antibodies to RVFV using a serum neutralisation test (SNT). Animals without detectable antibodies (n=23) were then randomly allocated to either a test group (n=12) or a control group (n=11). Daily rectal temperature measurements were taken and weekly semen evaluations were conducted. Blood samples were drawn weekly to assess serum antibody titres.
Seven animals were subsequently eliminated from the statistical analysis because of potential confounding factors. Of these seven, five animals had extremely poor semen quality at the start of the trial, one animal was found to have a persistent febrile response commencing at the start of the trial, and one animal had seroconverted to Rift Valley fever virus in the period between the initial screening and onset of the trial.
Logistic regression analysis was performed on data gathered from the remaining animals to determine whether an association existed between animal group, rectal temperature and semen quality parameters. It was found that no correlation existed between treatment group and values obtained for the semen quality parameters measured. There was no statistically significant post-vaccination temporal decline in the percentage of live morphologically normal spermatozoa, or the percentage of progressively motile spermatozoa, either when assessed amongst all animals or when assessed within individual groups. Based on the data from this trial, the hypothesis was not rejected.
Despite this finding, it should be stated that the elimination of animals from the analysis had some effect on the statistical power of the study. A repeat of the trial with a larger sample size and a more comprehensive pre-screening process to avoid the inclusion of animals with poor semen quality may be indicated.Dissertation (MMedVet)--University of Pretoria, 2014.
tm2015
Production Animal Studies
MMedVet
Unrestricted
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Gudka, Masumi. "Assessment of pesticide concentrations in environmental and biological parameters from two Kenyan Rift Valley Lakes." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12083.
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Includes abstract.Includes bibliographical references.
In the last two decades Kenyan agriculture has developed rapidly. In particular, horticultural and floricultural activities have intensified on the riparian fringe of Lake Naivasha, a RAMSAR site. The lake supports a large variety of wildlife and avifauna in particular. In the 1980s, the African Fish-Eagle (Haliaeetus vocifer) population on the lake was the densest in Africa. As a top predator resident in the Kenyan Rift Valley Lakes the African Fish-Eagle is a good indicator of general ecosystem health but is also highly susceptible to toxic effects of pesticide contamination...Globally, most organochlorine pesticides have been banned, but endosulfan, HCH and methoxychlor are widely used in Kenya, while aldrin, dieldrin and lindane are restricted and DDT, endrin, and heptachlor banned. Studies examining residue levels of these harmful chemicals in African Fish-Eagles are limited to small sample sizes examined in the 1970s and 1980s. This study is the first comprehensive investigation of organochlorine residue contamination in biological and environmental parameters from Lake Naivasha and the control water body at Lake Baringo.
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Ermler, Megan Elizabeth. "MAVS is Essential for Regulation of Innate Immune Signaling during Rift Valley Fever Virus Infection." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1378752537.
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Mohammed, Wolela Ahmed. "Sedimentology, diagenesis and hydrocarbon potential of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK and USA)." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394602.
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Galindo, Cardiel Iván José. "Sheep experimental model for rift valley fever virus Infection for the study of immunopathogenesis, pathology and vaccinology." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/457755.
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El virus de la Fiebre del Valle del Rift (RVFV) es un flebovirus zoonótico transmitido por mosquitos que afecta a los rumiantes causando abortos y hepatitis aguda con necrosis multifocal. Los síntomas de la RVF varían desde el síndrome gripal hasta la retinitis y la encefalitis. En esta tesis, mostramos la susceptibilidad leve-subaguda de las ovejas Ripollesas de 9-10 semanas de edad a la infección por RVFV. Cuatro aislamientos virales diferentes de brotes de campo se replicaron de forma eficiente in vivo tras la inoculación subcutánea experimental, detectándose viremia y diseminacion viral dependientes del aislado de RVFV. Se demostró la transmisión horizontal a un cordero centinela no infectado. La infección en corderos únicamente causó pirexia transitoria, aunque se observó opacidad corneal ("ojo azul") en 3 de 16 ovejas inoculadas subcutáneamente. En una aproximación preliminar, se investigó el tejido formolado y parafinado procedente de estos animales afectados por la opacidad corneal mediante histopatología y qRT-PCR, para su caracterización. En cuatro corderos infectados se diagnosticó uveítis anterior con endotelitis linfoplasmocítica. Para evaluar la protección conferida por una única dosis subcutánea de una vacuna de virus Ankara modificado (MVA) que codifica las glicoproteínas Gn y Gc de RVFV en corderos, se inmunizaron 3 grupos de 6 a 7 corderos de 5-7 semanas de edad de la siguiente manera: Un grupo vacunal (denominado rMVA-GnGc), un segundo grupo control vectorial (vector MVA) y un tercer grupo control no vacunado (solución salina). Catorce días más tarde, todos los animales se sometieron a un desafío subcutáneo con 105 TCID50 del aislamiento virulento RVFV 56/74 y se evaluó la eficacia de la vacuna usando puntos finales estándar. Dos corderos (uno del grupo vacunado y uno del control vectorial) sucumbieron al desafío, mostrando lesiones hepáticas características. Los corderos de los grupos control vectorial y control no vacunado fueron febriles de los días 2 a 5 después del desafío (pc) mientras que los del grupo rMVA-GnGc mostraron un único pico de pirexia al día 3 pc. Se detectó ARN de RVFV en ambos hisopados nasal y oral de los días 3 a 7 pc en algunos corderos de los grupos control vectorial y no vacunado, pero no se pudo detectar diseminación viral en los corderos supervivientes vacunados. Caracterizamos patológicamente la nueva lesión ocular detectada en un abordaje secundario. Se seleccionaron 2 grupos de 5 corderos por grupo (n = 10) de la base de datos histórica de infecciones experimentales de RVFV realizadas en el Centro de Investigación en Sanidad Animal (España, NBS3), en base a sus datos clínicos, viremia y diagnóstico de lesiones ocular y hepática. Se caracterizó la uveítis anterior diagnosticada (8 de 10) con endotelitis linfoplasmocítica (2 de 10). CD3, CD20 e infiltrados inflamatorios mononucleares positivos a la lisozima se observaron en ojos parafinados RVFV-positivos. El marcaje positivo de CD20 sólo se observó en los infiltrados en uvea anterior. También se diagnosticó una nueva retinitis T dependiente (CD3 positivo) en 5 de 10 corderos infectados con RVFV. Se desarrolló un protocolo de inmunoquímica contra RVFV basado en un anticuerpo monoclonal murino. En conclusión, la raza Ripollesa se infecta fácilmente con RVFV sin manifestaciones clínicas evidentes. Un modelo de desafío con corderos de 5 a 10 semanas de edad ha demostrado ser eficaz para testar vacunas. Se sugiere que una sola dosis de la vacuna rMVA-GnGc puede ser suficiente para reducir la diseminación de RVFV y la duración de la viremia, pero no proporciona inmunidad estéril ni protección contra la enfermedad. Hasta donde sabemos, esta es la primera descripción patológica de uveítis anterior con lesión retiniana en un modelo ovino, muy parecida a las lesiones oculares humanas.Rift Valley Fever Virus (RVFV) is a mosquito-borne zoonotic phlebovirus that primarily affects ruminants by causing abortions and acute hepatitis with multifocal necrosis as major findings. Human RVF symptoms range from flu-like syndrome to retinitis and encephalitis. The increasing interest in RVFV deserve revisiting experimental sheep infection. In this thesis, we show the susceptibility of 9–10 weeks old European sheep (Ripollesa breed) to RVFV infection, showing a mild, subacute form of disease. Four different viral isolates from field outbreaks efficiently replicated in vivo after subcutaneous experimental inoculation, and consistent viral loads in blood and RVFV-isolate dependent virus shedding were detected, showing horizontal transmission to a noninfected, sentinel lamb. RVFV infection caused transient pyrexia in old lambs and no other clinical symptoms were observed, although corneal opacity (“blue eye”) was found in 3 out of 16 subcutaneously inoculated sheep. To better characterize this corneal opacity, in a preliminary approach, formalin-fixed paraffin wax-embedded tissue from these ocular condition-affected animals was investigated by histopathology and quantitative real time reverse transcriptase polymerase chain reaction. Anterior uveitis with lymphoplasmacytic endotheliitis was diagnosed in these four RVFV-infected lambs. To evaluate the protection conferred by a single subcutaneous dose of a modified vaccinia virus Ankara (MVA) vectored vaccine encoding the RVFV glycoproteins Gn and Gc in lambs, 3 groups of 6 to 7 Ripollesa lambs of 5–7 weeks old were immunized as follows: one group received the vaccine (termed rMVA-GnGc), a second group received an MVA vector (vector control) and a third group received saline solution (non-vaccinated control). Fourteen days later, all animals were subcutaneously challenged with 105 TCID50 of the virulent RVFV isolate 56/74 and vaccine efficacy assessed using standard endpoints. Two lambs (one from the vaccine group and one from the vector control group) succumbed to RVFV challenge, showing characteristic liver lesions. Lambs from both the vector control and non-vaccinated groups were febrile from days 2 to 5 post challenge (pc) while those in the rMVA-GnGc group showed a single peak of pyrexia at day 3 pc. RVFV RNA was detected in both nasal and oral swabs from days 3 to 7 pc in some lambs from the vector control and non-vaccinated groups, but no viral shedding could be detected in the surviving lambs vaccinated with rMVA-GnGc. We characterize pathologically the new ocular detected condition in a secondary approach. Two groups of five lambs per group were selected (n=10) from the historical database of RVFV experimental infections performed in Center of Research in Animal Health (Spain, NBS3 facility) in the basis of their clinical data, viremia and diagnosed ocular and hepatic lesions (two previous experiments). The previously diagnosed anterior uveitis (8 out of 10) with lymphoplasmacytic endotheliitis (2 out of 10) was characterized. CD3, CD20 and lysozyme-positive mononuclear inflammatory infiltrates were observed in RVFV-positive paraffin-embedded eyes. CD20 labelling was only observed in infiltrates in anterior uvea. A novel T-cell dependent retinitis was also diagnosed in 5 out of 10 RVFV-infected lambs based on CD3-positive labelling. An immunochemistry protocol based on a murine monoclonal antibody was developed at CReSA BLS2 facility. In conclusion, Ripollesa sheep are readily infected with RVFV without apparent clinical manifestations. A 5-10 weeks old Ripollesa breed challenge model has proven to be effective in vaccine testing because of its susceptibility to virus. It is suggested that a single dose of the rMVA-GnGc vaccine may be sufficient to reduce RVFV shedding and duration of viremia but does not provide sterile immunity nor protection from disease. To our knowledge, this is the first pathological description of RVFV-related anterior uveitis with retinal injury in a RVFV-challenge sheep model, resembling ocular human lesions.
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Balogh, Aaron Michael. "Virulence characterization of Rift Valley fever virus strains and efficacy of glycoprotein subunit vaccines in mice." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/34625.
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Master of ScienceDepartment of Diagnostic Medicine/Pathobiology
Juergen A. Richt
Rift Valley fever virus (RVFV) is a vector-borne zoonotic pathogen endemic to sub-Saharan Africa and the Arabian Peninsula that causes severe disease in ruminants and humans. RVFV is a significant threat to US livestock and public health due to a lack of licensed, efficacious vaccines and its ability to become established in non-endemic areas. Subunit vaccine candidates based on RVFV N- and C-terminal glycoproteins (Gn and Gc) are a viable option for use in ruminants due to their ease of production, safety, and ability to induce immune responses that offer differentiation between infected and vaccinated animals (DIVA). Importantly, subunit Gn+Gc vaccine candidates have demonstrated efficacy in sheep. However, despite the efficacy of a dual glycoprotein vaccine, no studies have directly compared protective efficacies of the individual glycoproteins. Furthermore, although RVFV demonstrates 2.1% maximum pairwise amino acid strain divergence within Gn/Gc ectodomains, it remains unclear how this may affect cross-protective vaccine efficacy. In this study, we used a BALB/c mouse model to determine the median lethal dose (LD₅₀) of 3 wildtype RVFV strains and used this information to standardize challenge doses in subsequent vaccine efficacy studies using baculovirus-expressed Gn/Gc antigens derived from RVFV strain Zagazig Hostpital 1977 (ZH548). Strains Kenya 2006 (Ken06) and Saudi Arabia 2001 (SA01) demonstrated equally high virulence (LD₅₀= 7.9pfu), while recombinant strain South Africa 1951 (rSA51) was less virulent (LD₅₀=150pfu). Following prime-boost vaccination, 100% (10/10) of the Gn+Gc vaccinated mice survived challenge with x1000 LD₅₀ Ken06 and SA01, while only 50% (5/10) of Gn+Gc vaccinated mice survived challenge with rSA51. Additionally, 90% (9/10) of Gn-only vaccinated and 40% (4/10) of Gc-only vaccinated mice survived challenge with Ken06. These data suggest that a Gn-only subunit vaccine is an efficacious alternative to dual glycoprotein vaccine candidates and that our ZH548-derived Gn+Gc vaccine has the potential to cross-protect against divergent RVFV strains. Results from this study can be used to optimize current vaccine formulations and inform future vaccine efficacy and licensure studies in ruminants.
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Ahmed, Hassan Ahmed Osama. "Rift Valley fever : challenges and new insights for prevention and control using the “One Health” approach." Doctoral thesis, Umeå universitet, Virologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-127095.
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Rift Valley fever (RVF) is an emerging viral zoonosis that causes frequent outbreaks in east Africa and on the Arabian Peninsula. The likelihood of RVF global expansion due to climate change and human anthropogenic factors is an important issue. The causative agent, RVF virus, is an arbovirus that is transmitted by several mosquito species and is able to infect a wide range of livestock as well as people. The infection leads to mass abortions and death in livestock and a potentially deadly hemorrhagic fever in humans. RVF has severe socio-economic consequences such as animal trade bans between countries, disruption of food security, and economic disaster for farmers and pastoralists as well as for countries. Human behavior such as direct contact with infected animals or their fluids and exposure to mosquito bites increases the risk for contracting the disease. To better understand the challenges associated with RVF outbreaks and to explore prevention and control strategies, we used the One Health approach. The local community had to be involved to understand the interaction between the environment, animals, and humans. We focused on Sudan, Saudi Arabia, and Kenya. First, we systematically reviewed the literature and then we performed cross sectional community-based studies using a special One Health questionnaire. Climatic and remote sensing data were used in combination with statistics to develop a sub-region predictive model for RVF. For both Saudi Arabia and Sudan, the ecology and environment of the affected areas were similar. These areas included irrigation canals and excessive rains that provide an attractive habitat for mosquito vectors to multiply. The surveillance systems were unable to detect the virus in livestock before it spread to humans. Ideally, livestock should serve as sentinels to prevent loss of human lives, but the situation here was reversed. Differences between countries regarding further spread of RVF was mainly determined by better economic and infrastructure resources. In Sudan, there was a lack of knowledge and appropriate practices at the studied community regarding RVF disease symptoms and risk factors for both animals and humans. The community was hesitant in notifying the authorities about RVF suspicion in livestock due to the lack of a compensation system. The perceived role of the community in controlling RVF was fragmented, increasing the probability of RVF transmission and disease. In Kenya, our study found that better knowledge about RVF does not always translate to more appropriate practices that avoid exposure to the disease. However, the combination of good knowledge, attitudes, and practices may explain why certain communities were less affected. Strategies to combat RVF should consider socio-cultural and behavioral differences among communities. We also noticed that RVF outbreaks in Kenya occurred in regions with high livestock density exposed to heavy rains and wet soil fluxes, which could be measured by evapotranspiration and vegetation seasonality variables. We developed a RVF risk map on a sub-regional scale. Future outbreaks could be better managed if such relevant RVF variables are integrated into early warning systems. To confront RVF outbreaks, a policy is needed that better incorporates ecological factors and human interactions with livestock and environment that help the RVF pathogen spread. Early detection and notification of RVF is essential because a delay will threaten the core of International Health Regulations (IHR), which emphasizes the share of information during a transboundary disease outbreak to avoid unnecessary geographical expansion.
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Hofmann, Barbara. "How do faults grow in magmatic rifts? : LiDAR and InSAR observations of the Dabbahu rift segment, Afar, Ethiopia." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/7546/.
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Dyke intrusions and normal faulting play an important role during continental break-up but little is known about how the normal faults develop. Direct evidence of dyke-induced faulting is limited by the lengthy repeat times between individual rifting episodes, the small amount of subaerial rift zones and until recently the technical ability to record small surface changes across large areas. The most recent (2005-2010) rifting episode at the Dabbahu rift segment, Afar, Ethiopia provided a unique opportunity to study dyke-induced fault growth. The combination of new high-resolution topographic LiDAR data and interferometric synthetic aperture radar (InSAR) data provides information of cumulative as well as incremental fault throw. In this thesis I use high-resolution LiDAR data of the Dabbahu rift segment to reveal a dense network of short fault segments (>3400) at various stages of fault linkage set in flood basalt plains. I develop and present a semi-automatic algorithm that extracts throw along surface fault traces from the high-resolution LiDAR DEM. The largest amount of throw (~80 m) is found on faults towards the east of the rift segment. At the central Ado’Ale volcanic edifice predominant bookshelf faulting is evident which might be an indication of a lateral shift of the dykes towards the east. I use the throw data to derive a strain field for the rift. Faults record ~140 m of extension, implying extensive resurfacing. I derived displacement data from two LiDAR surveys and InSAR data, for two separate dyke intrusions. Both data sets show that faults are re-activated in a broad, 3-4 km wide, asymmetric zone parallel to the dyke induced subsidence with the majority of the new throw being accumulated on 1-2 large west-dipping fault structures in the east. The incremental displacement-length, d − L, data presented here is the first quantitative study of accumulation of new fault throw across an entire rift segment. Incremental throw across linkage zones suggest two types of behaviour once fault linkage is complete. 1) Individual fault segments maintain the ability to slip independently. This was previously only observed during analogue modelling. 2) The connected faults act as one throughgoing fault with slip unaffected by the linkage zone. The combination of these two processes might be responsible for the commonly observed small-scale corrugation in d − L data. In contrast to published fault growth models, I present evidence that the remnant fault tip of a linkage zone does not necessarily become inactive once linkage is complete, and that linkage zones do not ‘catch up’ through accelerated throw once linkage is complete.
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Girma, Woldetinsae. "The lithosphere of the East African rift and plateau (Afar-Ethiopia-Turkana) insights from integrated 3-D density modelling /." [S.l.] : [s.n.], 2005. http://e-diss.uni-kiel.de/diss_1478/d1478.pdf.
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