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.

No description available.

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.

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

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.

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.

Ph. D.

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.

Thesis (M.S.) -- Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

[Truncated abstract] In March 2005, the Indian Ocean island of Reunion, a former colony and now overseas department of France, saw the first cases of what was to become a massive epidemic of the mosquito borne viral infection Chikungunya. More than 250,000 people, one third of the Island's population, were subject to high fevers, rash, and joint and muscle pains over the next 18 months, yet the public health authorities in metropolitan France were arguably slow to take the epidemic seriously. The research presented here explores attitudes underlying the management of the epidemic by examining both metropolitan and local representations of mosquito borne disease from historical, epidemiological and media perspectives. The research seeks to answer the general question Does colonial history continue to influence the representation and management of mosquito borne disease in Reunion? Three parallel approaches are taken to answering this question, using a common framework of tropicality (a Western discourse that exalts the temperate world over its tropical counterpart, and overlaps with colonialism and orientalism). ... Several factors are likely to have contributed to the persistence of tropicality in public health practice in Reunion: Othering as a universal phenomenon; the cost of administering interventions to combat tropical diseases in the remote environments of French overseas departments and territories; the denial of a serious public health risk as a cultural trait in Reunion; and the significant role of the colonies in forming and maintaining the French national identity. It has to be acknowledged that historically, tropicalism does appear to have played one positive role in the management of mosquito borne disease: