The incidence of mosquito-borne human diseases is increasing worldwide, with effective chemical control limited due to widespread insecticide resistance in the insect. Recent evidence also suggests that bacterial symbionts of mosquitoes, known to be essential in nutritional homeostasis and pathogen defense, may play a significant role in facilitating mosquitocide resistance. Here, I examined the metabolic detoxification and toxicity of two mosquitocides, propoxur and naled, and the capacity of bacterial symbionts to modify the detoxification of the mosquitocides and, thus, alter their toxic action in the yellow fever mosquito, Aedes aegypti. The insecticide synergists piperonyl butoxide (PBO), triphenyl phosphate (TPP), and S,S,S-tributyl phosphorotrithioate (DEF) were used to examine the metabolic detoxification and toxic action of the two mosquitocides in mosquito larvae. A significant increase in the toxicity of propoxur was observed when applied in combination with PBO; however, there was no corresponding decrease in AChE activity. Naled applied in combination with PBO resulted in a decrease in anticholinesterase activity (higher residual AChE activity) and a subsequent decrease in toxicity of the insecticide. This suggests that esterases play a major role in the metabolic detoxification of both insecticides in mosquito larvae. The acute toxicities of naled and propoxur to Ae. aegypti larvae were also studied following a reduction of bacterial symbionts with the broad-spectrum antibiotics gentamycin, penicillin, and streptomycin. Antibiotic-treated mosquito larvae showed increased susceptibility and a reduction in cytochrome P450 monooxygenase and general esterase activities when treated with naled and propoxur. A reduction of bacteria in mosquito larvae treated with broad-spectrum antibiotics, therefore, appears to affect the metabolic detoxification of standard-use mosquitocides, such as propoxur and naled. The results also suggest that the bacteria themselves may contain metabolic detoxification enzymes that are functionally similar to those in the mosquito larvae. Additional experiments, however, are needed to fully elucidate the contribution of bacterial symbionts in Ae. aegypti larvae in the metabolic detoxification of mosquitocides. / Master of Science in Life Sciences

The World Health Organization estimates that vector-borne diseases account for 17% of the global burden of all infectious diseases and has identified the mosquito as the most dangerous of all disease-transmitting insects, being responsible for several million deaths and hundreds of millions of cases each year. The study of mosquito genomics provides a deeper understanding of the molecular mechanisms involved in every aspect of vector biology, such as sex determination, host-parasite interaction, ecology, feeding behavior, immunity and evolutionary trends and can be used for the development of new strategies for vector control. We developed the first map of the mitotic chromosomes of the major vector for West Nile fever and lymphatic filariasis, Culex quinquefasciatus. The map was then successfully utilized for mapping of approximately 90% of available genetic markers to their precise positions on the chromosomes. Idiograms were integrated with 140 genetic supercontigs representing 26.5% of the genome. A linear regression analysis demonstrated good overall correlation between the positioning of markers on physical and genetic linkage maps. This will improve gene annotation and help in distinguishing potential haplotype scaffolds and regions of segmental duplications. It will also facilitate identification of epidemiologically important genes that can be used as targets for the vector control and provide a better framework for comparative genomics that will help understanding of the evolution of epidemiologically important traits. In another study, we confirmed the presence of the newly described species, Anopheles daciae, in regions of Russia using molecular data. Although sympatric with its sibling species, Anopheles messeae, five nucleotide substitutions in the internal transcribed spacer 2 of ribosomal DNA can be used to distinguish the morphologically similar species. Chromosome rearrangements have a significant impact on mosquito adaptation and speciation. Using sequencing data in combination with karyotyping, we demonstrated that significant differences in inversion frequencies distinguish An. messeae from An. daciae, suggesting that these inversions are actively involved in adaptation and speciation. It is essential to have reliable toolbox for correct identification of these species and to know their range for future possible malaria outbreaks prevention. / Ph. D. / The more you study, the more you know The more you know, the more you forget The more you forget, the less you know So why study? According to the World Health Organization, mosquitoes are one of the deadliest animals in the world. They spread disease to humans resulting in hundreds of millions of illnesses and several million deaths every year. Study of the mosquito genome can help us understand vector biology and speciation and can be used to develop new strategies for vector control. Culex quinquefasciatus, the southern house mosquito, is one of the major vectors for the West Nile virus in the U.S. and for lymphatic filariasis, a disabling and disfiguring disease, worldwide. The traditional methods of control are of limited effectiveness because of high insecticide resistance in many populations of the mosquito. To enhance our resources for the control strategies, we developed physical maps of the chromosomes for this mosquito and effectively integrated it with available genetic linkage map. This work will help to identify epidemiologically important genes that can be used as targets for the vector control. Malaria vectors, mosquitoes from the genus Anopheles, are known for their ecological plasticity, which can be partially explained by chromosome rearrangements called inversion. A global malaria eradication program significantly reduced the number of deaths related to malaria, especially in Europe and the U.S. However, malaria outbreaks can occur anywhere competent vectors occur. We studied Anopheles messeae, one of the major European malaria vectors and its closely related species, Anopheles danciae. We report for the first time the presence of An. daciae in Russia and demonstrate that its distribution overlaps with that of An. messeae. Using genetic sequence data in combination with chromosome structure, we demonstrated that significant differences in inversion frequencies reliably distinguish An. messeae from An. daciae. These inversions may be involved in adaptation and speciation of these two species. It is essential to have reliable toolbox for correct identification of these species and to know their range for future possible malaria outbreaks prevention.

This study investigated aspects of the breeding biology, ecophysiology, morphology, over-wintering and population dynamics of the pre-imaginal stages of members of the Anopheles gambiae complex in northern Natal, South Africa, Investigation of the breeding biology, concentrated on breeding site utilisation by the different members of the Anopheles gambiae complex. Surveillance personnel were unable to locate the breeding sites of Anopheles arabiensis and postulated that location and description of these would offer a unique opportunity for control. The difficulty in locating the breeding sites of An. arabiensis at certain localities was found to be a product of their low density, presumably as a result of the intra-domiciliary, residual insecticide spray programme. The effect of temperature on larval physiology and adult morphology was investigated. terms of their implications Anopheles gambiae complex. The findings are discussed in for anopheline taxonomy and the The effect of temperature on larval growth rates was investigated in both the field and laboratory. The finding of this part of the study indicate that the larval stages play an important role in the over-wintering of populations within the region. The control implications of these findings and winter breeding site localisation are discussed. A theory for the so called 'late season transmission i.e. Apri-May, within the province and southern Africa is proposed. The population dynamics of An. merus were investigated, together with the effect of abiotic factors such as temperature, salinity and rainfall. The effect of sampling bias due to factors such as behavioural avoidance were studied. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1991.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2005. / Title from title page screen (viewed on July 13, 2005). Thesis advisor: Reid R. Gerhardt. Document formatted into pages (xii, 77 p. : ill. (some col.), maps (some col.)). Vita. Includes bibliographical references (p. 67-76).

Arthropod-borne viruses, arboviruses, have the ability to replicate in both vertebrates and invertebrates and are transmitted to susceptible vertebrate hosts by vectors such as mosquitoes and ticks. Ticks are important vectors of many highly pathogenic arboviruses, including the flavivirus tick-borne encephalitis virus (TBEV) and the nairovirus Crimean-Congo haemorrhagic fever virus. In contrast, alphaviruses are principally mosquito-borne and have been isolated only rarely from ticks; ticks have not been implicated as their vectors. Nevertheless, the alphavirus Semliki Forest virus (SFV) replicates in cell lines derived from many different tick species, including those of the genus Ixodes, which includes vectors of TBEV and its lesspathogenic relative Langat virus (LGTV). In vertebrate cells, arboviruses generally cause cytopathic effects; however, arbovirus infection of arthropod cells usually results in a persistent low-level infection without cell death. While little is known about antiviral immunity in tick cells, the immune system of other arbovirus vectors such as mosquitoes has been studied extensively over the last decade. In insects, pathways such as RNA interference (RNAi), JAK/STAT, Toll, Imd and melanisation have been implicated in controlling arbovirus infection, with RNAi being considered the most important antiviral mechanism. In tick cells, RNAi has been shown to have an antiviral effect, but current knowledge of other immunity pathways is limited and none have been implicated in the antiviral response. In the present study, SFV and LGTV replication in selected Ixodes spp. tick cell lines was characterised and the Ixodes scapularis-derived cell line IDE8 was identified as a suitable cell line for this project. Potential antiviral innate immunity pathways were investigated; putative components of the tick JAK/STAT, Toll and Imd pathways were identified by BLAST search using available sequences from well-studied arthropods including the fruit fly Drosophila melanogaster. Using gene silencing, an attempt was made to determine whether these pathways play a role in controlling SFV and LGTV infection in tick cell lines. Selected genes were silenced in IDE8 cells using long target-specific dsRNA and cells were subsequently infected with either SFV or LGTV. Effects of gene silencing on virus replication were assessed by quantitative real time PCR (qPCR) or luciferase reporter assay. Effects on infectious virus production were measured by plaque assay. Replication of the orbivirus St Croix River virus (SCRV), which chronically infects IDE8 cells, was also quantified by qPCR after silencing of selected genes. Interestingly, SFV or LGTV infection of IDE8 cells resulted in a significant increase in SCRV replication, possibly as a result of interference with antiviral pathways by SFV and LGTV or possibly due to diversion of cellular responses from sole control of SCRV. No evidence for an antiviral role for the JAK/STAT or Toll pathways was found in IDE8 cells. However, an antiviral effect was observed for protein orthologues putatively involved in the RNAi response. Argonaute proteins play an important role in translation inhibition and target degradation mediated by RNAi, and silencing of selected Argonaute proteins resulted in a significant increase in SFV and SCRV replication. The carboxypeptidase CG4572 is essential for an efficient antiviral response in D. melanogaster, and supposedly involved in the systemic RNAi response. A putative tick orthologue of CG4572 was identified and this appeared to be involved in the antiviral response in IDE8 tick cells. When expression of CG4572 was silenced and cells subsequently infected with SFV or LGTV, replication of both viruses was significantly increased. In addition, it was shown that three mosquito orthologues of CG4572 also had an antiviral role against SFV in Aedes mosquito cells. In conclusion, of the tick cell lines investigated, IDE8 provided a suitable model system for investigating tick cell responses against arboviruses and new insight into the nature of the tick cell antiviral response was gained.

Mosquitoes pose a serious threat to the economy, health status, and biosecurity of countries around the world. Mosquitoes kill an average of 700,000 people per year. The global expansion of air, sea, and land transport networks has greatly enhanced the spread of mosquitoes internationally. In the Pacific, the number of mosquito-borne diseases occurring has been on the rise in recent years, possibly as a result of human-mediated dispersal of larvae and adult mosquitoes. The Kingdom of Tonga has had numerous outbreaks of dengue fever and chikungunya virus in recent years. Previous research has catalogued species occurrences and distributions throughout Tonga. However, it is unknown whether new species have arrived in Tonga, and if distribution of previously found species has changed since the last comprehensive survey in 2006. Present research aims to update the literature by conducting a mosquito survey at 84 sites across the four islands of Tongatapu, Pangaimotu, ‘Oneata, and ‘Eua to record the distribution and occurrence of mosquito larvae. Nine mosquito species were collected: Aedes aegypti Linnaeus, A. albopictus Skuse, A. tongae Edwards, A. horrescens Edwards, A. vexans nocturnus Theobold, Culex annulirostris Skuse, C. albinervis Edwards, C. quinquefasciatus Say and C. sitiens Wiedemann. The collection of A. albopictus is the second time that this species has been recorded in Tonga. Moreover, the spatial extent of this species throughout Tonga was far greater than previously recorded. A major outcome of this survey has been the creation of an identification key for the mosquito larvae species of Tonga. This key should increase the accuracy of positive mosquito larvae identifications in Tonga. Mosquitoes were more frequently collected in artificial (e.g., used car tyres, fuel drums, containers) than natural (e.g., pools, ponds, tree holes) habitats. Car tyres, water containers, fuel drums, fridges, washing machines, and ponds were the most common habitats in which mosquito larvae were found. Aedes aegypti, A. albopictus, and C. quinquefasciatus were the three most common mosquito species collected, whereas A. tongae, A. horrescens, A. vexans nocturnus, C. annulirostris, C. sitiens, and C. albinervis were less frequently found. Multiple logistic regression analyses indicated that habitat volume had a significant positive effect on the presence of A. albopictus and A. tongae, whereas conductivity had a significant positive effect on the presence of C. annulirostris. Additionally, the volume by temperature interaction was a significant predictor of species presence for A. aegypti, A. albopictus, and C. annulirostris (as habitat volume increases, the effect of temperature went from neutral to negative). This suggests that larger, cooler habitats favour colonisation by these species. The number of artificial habitats (particularly used car tyres) present may have significantly increased since previous studies. Management should therefore focus on implementing community-run mosquito projects aimed at reducing the number of artificial habitats capable of being colonised by mosquito larvae. Covering, tipping out water, and infilling these habitats with soil to prevent mosquito oviposition is a pragmatic and straightforward mosquito control solution. This should immensely reduce the abundance of mosquitoes and may prevent disease outbreak in Tonga.

No description available.

Long-term insect abundances have been studied to investigate factors structuring the insect communities of the temporary wetlands around the River Dalälven floodplain. In the wet meadows and swamps in the River Dalälven floodplains recurrent floods are the ultimate prerequisite for high production of floodwater mosquitoes. In the larval stages these make up a superabundant potential prey for aquatic predatory insects while as adults they become nuisance for people and animals. Mosquito control with Bacillus thuringiensis israelensis (Bti) has been carried out in parts of the floodplain wetlands since 2002. This study investigate potential long-term effects of Bti on non-target insects in general, and non-biting midges (Diptera: Chironomidae) and aquatic predator insects in special in 10 temporary wetlands. Diving-beetles (Coleoptera: Dytiscidae) were the most common aquatic predatory insects in temporary flooded wetlands, and we found no indications that diving-beetles were negatively affected by mosquito larvae reduction with Bti-treatments. Non-target Bti-effects on the insect community in general, measured as increase or decrease of insect abundances, in general showed no effects of Bti except for Coleoptera. The non-biting midges were studied on species level, since this taxon previously has been associated with negative Bti non-target effects in the short-term. We found no reduced production of chironomids at neither family, nor subfamily level in Bti-treated as compared to untreated wetlands. We conclude that other factors than the occasional Bti-treatments dominate in structuring the chironomids fauna. For example, hydrology measured as floods and hydroperiod had substantial impact on insect emergence Increased hydroperiod was associated with lower insect emergence for the majority of the studied taxa, indicating an insect fauna adapted more to terrestrial conditions. In the final study, we developed and applied a molecular method to study interspecific predator – prey relationships between medium-sized diving beetles and floodwater mosquito larvae. Gut content analyses showed that floodwater mosquito larvae are a regular, but limited, part of the diet of medium-sized diving beetles. This thesis is one of the first long-term studies of insects of temporary wetlands in relation to mosquito control actions. The results indicate that hydrology is one of the major factors influencing and structuring the insect communities of the temporary flooded wetlands in the River Dalälven floodplains, and that mosquito control actions with Bti only have marginal effect on insect abundances.

The materials synthesised in this study were designed to have novel morphology coupled with a tightly controlled surface composition that could be varied depending on a application. Preparations with simple single metal oxides (i.e. TiO2, SiO2, Al2O3 and ZrO2) were used as the starting point with the latter stages involving multi-metal oxide coatings and materials. The research was divided into three interconnected areas; i) biotemplating, ii) alternative synthetic morphologies to biotemplating and iii) the synergy between microparticles and insecticides. For the investigation into biotemplating pollen was chosen as the main example due to its ubiquity. Here, good replication of its structure with metal oxides can be achieved by two-dimensional solgel chemistry. Such materials can be further modified to have tunable surface chemistry through dopants and optical properties (i.e. fluorescence) through the use of dyes. Materials were extensively characterised using primarily spectroscopy (UV and IR) and microscopy (i.e. SEM coupled with EDX elemental analysis). These were considered for several applications and examples investigated here included as a taggant technology and photocatalytic removal of methyl orange in an aqueous environment (TiO2-pollen only). For the latter, results have been compared with those of a commercially available alternative (P25) where the preliminary results are very promising. The method of overcoating was also shown to be transferrable to other flora and fauna biotemplates. Synthetic alternatives for the biotemplated pollen were considered in the second investigative area where solution sol-gel processes such as the Stöber method were considered in addition to other suspension based precipitation methods (i.e. refluxes and microemulsions). Processes developed in the biotemplating research were applied here and analysed again using spectroscopy and microscopy as the main techniques. As part of this aspect, a novel fast-drying water-in-oil microemulsion delivery and preparative system was also developed using low boiling point solvents such as isopentane and ethanol and low toxicity sucrose ester surfactants. Hollow oxide shells could be prepared in these using a novel low-temperature route that were comparable in thickness (but significantly smaller in size) to hollow pollen replicas. In this second area attention was shifted to more focus on oxides of Si and Al (as opposed to TiO2 that used extensively in biotemplating) to broaden the scope of the research and investigate other potential applications, such as nanoabrasives (surface roughness and ability to cleave DNA). The third and final area of interest used the materials from the previous two aspects in coatings that were applied to investigating the knockdown (KD) and total mortality (TM) of selected arthropods. Here mosquitoes of the A. Gambiae and S. Aegypti genus were considered with particular focus on synergistic effects with existing commercial insecticides (using mainly CDC bottle tests). Microscopy was used as the primary characterisation technique here to determine particle transfer after each assay. In these tests %TM suggested SiO2 microspheres were particularly effective at in enhancing mortality of the commercial l-cyhalothrin insecticide. Additionally, novel methods of recording mosquito behaviour was investigated through optical and thermographic stills and videos.

No description available.