Dentos 1932

https://ecommons.luc.edu/dentos/1016/thumbnail.jp

Associative Learning Capabilities of Adult Culex quinquefasciatus Say and Other Mosquitoes

The association of olfactory information with a resource is broadly known as olfactory-based associative learning. From an ecological perspective, associative learning can reduce search time for resources and fine tune responses to changing biotic and abiotic factors in a variable environment, which in mosquitoes has implications for pathogen transmission and vector control strategies. The purpose of this dissertation was to examine the ability for olfactory-based associative learning across the major life history domains of mosquitoes. Six different experiments comprise this dissertation. The first was to evaluate the response of mosquitoes following conditioning to 5, 10 or 50% sucrose concentrations with individual level mosquito conditioning and testing and introduction of statistical analysis with binary logistic regression. Mosquitoes did not respond in a dose dependent manner with respect to positive response to target odors following conditioning. This effect appears to be related to the mosquitoes' prior exposure to sugar as those exposed to 10% sucrose before conditioning did not prefer 50% sucrose but significantly fewer chose 5% sucrose. In an evaluation of host associated odors and second blood meal choice by females using a dual-choice olfactometer no significant effects were observed. The lack of significance may have been due to insufficient sample sizes, problems with odor collection or physiological state of mosquitoes. Effects of predatory mosquitofish on larval development and female oviposition choice were evaluated by rearing in separated habitats under three different treatments followed by an oviposition choice assay. Females did not prefer their natal habitat or avoid predators but chose substrate that had contained mosquitofish fed conspecific larvae. Mosquitofish affected larval development with acceleration in treatments with mosquitofish fed Tetramin® and delayed pupation in treatments with mosquitofish fed conspecific larvae. Mosquito memory length was evaluated by conditioning and testing at six time intervals from colony and field populations at two ages. Younger mosquitoes showed higher levels of positive response after conditioning at all time intervals except the longest (24h). Finally the olfactory-based associative learning ability of Anopheles cracens was evaluated. Significant evidence for learning was observed in males but not females at a memory length interval of 24h

Influence de la mutation kdr (L1014F) sur la réponse comportementale d’Anopheles gambiae aux insecticides pyréthrinoïdes.

The blood feeding behaviour is a crucial step in the reproductive cycle of female mosquitoes for egg maturation. However the widespread use of insecticide treated bed nets reduce the ability of mosquitoes to feed on human host. In this context of integrated vector control strategies, mosquitoes have evolve physiological and behavioural adaptations to scope the deleterious effect of insecticides. Despite the progress made on understanding of physiological resistance, few data exist on effects of insecticide treated nets on host seeking behaviour. The aim of my thesis was to determine whether host seeking behaviour of Anopheles gambiae in the presence of insecticide-treated materials is modulated by the presence of the kdr L1014F mutation which confers resistance to pyrethroids used on treated bed nets. Firstly, our results show that the kdr gene modulate the host seeking behaviour in the presence of insecticide treated nettings and the fitness of kdr-resistant mosquitoes. Homozygous resistant mosquitoes for kdr gene have oriented flight to host odours in the presence of permethrin treated net compared to untreated net. The analysis of the performance of the three genotypes to pass through a hole on untreated net in the presence of a vertebrate host showed a cost of kdr mutation on behavioural activity of resistant mosquitoes. In addition, this work highlighted a high performance of heterozygous (overdominance) to pass through a hole treated net to reach a vertebrate host. Finally, our data reveals that a sub-lethal exposure of resistant mosquitoes to two pyrethroid treated nets has a contrasting effect on blood feeding rate. In addition, the pre-exposure of the three genotypes to pyrethroid impact the biting behaviour of susceptible and resistant mosquitoes by reducing the feeding duration, pre-diuresis duration and blood meal size. All of these results are discussed in the context of blood seeking behaviour in natural conditions. Through the study of 3 complementary behavioural sequences, our results brought new insights about the malaria vector behavior in front of pyrethroid-impregnated bed nets and highlighted complex gene-environment interactions.Les parasites du genre Plasmodium responsables du paludisme sont transmis du moustique à l’homme et de l’homme au moustique pendant la prise du repas de sang. L’utilisation massive des moustiquaires imprégnées d’insecticides pyréthrinoïdes vise à limiter la prise du repas de sang et à réduire la survie des moustiques. Dans un contexte de lutte antivectorielle généralisée, des mécanismes d’adaptations physiologiques et comportementaux ont été sélectionnés chez les populations d’Anophèles vecteurs. Les mécanismes de résistances physiologiques font l’objet d’un large effort de recherche alors que nous ne disposons que de peu de connaissances sur le comportement de recherche et de piqûre d’un homme protégé par une moustiquaire. L’objectif de ce travail de thèse était de contribuer à la compréhension des interactions entre un mécanisme de résistance physiologique aux insecticides, le comportement des moustiques et les outils de lutte antivectorielle. Pour réaliser cette étude, nous avons testé l’effet de la moustiquaire imprégnée d’insecticide sur le comportement de recherche de l’hôte chez Anopheles gambiae en relation avec le génotype kdr L1014F, qui confère une résistance aux pyréthrinoïdes utilisés sur les moustiquaires imprégnées. Dans la première partie, nous avons analysé l’effet de l’insecticide pyréthrinoïde présent sur la moustiquaire sur l’attractivité de l’hôte chez An. gambiae. Nos resultats ont montré que les moustiques résistants étaient plus attirés par un hôte protégé par une moustiquaire traitée de perméthrine comparé une moustiquaire non traitée. Nous avons ensuite analysé la performance des trois génotypes kdr à atteindre un hôte protégé par une moustiquaire et leur activité comportementale au contact de la moustiquaire. Nous avons mis en évidence d’une part d’un coût adaptatif du gène kdr sur l’activité comportementale des moustiques résistants et d’autre part, une meilleure performance des hétérozygotes (superdominance) pour localiser une faille sur une moustiquaire traitée afin d’atteindre un hôte protégé. Enfin, nos expériences ont porté sur l’effet d’une exposition sublétale des moustiques à des insecticides pyréthrinoïdes sur le comportement de piqûre lors de la recherche d’un hôte protégé. Cette préexposition aux pyréthrinoïdes a eu un effet contrasté sur le taux de gorgement des moustiques résistants toutefois elle a réduit la durée de gorgement, de prédiurèse ainsi que le volume de repas de sang des trois génotypes. À travers l’étude de 3 séquences comportementales, nos résultats ont permis d’apporter des informations cruciales sur le comportement des anophèles vecteurs du paludisme face aux moustiquaires imprégnées et ouvre la voie à de nombreuses pistes de recherches

All quiet on the home front? : the impact of the Second World War on the township of Mosgiel

The Second World War proved a momentous time for those living in New Zealand. Life for civilians on the home front was affected to a much greater extent than it had been in 1914-18. This heightened 'total war' prompted many changes to the lifestyles and living conditions of New Zealanders. To manage the national demands of this conflict, Peter Fraser's Labour government took firm control of the society and economy. As the War situation required, it implemented various bureaucratic measures such as rationing, industrial manpower regulations, a blackout and other civil defence measures. As well as these rules and regulations, citizens faced the problem of shortages, the uncertainty of loved ones overseas and the alarming progress of the Japanese in the Pacific. The War, then, impacted on people and communities across the country. Even the isolated south of the South Island, far from most of the country's main war efforts, could not escape the effects wrought from this conflict. Little research, however, has been done on this exciting and vibrant period of New Zealand history. Thus, to test the extent of the impact, this thesis focuses on the southern township of Mosgiel. In 1939, Mosgie1 was a town of just over two thousand inhabitants, situated at the northern foothills of the Taieri Plains, a short drive from Dunedin. It felt the pressure of war in the same ways as other towns, yet perhaps because of its small size, close community and southern isolation, it appears to have fared better than many. The chapters follow a logical path, dealing with each of the main aspects of Mosgiel society and economy, assessing each to determine the War's effects. Although it had a nearby military presence, formed both a Home Guard and an Emergency Precautions Organization, endured rationing, shortages, a blackout, manpowering and disruption to its businesses and workforce the community was able to adapt to, or deflect, many of the negative effects of the conflict. In the end, the overall impact of the War proved limited