The chemical defences of insects against predators are either passive or aggressive. Passive defence is achieved through crypsis, and aggressive defence is maintained by a conspicuous or 'aposematic' (Poulton, 1890) appearance that advertises some noxious quality of the insect harmful to a predator. Aposematism is mutually beneficial to both the bearer and its predator, whereas crypsis only benefits the prey species. It is therefore not surprising that the fascinating array of chemical defences in insects is both diverse and widespread (Roth and Eisner, 1962). Intro. p. 1.

Title from title page of PDF (University of Missouri--St. Louis, viewed March 9, 2010). Includes bibliographical references.

The family Culicidae has great public health importance for being composed by haematophagous insects in majority, which can be vector of diseases for the human being and other vertebrates. The knowledge about culicideos fauna, besides of data about various species that compose the Caatinga biome, can also bring information about species that are vector of pathogens, providing important tools in case of eventual epidemic outbreak at the region. The Caatinga biome occupies around 55% of all northeast region, representing 11% of Brazil s surface, and holds the position of the less preserved biome of the country, relative to its total area. This work aimed to realize a mosquitoes fauna survey, as well as ecologic aspects analysis for adult species in two areas of Caatinga and immature in three semi permanent breeding grounds. The study was realized in the city of Poço Redondo, semi-arid of Sergipe, where the Unidade de Conservação Monumento Natural Grota do Angico is located under exclusive domain of Caatinga. Collects were made monthly in two areas of Caatinga, between 5 p.m. and 8 p.m. using the Shannon trap for adults, and in three breeding grounds with plastic dipper method for mosquito larvae collects. On ecologic aspects analysis were used the Shannon diversity index, Pielou s equitability, Berger-Parker dominance, Nonmetric multidimensional scaling (NMDS) for species composition. A number of 1788 specimens were collected on total among adults and immature, distributed on ten genus, Aedes, Aedomyia, Anopheles, Coquilettidia, Culex, Haemagogus, Mansonia, Ochlerotatus, Psorophora and Uranotaenia and 21 species. The adults resulted in 583 specimens, 268 from shrubby Caatinga and 315 from arboreal Caatinga, dominant species were Mansonia (Man) indubitans and Ochlerotatus (Och) scapularis,there was no difference between these areas on species composition or abundance, however, the arboreal Caatinga was richer in species. In relation to the immature, breeding sede captured the larger number of specimens (N=590), followed by breeding cancela (N=436) and the smaller value on breeding trilha (N=179). Species composition did not show difference between breedings, dominant species were Anopheles (Nys) albitarsis and Culex (Cx) chidesteri. The presence of mosquitoes species with vector importance, some of that capable to adapt on anthropic ambient, associated with lack of knowledge about Caatinga s mosquitoes suggests future studies to avoid epidemiologic outbreaks in the Unidade de conservação Monumento Natural Grota do Angico . / A família Culicidae apresenta grande importância em saúde pública por ser composta de insetos em sua maioria hematófagos, os quais podem veicular diversas doenças para o homem e demais vertebrados. O conhecimento sobre a fauna de culicídeos, além de gerar informações sobre as espécies que compõem o bioma Caatinga, permite conhecer espécies vetoras de patógenos fornecendo importantes ferramentas em caso de eventuais surtos epidêmicos na região. O bioma Caatinga ocupa cerca 55% de toda a região Nordeste, representando 11% da superfície do Brasil, e detém a posição de bioma menos conservado em relação à área total. O presente trabalho objetivou realizar levantamento da fauna de mosquitos, bem como análise de aspectos ecológicos para as espécies de adultos em duas áreas de Caatinga e espécies de imaturos em três criadouros semipermanentes de solo. O estudo foi realizado no município de Poço Redondo, situado no alto sertão sergipano, na unidade de conservação Monumento Natural Grota do Angico, sob o domínio exclusivo de Caatinga. As coletas foram realizadas mensalmente em dois ambientes de Caatinga das 17 às 20 horas através de armadilha de Shannon para adultos, e em três criadouros de solo utilizando metodologia de concha para coleta de larvas. Para análise de aspectos ecológicos foram utilizados os índices de diversidade de Shannon, equitabilidade de Pielou, dominância de Berger-Parker e escalonamento multidimensional não métrico (NMDS) para composição de espécies. No total foram coletados 1788 espécimes entre adultos e imaturos, distribuídos em dez gêneros, Aedes, Aedomyia, Anopheles, Coquilettidia, Culex, Haemagogus, Mansonia, Ochlerotatus, Psorophora e Uranotaenia e 21 espécies. Os adultos somaram 583 exemplares, sendo 268 na Caatinga arbustiva e 315 na Caatinga arbórea, as espécies dominantes foram Mansonia (Man) indubitans e Ochlerotatus (Och) scapularis, a composição de espécies e a abundância não diferiram entre as áreas, no entanto a Caatinga arbórea apresentou maior riqueza de espécies. Em relação aos imaturos, no criadouro sede foi capturado maior número de espécimes (N=590), seguido do criadouro cancela (N= 436) e os menores valores no criadouro trilha (N= 179). A composição das espécies não variou entre as áreas, as espécies dominantes para imaturos foram Anopheles (Nys) albitarsis e Culex (Cx) chidesteri. A presença de espécies com importância vetorial, dentre elas algumas com capacidade de adaptação ao ambiente antropizado, aliada ao déficit de conhecimento sobre os mosquitos da Caatinga sugerem continuidade de estudos para evitar que quadros epidemiológicos possam se instalar na unidade de conservação Monumento Natural Grota do Angico.

Dengue is an important arboviral disease transmitted to humans through the bite of female mosquito Aedes aegypti. As there is no vaccine available, the control of disease occurs, mainly, by the reduction of mosquito population and personal protection to prevent contact between hosts and vectors. Given the increasing process of chemical resistance to insecticides, natural products emerge as safer alternatives for integrated control of endemic diseases. The aim of this work was to evaluate the larvicidal and repellent activities of essentials oils extracted from Xylopia laevigata, Xylopia frutescens and Lippia pedunculosa and of their majority compounds, piperitenone oxide and r-limonene. The larvicidal activity was investigated by exposure of third instar larvae to different concentrations of essentials oils. After 24 hours of exposition, larvae showing lack of mobility or inability to move to water s surface were considered as dead. The repellency effect was based on the suppression of mosquitoes landing on human skin. Essentials oils were diluted in ethanol and applied directly over the volunteer s skin. For each essential oil were performed 12 tests, in which oils concentrations ranged from 0.1 to 10%. The essential oil of L. pedunculosa and its major volatile compounds were shown to be toxic for Ae. aegypti larvae, with CL50 lower than 60 ppm. In the other hand, plants of Xylopia genus just proved to be toxic to Ae. aegypti when in concentrations higher than 1000 ppm. This fact make their use in large-scale unfeasible. All plants tested provided some degree of protection against mosquitoes landing. However only the essential oil of L. pedunculosa and piperitenone oxide provided 100 % of protection against mosquito landings when tested in concentrations lower than 1%. Although its performamnce against dengue mosquitoes, the essential oil of L. pedunculosa shows toxicity the human skin. Therefore, further studies are required to get formulations which are able to provide longer time protection. / A dengue é uma importante arbovirose transmitida ao homem por meio da picada do mosquito fêmea Aedes aegypti. Como não há vacinas, o controle da transmissão da doença se dá, principalmente, com a redução da população de mosquitos e a adoção de medidas de proteção individual que impeçam o contato entre hospedeiros e vetores. Diante do agravamento do processo de resistência aos inseticidas químicos, os produtos de origem vegetal se apresentam como alternativas mais seguras para o controle integrado de doenças vetoriais endêmicas. O objetivo deste trabalho foi avaliar a atividade repelente e larvicida dos óleos essenciais extraídos das plantas Xylopia laevigta, Xylopia frutescens e Lippia pedunculosa, bem como seus constituintes voláteis, óxido de piperitenona e r-limoneno sobre mosquitos Ae. aegypti. A atividade larvicida foi investigada a partir da exposição de larvas de terceiro estádio às diferentes concentrações dos óleos essenciais e componentes voláteis. Após 24 horas de exposição foram contabilizadas as larvas mortas, considerando mortalidade a ausência de mobilidade ou incapacidade da larva em se mover até a superfície da água. A ação repelente foi observada a partir da supressão de pousos dos mosquitos sobre a pele humana. Os óleos essenciais e compostos químicos foram diluídos em etanol e aplicados diretamente sobre a pele dos voluntários. Para cada produto foram realizados doze testes, nos quais as concentrações variavam de 0,1 à 10%. Tanto o óleo essencial obtido a partir da L. pedunculosa quanto os seus principais compostos voláteis mostraram-se tóxicos para larvas de Ae. aegypti, apresentando CL50 inferior à 60 ppm. Em contrapartida, as plantas do gênero Xylopia apenas mostraram-se tóxicas para as larvas quando em concentrações superiores à 1000 ppm, fato que inviabiliza a sua utilização em larga escala. No que diz respeito à ação repelente, todos os produtos avaliados forneceram algum grau de proteção contra pouso de mosquitos adultos sobre a pele humana. Entretanto, apenas o óleo essencial da L. pedunculosa e o óxido de piperitenona foram capazes de fornecer 100% de proteção, quando testados em concentrações inferiores a 1%. Apesar de eficaz na repelência contra o mosquito transmissor da dengue, o óleo essencial da L. pedunculosa apresentou toxidade sobre a pele humana. Portanto, mais estudos fazem-se necessários a fim de que sejam elaboradas formulações de uso tópico capazes de veicular adequadamente os constituintes químicos dos óleos por um prolongado período de tempo.

PhD (Mathematics) / Department of Mathematics and Applied Mathematics / In this study, we developed multiscale models of vector-borne diseases. In general, the transmission of vector-borne diseases can be considered as falling into two categories, i.e. direct transmission and environmental transmission. Two representative vector-borne diseases, namely; malaria which represents all directly transmitted vector-borne diseases and schistosomiasis which represents all environmentally transmitted vector-borne diseases were studied. Based on existing mathematical modelling science base, we established a new multiscale modelling framework that can be used to evaluate the effectiveness of vector-borne diseases treatment and preventive interventions. The multiscale models consisted of systems of nonlinear ordinary differential equations which were studied for the provision of solutions to the underlying problem of the disease transmission dynamics. Relying on the fact that there is still serious lack of knowledge pertaining to mathematical techniques for the representation and construction of multiscale models of vector-bone diseases, we have developed some grand ideas to placate this gap. The central idea in multiscale modelling is to divide a modelling problem such as a vector-bone disease system into a family of sub-models that exist at different scales and then attempt to study the problem at these scales while simultaneously linking the sub-models across these scales. For malaria, we formulated the multiscale models by integrating four submodels which are: (i) a sub-model for the mosquito-to-human transmission of malaria parasite, (ii) a sub-model for the human-to-mosquito transmission of malaria parasite, (iii) a within-mosquito malaria parasite population dynamics sub-model and (iv) a within-human malaria parasite population dynamics sub-model. For schistosomiasis, we integrated the two subsystems (within-host and between-host sub-models) by identifying the within-host and between-host variables and parameters associated with the environmental dynamics of the pathogen and then designed a feedback of the variables and parameters across the within-host and between-host sub-models. Using a combination of analytical and computational tools we adequately accounted for the influence of the sub-models in the different multiscale models. The multiscale models were then used to evaluate the effectiveness of the control and prevention interventions that operate at different scales of a vector-bone disease system. Although the results obtained in this study are specific to malaria and schistosomiasis, the multiscale modelling frameworks developed are robust enough to be applicable to other vector-borne diseases. / NRF