Dissertations / Theses on the topic 'Aedes aegypti Infection Rate'

Cercariae of the digenean Plagiorchis elegans cause high levels of morbidity and mortality among larvae of Aedes aegypti . The impact of this parasite on the larval population dynamics of the experimental host as mediated through intraspecific competition, egg hatchability and ovipositional preference was assessed by calculating the probability of pre-imagos to develop from one stage to the next, or to die within consecutive 24 h intervals. Attractiveness of the water to ovipositing females in a dynamic larval population was not affected by exposure to the parasite, but varied significantly over time, regardless of food abundance. In optimally fed populations, these changes were positively correlated with pupal production, but were not affected by early instar development. Most of the entomopathogenic effects of the parasite were expressed in the pupal stage. Thus, exposure to the parasite significantly reduced adult emergence, but did not greatly impair pre-imago development. Nonetheless, exposure to various levels of the parasite significantly increased mortality of all larval stages. Suboptimally fed larval populations displayed severely impaired development and produced few adults. Exposure to P. elegans increased adult production slightly, suggesting depensatory mortality. In nutritionally stressed populations, no correlation was found between biomass and ovipositional preference, but attractiveness of the water was significantly increased by the removal of individuals by pupation or mortality. Egg hatchability was not significantly affected by population structure, but varied with the nutrient content of the water. This study provides new insight into the use of parasites as agents in the biological control of mosquitoes.

Doctor of Philosophy
Department of Biology
Rollie J. Clem
Each year, over 500 million people are infected with mosquito-borne diseases, including malaria, yellow fever and dengue fever, which cause several million deaths, and long-term disability and suffering. This dissertation focused on the mosquito Aedes aegypti, a vector for dengue virus and yellow fever virus. Since Sindbis virus (SINV) is an arthropod-borne virus (arbovirus) that is vectored by A. aegypti and is well characterized at the molecular level, the SINV - A. aegypti model was used to determine whether apoptosis plays a role in the control of vector competency. In Chapter 2, the effects of inducing or inhibiting apoptosis on SINV replication were tested in mosquito cells. It was observed that recombinant SINVs expressing pro-apoptotic genes caused extensive apoptosis in mosquito cells, with decreased virus production after the cells underwent apoptosis. Infection of mosquito cells with SINV expressing the caspase inhibitor P35 inhibited actinomycin D-induced apoptosis, but had no observable effects on virus replication. This study was the first to test directly whether inducing or inhibiting apoptosis affects arbovirus replication in mosquito cells. Chapter 3 examined the effects of silencing apoptosis regulatory genes on SINV replication and dissemination in A. aegypti. Genes which either positively or negatively regulate apoptosis were silenced by RNA interference in mosquitoes, which were then infected with a recombinant SINV expressing green fluorescent protein (GFP). Reciprocal effects were observed on both the occurrence and intensity of expression of GFP in various tissues. These results suggest that systemic apoptosis positively influences SINV replication in A. aegypti. This was the first direct study to explore the role of apoptosis in determining mosquito vector competence for arboviruses. Finally, in Chapter 4, the mechanisms of apoptosis were explored in A. aegypti. Overexpression of IAP antagonists caused extensive cell death in mosquito cells, while silencing the expression of IAP antagonists attenuated apoptosis. The results showed that the IAP binding motif (IBM) of IAP antagonists was critical for their binding to AeIAP1. The IAP antagonists released initiator and effector caspases from AeIAP1 by competing for the binding sites and caused caspase-dependent apoptosis. These findings imply that the mechanisms of IAP antagonists regulating apoptosis are conserved between mosquitoes and the model insect where apoptosis has been mainly studied, Drosophila melanogaster.

Au cours des dernières années, de nombreuses épidémies ont emergé ou ré émergé, et sont causées par des arbovirus (arthropod-borne viruses), des virus transmis à des vertébrés par des insectes piqueurs vecteurs. Avec l'augmentation de la densité humaine dans certaines zones géographiques et le réchauffement climatique qui contribuent à l'expansion géographique des vecteurs, les maladies induites par ces virus (arboviroses) ont un impact de plus en plus important sur la santé humaine et l'économie mondiale. Il est donc déterminant d'augmenter nos connaissances sur les systèmes mis en jeux pour garantir la sécurité sanitaire des populations exposées. Les enjeux actuels reposent aussi bien sur la compréhension des virus que sur la compréhension de l'alternance d'hôtes, directement responsables de l'émergence et la dissémination des agents infectieux. Les moustiques sont des vecteurs majeurs des arbovirus comme la dengue (genre Flavivirus) et le Chikungunya (genre Alphavirus). Transmis par les mêmes moustiques Aedes aegypti et Aedes albopictus, le virus de la Dengue (DENV) est responsable de la plus importante arbovirose en zone tropicale, et le virus Chikungunya (CHIKV) est responsable dans le monde entier de centaines de milliers de cas d'infection, et les épidémies récentes ont touché les pays européens. Ainsi, il a été observé que le moustique Ae. albopictus pouvait porter simultanément CHIKV et DENV, et des cas de co-infections humaines ont été observés en Afrique. Toutefois, bien qu'en théorie les deux virus soient capables d'infecter les mêmes cellules chez l'insecte ou l'homme, il n'y a aucune étude détaillée sur les interactions au niveau cellulaire entre CHIKV et DENV lors de la co-infection d'une cellule. C'est pourquoi il est indispensable d'accroitre nos connaissances sur l'interférence éventuelle entre les virus Chikungunya et Dengue pour l'utilisation de voies cellulaires communes chez les insectes vecteurs et l'hôte humain lors de co-infection
Emergence and geographical extension of dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses increase simultaneous outbreak in an increasing number of countries. To date, no vaccine or cure have yet been developed against these diseases those cause a tremendous impact on human health and in the economy worldwide. During recent simultaneous outbreaks, up to 12% of patients have been diagnosed to be co-infected by CHIKV and DENV. In addition, it was shown that the mosquitoes Aedes albopictus could carry and transmit simultaneously CHIKV and DENV. However, the pathology, as well as the epidemiology of a pathogen, relies on the interactions between several infectious agents present within an organism or a community in the environment. It is crucial to consider to which extent a host infected by a first microorganism is modified and whether its reaction to the infection by a second microorganism is consequently altered. However, there is no extensive report of Alphavirus-Flavivirus or Flavivirus- Flavivirus interactions. Our global objective is to characterize these co-infections in both mosquitoes and humans, at the cell and molecular level. To this aim, we started this project by performing sequential co- infection in different cell lines from Aedes albopictus and Aedes aegypti. We found that the permissiveness and production of DENV is enhanced in presence of CHIKV. On the contrary, there is no effect of DENV pre-infection on subsequent CHIKV co-infection. We generalized the synergistic phenomena and we showed that CHIKV pre-infection also increased the infection by DENV-1, DENV-3 and DENV-4, but also by two others re-emerging Flaviviruses, the Yellow Fever Virus (YFV), and the Zika Virus (ZIKV). Remarkably, we succeeded to establish a mosquito model of co-infection of Aedes aegypti mosquito after by different two feedings at 4 days interval. Using this sequential co-infection, we were able to show that a pre-infection of Aedes aegypti by CHIKV increase the level of DENV-2 RNA in salivary glands compare to mono-infected mosquitos. This phenotype is reminiscent of the phenotype we observed in vitro during successive infections. Altogether, our study paves the way to the characterization of molecular interaction between Flaviviruses and Alphaviruses in mosquito in vitro and in vivo. This study can be crucial for a better understanding of disease and epidemiology during simultaneous outbreaks

Plagiorchis elegans is a typical digenean parasite that cycles through aquatic molluscs and insects as intermediate hosts. During emergence of P. elegans cercariae, infected snails moved to the top of the water column where they remained immobile for 2-3h. Consequently, the cercariae formed a dense cloud which dispersed slowly. The infectivity of cercariae was $<$20% upon emergence and peaked at 76% 4-6h later. This delay in reaching maximum infectivity may be an adaptation to prevent superinfection and the associated mortality of insect hosts. Cercariae transformed into metacercariae after penetrating Aedes aegypti larvae, the experimental insect host. Overall development of metacercariae, and excystment of infective metacercariae in vitro, was temperature dependent. However, there was an initial 8-hour period of obligatory host-parasite contact that was temperature independent. This may represent a period of major nutrient acquisition since young metacercariae were more active metabolically than older metacercariae, as measured by the in vitro uptake of $ sp3$H-glucosamine and $ sp3$H-leucine. Mosquitoes may have mechanisms to reduce losses of larvae to parasites. Oviposition by adult A. aegypti was reduced in waters that had previously contained P. elegans-infected larvae. We propose that this selective oviposition was due to the production of an oviposition deterrent compound produced by parasitized larvae that serves to reduce oviposition in sites detrimental to larval development.

Doctor of Philosophy
Department of Division of Biology
Rollie J. Clem
Mosquitoes are carriers of a variety of harmful human pathogens, including viruses. In order to be successfully transmitted, a virus must evade mosquito immune responses. In this work, the innate immune role of apoptosis in mosquito-virus interactions was examined utilizing the disease vector Aedes aegypti and Sindbis virus. Ae. aegypti is the main vector for yellow fever and dengue virus, which result in over 100 million infections per year. Sindbis virus (Togaviridae) can be transmitted to vertebrates by Ae. aegypti in the laboratory. Sindbis is also well characterized molecularly, making it a good model system for understanding virus-vector interactions. Sindbis MRE-16 recombinant virus clones were utilized to express either an antiapoptotic or pro-apoptotic gene during virus replication. Mosquitoes were infected with recombinant virus clones during a blood meal or by intrathoracic injection. Midgut tissue and whole body samples were analyzed for virus infection and dissemination. Virus was also quantified in saliva and mosquito survival was assayed. Decreased infection in the midgut and delayed virus replication were observed in mosquitoes that were infected with virus expressing a pro-apoptotic gene. Infection with this virus clone also resulted in less virus in the saliva and reduced survival of infected mosquitoes. In addition, negative selection against pro-apoptotic gene expression during virus replication was observed. Collectively, these data suggest that apoptosis can serve as an antiviral defense in Ae. aegypti and may potentially be exploited to control virus transmission. An additional study included in this dissertation focused on zebrafish development and migration of somitic precursors from the tailbud. The tailbud consists of a population of stem cells at the posterior tip of the embryonic tail. The exit of these stem cells from the tailbud is required for the formation of tail somites. A novel double mutant was identified that lacked the t-box transcription factor spadetail and the BMP inhibitor chordin. Double mutants completely lacked somites and had an enlarged tailbud due to accumulation of stem cells that were unable to exit the tailbud. This study indicates the importance of BMP inhibition and spadetail expression in the proper exit of muscle precursors from the tailbud.

Doctor of Philosophy
Department of Diagnostic Medicine/Pathobiology
Stephen Higgs
The genetic composition of arboviruses is a critical determinant of viral infectivity and the capacity for virus dissemination in arthropod vectors. Due to concerns related to a hypothetical potential for loss of attenuation, the supression of vector infection and dissemination is a critical component for the rationale-based design of live-attenuated flavivirus vaccine candidates. The yellow fever virus (YFV) 17D vaccine virus is not only attenuated in vertebrates, but also has low infectivity for Aedes agypti mosquitoes and since it does not disseminate, it is not transmissible. Using a reverse genetics system, the mutations present in the envelope protein YFV 17D virus were characterized in Ae. aegypti to determine the role of mutations in limiting the viral infectivity and dissemination capacity. This knowledge would contribute to the rational design of live attenuated vaccines with the desirable phenotype of being nontransmissible by arthropod vectors. The upper lateral portion of the YFV 17D envelope (E) protein domain III (EDIII) habors the T380R mutation in the FG loop. Experiments demonstrated that the T380R mutation was associated with the viral infectivity phenotype for mosquitoes, but did not influence dissemination into the secondary tissues. The G52R mutation in the molecular hinge region that is located between E protein domains I (EDI) and II, significantly reduced viral infectivity for mosquitoes. In contrast, when cloned into the Asibi wildtype virus genetic backbone, the T173I mutation in the loop structure between the G0 and H0 β- strands did not attenuate viral infection and dissemination. The double mutant virus containing both the G52R and T173I mutations in the E protein, showed a similar attenuated reduced infectivity to the single G52R mutant. The M299I mutation in the linker region between EDI and EDIII resulted in a significantly lower viral infectivity at the initial phase of viral infection at 7 days post-infection in Ae. aegypti. In conclusion, the characterization on four mutations in the YFV 17D vaccine E protein have demonstrated three genetic loci, that can influence the process of YFV infection in Ae. aegypti. These results provide new knowledge and understanding which may have broad applications for the rationale design of safe flavivirus vaccines, via targeting genetic loci and introducing specific mutations that preclude infection of, and transmission by arthropod vectors.

Despite the advances made since the advent of germ theory, infectious diseases still wreak havoc on human societies, not only affecting us directly but impacting the crops and livestock upon which we rely. Infectious diseases also have dramatic effects on wildlife ecology. Therefore research into infectious diseases could not only directly lead to the improvement and saving of human lives, but aid in food security and the conservation of many wildlife species. Of vital importance in understanding the ecology of infectious diseases are the mechanisms by which they persist in host populations. One possible mechanism is vertical transmission: the transmission of a pathogen from a parent to its offspring as a result of the process of host reproduction. Another possible mechanism is inapparant infections, where an infected host does not display symptoms. Focusing on dengue fever and the Plodia interpunctella granulovirus laboratory system, this PhD thesis looks at the role these two mechanisms play on the persistence of two viral infections and their ecology. Regarding the Plodia interpunctella granulovirus (PiGV) low host food quality led to greater detection of vertically transmitted inapparant PiGV, but did not lead to its activation to an apparent form. Host inbreeding did not lead to vertically transmitted inapparant PiGV’s activation, nor had an effect on its vertical transmission. The vertical infection rate of PiGV was very low. I would therefore suggest that it may be better to use an insect virus system with a higher rate of vertical infection in future research into vertically transmitting inapparent infections. Regarding dengue virus I conclude that vertical transmission is not likely to play a role in the persistence of this virus. However modelling work found that inapparent infections could provide dengue viruses with a means of persistence and should be subject to further research.

Glucose was present in substantially greater concentrations in whole body extracts of fourth instar Aedes aegypti L. larvae than was trehalose; in contrast, trehalose was more abundant than glucose in haemolymph extracts. Preliminary studies suggested that infection of Ae. aegypti by the entomopathogenic digenean Plagiorchis elegans Rudolphi alters the carbohydrate metabolism of fourth instar larvae. Within 24 hours of cercarial penetration, total body extracts of infected fourth instar larvae exhibited decreased trehalase activity, increased trehalose-6-phosphatase activity, and an accumulation of trehalose in comparison to uninfected larvae. Concentrations of glucose, glycogen and lipids, and the activity of glycogen phosphorylase a were similar in extracts of infected and control larvae. The predominant fatty acids, in both control and infected larvae, were C 18:0, C 18:1 and C 18:3. There were no significant differences in the types and proportions of fatty acids found in control and infected larvae. Parasitic infection is discussed in terms of impaired trehalose metabolism.

Orientador: Cláudia Pio Ferreira
Abstract: This thesis presents two manuscripts previously sent to publication in scientific journals. In the first manuscript, a delay differential equation model is developed to study the dynamics of two Aedes aegypti mosquito populations: infected by the intracellular bacteria Wolbachia and non-infected (wild) individuals. All the steady states of the system are determined, namely extinction of both populations, extinction of the infected population and persistence of the non-infected one, and coexistence. Their local stability is analyzed, including Hopf bifurcation, which promotes periodic solutions around the nontrivial equilibrium points. Finally, one investigates the global asymptotic stability of the trivial solution. In the second manuscript, after rearing soybean looper Chrysodeixis includens in laboratory conditions, thermal requirements for this insect-pest are estimated, from linear and nonlinear regression models, as well as the intrinsic growth rate. This parameter depends on the life-history traits and can provide a measure of population viability of the species.
Doutor

La dengue circule en Polynésie française sur un mode épidémique depuis plus de 35 ans. Néanmoins, en dépit de la taille relativement faible de la population de Polynésie française, la circulation de la dengue peut persister à de faibles niveaux pendant de nombreuses années. L’objectif de ce travail de thèse est de déterminer si l'épidémiologie de la dengue dans le système insulaire de la Polynésie française répond aux critères d’un contexte de métapopulation. Après avoir constitué une base de données regroupant les cas de dengue répertoriés sur les 35 dernières années, nous avons réalisé des analyses épidémiologiques descriptives et statistiques. Celles-ci ont révélé des disparités spatio-temporelles distinctes pour l’incidence de la dengue des archipels et des îles, mais la structure de l'épidémie globale à l’échelle de la Polynésie française pour un même sérotype ne semble pas être affectée. Les analyses de la métapopulation ont révélé l'incidence asynchrone de la dengue dans un grand nombre d’îles. Celle-ci s’observe plus particulièrement par la différence de dynamique de l’incidence entre les îles plus peuplées et celles ayant une population plus faible. La taille critique de la communauté nécessaire à la persistance de la dengue n’est même pas atteinte par la plus grande île de Polynésie Française, Tahiti. Ce résultat suggère que la dengue peut uniquement persister grâce à sa propagation d’île en île. L'incorporation de la connectivité des îles à travers des modèles de migration humaine dans un modèle mathématique a produit une dynamique de la dengue davantage en adéquation avec les données observées, que les tentatives de modélisation traitant la population dans son ensemble. Le modèle de la métapopulation a été capable de simuler la même dynamique que les cas de dengue observés pour l'épidémie et la transmission endémique qui a suivi pour la période de 2001 à 2008. Des analyses complémentaires sur la différenciation de l'incidence de la maladie et de l'infection seront probablement instructives pour affiner le modèle de métapopulation de l'épidémiologie de la dengue en Polynésie française
Dengue has been epidemic in French Polynesia for the past 35 years. Despite the relatively small population size in French Polynesia, dengue does not disappear and can persist at low levels for many years. In light of the large number of islands comprising French Polynesia, this thesis addresses the extent to which a metapopulation context may be the most appropriate to describe the epidemiology and persistence of dengue in this case. After compiling a database of dengue cases over the last 35 years, we used a number of descriptive and statistical epidemiological analyses that revealed distinct spatio-temporal disparity in dengue incidence for archipelago and islands. But the global structure of the epidemics of the same serotype were not affected. Metapopulation analyses revealed asynchronous dengue incidence among many of the islands and most notably larger islands lagged behind the smaller islands. The critical community size, which determines dengue persistence, was found to exceed even the largest island of Tahiti, suggesting that dengue can only exist by island-hopping. Incorporation of island connectedness through patterns of human migration into a mathematical model enabled a much better fit to the observed data than treating the population as a whole. The metapopulation model was able to capture to some extent the epidemic and low level transmission dynamics observed for the period of 2001-2008. Further analyses on differentiating incidence of disease and infection will likely prove informative for the metapopulation model of dengue epidemiology in French Polynesia

A Dengue, que se tornou um grave problema de Saúde Pública, é uma endemia viral com quatro sorotipos conhecidos. Atualmente todos circulam no Brasil. Os vetores do vírus são os mosquitos Aedes aegypti, adaptados ao ambiente urbano. A ocorrência das epidemias de dengue são associadas à presença do Ae. aegypti, ao clima favorável, ao conhecimento e atitude da população, a eficácia e cobertura dos programas governamentais de controle e vigilância do vetor, à má disposição de resíduos sólidos, a estrutura de saneamento, ao grau de urbanização, a densidade do vetor, a mobilidade da população e circulação dos sorotipos do vírus. Os objetivos desta pesquisa foram verificar se o modelo de Vigilância Ambiental em Saúde e Educação Ambiental reduz a frequência de infestação do Ae. aegypti e, consequentemente, o risco de incidência e analisar a distribuição espacial dos criadouros do mosquito do gênero Aedes aegypti na cidade de Araguari, MG. O desenho de estudo adotado foi o ecológico e a teoria dos Complexos Patogênicos. Utilizou-se dados epidemiológicos, entomológicos, climatológicos, espaciais, divididos por setores censitários, e os programas livres Google Earth para geocodificação e Terra View para espacialização dos criadouros, geração de buffers com raio de abrangência de 280 metros, para análise estatística utilizando o estimador de Kernel e geração dos mapas de Densidade dos Criadouros. Para verificar a efetividade do conjunto de ações, realizou-se uma comparação de médias dos índices de infestação prediais, dos Distritos de Piracaíba e Amanhece, considerando o período antes, durante e depois do conjunto de ações realizadas no Distrito de Amanhece. Utilizou-se o programa estatístico Action versão 4.5, o teste de Kruskal-Wallis, segundo método Kruskal- Wallis rank sum test e o Graph Pad Prism 5.0. Em todo este período de estudo, a temperatura e a umidade relativa se apresentaram em condições ótimas ao Ae. aegypti. A comparação entre o antes, o durante e o depois, não teve resultado estatisticamente significativo, no entanto de qualquer forma pôde ser observado que as ações reduziram a infestação predial a níveis inferiores à 1% no Distrito de Amanhece. A distribuição geográfica dos criadouros aponta que praticamente todos os setores censitários da cidade de Araguari estiveram em situação de risco, em diferentes graus, no período analisado. Concluiu-se com esta pesquisa que o modelo de ações desenvolvido no Distrito de Amanhece pode ser desenvolvido em localidades tais como a cidade de Araguari. A infestação predial foi registrada durante todo o período pesquisado e a presença de criadouros corroborou para a infestação do Aedes aegypti, no decorrer dos anos. O aumento da infestação do Ae. aegypti inicia entre os meses de outubro e novembro, com os maiores índices sendo registrados entre os meses de janeiro a março, reduzindo-se efetivamente, em abril e junho. Os tipos de criadouros predominantes na cidade de Araguari foram os depósitos móveis, ao nível do solo para armazenamento doméstico, lixo, sucata e materiais de construção. A participação pró ativa da comunidade e sua sensibilização são imprescindíveis para controle do mosquito e redução do risco de Dengue em Araguari.
Dengue is an endemic viral which became a serious public health problem. It has four serotypes, all circulating in Brazil. The vectors of the virus are mosquitoes Aedes aegypti, adapted to the urban environment. The occurrence of dengue epidemics is associated with the Ae. aegypti presence, favorable climate, information about prevention and preventive attitudes by the citizens, the effectiveness and coverage of control programs and vector surveillance, disposal solid waste, sanitation, urbanization, density of the vector, population mobility and dengue virus circulation. The main aim of the study was to verify whether the model of Environmental Health Surveillance and Environmental Education reduces Ae. aegypti infestation and therefore the risk of incidence and analyze the spatial distribution of mosquito breeding in Araguari, MG. This is an ecological study and the theory which was applied was pathogenic complex. It was used epidemiological, entomological, climatological and space data, Google Earth for geocoding and Terra View for spatialization. The averages of infestation levels from Districts of Piracaíba and Amanhece were compared to verify the effectiveness of the actions considering the period before, during and after the set of actions performed in the District of Amanhece. Statistical programs, Action and Graph Pad Prism, were used. Throughout this study period, the temperature and relative humidity were relevant to the Ae. aegypti. The comparison between before, during and after the set of actions showed that there was not a statistically significant result, but anyway it could be observed that the actions reduced the infestation to levels lower than 1% in Amanhece. The geographical distribution of breeding shows that Araguari was at risk, in the analyzed period. The conclusion of this research was that the model actions developed in the District of Amanhece can be applied in locations such as the city of Araguari. The infestation was recorded during all the survey period and the presence of breeding confirmed the infestation of Ae. aegypti, over the years. The infestation of Ae. aegypti starts to increase between October and November, with the highest rates being recorded from January to March, and being effectively reduced in April and June. In Araguari prevails deposits mobile ground level storage to household waste, scrap, and construction materials. proactive participation and awareness of the community are essential for controling the mosquito breeding and so reducing the risk of Dengue.

碩士
東海大學
生物學系
85
Abstract： Aedes aegypti (L.) and Ae. albopictus (Skuse) are dengue vectors. In Taiwan, Ae. albopictus is found throughout the island below 1,500m in elevation, while Ae. aegypti is distributed in the southern part of the island below 1,000m. Theses two species are very similar in morphology and ecology, but have very different distributions. Here we investigate the effects of temperature and gregarine infection on Ae. aegypti and Ae. albopictus. Data of gregarine infection were collected in the field from June 1995 to March 1997. In the laboratory, a 3-factor (temperature, competition conditions and different gregarine infection conditions) experiment was conducted. Field data show that: both gregarine infection intensity and percentage are significantly lower for Ae. aegypti than Ae. albopictus; Aedes albopictus cooccurring with Ae. aegypti experience a lower percentage of gregarine infection; and the high infection rates of Ae. albopictus are positively correlated with experiment duration and negatively correlated with water temperature. From the 3-factor experiment, we found: effect of infection by Ascogregarina taiwaneasis increases with the length of male wing for both Ae. aegypyi and Ae. albopictus, and lowers the emergence rate of Ae. aegypti only; emergence rate of Ae. aegypti is higher than Ae. albopictus under high temperature condition (30℃) and there is no difference under low temperature conditions. These results suggest that A. taiwanesis is the key factor limiting the distribution of Ae. aegypti in Taiwan.

I tested a theoretical model proposing that anemia favors transmission of blood-borne parasites to vectors by accelerating the blood-feeding rate. Using Aedes aegypti, the yellow fever mosquito, initially, I was not able to confirm this phenomenon either in an artificial or a live system; anemia did not correlate with blood-feeding rate, time or volume. I then analyzed the feeding rate over different time intervals to examine the possibility that inconsistent feeding rates masked the expected results; a comparison of the blood-feeding rate at one particular time period supports the theory. I then continued investigating the influence of anemia on egg production of mosquitoes and found that anemia has negative influence on vector's fecundity. I conclude that although anemia has opposite influences on mosquitoes in blood-feeding rate and egg production, they can get, at least under certain conditions, benefit from blood-feeding on anemic hosts.
Graduation date: 1992

碩士
國防醫學院
微生物及免疫學研究所
102
Though dengue virus infection is a major public health problem around the word, the mechanisms of antiviral immunity in the vector mosquitoes are poorly understood. The drosophila Dicer-2 was demonstrated to activate antiviral gene, Vago, and ortholog Vago of Culex mosquito was also revealed to up-regulated in response to West Nile virus infection. In this pilot study, we demonstrated that Aedes aegypti Vago was also a secreted peptide and could restrict dengue virus infection by activation the Jak-STAT pathway. The Aedes Vago gene was cloned and expressed, and polyclonal antibody against the protein was produced. Knockdown the Vago, Dicer-2, or STAT gene in Aedes aegypti cell line and Aedes aegypti mosquito with specific siRNA then infected with dengue virus showed virus up growth, while overproduction of Vago in Aedes aegypti cell line revealed down growth of dengue virus. Real time PCR assay of Vago, Dicer-2, STAT, and dengue viral gene and Western blot assay of Vago protein were carried out in the above experimental knockdown or overexpression procedures. This study revealed that the Aedes aegypti Vago could antagonize dengue virus infection through this mosquito immune pathway.

碩士
國立臺灣大學
免疫學研究所
106
Dengue virus (DENV) is transmitted to humans by Aedes aegypti mosquitoes. Arboviruses are known to take advantage of the immunomodulatory properties of mosquito salivary proteins in order to enhance their infectivity in the vertebrate hosts. However, the mechanism of how DENV infection of the mammalian host is regulated by mosquito saliva and its component(s) remains poorly understood. In this study, we discovered that saliva from DENV-infected mosquito stimulated macrophage responses by enhancing DENV-induced TNF production. Moreover, saliva from DENV-infected mosquitos induced more severe hemorrhage and inflammation in Stat1-/- mice than DENV mixed with naïve saliva. Plaque assay results showed that Stat1-/- mice inoculated with saliva from DENV-infected mosquitos had viremia on day 6 after infection whereas mice infected with DENV obtained from culture or mice infected with DENV mixed with saliva from naïve mosquitos did not. Furthermore, we discovered that the expression of mosquito salivary factor SRPN23, a serine protease inhibitor, in salivary gland was regulated by DENV infection. Interestingly, silencing SRPN23 reduced DENV replication in the mosquito. While mice given DENV mixed with saliva from UV-inactivated LacZ-silenced mosquitos had higher viral titer in the serum than mice given DENV alone on day 3, silencing SRPN23 reversed the effect. Furthermore, mice given DENV mixed with saliva from UV-inactivated SRPN23-silenced mosquitos had lower Tnf mRNA expression in the abdominal skin compared to those receiving saliva from UV-inactivated LacZ-silenced mosquitos. This study revealed that mosquito saliva increases hemorrhage severity during DENV infection in the mammalian host and showed that potentially salivary factor SRPN23 is involved in the regulation of Tnf mRNA and viral spread into the bloodstream.

碩士
國立臺灣海洋大學
海洋生物研究所
102
The objective of this thesis is to study the biological effects of hatch rate and physiological patterns of eggs of Aedes aegypti induced by ultrasound exposure. In order to analyse the influences of biological effects of ultrasound in vivo, the eggs of Aedes aegypti in this research exposed to continuous-wave ultrasound. After ultrasonic affect to eggs of Aedes aegypti and Megacyclops formosanus in many different continuous-time and distance, obtained the hatch rate of eggs of Aedes aegypti and survival rate of Megacyclops formosanus. From distance,the longer the continuous-time,can make the hatch rate of eggs of Aedes aegypti and survival rate of Megacyclops formosanus lower. From continuous-time, the distance from ultrasonic machine to sample shorter, the hatching rate of eggs of Aedes aegypti and survival rate of Megacyclops formosanus is more significant impact. The results of this study showed that ultrasonic can be used in prevention and control of dengue mosquitoes and reduce mosquito density, has the potential to reduce the risk of dengue infection.