Source: Masters Abstracts International, Volume: 47-06, page: 3395. Advisers: Kristy O. Murray; George L. Delclos. Includes bibliographical references.

Zika (ZIKV), La Crosse (LACV), and Cache Valley (CVV) viruses are mosquito-vectored diseases that cause significant morbidity and mortality in humans and animals. Transmission of these viruses are dependent on numerous factors including vector competence and the effects of mosquito-virus interactions. We conducted vector competence studies of local Aedes and Culex mosquitoes for ZIKV and CVV, and found that all Aedes mosquitoes were competent for CVV and only Aedes albopictus and Aedes japonicus were competent for ZIKV. Vector competence for CVV was dose-dependent, where mosquitoes orally infected with high titers developed higher transmission rates. We also found that vector competence for ZIKV was limited by midgut and salivary gland barriers. Second, we looked at the effects of LACV and ZIKV infection on repellent response in Aedes mosquitoes and found that infected mosquitoes were refractory to low concentrations of DEET, picaridin, and PMD. Increasing concentrations of the repellents to ≥10% was able to increase percent protection (%p) against infected and uninfected mosquitoes. Lastly, we determined the effects of ZIKV and LACV infection on oxidative stress and glutathione-S-transferase (GST) activity in Aedes albopictus. Virus infection had no effect on oxidative stress, but GST activity was significantly different for mosquitoes 3-days post-exposure. We found that oxidative stress levels and GST activity had an inverse relationship for infected and uninfected mosquitoes, where oxidative stress decreased and GST activity increased over the 10-day test period. This indicates that GSTs may aid in controlling byproducts of oxidative stress. The results from this entire study identified competent vectors for emerging arboviruses and demonstrated the behavioral and physiological effects of virus infection in the mosquito vector. / Doctor of Philosophy / Zika (ZIKV), La Crosse (LACV), and Cache Valley (CVV) viruses are transmitted by mosquitoes and can make humans and animals very sick. There are many biological factors that determine if a mosquito can transmit a virus and these viruses can change the biology of a mosquito. We conducted laboratory studies to see if Aedes and Culex mosquitoes can transmit ZIKV and CVV. We found that all Aedes mosquitoes were able to transmit CVV and only the Asian tiger mosquito and Asian rock pool mosquito were able to transmit ZIKV. Mosquitoes infected with high amounts of CVV developed higher transmission rates. We also found that transmission of ZIKV was limited by barriers in the mosquito midgut and salivary glands. Second, we looked at the effects of LACV and ZIKV infection on how Aedes mosquitoes respond to repellents and found that infected mosquitoes were less sensitive to low concentrations of DEET, picaridin, and PMD. Increasing concentrations of the repellents to 10% or higher was able to provide adequate protection against infected and uninfected mosquitoes. Lastly, we determined the effects of ZIKV and LACV infection on oxidative stress and glutathione-S-transferase (GST) activity in the Asian tiger mosquito. Virus infection did not change oxidative stress, but GST activity was higher in infected mosquitoes tested after 3 days after infection. We found that oxidative stress decreased and GST activity increased over the 10-day test period. This indicates that GSTs may help control damaging products from oxidative stress. The results from this entire study identified what mosquitoes were able to transmit emerging mosquito-borne viruses and demonstrated the biological effects of virus infection in the mosquitoes.

Les femelles moustiques peuvent être vectrices de nombreux agents infectieux (virus, protozoaires, helminthes) pour l'Homme, qui peuvent être la cause de maladies graves comme le paludisme et la dengue. Ces maladies menacent respectivement 50 et 40% de la population mondiale ; le paludisme étant responsable de près d'un million de décès par an. Les méthodes de lutte anti-vectorielle destinées à limiter les populations vectrices et stopper la transmission de maladies, se heurtent au développement incessant de résistances de la part des moustiques et des agents infectieux vis-à-vis des traitements employés. Bien que certaines régions du monde aient réussi à stopper efficacement la transmission de certaines de ces maladies, une grande partie des régions tropicales reste menacée. De plus l'expansion rapide de certaines espèces vectrices, telles qu'Aedes albopictus, accroît les risques sanitaires dans de nouvelles régions du globe. La technique de l'insecte stérile (TIS), qui a permis l'éradication ou la suppression des populations de nombreux insectes nuisibles aux cultures et à l'Homme, représente un moyen de lutte prometteur contre les moustiques. Cette technique s'appuie sur le lâcher en masse de mâles stérilisés par rayonnements ionisants qui, en transférant un sperme stérile aux femelles sauvages, vont permettre une diminution progressive de la population cible. Suite à l'épidémie de chikungunya à l'île de la Réunion en 2005 et face aux menaces permanentes de recrudescence de la dengue et du paludisme, les services de lutte anti-vectorielle réunionnais mettent en place d'importants moyens de lutte contre les populations de moustiques concernées. Toutefois, ces mesures ne permettant pas une diminution durable des densités de vecteurs, une étude de faisabilité est en cours quant à l'utilisation de la TIS pour diminuer et contrôler les populations d'Aedes albopictus, vecteur de la dengue et du chikungunya, et d'Anopheles arabiensis, vecteur du paludisme.Ce travail de thèse s'inscrit dans le cadre du projet TIS Réunion, dans le but d'étudier la biologie et le comportement des souches destinées aux lâchers de mâles stériles. Dans un premier temps, cette étude s'intéresse à la comparaison entre les souches d'élevage d'Anopheles arabiensis et les souches sauvages, ainsi qu'aux modalités de stérilisation des mâles de la souche à sexage génétique. Une seconde partie est consacrée à l'étude de l'effet de l'irradiation sur les mâles d'Aedes albopictus, en étudiant plus particulièrement leur stratégie de reproduction, leur capacité d'insémination en laboratoire, ainsi que leur compétitivité sexuelle et longévité face aux mâles sauvages en conditions semi-contrôlées.

Submitted by Anderson Silva (avargas@icict.fiocruz.br) on 2012-07-16T17:21:08Z No. of bitstreams: 1 marcio_g_mocellin_ioc_bp_0031_2010.pdf: 3032579 bytes, checksum: 7aed3538611cf2e56bbf30c397b03c42 (MD5) / Made available in DSpace on 2012-07-16T17:21:08Z (GMT). No. of bitstreams: 1 marcio_g_mocellin_ioc_bp_0031_2010.pdf: 3032579 bytes, checksum: 7aed3538611cf2e56bbf30c397b03c42 (MD5) Previous issue date: 2010 / Capes / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Rio de Janeiro, RJ, Brasil. / Aedes aegypti e Aedes albopictus têm preferência por criadouros artificiais embora possam utilizar criadouros naturais. O encontro de formas imaturas destes vetores da dengue em bromélias tem levado a reflexões sobre o papel de bromeliáceas na proliferação e persistência destes mosquitos. Embora nenhum estudo sistematizado tenha sido feito no Rio de Janeiro para avaliar a importância sanitária deste criadouro no ambiente urbano, a eliminação dessas plantas pela população e a realização de tratamento das mesmas com inseticidas foram implementadas, principalmente com vistas ao combate a Ae. aegypti especialmente durante epidemias. O presente trabalho avalia a presença de Culicídeos em bromélias, com enfoque para Ae. aegypti, em cinco bairros ou favela com características urbanísticas, demográficas e ambientais distintas, no Rio de Janeiro: Amorim (favela), Curicica, Tubiacanga (bairros suburbanos), Urca e Vila Valqueire (urbanos), de outubro de 2008 a outubro de 2009. Sessenta bromélias foram marcadas em cada bairro e examinadas quinzenalmente. A água das axilas foliares de cada planta era totalmente aspirada e aferido o seu volume, e contado o número de axilas foliares contendo água no momento da coleta. O material era levado ao laboratório onde as formas imaturas eram identificadas segundo a espécie a partir de caracteres de formas imaturas ou de adultos emergidos de pupa, e a água analisada segundo sete parâmetros físico-químicos. Criadouros encontrados em oito casas ao redor daquela onde se achavam bromélias marcadas, também foram examinados. Foi coletado um total de 2.368 larvas. A composição da fauna e a frequência das espécies de mosquitos variaram segundo o bairro. Wyeomyia sp. e Ae. aegypti foram as mais frequentes. O gênero Wyeomyia foi o mais abundante nas bromélias urbanas, especialmente em bairros com proximidade com áreas verdes, e houve uma correlação negativa entre a frequência desse táxon e a de Ae. aegypti. O gênero Wyeomyia mostrou-se presente em todos os meses do ano, enquanto que a maior frequência de Ae. aegypti foi entre os meses de dezembro a junho, com um pico em março. Os dados da temperatura mostrou correlação positiva com a abundância de Ae. aegypti e com o gênero Wyeomyia. Não foi possível encontrar qualquer tipo de correlação entre os resultados obtidos na medição dos fatores físico-químico do microambiente das bromélias e a constituição da fauna de mosquitos, e nem em relação ao número de larvas coletadas. Foi verificada uma influência, diretamente proporcional, da densidade populacional de Aedes aegypti nos criadouros artificiais no ambiente urbano com a densidade da fauna dessa espécie de mosquito nas bromélias. Não houve aumento significativo da população de Ae. aegypti nas bromélias quando efetuada a ação de controle sobre os principais criadouros artificiais ao seu redor. Embora Ae. aegypti seja encontrado nas bromélias urbanas, os resultados sugerem que as bromélias não se constituem criadouros importantes para a manutenção e proliferação deste vetor e, desta forma, não poderiam, isoladamente, manter uma epidemia de dengue, além de não ter sido observada preferência de Ae. aegypti pelas bromélias quando comparadas a outros criadouros, tais como caixas d’água, pneus, tonel, prato plástico, ralo e prato de xaxim. / Aedes aegypti and Aedes albopictus are dengue vectors that usually breed in artificial containers, although they may use natural larval habitats. The findings of immature forms of these mosquitoes in bromeliads have led some authors to investigate the potential role of these plants in their proliferation and persistence. Removal of these plants or their treatment with insecticides have been undertaken during dengue outbreaks in Brazil despite uncertainty as to their importance as productive habitats for dengue vectors. The present study aimed at evaluating Culicidae fauna constitution in bromeliads, with emphasis in Ae. aegypti, in five districts and a slum with different urban, demographic and environmental characteristics in the city of Rio de Janeiro: Amorim (slum), Curicica, Tubiacanga (suburban districts), Urca and Vila Valqueire Vila (urban), from October 2008 to October 2009. Sixty bromeliads were marked at each district/slum and examined fortnightly. The water hold in each plant was completely aspirated and measured, and the number of leaf axils holding water at the time of collection was recorded. The immature mosquitoes were taken to the laboratory for species identification from characters of larvae or adults emerged from pupae, and the aspirated water was analyzed according to seven physical and chemical parameters. Any other larval habitats found in eight dwellings around that with marked and sampled bromeliads were also examined. A total of 2,368 mosquitoes were collected. The fauna composition and frequency of mosquito species varied according to the collecting site. Wyeomyia sp. and Ae. aegypti were the frequent. The genus Wyeomyia was the most abundant taxon in the bromeliads, especially in districts close to or with more abundant vegetal coverage, such as Vila Valqueire and Amorim, and its frequency exhibited negative correlation with that of Ae. aegypti. The genus Wyeomyia was collected in all months, whereas the highest frequency of Ae. aegypti was recorded from December to June, peaking in March. The temperature was positively correlated with the abundance of Ae. aegypti and with the genus Wyeomyia. There was no correlation between physical-chemical characteristic of the water hold in bromeliads with the fauna constitution neither with number of larvae collected. The frequency and abundance of Ae. aegypti in artificial larval containers in the districts/slum was directly proportional to those in the marked bromeliads. There was no significant increase in the Ae. aegypti population in bromeliads when control measures were applied to the main artificial larval habitats in the same district. Although Ae. aegypti has been found in bromeliads at the investigated human disturbed sites, the results demonstrate that bromeliads are not important producers of Ae. aegypti comparatively to other larval habitats, hence, bromeliads should not be consider an important focus for dengue control. Ae. aegypti does not prefer to breed in bromeliads when compared to other breeding sites, such as water tanks, tires, metal drums, pots, drain and plant dishes.

In under 6 decades dengue has emerged from South East Asia to become the most widespread arbovirus affecting human populations. Recent dramatic increases in epidemic dengue fever have mainly been attributed to factors such as vector expansion and ongoing ecological, climate and socio-demographic changes. The failure to control the virus in endemic regions and prevent global spread of its mosquito vectors and genetic variants, underlines the urgency to reassess previous research methods, hypotheses and empirical observations. This thesis comprises a set of studies that integrate currently neglected and emerging epidemiological, ecological and evolutionary factors into unified mathematical frameworks, in order to better understand the contemporary population biology of the dengue virus. The observed epidemiological dynamics of dengue are believed to be driven by selective forces emerging from within-host cross-immune reactions during sequential, heterologous infections. However, this hypothesis is mainly supported by modelling approaches that presume all hosts to contribute equally and significantly to the selective effects of cross-immunity both in time and space. In the research presented in this thesis it is shown that the previously proposed effects of cross-immunological reactions are weakened in agent-based modelling approaches, which relax the common deterministic and homogeneous mixing assumptions in host-host and host-pathogen interactions. Crucially, it is shown that within these more detailed models, previously reported universal signatures of dengue's epidemiology and population genetics can be reproduced by demographic and natural stochastic processes alone. While this contrasts with the proposed role of cross-immunity, it presents demographic stochasticity as a parsimonious mechanism that integrates, for the first time, multi-scale features of dengue's population biology. The implications of this research are applicable to many other pathogens, involving challenging new ways of determining the underlying causes of the complex phylodynamics of antigenically diverse pathogens.