Arthropod-borne viruses (arboviruses) belonging to the Togaviridae, Flaviviridae and Bunyaviridae pose a significant threat to human and animal health worldwide. Many of these (re-)emerging viruses have increased in geographic range and severity. Developing vaccine strains of these viruses that cannot infect, or be transmitted by, mosquito vectors would be useful tools to block virus transmission cycles in their vectors. Exploiting the miRNA pathway to generate viruses that are attenuated, or restricted in their replication, has recently received much attention due to the site-specific expression of miRNAs within a host organism. Recently it has been shown for a number of single-stranded and segmented viruses, that virus spread can be restricted in a cell- or tissue-specific manner by engineering miRNA recognition elements (MREs), which are complementary to cellular or tissue-specific miRNAs, into the virus genome. The aim of this proof-of-principle study was to generate recombinant Semliki Forest viruses (rSFVs) that are unable to replicate in aedine mosquito cell lines. RNA was extracted from uninfected and SFV4-infected Aag2 (Ae. aegypti) and U4.4 (Ae. albopictus) cells and analysed using high-throughput Illumina Solexa sequencing in order to identify mosquito-specific miRNAs. Several of the most highly abundant mosquito-specific miRNAs were selected and MRE cassettes were designed. MRE cassettes were cloned into the SFV4 backbone to produce rSFV, which were able to replicate in mammalian BHK-21 cells but unable to replicate in mosquito-derived cells. Each cassette encoded a Gaussia luciferase (Gluc) reporter gene and four copies of each MRE under the control of a duplicated subgenomic promoter. The resulting viruses were viable, infectious and were used to determine the effect of mosquito-specific MREs on virus replication. A significant reduction was observed in both luciferase (~4 – 5 logs) and virus (~3 logs) production in mosquito cells infected with the rSFVs. Further characterisation of the three most inhibited rSFVs (SFV4-MRE276, SFV4-MRE2940 and SFV4-MRE2945) suggested that the insertion of the MRE cassette into the SFV4 backbone had no significant effect on the growth kinetics of these viruses. Each virus replicated to titres comparable to wildtype (wt) SFV. In stability assays, the rSFVs virus maintained high luciferase expression and high virus titre for 5 low multiplicity passages in mammalian cells. Taken together, these results suggest that the incorporation of MRE cassettes into the SFV4 genome did not affect the stability of, or ability for, these recombinant viruses to replicate, efficiently in a mammalian system. rSFV stability in mosquito cells is questionable as luciferase expression was not maintained over 5 low multiplicity passages in these cells. In order to take this work forward, characterisation of the rSFVs in various mosquito species is required in order to determine whether or not these results are replicated in vivo. In order to apply this technology to a virus that is economically important, the three most effective MREs were cloned into an attenuated Rift Valley Fever virus (RVFV) strain, MP12. The Gluc reporter was removed from the MRE cassettes due to size constraints of the RFVF plasmids. Modified MRE cassettes were cloned into the S and L segments, specifically into the 3’ untranslated regions (UTRs) of the NSs and L genes, to generate single or double rRVFV mutants. All viruses were rescued and were viable. Infected cells displayed cytopathic effect characteristic of RVFV-infected cells. Single S segment mutant viruses reached similar titres to, and took the same amount of time to rescue as, wtRVFV. L segment and double segment mutants (recombinant viruses with MREs in both the S and L segments) reached titres two logs lower and took two days longer to rescue than wtRVFV. This suggests that the incorporation of the MRE cassettes into the L segment UTR is affecting virus transcription or translation in some way. Unfortunately, due to time constraints, further characterisation of these viruses could not be carried out. The technology described here may provide an innovative way to create environmentally contained vaccines that are no longer transmitted by their mosquito vectors.

Insecticide resistance in malaria vector mosquitoes reduces the efficacy of insecticide in killing and can therefore cause a major problem for malaria vector control by insecticides. In Mozambique, pyrethroid resistance in Anopheles funestus was first detected in December 1999 in the southern corner of Maputo Province. Since then, various collections have been made at selected sites throughout the country and WHO standard susceptibility tests and biochemical assays were conducted to determine the susceptibility status and the major resistance mechanisms, in the Fl generation of field collected mosquitoes. Three malaria vector species: Anopheles funestus s.s., Anopheles gambiae s.s. and Anopheles arabiensis were identified in this study by Polymerase Chain Reaction (PCR) and their distributions plotted. The susceptibility data indicate that the Anopheles funestus s.s population in southern Mozambique is widely resistant to pyrethroid and with low levels of carbamate resistance evident at six localities. No resistance to organophosphate and DDT was observed at any study sites. Biochemical tests indicate the presence of an altered acetlylcholinesterase in all collection localities with the exception of Massinga district. Elevated esterase activity with substrate a-naphthyl acetate were detect in Boane with a probable role in organophosphate resistance. Elevated GST were detected in Boane, Moamba and Catembe. Very low levels monooxygenase titres were registered in all the localities in Mozambique, which suggest that this resistance mechanism is not operating in these areas. Pyrethroid resistance in the Anopheles gambiae complex was detected only in Anopheles arabiensis from one locality. No resistant to other groups of insecticide were observed. Altered acetlylcholinesterases were registered in all collection localities and in both species: Anopheles gambiae s.s. and Anopheles arabiensis. Elevated esterase with substrate a-naphthyl acetate were detected in Anopheles arabiensis at only one locality. Elevated GSTs were detected at all localities and in both species. The implications of the findings for malaria vector control in Mozambique are discussed. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-03-08T11:46:19Z No. of bitstreams: 1 texto completo.pdf: 811660 bytes, checksum: 22a429ae96272122735337467c7e7599 (MD5) / Made available in DSpace on 2017-03-08T11:46:19Z (GMT). No. of bitstreams: 1 texto completo.pdf: 811660 bytes, checksum: 22a429ae96272122735337467c7e7599 (MD5) Previous issue date: 2000-09-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho tem por objetivo verificar, nos parâmetros morfológicos e biológicos, após a exposição das larvas de Culex. quinquefasciatus à concentração de 1,5 ppb de ivermectina, o comportamento e a sobrevivência de C. quinquefasciatus, as possíveis alterações morfológicas no corpo gorduroso das larvas, as possíveis alterações no número de ínstares, número médio de ovos por postura da fêmea, duração do período larval e a assimetria flutuante nos adultos. Na sua execução foram utilizadas 601 larvas de 3o e 4o ínstar do mosquito como material biológico, que foram obtidas de criação semi natural. As larvas foram colocadas em recipientes plásticos num período de 30 minutos de exposição à droga. Após a exposição à solução do fármaco, foram lavadas em água desclorada e colocadas em gaiolas teladas para acompanhamento do desenvolvimento. Após a postura, os ovos foram separados e as larvas eclodidas, contadas. Algumas larvas submetidas a 1,5 ppb de ivermectina, foram utilizadas para o preparo de amostras para estudos em histologia. Para a análise de assimetria flutuante, 40 machos e 43 fêmeas adultas do grupo controle e 39 machos e 40 fêmeas adultas, sobreviventes das larvas expostas à concentração de 1,5 ppb de ivermectina, foram selecionados e destes, retiradas suas asas para posterior observação através do microscópio estereoscópico com câmera de vídeo acoplada. Foram realizadas medidas de comprimento das nervuras R3, R4+5, M1, M2, M3+4 e do perímetro das nervuras M1 e M2. Os resultados obtidos neste trabalho mostraram que a ivermectina na concentração de 1,5 ppb causou paralisia nas larvas com 73,38% de mortalidade, aumento das gotículas de lipídios no corpo gorduroso larval e uma diminuição do número de posturas. Foi verificado também, alteração na assimetria flutuante (AF), sendo maior no grupo controle e nas fêmeas. / The present work aims to investigate the behavior and the survival rate of Culex. quinquefasciatus, and to determine the lethal effect of ivermectin based on morphologic and biologic parameters of a 1.5 ppb concentration of C. quinquefasciatus larvae, and possible alterations of their fat body. Larvae of mosquito were obtained from semi-natural breeding as biologic material. Changes in the number of instars, average number of eggs per laying, length of the larval stage and fluctuating asymmetry (FA) were studied in adults. For this experiment, 601 larvae of 3rd and 4th instars of the mosquito were obtained and placed in plastic containers and exposed for 30 minutes. The laid eggs were separated and the hatched larvae were counted. Some larvae submitted to 1.5 ppb of ivermectin were used to prepare samples for histologic study. For asymmetry analyses, 40 floating males and 43 adult females of the control group which survived exposure to 1.5 ppb of ivermectin were selected and from them, the posterior observation through stereoscopic microscope with video camera mounting. R3, R4+5, M1, M2, M3+4 nervures and the perimeter of M1 and M2 nervures were measured. The results obtained show that ivermectin in a concentration of 1.5 ppb caused paralysis to the larvae with a mortality rate of 73.38%, an increase in the number of lipid droplets in the fat body and an reduction of the number of egg layings in the adult. It was also observed that the FA is larger in females than in males and also larger in the treated group than in the control one.

Submitted by Amanda Silva (amanda.osilva2@ufpe.br) on 2015-03-11T13:04:50Z No. of bitstreams: 2 TESE Iêda Freire Santos.pdf: 3491878 bytes, checksum: b992e484e2a5fd51a96d3ab78505d583 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-11T13:04:50Z (GMT). No. of bitstreams: 2 TESE Iêda Freire Santos.pdf: 3491878 bytes, checksum: b992e484e2a5fd51a96d3ab78505d583 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014-07-30 / CNPq; PAPES VI / As glutationas S-transferase (GSTs) constituem uma superfamília de enzimas envolvida em diversos processos biológicos, por exemplo, detoxificação metabólica, transporte intracelular de substratos hidrofóbicos e proteção contra radicais livres. Em artrópodes, as classes delta e epsilon destacam-se por sua função no metabolismo de inseticidas. Até o momento, pouco se conhece sobre a diversidade dos genes GSTs dentro e entre as populações, assim como a função desses genes em outros processos biológicos, tais como no desenvolvimento e na resposta ao estresse. Este trabalho teve o objetivo de analisar a diversidade genética e padrões de transcrição de genes GSTs em Aedes aegypti e Culex quinquefasciatus. Sequências de DNA foram obtidas por amplificação e sequenciamento, enquanto a expressão gênica foi realizada por experimentos de RT-PCRq. Os resultados revelaram ausência de polimorfismo nos genes GSTE2 e GSTE3 de Ae. aegypti, além de assinaturas de seleção em três populações de Cx. quinquefasciatus. Após a infecção com o vírus Dengue (DENV), Ae. aegypti mostrou regulação gênica tecido-específica para os quatro genes avaliados ao longo do tempo, com destaque para GSTO e GSTX1. A expressão dos genes GSTE2 e GSTE3 em Cx. quinquefasciatus variou de acordo com o tecido, o estágio de vida e o sexo analisado. A partir dos resultados observados, pode-se concluir que: 1) os genes GSTEs provavelmente estão sendo selecionados ao longo do tempo, indicando que eles desempenham importante papel na sobrevivência desses culicídeos na natureza; 2) os mosquitos Ae. aegypti e Cx. quinquefasciatus são capazes de regular a expressão dos genes GSTs, no tempo e no espaço, de acordo com a natureza do estímulo.

Made available in DSpace on 2014-06-12T15:06:07Z (GMT). No. of bitstreams: 2 arquivo1941_1.pdf: 214139 bytes, checksum: 2447955ff3ac59070b8d1da3050633d3 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2003 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Armadilhas de oviposição associadas ao Bacillus thuringiensis var. israelensis (Bti) foram usadas para investigar a postura e eclosão de ovos de Aedes spp em condições de campo, objetivando relacionar variações populacionais desses mosquitos com períodos chuvosos e secos. Avaliou-se também o efeito da estocagem sobre a viabilidade dos ovos recuperados nas ovitrampas. As análises foram feitas em ovos oriundos de palhetas de eucatex recolhidas das armadilhas contendo infusão de gramínia Eleusine indica (Poaceae) a 30% e Bti, após 21 dias de permanência em campo, entre abril e setembro de 2002. As maiores taxas de postura foram observados nos meses de agosto (26,27%) e setembro (25,11%), quando os níveis pluviométricos ficaram abaixo de 281 mm. Independente do período estudado e das condições pluviométricas, em média 38,80±07,03% dos ovos de Aedes spp. estavam eclodidos nas ovitrampas em situação de campo. Em nossas condições de estudo a menor taxa de ovos viáveis foram obtidas com 172 dias (2,47%), aumentando significativamente com a redução do tempo de estocagem, atingindo 38,85% no período de 60 dias (mínimo utilizado em nossa amostra). Aedes aegypti (Linnaeus, 1762), representou 91% e Aedes albopictus (Skuse, 1894), 9% da amostra analisada (setembro 2002), com proporção macho/fêmea de 1:1,1 e 1:1 respectivamente. Estes resultados permitem concluir que os altos índices de eclosão dos ovos no período chuvoso, em detrimento da baixa atividade de postura permitem a manutenção da população em níveis compatíveis com o recrudescimento dos mosquitos no período de seca. Esta condição é reforçada pelo longo período de viabilidade dos ovos. Além disso, A. aegypti foi mais freqüente nas ovitrampas, não havendo diferença na sexagem de ambas as espécies

Made available in DSpace on 2014-06-12T15:07:01Z (GMT). No. of bitstreams: 2 arquivo3001_1.pdf: 1265385 bytes, checksum: 195917f7eadaa711ca792e1630574a84 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco / Um dos determinantes envolvidos no complexo ciclo de transmissão da dengue é o nível de susceptibilidade do Aedes aegypti ao vírus dengue (DENV), ou seja, a competência vetorial, que varia entre populações de mosquitos. Identificar moléculas envolvidas na interação mosquito-vírus pode auxiliar no conhecimento dos mecanismos envolvidos na competência vetorial, até então pouco elucidados. Estudos recentes mostraram a participação de certos mecanismos na interação mosquito-DENV, porém, pouco se sabe do real papel destes na modulação da competência vetorial em mosquitos de campo ou até da relação entre eles. Mediante isso, objetivamos analisar a expressão de três moléculas representantes de diferentes mecanismos de defesa antiviral no Ae. aegypti, em resposta à infecção com vírus dengue sorotipo 2 (DENV-2), sendo elas REL1, HOP e Dicer-2, em populações de campo e de laboratório do mosquito. Para isso, as diferentes linhagens foram artificialmente infectadas com DENV-2, e tecidos variados foram coletados em diversos momentos após infecção. Tanto a quantificação viral quanto a expressão das moléculas selecionadas nas amostras foram realizadas por PCR em tempo real quantitativo (qRT-PCR). Os resultados mostraram que tanto o padrão de infecção viral quanto a expressão das moléculas variaram entre as populações de A. aegypti nos diferentes momentos após infecção com DENV-2. Os resultados aqui obtidos poderão ser bastante relevantes na pesquisa da interação vetor-vírus e poderão auxiliar no desenvolvimento de novas estratégias de controle da dengue, como na pesquisa com mosquitos transgênicos

Submitted by Fernanda Rodrigues de Lima (fernanda.rlima@ufpe.br) on 2018-08-28T21:53:15Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Abigail Marcelino dos Santos Silva.pdf: 4737414 bytes, checksum: 6d5e7224ed503576d6f5980323a0d5e5 (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-09-06T22:53:30Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Abigail Marcelino dos Santos Silva.pdf: 4737414 bytes, checksum: 6d5e7224ed503576d6f5980323a0d5e5 (MD5) / Made available in DSpace on 2018-09-06T22:53:30Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Abigail Marcelino dos Santos Silva.pdf: 4737414 bytes, checksum: 6d5e7224ed503576d6f5980323a0d5e5 (MD5) Previous issue date: 2015-09-15 / A falta de padronizações sistemáticas deixa questões em aberto na identificação das espécies crípticas dos complexos Lutzomyia longipalpis e L. umbratilis, que incluem vetores dos agentes etiológicos das leishmanioses no Brasil. As metodologias de identificação taxonômica têm contribuído para um maior conhecimento da diversidade biológica. Porém o status taxonômico destes dois grupos de flebotomíneos ainda permanece incerto no Brasil. A filogenética molecular é uma ferramenta essencial para investigação de espécies crípticas. Para inferência filogenética com dados de sequências de nucleotídeos existem métodos estatísticos de inferência, inclusive métodos baseados em probabilidade. Estão disponíveis em duas abordagens: Máxima Verossimilhança (MV) e Bayesiana (BE). Neste trabalho foi avaliada a adequação destas abordagens na investigação das referidas espécies crípticas utilizando um marcador mitocondrial (citocromo oxidase I – COI) e um nuclear (gene period – per). Para o complexo L. umbratilis, o método BE apresentou árvores filogenéticas com maiores probabilidades, ou seja, com melhores resultados em relação às árvores inferidas por MV, principalmente com a utilização do marcador COI. Já para o complexo de espécies L. longipalpis, o método BE apresentou a melhor árvore filogenética em relação ao método MV e apenas utilizando o marcador nuclear period. Tendo alcançado melhores resultados com o marcador mitocondrial COI, para L. umbratilis, e period, para L. longipalpis, e com a abordagem BE, conclui-se que esta abordagem juntamente com os respectivos marcadores teve maior adequação do que a abordagem MV. / The lack of systematic standardization leaves open questions in the identification of cryptic species complex of Lutzomyia longipalpis and L. umbratilis, including vectors of etiological agents of leishmaniasis in Brazil. The taxonomic identification methodologies have contributed to a better understanding of biological diversity. But the taxonomic status of these two sandflies groups remains uncertain in Brazil. Molecular phylogenetics is an essential tool for research cryptic species. For phylogenetic inference nucleotide sequence data are statistical inference methods, including methods based on probability. two approaches are available: Maximum Likelihood (ML) and Bayesian (BE). This work evaluated the adequacy of these approaches in the investigation of these cryptic species using a mitochondrial marker (cytochrome oxidase I - COI) and nuclear (gene period - per). For the complex L. umbratilis the method presented phylogenetic trees BE with higher probability, that is, with better results in respect of trees inferred by MV, especially with the use of the COI marker. As for the species complex L. longipalpis, the BE method presented the best phylogenetic tree in relation to the MV method only using the nuclear period marker. Having achieved better results with the mitochondrial marker COI to L. umbratilis, and period to L. longipalpis, and with BE approach, it is concluded that this approach together with their markers had better match than the MV approach.

Cyanobacteria (blue-green algae) produce a diverse array of toxic or otherwise bioactive metabolites. These allelochemicals may also play a role in defense against potential predators and grazers, particularly aquatic invertebrates and their larvae, including mosquitoes. Compounds derived from cyanobacteria collected from the Florida Everglades and other Florida waterways were investigated as insecticides against the mosquito Aedes aegypti, a vector of dengue and yellow fever. Screening of cyanobacterial biomass revealed several strains that exhibited mosquito larvicidal activity. Guided via bioassay guided fractionation, a non-polar compound from Leptolyngbya sp. 21-9-3 was found to be the most active component. Characterization revealed the prospective compound to be a monounsaturated fatty acid with the molecular formula C16H30O2. This is the first evidence of mosquito larvicidal activity for this particular fatty acid. With larvicidal becoming more prevalent, fatty acids should be explored for future mosquito control strategies.

archives@tulane.edu / In a laboratory setting, mosquito blood feeding is an essential step in investigating many aspects of mosquito biology. Standard laboratory procedures often place the blood membrane feeder on top or inside the cage. Previous research has suggested that blood feeding position improves mosquito feeding but was limited to vertical and horizontal placements. To enhance the current understanding of mosquito feeding behavior, this study sought to further optimize feeding at multiple angles between 0° and 180°. Aedes aegypti Rockefeller, field-derived New Orleans Aedes aegypti, field-derived New Orleans Aedes albopictus and Culex quinquefasciatus Orlando were tested to evaluate blood feeding success. A Hemotek feeding membrane system was attached to a custom-designed apparatus and four distinct mosquito colonies were fed separately during 30 minute feeding trials. Once fed, all mosquitoes were placed into emergence chambers and their eggs were collected. Ae. aegypti Rockefeller, field New Orleans Ae. aegypti and Cx. quinquefasciatus Orlando fed better at all angles measured compared to the control, suggesting that this trait has a potential role in mosquito feeding behavior. Lab-adapted mosquitoes laid on average more eggs at vertical and horizontal angles, suggesting physiological constraints. Feeding angle is proven to have an impact on mosquito feeding which may help improve future mosquito feeding assays. / 1 / Chance Erik Liedig

Transposable elements (TEs) are mobile genetic elements. They are a significant component of many eukaryotic genomes. They are involved in chromosomal rearrangement by serving as substrates for homologous recombination, in creating new genes through a process of TE "domestication", and in modifying and shuffling existing genes by transducing neighboring sequences (Lander et al., 2001). Therefore, both active and inactive TEs are potentially potent agents for genomic change (Kidwell and Lisch, 2001, 2002; Rizzon et al., 2002; Petrov et al., 2003). In the meantime, active TEs are being explored as useful tools for genetic transformation and possible gene drive mechanisms to deliver genes in natural populations (Ashburner et al.,1998; Alphey et al.,2002; Handler and O'Brochta, 2004). My thesis project focuses on AGH1, a novel DNA-mediated TE in Anopheles gambiae and related mosquitoes. I have studied its genomic structure, insertion polymorphism, evolution, and transposition activity. As part of the sequence and structural characterization of AGH1 in the A. gambiae genome, the boundaries of AGH1were determined. The TA target site duplications flanking AGH1 were verified by comparing a genomic sequence that had an AGH1 insertion with the sequence of a corresponding empty site. AGH1 has relatively long, 350bp, TIRs (Terminal inverted repeats). In addition to the transposase ORF (ORF1) that contains a DD34E catalytic motif, it contains an unusual ORF2 with unknown function. Phylogenic analyses clearly suggest that unlike most DD34E transposons that are similar to the Tc1 family, AGH1 belongs to a different clade that is related to the previously characterized fungal TE Ant and protozoan TEC1 and TEC2. Truncated AGH1 and AGH1-related MITE (Miniature inverted-repeat TE) families were also identified. AGH1 insertion polymorphism was studied using 4 natural populations that belong to two molecular forms of A. gambiae, M and S. AGH1 insertions showed considerable differences between M and S forms and the insertions of AGH1 are highly variable in two populations of M. These results are potentially significant in light of the hypothesis that M forms are newly derived incipient species that are only found in West Africa. PCR and sequencing results showed more than 99% sequence identity between AGH1 sequences in A. gambiae, A. arabiensis, and A. melas, which may indicate either purifying selection or recent horizontal transfer. To assess whether AGH1 is currently active, inverse PCR was performed which provided evidence for extrachromosomal circular AGH1 that may be a product of imprecise excision. RT-PCR detected transcripts for both intact and truncated transposase. Preliminary TE display experiments using genomic DNA isolated from different passages of an A. gambiae Sua1B cell line showed possible new insertions and deletions of AGH1 related elements, which may have been mobilized by AGH1. In summary, the structural and genomic characteristics of AGH1 and the phylogenetic relationship between AGH1 and other known transposons in the IS630-Tc1-mariner superfamily have been determined. Significant divergence was shown between M and S forms of A. gambiae according to AGH1 insertion patterns. Observations of high level of insertion polymorphism and low insertion frequency per site in M populations are preliminary indications that AGH1 may be active in some populations. AGH1 has at least been recently transposing and there are also indications for its current activity in A. gambiae cell lines. If AGH1 is indeed active, it has the potential to be used as genetic tools to study mosquito biology and to spread refractory genes into the field populations to help control mosquito-borne diseases. Although a few active DNA transposons have been discovered in different insects and are being used as tools to transform mosquitoes, no DNA active transposons have been reported in mosquitoes. It is our hope that active endogenous DNA transposons may present new features that will help us overcome some of the deficiencies of current transformation tools developed based on exogenous transposons. In addition, the discovery of an active DNA transposon will help us understand how TEs spread in natural populations of mosquitoes, which is critical if we are to use TEs to drive refractory genes into mosquito populations to control vector-borne infectious diseases. The differential insertion patterns of AGH1 in M and S populations are consistent with the hypothesis that the M and S forms of A. gambiae are in the process of incipient speciation. AgH1 showed much higher levels of insertion polymorphisms in two west African populations of the M molecular form compared to two east African S populations. Similarly, the maximum level of chromosomal differentiation is observed in west African dry savannah areas, while a much lower degree of chromosomal polymorphism is observed in east Africa. Therefore our insertion data support the hypothesis that the speciation process is likely to be originated in west Africa, probably as the result of the need of ecological flexibility created by the greater ecological variability of this region. From a biomedical perspective, this type of analysis is critical because the genetic differences between M and S forms may directly impact the effectiveness of mosquito control measure and perhaps disease transmission. / Master of Science