Insecticide-treated nets (ITN) are an effective tool to reduce the burden of malaria in Africa. To address questions concerning the sustained impact of ITN in the face of changing transmission intensity and spreading insecticide resistance a series of four entomological investigations was undertaken in Tanzania. / First, a longitudinal survey of vector populations at different altitudes was conducted in the Hai District, Kilimanjaro Region, Tanzania. Entomological parameters relevant to malaria transmission were measured. Vector densities and entomological inoculation rates decreased dramatically with increasing altitude. Seasonal variations in the host preference and resting behaviour of Anopheles arabiensismay influence malaria transmission and control. / Second, the insecticide susceptibility status of vector populations from agricultural sites in the Kilimanjaro Region was evaluated. Malaria vectors from six sites were highly susceptible to diagnostic concentrations of pyrethroid insecticides and DDT in susceptibility tests. Permethrin tolerance in populations of An. arabiensis from an irrigated rice-growing area was not directly related to agricultural use of insecticides. Synergist bioassays indicated the contribution of a metabolic oxidase-based mechanism to the observed resistance while the knockdown resistance (kdr) mechanism was not detected. Close monitoring of resistance development in this area is needed. / Third, the biological efficacy of ITN and the insecticide susceptibility status of mosquito populations from areas with long-term use of ITN were investigated. Data were compiled from national surveys and long-term ITN projects to examine trends in resistance development in Tanzania. Anopheles species were highly susceptible to ITN and diagnostic concentrations of pyrethroid insecticides, while 'nuisance-biting' Culex quinquefasciatus displayed low susceptibility to these compounds. Low efficacy of ITN against C. quinquefasciatus has implications for user acceptance of ITN. / Finally, a novel method for kdr genotyping was developed and evaluated. Sequence specific oligonucleotide probes (SSOP) were used to identify kdr mutations in Anopheles gambiae s.l. in a high-throughput enzyme-linked immunosorbent assay (ELISA) format. Evaluation of the method on field-collected specimens detected the leucine-phenylalanine kdr mutation in two individual An. arabiensis, raising implications for the geographic spread of kdr-based resistance. The novel SSOP-ELISA method is a useful tool for high-throughput screening allowing sensitive detection of insecticide resistance.

Identifying the molecular interactions of pathogens in different mosquito species is critical for understanding how mosquitoes transmit diseases. In this study, the role of the Jak-STAT immune signalling pathway in two different mosquito species, (Aedes aegypti L.) and (Culex quinquefasciatus L.) was assessed. Using in silico analysis tools, cell culture, and molecular techniques, changes in gene expression were assessed during lipopolysaccharide (LPS) challenge and West Nile virus (WNV) infection in the two species. It was found that activation of the Jak-STAT pathway occurred more quickly in Ae. aegypti cells compared to Cx. quinquefasciatus cells during LPS exposure. During WNV infections, no significant differences were observed, although preliminary evidence suggests that differential activation of the Jak-STAT pathway may exist between the two species. This research extends our understanding of the mosquito immune system while demonstrating the critical importance of vector-virus interactions across different mosquito species.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisors: Jack B. Gingrich and Douglas W. Tallamy, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.

Made available in DSpace on 2016-03-08T14:03:47Z (GMT). No. of bitstreams: 2 luana_ferreira_ioc_dout_2014.pdf: 11732289 bytes, checksum: 1ef56f743ff0c803375a1307f2379adc (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2016-01-13 / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Rio de Janeiro, RJ, Brasil / Diversos parasitas, agentes etiológicos de uma série de agravos, são transmitidos por mosquitos vetores em todo o mundo. A despeito de sua importância médica, ainda existem muitas lacunas no conhecimento da embriogênese desses insetos. Ovos de espécies do gênero Aedes resistem à dessecação, e são capazes de sobreviver vários meses no seco em estado de quiescência ao final da embriogênese. Entretanto, ovos de espécies de outros gêneros, como Anopheles e Culex, não possuem capacidade de resistir a longos períodos de exposição ao seco, apesar de adquirirem algum grau de impermeabilidade. Nos mosquitos Aedes aegypti e Anopheles gambiae tem sido mostrado que, durante a embriogênese, a síntese da cutícula serosa (CS), que contém quitina, coincide com a aquisição da resistência dos ovos à dessecação (ROD). O objetivo deste trabalho foi investigar, comparativamente, a embriogênese de diferentes mosquitos vetores, para elucidar semelhanças e diferenças na ROD. A maior parte do trabalho foi realizada com as espécies Ae. aegypti, An. aquasalis e Cx. quinquefasciatus. Verificamos que para An. aquasalis e Cx. quinquefasciatus a formação da CS também é simultânea à aquisição de ROD e contém quitina. O tempo requerido para a finalização da embriogênese de Ae. aegypti, An. aquasalis e Cx. quinquefasciatus é, respectivamente, 77,4, 51,3, e 34,2 horas após a postura A formação da CS ocorre em estágio embrionário equivalente para Ae. aegypti e An. aquasalis e um pouco mais tardio para Cx. quinquefasciatus. Ao final da embriogênese diferentes níveis de ROD foram detectados: alto para Ae. aegypti, médio para An. aquasalis e baixo para Cx. quinquefasciatus. Com o objetivo de entender essas diferenças, avaliamos, comparativamente, alguns aspectos físicos dos ovos: comprimento, largura, área, volume, peso e a superfície da casca. Apesar de diferenças interessantes e significativas terem sido observadas, não foi possível estabelecer correlação direta entre ROD e tais aspectos, quando avaliados individualmente. Quantificação do polissacarídeo quitina revelou tendência de maior conteúdo em cascas de ovos de espécies mais resistentes ao seco. Além disso, diferenças significativas foram encontradas no grau de melanização dos ovos das diferentes espécies, sugerindo que ovos mais melanizados são mais resistentes ao seco. Essa hipótese foi testada utilizando o mutante GORO da espécie An. quadrimaculatus. Nesta linhagem a melanização não ocorre corretamente, e as cascas de seus ovos têm aparência dourada. Em contraste, seu equivalente selvagem (WT) possui ovos de casca escura Ovos GORO possuem ROD deficiente: quando expostos ao seco por 10 horas após a formação da CS, apenas 12,3% são viáveis, em contraste com 66,5% de ovos WT. Nossos resultados confirmam de forma direta que, além da quitina da CS, a melanização da casca dos ovos é importante para a impermeabilização dos ovos de insetos / Several parasites, etiologic agents of a number of diseases, are transmitted by mosquito vectors worldwide. Despite their medical importance, many gaps in our knowledge about the embryogenesis of these insects still remain. Eggs from the Aedes genus resist to desiccation, and are able to survive several months in dry conditions in a quiescent status at the end of embryogenesis. In contrast, eggs belonging to other genera, like Anopheles and Culex, do not withstand long periods of exposure in dry conditions, although they acquire some degree of impermeability. It has already been demonstrated that, in the course of Aedes aegypti and Anopheles gambiae embryogenesis, the synthesis of the serosal cuticle (SC), which contains chitin, coincides with the acquisition of egg resistance to desiccation (ERD). The aim of the present work was to investigate, under a comparative basis, the embryogenesis of different mosquito vectors, in order to elucidate ERD similarities and differences. Most of the work was performed with Ae. aegypti, Anopheles aquasalis and Culex quinquefasciatus. We found that, for An. aquasalis and Cx. quinquefasciatus, ERD acquisition is also simultaneous to the development of SC, a layer containing chitin. Time required for embryogenesis completion is 77.4, 51.3, and 34.2 hours after egglaying for respectively Ae. aegypti, An. aquasalis and Cx. quinquefasciatus. The formation of SC occurs in an equivalent embryonic stage for Ae. aegypti and An. aquasalis, but a little later for Cx. quinquefasciatus. At the end of embryogenesis different ERD levels were detected: high for Ae. aegypti, medium for An. aquasalis and low for Cx. quinquefasciatus. In order to understand these differences, we comparatively evaluated some physical aspects of the eggs: length, width, area, volume, weight and eggshell surface appearance. Although interesting and significant differences have been observed, it was not possible to establish any direct correlation between ERD and these physical aspects, when individually considered. Quantification of chitin revealed tendency of higher amount of this polysaccharide in the eggshells of species more resistant to desiccation. Furthermore, significant differences were found in the degree of melanization of eggs from the different species, suggesting that more melanized eggs are also more resistant to dry conditions. This hypothesis was tested using the An. quadrimaculatus GORO mutant. In this strain, melanization does not occur properly, and the eggs have a golden appearance. Eggshells from the wild type (WT) strain, in contrast, are dark. GORO eggs exhibit a defective ERD: when exposed to dry conditions during 10 hours after the SC formation only 12.3% are viable, in contrast with 66.5% of WT eggs. Our results confirm, directly, that beyond the chitin present in the SC, the eggshell melanization is an important factor towards insect eggs impermeability

Apresenta-se estudo da secção Spissipes de Culex (Melanoconion), baseado em caracteres morfológicos do cibário feminino. Após tecer considerações, incluindo o histórico, sobre os estudos taxonômicos do subgênero, considera-se a oportunidade do presente estudo, visando o encontro de novos elementos à taxonomia do grupo. De início procede-se à descrição morfológica geral do cibário, assinalando as diversas estruturas passíveis de serem utilizadas na caracterização taxonômica. Segue-se a descrição concernente a 14 (quatorze) espécies das 21 (vinte e uma) atualmente incluídas na secção Spissipes. O trabalho termina com discussão sobre os resultados obtidos. Estes vieram revelar a utilidade, a nivel específico, dos caracteres estudados. Boa parte deles, revelou-se passível de emprego a nivel de grupo. Nesse sentido, apresentaram aspectos característicos as seguintes espécies: Culex faurani Duret, Cx.lopesi Sirivanakarn e Jakob, Cx.nicaroensis Duret, Cx., ocossa Dyar e Knab, Cx. Spissipes Theobald e Cx.taeniopus Dyar e Knab. O trabalho conclui apresentando chave tentativa para identificação mediante o emprego desses caracteres. / The present paper describes some characters of the female cibarium, specially the cibarial armature of certain mosquitoes species commonly placed in the Spissipes section of the Culex (Melanoconion). After giving an account of the subgenus taxonomic history, the opportunity to find new subgeneric characters for taxonomic studies, is taken into consideration. Firstly is given a detailed description of the cibarium anatomy. Then are pointed out those structures of the bucal cavity, which may be useful to support the subgeneric classification. After this, descriptions of the adults female cibaria of 14 species, included in the Spissipes section, are given. Taxonomic implications of the cibarial characters are discussed. Our studies have shown that they may be useful in the subgeneric classification at specific level, as well as at group level. Particularly, characteristics features have been shown by some species as: Culex faurani Duret, Cx.lopesi Sirivanakarn and Jakob, Cx.nicaroensis Duret, Cx.ocossa Dyar and Knab, Cx. Spissipes Theobald and Cx.taeniopus Dyar e Knab. Finally, a tentative identification key is presented.

Made available in DSpace on 2014-06-12T15:06:47Z (GMT). No. of bitstreams: 2 arquivo2001_1.pdf: 371348 bytes, checksum: c811904cc53493c5f48ed09185693771 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2000 / Filariose linfática é uma das doenças mais importantes, cujo agente etiológico é transmitido por mosquitos. O conhecimento das relações vetor/parasito, principalmente no que se refere a capacidade reprodutiva, são essenciais para o desenvolvimento de medidas de controle. Este estudo foi realizado para determinar o efeito do parasito filarial sobre a fecundidade do Culex quinquefasciatus, vetor da Wuchereria bancrofti na Região Metropolitana do Recife. Outros fatores relacionados ao potencial reprodutivo dos mosquitos como tamanho das fêmeas, fertilidade, quantidade de sangue ingerido durante a alimentação e mortalidade, também foram analisados. Mosquitos provenientes de pupas coletadas no campo foram infectados através de alimentação artificial, usando sangue com parasitemias variando entre 724 e 2.900 microfilárias (mf/ml). A fecundidade foi medida como o número total de ovos produzidos no 10 ciclo gonotrófico e a fertilidade como o percentual de larvas eclodidas e viáveis. O volume de sangue ingerido foi expresso como a quantidade de hematina excretada nas fezes durante 3 dias após a alimentação. O tamanho da asa medido sob lente ocular micrométrica determinou o tamanho do mosquito. Os resultados mostraram um aumento significativo na produção de ovos nos grupos de fêmeas alimentadas em sangue contendo menos que 1150 mf/ml. Ao contrário, uma redução na produção de ovos foi observada nos mosquitos alimentados em sangue com parasitemias acima de 1500 mf/ml. Nenhuma diferença na fertilidade e ingestão de sangue foi observada quando mosquitos infectados e não infectados foram comparados. Uma relação positiva foi encontrada entre o tamanho do mosquito e produção de ovos em fêmeas não infectadas. Entretanto, nenhuma relação foi observada nos grupos infectados. Estes resultados sugerem que a fecundidade do C. quinquefasciatus infectado com W. bancrofti é influenciada pela densidade do parasito e pelo tamanho do mosquito

Culex mosquitoes are known for carrying several harmful viruses in the United States. Culex tarsalis is found in rural as well as some residential areas in the Western United States, so they are under insecticide pressure from both agricultural spraying and vector control. In response to insecticide pressure, mosquitoes can evolve two primary resistance mechanisms: target site insensitivity, as a result of DNA mutation, and elevated levels of detoxifying enzymes (GST, alpha and beta esterases, and P450 oxidases). The two types of target site insensitivity studied here in Cx. tarsalis are kdr, which is a mutation in the para-type voltage gated sodium channel and ace-1, which is a mutation in acetylcholinesterase gene. This study focused on a population of Cx. tarsalis in Sutter County, where insecticide use shifted from sumithrin to Naled over the course of the summer. The goal of this study was to determine if there was resistance to insecticides and characterize the mechanisms of resistance. Mosquitoes were separated into resistance levels based on CDC bottle bioassay results using Naled, sumithrin, and permethrin insecticides. Mosquitoes were used to test for elevated levels of detoxifying enzymes and genetic qPCR testing for either kdr and ace-1 mutations. Bottle bioassay results suggest Cx. tarsalis populations from Sutter County are mostly resistant to pyrethroids while not being resistant to organophosphates. Enzymatic assays suggest high concentrations or activities of detoxifying enzymes are commonly seen in resistant individuals, occasionally elevated levels of multiple enzymes within an individual. The ace-1 mutation was seen in a single susceptible individual (0.036%). Either one or two kdr alleles were present in every single semi-resistant or resistant mosquito tested.

The vectors of avian malaria (Haemosporida) are an understudied component of wildlife disease ecology. Most studies of avian malaria have focused on the secondary bird hosts. This imbalance leaves a significant gap in our knowledge and understanding of the insect hosts. This study investigates the diversity of malaria parasites carried by mosquitoes (Diptera, Culicidae) in the state of Mississippi. Using PCR techniques, haemosporidian infection rates were determined and parasites were identified in a phylogenetic context to those previously annotated. A total of 27,157 female mosquitoes representing 15 species were captured. Five of those species tested positive for malaria parasites with an overall infection rate of 4 per 1000 mosquitoes infected. Mosquitoes were shown to harbor Plasmodium and Haemoproteus parasites. Surprisingly, a unique lineage of parasites was discovered in Anopheles mosquitoes potentially representing a new genus of haemosporidian parasites, reinforcing the need to continue investigating this diverse group of parasites.

No description available.

No description available.