Actuellement, la plupart des textiles utilisés pour limiter les contacts avec les moustiques vecteurs de maladies sont imprégnés d’insecticides pyréthrinoïdes possédant une action insecticide et répulsive. Cependant, l’apparition de résistances au sein des populations de moustiques remet en cause cette efficacité.La nouvelle stratégie de lutte contre les moustiques s’appuie sur l’effet synergique obtenu lors d’une association de deux molécules de familles chimiques différentes à effet insecticide et répulsif. Les effets de deux répulsifs, le DEET et l’IR3535 ont été étudiés sur des cellules neurosecrétrices isolées du système nerveux central de la blatte Periplaneta americana. A l’aide de la technique d’imagerie calcique, il a été possible de montrer que ces composés induisent une augmentation dose-dépendante complexe de la concentration en calcium intracellulaire. L’utilisation d’outils pharmacologiques spécifiques a permis de caractériser les cibles et les évènements moléculaires impliqués dans ces effets. A partir de ces résultats, l’IR3535 s’est avéré être le meilleur répulsif pour une association avec un insecticide néonicotinoïde, le thiaclopride. Grâce à la technique électrophysiologique du patch-clamp adaptée sur neurones d’insecte, l’effet synergique produit par l’association IR3535/thiaclopride a été observé et le rapport de concentrations répulsif/insecticide qui donne le meilleure effet synergique sur le courant entrant induit par le thiaclopride déterminé. Des tests en cône réalisés sur moustiques in vivo ont confirmé cet effet synergique,démontrant l’intérêt de proposer l’associationIR3535/thiaclopride comme nouvelle stratégie de lutte anti-vectorielle. / Today, most of the textiles used to limit contact with mosquitoes are impregnated with pyrethroid insecticides having both insecticidal and repellent activities. However, the development of resistance in mosquito populations reduces their efficacy. The new strategy proposed against mosquito-transmitted diseases is based on the potential synergy observed with the combination of two different compounds with insecticidal and repellent effects. In this context, the effects of two repellents DEET and IR3535 have been studied on neurosecretory cells isolated from the central nervous system of the cockroach Periplaneta Americana. Using calcium imaging, both DEET and IR3535 induce a dose-dependent complex elevation of intracellular calcium concentration. Specific pharmacological tools have allowed to characterize the different targets together with the molecular events involved in the repellent-induced calcium rise. From these results, it has been possible to identify IR3535 as the most suitable compound to be used in association with the insecticide neonicotinoid, thiacloprid. Using the whole-cell patch-clamp technique adapted on isolated insect neurons, the synergistic effect of the IR3535/thiacloprid mixture has been observed on the thiacloprid-induced current and the most efficient ratio between repellent and insecticide has also been determined. In addition, cone tests performed on in vivo mosquitoes confirm this synergistic effect, demonstrating that IR3535/thiacloprid mixture could bean alternative strategy in the management of chemical use against resistant mosquitoes.

The proposed release of genetically modified mosquitoes (GMM) in the Florida Keys to combat the spread of diseases such as Zika prompted heated local debate, turning a seemingly routine mosquito control policy into a public scientific controversy. Arguments about the GMM derive from inventional commonplaces where the historical conflict between democratic systems of civic deliberation and the epistemic authority of expertise is instantiated. This project analyzes the topoi that Keys participants gather around to generate their argumentative positions as published in public, local print and digital news articles, blog posts, and letters to the editor between 2011 and 2016. Investigating the commonplaces that orient the argumentative trajectories of Keys participants reveals that each relational topos intersects with individual worldviews, risk assessments, and standards and can therefore be used for contradictory arguments. The many complex and connected factors that influence participant positions must be appreciated and acknowledged in any such civic deliberation about a science-related policy or technology. There is no easy resolution for such conflicts, such as clarifying scientific data for the public, to generate consensus; the irresolvable tension between democracy and expertise underlies public scientific controversies and requires mutual respect and appreciation for the varied reasons why people disagree to move towards more productive civic discourse.

Plasmodium falciparum is a protozoan parasite that causes a severe form of malaria, a mosquito-borne infectious disease in humans. P. falciparum encodes a number of proteins to facilitate its life-cycle, including a type II heat shock protein 40 (Hsp40), Pfj2. Pfj2 shows a degree of homology to human ERdj5, a resident protein of the endoplasmic reticulum (ER) that promotes protein quality control by facilitating the degradation of misfolded proteins. The overall aim of this study was to further understand the function of Pfj2 in the P. falciparum cell by characterising it biochemically. A bioinformatic analysis of Pfj2 was carried out to enable the identification of a potential ER signal sequence and cleavage site. Furthermore, an analysis of Pfj2 protein sequence was performed to compare domain similarities and identities with typical type II Hsp40s namely, human ERdj5, S. cerevisiae Sis1, human Hsj1a and human DnaJB4. The method used included the insertion of the codon-optimised coding sequence for the processed ER form of Pfj2 into the prokaryotic expression vector, pQE30, to enable overproduction of a histidine-tagged protein. A 62 kDa His₆-Pfj2 was successfully expressed in Escherichia coli and purified using denaturing nickel affinity chromatography. ATPase assays were performed to determine the ability of His₆- Pfj2 to stimulate the chaperone activity of the ER Hsp70, also called immunoglobulin binding protein (BiP). Initial studies were conducted on readily available mammalian His₆-BiP as a control, which was shown to have an intrinsic activity of 12.07±3.92 nmolPi/min/mg. His₆- Pfj2 did not stimulate the ATPase activity of mammalian His₆-BiP, suggesting that it either could not act as a co-chaperone of mammalian His₆-BiP (specificity), or it required a misfolded substrate in the system. Therefore, ongoing studies are addressing the interaction of Pfj2 and misfolded substrates with P. falciparum BiP. The results of these studies will further our understanding of a poorly-studied parasite chaperone that represents a potential drug target for development of novel strategies for the control of a serious human disease

Les moustiques jouent un rôle essentiel dans la dynamique de transmission du paludisme. Plusieurs traits d’histoire de vie de ces insectes hématophages vont, en effet, intervenir dans le calcul du taux reproductif de base du parasite. Parmi eux, la probabilité et l’intensité d’infection des vecteurs, suite à la prise d’un repas de sang infectieux, sont des facteurs primordiaux pour la transmission de Plasmodium. Pourtant, au sein d'une même population, une réelle hétérogénéité d’infection des moustiques a été observée: alors que certain ne sont pas infectés, que d'autres le sont faiblement, une partie des vecteurs vont présenter des taux d'infection extrêmement forts. Identifier les sources de variations responsables de cette hétérogénéité est indispensable pour comprendre la dynamique de transmission de Plasmodium. Certains paramètres d’origine génétique et environnementale, tel que la température et la nutrition, ont déjà clairement été identifiés comme ayant un impact sur le taux d’infection des moustiques. Néanmoins, de nombreux facteurs restent encore à explorer. En utilisant un système expérimental composé du parasite de la malaria aviaire Plasmodium relictum, de son vecteur naturel le moustique Culex pipiens et de l’un de ses hôtes vertébrés Serinus canaria, nous nous sommes intéressés aux effets de certains de ces paramètres, peu pris en compte jusqu’à présent, sur l’infection des moustiques. Nous avons notamment pu mettre en évidence des conséquences importante de l’infection parentale, de l’âge des vecteurs, ainsi que de leur fond génétique. Parallèlement, nous nous sommes intéressés à un facteur souvent laissé de côté, l’effet « hôte vertébré » sur l’infection des moustiques. Dans cette dernière partie, on a pu observer que la dynamique d’infection du parasite au sein de l’hôte influence de manière importante le taux de transmission de Plasmodium. Les sources d’hétérogénéité d’infections des moustiques sont donc multiples et l’ensemble des membres de cette association tripartite hôte/parasite/vecteur vont pouvoir influencer de manière importante la dynamique de transmission du parasite. / Mosquitoes play a key role in the dynamics of malaria transmission. Indeed, several life history traits of these bloodsucking insects are closely associated with the basic reproductive rate of the malaria parasite. One of the most important parameters for the transmission of Plasmodium is the rate and intensity of the mosquito infection. However, within a single population, a great heterogeneity of mosquito infection levels is often observed: some mosquitoes are not infected, others are only weakly infected, and yet others have extremely high infection rates. Identifying the sources of variation responsible for this heterogeneity is essential in order to understand the transmission dynamics of Plasmodium. Certain genetic and environmental (temperature, nutrition) parameters have already been identified as having an impact on mosquito infection rates. Nevertheless, many factors remain to be explored. Using an experimental system composed of the avian malaria parasite Plasmodium relictum, its natural vector Culex pipiens and one of its vertebrate host Serinus canaria, we have investigated the effect of several seldom investigated parameters on the infection of mosquitoes. We observed surprising effects of the effect of parental infection, mosquito age and genetic background. In parallel, we also studied a rarely investigated parameter: the impact of the vertebrate host on the mosquito infection rate. We showed that parasite infection dynamics within the host, at short but also long time scales, significantly influence the transmission of Plasmodium to the vector. The sources of heterogeneity of mosquito infection are therefore multiple and all members of this tripartite partnership (i.e. host / parasite / vector) are able to significantly influence the transmission dynamics of the parasite.

Degraded pollinator habitat may have far-reaching consequences for recovery of imperiled flowering plant populations. Studies indicate that broad-spectrum insecticides used in mosquito abatement are detrimental to non-target invertebrates, including pollinators. A decline in efficient pollinators can reduce plant fitness by decreasing reproductive output and constraining genetic diversity, a challenge for rare plants. In 2015, I monitored flower visitation and fruit set of three imperiled plant species throughout protected areas on three islands in The Lower Florida Keys. These islands consist of conservation land fragmented by intermittently dispersed residential neighborhoods that seasonally spray insecticides for mosquito control. Flowers open at treatment sites had decreased flower visitor activity following insecticide applications, but only species that require invertebrate agents for pollen transfer had significantly reduced fruit set. Implications of mosquito insecticides near conservation lands may pose immediate threats to invertebrate pollinators and flowering plants that require pollinators for reproduction, although long-term threats to genetic diversity are unknown for automatic self-pollinating species.

Thesis (M.Sc. (Statistics)) -- University of Limpopo, 2020 / Malaria is a mosquito borne disease, a major cause of human morbidity and mortality in most of the developing countries in Africa. South Africa is one of the countries with high risk of malaria transmission, with many cases reported in Mpumalanga and Limpopo provinces. Bayesian and classical methods of estimation have been applied and compared on the effect of climatic factors (rainfall, temperature, normalised difference vegetation index, and elevation) on malaria incidence. Credible and confidence intervals from a negative binomial model estimated via Bayesian estimation-Markov chain Monte Carlo process and maximum likelihood, respectively, were utilised in the comparison process. Bayesian methods appeared to be better than the classical method in analysing malaria incidence in the Limpopo province of South Africa. The classical framework identified rainfall and temperature during the night to be the significant predictors of malaria incidence in Mopani, Vhembe and Waterberg districts of Limpopo province. However, the Bayesian method identified rainfall, normalised difference vegetation index, elevation, temperature during the day and temperature during the night to be the significant predictors of malaria incidence in Mopani, Sekhukhune, Vhembe and Waterberg districts of Limpopo province. Both methods also affirmed that Vhembe district is more susceptible to malaria incidence, followed by Mopani district. We recommend that the Department of Health and Malaria Control Programme of South Africa allocate more resources for malaria control, prevention and elimination to Vhembe and Mopani districts of Limpopo province. Future research may involve studies on the methods to select the best prior distributions. / National Research Foundation (NRF)

Background: The mosquito Aedes aegypti has long been a vector for human illness in the Southeastern United States. In the past, it has been responsible for outbreaks of dengue, chikungunya, and yellow fever and, very recently, the Zika virus that has been introduced to the region. Multiple studies have modeled the geographic distribution of Ae. aegypti as a function of climate factors; however, this ignores the importance of humans to the anthropophilic biter. Furthermore, Ae. aegypti thrives in areas where humans have created standing water sites, such as water storage containers and trash. As models are developed to examine the potential impact of climate change, it becomes increasingly important to include the most comprehensive set of predictors possible. Results: This study uses Maxent, a species distribution model, to evaluate the effects of adding poverty and population density to climate-only models. Performance was evaluated through model fit statistics, such as AUC, omission, and commission, as well as individual variable contributions and response curves. Models which included both population density and poverty exhibited better predictive power and produced more precise distribution maps. Furthermore, the two human population characteristics accounted for much of the model contribution-more so than climate variables. Conclusions: Modeling mosquito distributions without accounting for their dependence on local human populations may miss factors that are very important to niche realization and subsequent risk of infection for humans. Further research is needed to determine if additional human characteristics should be evaluated for model inclusion.

No description available.

Needles are commonly used to reach target locations inside of the human body for various medical interventions such as drug delivery, biopsy, and brachytherapy cancer treatment. The success of these procedures is highly dependent on whether the needle tip reaches the target. One of the most significant contributors to the target accuracy is the needle insertion force that causes needle-tip deflection, tissue deformation, and tissue damage. Recently there has been tremendous interest in the medical community to develop innovative surgical needles using biologically-inspired designs. It is well known that insects such as honeybee and mosquito steer their stingers effortlessly to a specific target and release their venom in a certain path through the skin with minimal force. These unique traits inspire this dissertation work to develop bioinspired needles and to study the insertion mechanics of these needles for reducing the insertion force, needle-tip deflection, tissue deformation, and tissue damage. In this work, the insertion mechanics of honeybee-inspired needles with applied vibration in polyvinyl chloride (PVC) tissue phantom and chicken breast tissues was first investigated. It was observed that the insertion force was decreased by 43% and the needle tip deflection was minimized by 47% using honeybee-inspired needles. Furthermore, the insertion mechanics of mosquito-inspired needles in PVC tissue phantom and bovine liver tissues were studied. Design parameters such as maxilla design on the needle body, labrum-tip, vibration, and insertion velocity were considered. It was found that the insertion force was reduced by 60% in PVC tissues and 39% in bovine liver tissues using mosquito-inspired needles. To validate the developed bioinspired needle prototypes, a size scale study was performed using insertion test in a PVC tissue phantom. It was confirmed that the insertion force was decreased by 38% using different needle sizes. An analytical LuGre friction model was used to explain the insertion mechanics and to confirm the experimental results. Lastly, to investigate the effect of the insertion force reduction, the tissue deformation and the tissue damage studies were performed. Using a novel magnetic sensing system, it was observed that the tissue deformation caused by mosquito-inspired needles was decreased by 48%. A histological study was performed to quantify the tissue damage in bovine liver tissues. It was observed that the tissue damage of mosquito-inspired needles was reduced by 27% compared to standard needles. In conclusion, this dissertation study shows that applying bioinspired needle designs and vibration during insertion into tissues reduces the insertion force, the needle-tip deflection, the tissue deformation, and the tissue damage. The outcome of this study will benefit medical communities to advance the bioinspired needles for vibration-assisted clinical procedures. / Mechanical Engineering

The world has never been more connected than it is today. While this is true for people, it is also true for Earth's flora and fauna. Unfortunately, this connectedness has contributed to unprecedented invasive species introductions around the world. Most introductions result in an introduced species dying out in the newly invaded territory and never becoming established. Other introduced species establish and persist for years, but never have a noticeable effect on local ecosystems. However, occasionally, an invasive species gets introduced to a new area and has negative impacts on native plant and animal life. The Indo-Pacific swimming crab, Charybdis hellerii, was introduced to the southern Indian River Lagoon (IRL) in the 1990s. Recently, it has been reported to be expanding its non-native range northward up the IRL and into more northerly east coast states. To better understand the ecological role C. hellerii fills in the lagoon and the threat it poses to the economically important and native Callinectes sapidus, this study utilized stable isotope analysis to assess dietary overlap and competition between these species. The results of this study indicate significant overlap in dietary resource usage suggesting C. hellerii is likely feeding on some of the same prey items and competing with native C. sapidus. Based on the increasing numbers of C. hellerii and their reported range expansion, they appear to be establishing populations in the U.S. and will continue to compete with C. sapidus. This could negatively impact C. sapidus populations in the IRL, which is bad for the crab, bad for the fishery, and bad for the lagoon. Further, competition in the IRL is concerning for the rest of the southeastern U.S. states that appear to be in the early stages of a C. hellerii invasion. The findings of this study illuminate the need for further research into the ecological niche C. hellerii is filling in the IRL and the interactions it is having with, as well as the effects it is having on, native species in the lagoon. This study and future research will allow fisheries managers to devise more effective strategies to limit the spread of C. hellerii and minimize the harm it can do in non-native environments.