Browsing by Subject "West Nile Virus"
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Item A comparison study of gravid and under house CO2 mosquito traps in Harris County, Texas(Texas A&M University, 2008-10-10) White, Stephanie LynHarris County Mosquito Control Division (HCMCD) is responsible for surveillance of mosquito species that are vectors of St. Louis Encephalitis (SLE) virus and West Nile Virus (WNV) within Harris County, Texas, including the Houston metroplex. The metroplex area has some unique attributes and a vast variety of environmental habitats that are attractive to vectors of arboviruses and for the transmission of arboviruses to the human population. Data describing the efficacy of Gravid (GV) and Underhouse (UH) CO2 traps were analyzed to determine if there is a significant difference between these two trap types with respect to the number of mosquitoes and the variety of mosquito species caught. This study was conducted during the off-peak HCMCD trapping season, to gain information in preparation for a yearround trapping program utilizing Underhouse CO2 traps for WNV and SLE virus surveillance. Adjusting for the week of collection, results suggest that Gravid traps caught significantly (P = 0.009) more mosquitoes (mean = 23.134 per trap) in the study area than Underhouse traps (mean = 3.616 per trap), and that Underhouse Traps caught a larger variety of mosquito species (n = 13) than Gravid Traps (n = 11), out of 15 total different species caught. Gravid and Underhouse traps caught 9 out of 15 of the same mosquito species during the study period. Culex quinquefasciatus mosquito catches in Gravid traps and temperature were strongly correlated (Spearman's Correlation Coefficient = 0.707, P = 0.005). Geographic Information System spatial analysis indicated clustering of Culex quinquefasciatus mosquito catches in both Gravid traps, week 9 and 21 (Moran's I = 0.69, P = 0.040 and 0.74, P = 0.021, respectfully ) and Underhouse traps, week 13 and 19 (Moran's I = 0.92, P = 0.002, and 0.89, P = 0.011, respectfully). It is recommended that Harris County Mosquito Control Division continue to utilize gravid traps as a primary method of surveillance. Gravid traps (16,194) caught 85% more mosquitoes than Underhouse traps (2,531) over the fourteen week study period. Their overall success far outweighs the additional materials or labor required for their use in a successful surveillance program.Item Assessment of U.S. Agriculture Sector and Human Vulnerability to a Rift Valley Fever Outbreak(2011-08-08) Hughes, Randi CatherineForeign animal disease outbreaks can cause substantial economic losses. Policy makers need information on both the vulnerability of the food supply to disease epidemics and the impacts of alternative protection actions. This research focused on the assessment of the U.S. agricultural sector and human vulnerability to a Rift Valley Fever (RVF) outbreak and the value of a select set of alternative disease control strategies. RVF is a vector-borne, zoonotic disease that affects both livestock and humans; thus both animal and human consequences of an outbreak were examined. This research was conducted in two parts. Livestock impact assessment used an integrated epidemic/economic model to examine the extent of RVF spread in the animal population and its consequences plus the outcome of implementing two different control strategies: emergency vaccination and larvicide vector control. The number of infected, aborted, and dead animals is best controlled by coupling vaccination along with larvicide, but results in the second highest median national welfare loss. Therefore, careful decisions must be made as to what actions should be taken. Total national producer welfare is reduced with each scenario, and is more severe than the total national welfare loss (producer, consumer, and processor together). Consumer welfare is increased with each scenario due to a drop in prices of some commodities, and in some instances, an increase in supply as well. The majority of the national welfare loss can be attributed to the producers' and processors' loss in welfare. The highest damages are seen in the regions of the outbreak such as the South Central (SC). Other regions such as the Corn Belt, Lake States, and South East regions also see high damages due to price changes. The outbreak did not have substantial price effect on dairy products, but did have noticeable price changes for live cattle such as heifer calves, stocked yearling, and dairy calves. Prices for substitutes such as pork, chicken, and turkey experienced a price reduction, which can also be a factor resulting in consumer welfare gains. Human impact assessment utilized an inferential procedure for estimating the human consequences which comprise of a cost of illness calculation to assess the dollar cost of human illnesses and deaths, as well as a Disability Adjusted Life Year calculation to give an estimate of the burden of disease on public health as a whole. With potential costs above $2 billion for human illness, and with this number not accounting for loss or damages to other sectors of the economy, it can be highly probable that investing in a human vaccination campaign can be cost-effective and possibly cost-reducing. This cost along with the economic loss of the agriculture sector suggests substantial potential losses to the U.S. if this hypothetical situation were to become reality. Combining total loss estimates from the cost of illness and ASM models, potential damage of a RVF outbreak could range from 121 million to 2.3 billion US 2010$. The results of this study show the economic damages of an outbreak in the livestock population being much greater relative to the outbreak in the human population (roughly 16 times greater). It should be pointed out that both cost estimates are most likely under estimated. The animal outbreak is not incorporating all susceptible livestock (e.g. hogs and goats), and the human illness is not incorporating other damages to society (e.g. damages due to loss of tourism). By providing estimates on the potential economic outcomes, policy makers can better choose where, when, and how to invest their resources.Item Mosquitoes and the urban environment : towards establishing a more sustainable planning framework for the control of mosquitoes and the health threats they may pose(2014-05) Fox-Baker, Daniel; Dooling, Sarah; Jha, ShaleneThis paper delves into the issue of mosquito control strategies through an examination of present day issues and evaluates literature on administrative, technical, regulatory and professional practices involved in reducing exposure to mosquito borne diseases and how are their strategies tailored to specific contexts. The main issue that this paper will attempt to address is the development of a more sustainable framework for the control of mosquitoes and their respective health threats. In order to accomplish this, an examination is conducted with stakeholders involved in public health and mosquito control at local, state and national levels who can comment on their activities with authority. A list of interview questions tailored to different groups of stakeholders is utilized with the intent of eliciting data that answer to my research questions. Through this process, I am able to examine the current processes that are in use within such organizations and determine whether they are efficient, forward thinking and effective in addressing the myriad issues involved in proper mosquito control when compared to current literature on the subject. It is expected that through this paper, a better understanding of the current mosquito control processes within L.A. and Houston will be developed resulting in the creation of better practices as a direct result of the investigation.Item Spatial analysis of West Nile Virus and predictors of hyperendemicity in the Texas equine industry(2009-05-15) Wittich, Courtney AnneWest Nile Virus (WNV) first appeared in Texas equids during June 2002. It has since spread rapidly across the state and apparently become endemic. Data from outbreaks occurring between 2002 and 2004 were analyzed to determine hotspots of equine WNV disease, identify environmental factors associated with outbreaks, and to create risk maps of locations with horses at a higher risk of the disease. Kriging was used to model the smoothed WNV attack rates, and interpolated rates were mapped to describe the spatial distribution of WNV disease risk in Texas. A retrospective time-space analysis using a Poisson model was conducted on each year?s data to identify clusters with high attack rates. The resulting overlapping yearly clusters were considered areas of hyperendemicity (hotspots). The counties identified as hotspots included Hockley, Lubbock, and Lynn (primary cluster) and Leon and Roberstson (secondary cluster). Environmental and geographic features were added to the disease maps and analyzed to determine possible environmental factors associated with outbreaks. Locations in close proximity to lakes, bird breeding routes, migratory flyway zones, crop farm and agricultural land, and all dense vegetation were found to be important environmental predictors. Finally, risk maps were created that combined surveillance data on WNV positive mosquito collections and wild bird WNV cases with previously identified environmental risk factors to predict areas of high occurrence of WNV. These risk maps could be used to implement various preventative measures to reduce the transmission of WNV in the Texas equine industry.Item Structural investigation of 1,8-dinitro-4,5-dihydroxyanthraquinone and implications for docking as a small molecule inhibitor into the protease of West Nile virus(2010-03-15) Jeff Allen Borgeson; Marc C. Morais, PhD; Stanley J. Watowich, PhD; Andres F. Oberhauser, PhDFlaviviruses pose a global threat to human health and the development of a broad spectrum drug would decrease the disease burden. The small molecule, 1,8-dinitro-4,5-dihydroxyanthraquinone has shown to bind the proteases of the dengue and West Nile viruses while also reducing their titers in cell-based assays. Structure-based analog design will likely be performed in the near future to increase its activity. However, the binding mechanism and conformation of the lead is unknown. The virtual screen that discovered this inhibitor showed it as having an unorthodox bend in the middle of the anthraquinone structure upon binding the protease. Upon further investigation, tautomerism and a bent configuration may exist in the small molecule. The structure of the small molecule was investigated for structural significance upon binding the dengue and West Nile protease and to see how it affects virtual screening efforts when using AutoDock as the structure-based docking program. It can be concluded that a stable tautomer does not exist in our crystal and that the conformation portrays a slight binding nature which could allude to a bent structure in polar solvents. Co-crystallization of the protease and the small molecule did not produce a crystal capable of solving the structure and virtual screening experiments would be virtually unaffected if the tautomer or bent structure was added to a small molecule database. The tautomer and bent structure may still provide slight differences in the binding affinity upon binding the West Nile NS2B-NS3 protease.