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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Vector Competence of Northern California Mosquitoes for Dirofilaria immitis (Spirurida: Onchocercidae)

Dian, Rebekah Lynn 01 January 2018 (has links) (PDF)
Dirofilaria immitis, commonly known as dog heartworm, is a dangerous filarial nematode that is transmitted by a mosquito vector. Although this parasite is historically localized to regions closer to the equator, the last few decades have experienced an increase in the amount of dog heartworm cases in Northern California, most notably in Lake and San Joaquin Counties. The primary vector of D. immitis in Northern California is Aedes sierrensis, but it is not prevalent enough in some counties to explain the increase in infections. Because of this, more prevalent and abundant species should be assessed for their ability to transmit heartworm. Culex pipiens complex (wild) and Culiseta incidens (laboratory-raised colonies) were chosen as potential vectors during this study due to their ability to meet several key vector criteria, their relative abundance in the areas of interest, and the fact that they habitually take bloodmeals from domestic dogs. Additionally, Ae. sierrensis colonies were used in this study, based on previous knowledge that they are highly competent vectors. Female mosquitoes were infected with 2.5, 5, or 10 mff/ul of D. immitis-infected blood, and decapitated at 15, 18, and 21 days post-infection. Mosquitoes were subsequently tested via qPCR for the presence and relative quantification of D. immitis DNA. We found that Ae. sierrensis and Cx. pipiens complex were both able to support the development of D. immitis to its infective stage, while Cs. incidens was not a competent vector. We also concluded that including a standard curve of known amounts of D. immitis larvae makes it possible to approximate the intensity of the infection in the mosquito. The identification of these important vectors, and the ability to assess infection intensity, may be helpful in the continued vector control efforts in Northern California and beyond.
182

Gap Junctions in the Mosquito, Aedes aegypti

Calkins, Travis L. January 2017 (has links)
No description available.
183

Negative photoaxis of mosquito larvae as a potential tool in the rapid bilogical monitoring of aquatic wastes (Diptera: Culicidae)

Knausenberger, Walter Ingolf 13 March 2009 (has links)
A little-known approach to toxicity testing--based on negative phototaxis of larval <u>Aedes aegypti</u>--was investigated as a contribution to the search for rapid methods applicable to the field of water pollution control. Zinc and copper were the toxicants tested. All tests were conducted with a standard "synthetic" dilution water. A mosquito colony was established to provide a uniform supply of test larvae. Preliminary tests were performed on the acute toxicity of zinc and copper against <u>A. aegypti</u> larvae, as well as tests on larval growth and development at various concentrations of the metals. For the photomigration toxicity tests, two juxtaposed troughs were used, one containing the test solution, the other a control. Third instar larvae migrated away from a six-watt fluorescent light for two minutes per run. This was repeated at intervals until 50% were unable to migrate 50 cm in 120 sec. Photographs were taken of the larval migrations. From the pictures an empirical criterion was derived (the 40-cm, 60-sec ET₅₀) through a series of graphical interpolations. All inactivation analyses were based on this criterion. From time-inactivation regression lines, exponential toxicity curves were obtained by interpolation. The curves were of an unusual shape, depicting the characteristic nature of the dosage-response. The sensitivity of the inactivation technique was comparable to that of the acute toxicity tests. However, inactivation was far quicker; depending on concentration, it occurred within one to five hours. By all methods used in this study, zinc and copper were judged to be slow-acting and of low overall toxicity. Copper was, however, consistently more toxic than zinc by at least one order of magnitude. The ET₅₀ in 10 ppm Cu⁺⁺ was 147 min.; in 10 ppm Zn⁺⁺, it was 209 min. Some possible improvements in technique were discussed. It was suggested that the photornigration approach to toxicity testing can be of definite practical use to biologists in water pollution control. / Master of Science
184

Effects of habitat and plant volatiles on mosquito spatial, seasonal, and chemical ecology

VanderGiessen, Morgen 03 June 2021 (has links)
Mosquitoes, by transmitting vector-borne diseases through their saliva, impact nearly half of the world's population. Mosquito survival is dependent on their sense of smell, or olfaction, which allows a mosquito to differentiate between plant nectar, required for metabolic processes, and host odors, which will help them navigate towards hosts, source of the blood required for producing eggs. Mosquitoes interpret and respond to chemical volatiles very differently depending on their environment (temperature, humidity, time of day, etc.) and species-specific host preferences (humans, mammals, etc.). However, the impact of ecological factors on mosquito prevalence, sugar-feeding, and host seeking is relatively unknown. In an attempt to address this knowledge gap, we first investigate how several ecological factors (i.e., temporal, seasonal, and topographical) affect mosquito sugar feeding and population dynamics. Second, we focused on the anthropophilic mosquito species Aedes aegypti to investigate the role of plant associated compounds in host-seeking behavior, such as those which are commonly found in personal care products (i.e., body washes). Our results demonstrate that several ecological factors alter mosquito prevalence and behavior, including both sugar and host seeking behaviors. We anticipate these results to be a starting point for mosquito control strategies that depend not only on olfactory perception of plant odors, but also on the ecological and species-specific characteristics which shape the dynamics of vector-borne diseases. / Master of Science in Life Sciences / Most female mosquitoes must feed on a blood source in order to produce eggs, but in doing this they can transmit viruses and pathogens between hosts through their saliva, which are contracted by 700,000 people per year. In order to survive and fly to locate these host sources, both female and male mosquitoes require sugar and carbohydrates present in plant nectar. Mosquito identification of nectar and blood sources is primarily dependent on their sense of smell, or olfaction, which allows a mosquito to identify and locate chemical odors. The interpretation of these chemical odors is context dependent on both the mosquitoes' hunger status, ideal host (human, mammal, bird, etc.) and environmental cues (temperature, humidity, time of day, etc.). It is relatively unknown how the combination of these biological and environmental factors influences mosquito survival and biting frequency. In order to better understand this relationship, we first investigated mosquito species' habitat preferences (i.e., urban and forested) and ecological factors (i.e., season, weather). Second, we focused on Aedes aegypti mosquitoes, which almost exclusively feed on humans in urban habitats, to investigate mosquito behavior in the presence of combined plant and human odors caused by the usage of fragrant personal care products that are scented with plant odors. Our results demonstrate that mosquito prevalence, host-seeking, and plant-seeking are highly dependent on chemical and ecological factors. We anticipate that this research has avenues for both improving mosquito control strategies and better understanding the ecological dynamics of vector-borne diseases.
185

Exploring the ecology of Orthobunyaviruses in Virginia and their pathogenesis in murine and poultry models

Lopez, Krisangel 07 January 2025 (has links)
Cache Valley virus (CVV) is a vector-borne, negative-sense RNA virus, in the genus orthobunyavirus. Cache Valley Virus is a widespread pathogen in North America, and since its first isolation in 1956, has been associated with multiple epizootics of CVV in ruminants, leading to spontaneous abortions and congenital malformations. As such, CVV is a virus of high economic relevance, but little is known about fundamental aspects of its biology. To address this gap of knowledge, I conducted a series of studies to better understand the pathogenesis and ecology of CVV. This work is divided into two facets; the first is the development of animal models to assess the pathogenesis of CVV in various host species, and the second is vector surveillance to better understand the ecology of orthobunyaviruses within the Commonwealth of Virginia. In the first two chapters, I address the lack of small animal models to study CVV. First, I developed a murine model and an in utero model that mimic the natural progression of disease observed in CVV infection. In the second chapter, I study the growth kinetics of CVV in avian cell lines and in commercial poultry species. In the last chapter, I explore the distribution and diversity of mosquitoes and arthropod-borne viruses in Virginia. Overall, these studies provide insight into CVV pathogenesis and in utero transmission, the role of domestic poultry in the maintenance and amplification of CVV, and lastly, evidence of mosquito species range expansion, and high viral diversity across the Commonwealth of Virginia. / Doctor of Philosophy / The world's deadliest animal is the mosquito. Mosquitoes can transmit a wide variety of diseases, including viruses. Cache Valley virus is a widespread virus in North America that can be transmitted by different species of mosquitoes. Cache Valley virus is associated with miscarriages and deformities in livestock, particularly in sheep, brain swelling, and death in humans. Nevertheless, studying Cache Valley virus to date has been very difficult as sheep and goats are the only available animals that show signs of illness, and they require large spaces to be studied. My research focused on developing a mouse and a bird infection model that could be used to observe how the virus grows, how the disease develops, and how it is passed down from parent to offspring. I also wanted to assess where Cache Valley virus circulates in nature in the Commonwealth of Virginia. To study Cache Valley virus circulation, mosquitoes were caught at multiple locations using Virginia as a study site and tested for the presence of virus. Although we did not detect Cache Valley virus in these samples, we found Jamestown Canyon virus, another important virus that has previously not been known to occur in Virginia. These studies allowed an in-depth look at Cache Valley virus ecology and shed light on the need for future mosquito monitoring across Commonwealth of Virginia.
186

Effect of carbon source on growth, sporulation, and development of mosquito toxicity by Bacillus sphaericus

Jelley, Scott Allen January 1985 (has links)
The goals of this research were 1) to provide nutritional information that would be useful for the classification of Bacillus sphaericus, a heterogenous bacterial species, 2) to determine nutritional characteristics that would assist in the design of a selective medium for the mosquito pathogenic strains of B. sphaericus and 3) to determine the effect of carbon supplementation of complex media on sporulation and mosquito toxicity of B. sphaericus. In general, the pathogenic strains which constitute DNA homology group IIA of the species, grew with a greater variety of compounds as sole carbon sources than did the non-pathogenic strains of the other homology groups. Within homology group IIA, strains of phage group 3, which are the most toxic, grew with the largest number of compounds as sole carbon sources. However, the nutritional characteristics did not allow the unequivocal differentiation of any one DNA homology group or phage group from all of the other groups. It was possible to differentiate a DNA homology group or phage group from some of the other groups. A defined medium containing malate and acetate as carbon sources was found to enable the cells to produce 1.1x10⁸ spores/ml and thus would be useful for studying the physiology of sporulation. Eighteen of 22 pathogenic strains were capable of growth in a liquid, defined medium with arginine as the sole carbon source, while only 2 of 17 non-pathogenic strains were capable of growth under these conditions. Thus, arginine may be useful as the carbon source in a selective medium for the mosquito pathogenic strains. Of several compounds which could be used by B. sphaericus as sole carbon sources, acetate was the most useful in increasing sporulation and mosquito toxicity when added as a supplement to a nutrient broth-yeast extract-mineral salts medium. A glycerol supplement to this medium led to accumulation of acetic acid and suppression of sporulation and toxin formation. An acetate supplement and a mineral salts (Ca²⁺, Mg²⁺, Mn²⁺) supplement were found to increase sporulation in a fishmeal medium and thus may be useful for commercial production of mosquito larvicides from B. sphaericus. / M.S.
187

Surface proteins of the mosquito-pathogenic strains of Bacillus sphaericus

Lewis, Lynn Owens January 1987 (has links)
Ph. D.
188

Effects of Fluid Properties on the Dynamics of Mosquitoes' Ingestion Pumps

Diggs, Shajaesza Dhakhai 12 June 2024 (has links)
Master of Science in Life Sciences / This thesis explores the feeding structures of insects, which have evolved over millennia to utilize a variety of dietary sources. It examines the mouthparts of insects feeding on plants, other bugs, or vertebrate blood, analyzing how these structures influence or limit their diet. Focusing particularly on mosquitoes, which are a significant public health threat due to their role as vectors of deadly diseases, we investigate the unique sexual dimorphism and diet, females' blood-feeding behaviors and the differences in the dual-pump feeding mechanisms of Aedes aegypti and Culex quinquefasciatus. Specifically, we investigated the effect of fluid viscosity on the sugar-feeding behavior and the pumping dynamics of males and females via force-feeding assays and electromyography (EMG) recording. Results showed varied pumping contraction frequencies among mosquito species and sexes that align with host feeding preferences. Furthermore, the study confirms that both species and sexes significantly influence sucrose intake, with Aedes aegypti females notably consuming more at higher concentrations, a trend not mirrored in Culex quinquefasciatus females. By studying the effects of fluid viscosity on feeding behavior and pumping dynamics, we inform computational models of the ingestion pumps that will help us gain insight into how the evolution of blood feeding.
189

Analysis of geographical and temporal patterns of malaria transmission in Limpopo Province, South Africa using Bayesian geo-statistical modelling.

Mgabisa, Aphelele Ronnie. 17 October 2014 (has links)
South Africa is at the southern fringe of sub-Saharan African countries which persist in experiencing malaria transmission. The purpose of the study is to analyse the geographical and temporal patterns of malaria transmission from 2000 to 2011 using Bayesian geostatistical modelling in Limpopo Province, South Africa. Hereafter, develop malaria case data-driven spatio-temporal models to assess malaria transmission in Limpopo Province. Malaria case data was acquired from the South African Medical Research Council (MRC). Population data was acquired from AfriPopo; and Normalised Difference Vegetation Index (NDVI), Land Surface Temperature (LST) and Land Cover data were acquired from MODerate-resolution Imaging Spectro-radiometer (MODIS). Rainfall, Altitude and distance to water bodies’ data were acquired from African Data Dissemination Service (ADDS), United States Geological Survey (USGS) and Environmental Systems Research Institute (ESRI), respectively. Bayesian spatio-temporal incidence models were formulated for Gibbs variable selection and models were fitted using the best set of environmental factors. Modelbased predictions were obtained over a regular grid of 1 x 1km. spatial resolution covering the entire province and expressed as rates of per 1 000 inhabitants for the year 2010. To assess the performance of the predicted malaria incidence risk maps, the predictions and field observations were compared. The best set of environmental factors selected by variable selection was Altitude and the night temperature of two months before the case was reported. The environmental factors were then used for model fitting and all of the covariates were important on malaria risk. Predictions were done using all the environmental factors. The predictions showed that Vhembe and Mopani district municipalities have high malaria transmission as compared to other district municipalities in Limpopo Province. Assessment of predictive performance showed scatter plots with the coefficient of determination ( R² ). The values representing the statistical correlation represented by the coefficient of determination ( R² ) were 0.9798 (January), 0.8736 (February), 0.8152 (March), 0.8861 (April), 0.9949 (May), 0.3838 (June), 0.7794 (July), 0.9235 (September), 0.8966 (October), 0.9834 (November) and 0.8958 (December). August had two values reported and predicted which resulted in R² of 1. The numbers of the The produced malaria incidence maps can possibly be considered as one of the baselines for future malaria control programmes. The results highlighted the risk factors of malaria in Limpopo Province which are the most important characteristics of malaria transmission. / M.Sc. University of KwaZulu-Natal, Durban, 2013.
190

A GIS model for predicting potential "high risk" areas of West Nile virus by identifying ideal mosquito breeding habitats

Wallis, Robert Charles, January 2005 (has links)
Thesis (M.S.) -- Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

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