Current methods of mosquito surveillance estimate general population abundances, but fail to represent the relationship of vector abundance to host density important to determining transmission risk of mosquito-borne pathogens (MBP). We sought to address this limitation by creating a novel mosquito trap that directly sampled mosquitoes seeking to feed on nesting birds. The primary objectives of this study were to (1) assess the efficiency of the Nest Mosquito Trap (NMT) and how this is affected by nest box size. (2) assess whether the NMT affects bird, specifically nest success in Prothonotary Warblers (Protonotaria citrea), and adult behavior. (3) compare our novel trap to existing methods. (4) profile the ecological parameters associated with bird/ mosquito interactions. Our results allow us to conclude that the NMT is not only an effective means of capturing host-seeking mosquitoes and measuring mosquito/ bird interactions, but does not have a deleterious effect on avian nesting success.

We develop and evaluate a novel host-vector model of West Nile virus (WNV) transmission that incorporates multiple avian host species and host stage-structure (juvenile and adult stages), with both species-specific and stage-specific biting rates of vectors on hosts. We use this model to explore WNV transmission dynamics that occur between vectors and multiple structured host populations as a result of heterogeneous biting rates. Our analysis shows that increased exposure of juvenile hosts results in earlier, more intense WNV transmission when compared to the effects of differential host species exposure, regardless of other parameter values. We also find that, in addition to competence, increased juvenile exposure is an important mechanism for determining the effect of species diversity on the disease risk of a community.

<p>No</p> / Dissertation

Le virus West Nile (VWN) est un virus neurotrope principalement transmis par piqûre de moustique et dont le réservoir est constitué par la faune aviaire sauvage. Les souches circulant en Europe appartiennent à 4 lignages génétiques différents à l’origine de nombreuses épidémies d’ampleur modérée à faible et limitées géographiquement, contrairement à ce qui a été observé en Amérique du Nord. En 1998 en Israël, une importante épidémie a a été associée pour la première fois à une forte mortalité de la faune aviaire sauvage. Le virus (souche IS-98-ST1, lignage 1a) a été isolé du cerveau d’une cigogne moribonde. L’objet de cette thèse a été de construire un clone infectieux de la souche IS-98-ST1 afin d’en explorer les propriétés de neuroinvasion et de pouvoir mettre en évidence les déterminants moléculaires de sa virulence.Le virus obtenu à partir de la construction clone infectieux s’est révélé posséder les mêmes propriétés biologiques que le virus parental, que ce soit in vitro sur cellules Vero ou in vivo sur souris sensibles ou résistantes ou encore sur l’embryon de poulet. L’embryon de poulet est présenté ici comme un nouveau modèle d’évaluation de la virulence du VWN. Un modèle cellulaire neuronale (lignée de neuroblastomes humains, SK-N-SH) est aussi évalué dans ce manuscrit. En conclusion, un nouvel outil de génétique inverse a été obtenu pour le VWN. Cet outil permettra de travailler sur l’impact de mutations ponctuelles, ou de modifications plus importantes touchant un ou plusieurs gènes viraux sur la virulence du VWN, spécifiquement dans le contexte européen. / West Nile virus (WNV) is a neurotropic virus mainly transmitted through mosquito bites. Wild birds represent the main reservoir hosts. Strains circulating in Europe belong to four lineages and have caused numerous but limited epidemics over the last few years. In 1998, an important outbreak associated to huge bird fatalities caused by a highly neuroinvasive strain (IS-98-ST1) took place in Israel. We aimed at producing a new infectious clone, based on the lineage 1a IS-98-ST1 WNV strain, for the characterization of its neuroinvasion properties as well as the molecular determinants of European WNV virulence. The growth kinetics of recombinant and parental WNV were similar in Vero cells. Moreover, the phenotypes of recombinant and parental WNV were indistinguishable in terms of viremia, viral load in the brain and mortality in susceptible and resistant mice. Finally, the pathobiology of the infectious clone was examined in embryonated chicken eggs, proposed as a new model for the evaluation of WNV virulence. The potential of human neuroblastoma cells (SK-N-SH) to discriminate between highly and mildly virulent WNV strains was assayed. In conclusion: a new molecular tool that is useful for the study of molecular determinants of WNV virulence has been generated. We take advantage of the high genetic stability of our one-piece infectious WNV cDNA clone to produce mutant viruses through the insertion of point mutations or the exchange of genetic fragments between WNV strains into the backbone of the IS-98-ST1 infectious clone.

Within the state of Florida, there are three arboviruses of public health importance that can cause neuroinvasive disease in humans: West Nile Virus, Saint Louis Encephalitis Virus, and Eastern Equine Encephalitis Virus. Mosquitoes (Diptera: Culicidae) within the genus Culex are known and suspected vectors of these diseases. The vectors of these diseases can be present in urban wetland habitats that allow for exposure to residential communities. Vector ecology must be investigated in order to understand the dynamics of disease transmission. In Hillsborough County, Florida the spatial and temporal distribution of these vectors are not well established. An ecological study was conducted in the University of South Florida's Ecopreserve using trapping methodologies to sample the adult and gravid females as well as collect the egg population. Collections were made at three spatial points for the duration of July through December 2013 and compared to meteorological variables. Culex erraticus, a proposed bridge vector of Eastern Equine Encephalitis, was the most abundant adult species and gravid female captured. Culex nigripalpus, primary Floridian vector of Saint Louis Encephalitis and bridge vector of West Nile Virus, was the second most abundant adult species caught as well as the majority of eggs collected. Based on the results collected, the presence of Culex erraticus and Culex nigripalpus was confirmed. The majority of Culex erraticus adults were collected in September and October and Culex nigripalpus adults were the highest in July and August. The results of the gravid and egg collection generated crucial insight regarding methodology for studying vector ecology within this urban wetland habitat. However, modeling at spatial points based on meteorological variables yielded inconsistent results that illicit further investigation regarding these arboviral vectors of disease.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 76-86).

Two cellular innate responses, the dsRNA protein kinase (PKR) pathway and the 2'-5' oligoadenylate synthetase (OAS)/RNase L pathway, are activated by dsRNAs produced by viruses and reduce translation of host and viral mRNAs. PKR activation results in eIF2a phosphorylation. As a consequence of eIF2a phosphorylation, stress granules (SGs) are formed by the aggregation of stalled SG proteins with pre-initiation complexes and mRNA. West Nile virus (WNV) infections do not induce eIF2a phosphorylation despite upregulation of PKR mRNA and protein suggesting an active suppression of PKR activation. Assessment of the mechanism of suppression of PKR activation in WNV-infected cells indicated that WNV infections do not induce PKR phosphorylation so that active suppression is not required. In contrast to infections with "natural" strains of WNV, infections with the chimeric W956 infectious clone (IC) virus efficiently induce SGs in infected cells. After two serial passages, the IC virus generated a mutant (IC-P) that does not induce SGs efficiently but does induce the formation of NS3 granules that persist throughout the infection. This mutant was characterized. 2'-5' oligoadenylate synthetases (OAS) are activated by viral dsRNA to produce 2-5A oligos that activate RNase L to digest viral and cellular RNAs. Resistance to flavivirus-induced disease in mice is conferred by the full-length 2'-5' oligoadenylate synthetase 1b (Oas1b) protein. Oas1b is an inactive synthetase that is able to suppress the in vitro synthetase activity of the active synthetase Oas1a. The ability of Oas1b to inhibit Oas1a synthetase activity in vivo and to form a heteromeric complex with Oas1a was investigated. Oas1b suppressed 2-5A production in vivo. Oas1a and Oas1b overexpressed in mammalian cells co-immunoprecipitated indicating the formation of heteromeric complexes by these proteins. Unlike mice, humans encode a single OAS1 gene that generates alternatively spliced transcripts encoding different isoforms. Synthetase activity has previously been reported for only three of the isoforms. The in vitro synthetase activity of additional OAS1 isoforms was analyzed. All tested isoforms synthesized higher order 2-5A oligos. However, p44A only produced 2-5A dimers which inhibit RNase L.

The question of how to create communities where people altruistically care for, and look out for each other’s health and well-being is increasingly a central question in academic literature. However, altruism has long been belittled or ignored in the literature in terms of its ability to influence human behaviour. This tendency appears to have been carried over into the management of West Nile Virus (WNV), a sometimes serious disease that has spread throughout North America since first arriving in 1999. Specifically, government health educators have focused only on telling the public how what are referred to here as Community Protective Measures (CPMs) such as the elimination of standing water, can reduce personal risk or protect family members from the disease, rather than explaining how these measures can help protect others in their community as a whole. As a different approach to addressing this issue, this study sought to determine which communities and people (1) were undertaking CPMs out of an altruistic concern for others in their community, or (2) could be encouraged to engage in CPMs by making salient the benefits of these measures to the community. Study results came back positive, those that live in urban areas, and married or widowed people as opposed to singles or divorcees, those with children exhibiting significantly more concern for others about the disease. Additionally, women; married or widowed people; those who have younger children (0-18 years old); and those who had certain strong positive feelings about their community, namely knowing people better in the community, being involved in the community, and having a sense that people help each other in the community; were significantly more likely to already be willing to take action against the disease at least partly for the purposes of protecting the health of others. Additionally, albeit not significantly, a trend was noted in this regard with respect to those that rented and those who had children.. With regard to those who could be encouraged for altruistic reasons to undertake CPMs, such was found to be significantly the case for those not living in an Adult Lifestyle Communities (ALCs); those living in a city, town, or hamlet for a long (11-25 years) period of time; younger individuals (18 -35 years old), and singles or divorcees as opposed to married or widowed individuals. Although not found to be significant, a trend in this regard was found with respect to those that perceived themselves to live in a small- or medium-sized neighbourhoods, urban as opposed to suburban areas, females, renters, and those without children. A pilot study in a community with the characteristics where respondents were found to respond to learning about the community benefits of CPMs, as well as efforts to instill the characteristics of places where people already tend to be altruistically inclined, is recommended. The thesis concludes by discussing how relying upon, and encouraging altruistic tendencies could be applied to a variety of issues ranging from the control of other infectious diseases, to encouraging other health promoting behaviour such as the donation of organs, to addressing wider national as well as global matters like poverty or global climate change. By doing so, health and other planners could potentially take a more holistic, less rational, and advocacy approach to planning that seeks to build community capacity to deal with problems rather than reacting on a problem-by-problem basis.

The question of how to create communities where people altruistically care for, and look out for each other’s health and well-being is increasingly a central question in academic literature. However, altruism has long been belittled or ignored in the literature in terms of its ability to influence human behaviour. This tendency appears to have been carried over into the management of West Nile Virus (WNV), a sometimes serious disease that has spread throughout North America since first arriving in 1999. Specifically, government health educators have focused only on telling the public how what are referred to here as Community Protective Measures (CPMs) such as the elimination of standing water, can reduce personal risk or protect family members from the disease, rather than explaining how these measures can help protect others in their community as a whole. As a different approach to addressing this issue, this study sought to determine which communities and people (1) were undertaking CPMs out of an altruistic concern for others in their community, or (2) could be encouraged to engage in CPMs by making salient the benefits of these measures to the community. Study results came back positive, those that live in urban areas, and married or widowed people as opposed to singles or divorcees, those with children exhibiting significantly more concern for others about the disease. Additionally, women; married or widowed people; those who have younger children (0-18 years old); and those who had certain strong positive feelings about their community, namely knowing people better in the community, being involved in the community, and having a sense that people help each other in the community; were significantly more likely to already be willing to take action against the disease at least partly for the purposes of protecting the health of others. Additionally, albeit not significantly, a trend was noted in this regard with respect to those that rented and those who had children.. With regard to those who could be encouraged for altruistic reasons to undertake CPMs, such was found to be significantly the case for those not living in an Adult Lifestyle Communities (ALCs); those living in a city, town, or hamlet for a long (11-25 years) period of time; younger individuals (18 -35 years old), and singles or divorcees as opposed to married or widowed individuals. Although not found to be significant, a trend in this regard was found with respect to those that perceived themselves to live in a small- or medium-sized neighbourhoods, urban as opposed to suburban areas, females, renters, and those without children. A pilot study in a community with the characteristics where respondents were found to respond to learning about the community benefits of CPMs, as well as efforts to instill the characteristics of places where people already tend to be altruistically inclined, is recommended. The thesis concludes by discussing how relying upon, and encouraging altruistic tendencies could be applied to a variety of issues ranging from the control of other infectious diseases, to encouraging other health promoting behaviour such as the donation of organs, to addressing wider national as well as global matters like poverty or global climate change. By doing so, health and other planners could potentially take a more holistic, less rational, and advocacy approach to planning that seeks to build community capacity to deal with problems rather than reacting on a problem-by-problem basis.

Cellular T-cell intracellular antigen-1 related protein (TIAR) binds to the 3' terminal stem-loop of the West Nile virus minus-strand RNA [WNV 3'(-) SL RNA]. TIAR binding sites were previously mapped on loop 1 (L1) and loop 2 (L2) of the 3' (-) SL RNA and mutations of these sites in a WNV infectious clone inhibited virus replication. In the present study, data from in vitro binding assays suggested that multiple TIAR proteins bind to each WNV 3′ (-) SL RNA in a positively cooperative manner. The tertiary structure of WNV 3′ (-) SL RNA was predicted and it was suggested that L2 forms an exposed loop while L1 forms an embedded loop. We propose that TIAR binds first to L2 and that this interaction facilitates the binding of a second TIAR molecule to L1. Data from in vitro assays also showed that TIAR binds specifically to the WNV 3' (-) SL RNA but not to the complementary WNV 5' (+) SL RNA and that the C-terminal prion domain of TIAR contributes to RNA binding specificity. Immunoprecipitation experiments indicated that TIAR interacts with the WNV 3' (-) SL RNA in cells. Colocalization of TIAR and viral dsRNA in the perinuclear region of WNV-infected cells was visualized using a proximity ligation assay. In WNV-infected, TIAR-overexpressing cells, increased extracellular virus yields, intracellular viral protein and RNA levels, and an increased ratio of viral plus-strand RNA to minus-strand RNA were observed. These data suggest that TIAR enhances WNV plus-strand RNA synthesis from the minus-strand template. WNV infections induce small TIAR foci formation in primate cells but not rodent cells. The TIAR foci are located in the perinuclear region and differ in size and location from arsenite-induced stress granules (SGs). However, the small TIAR foci contain many SG components, such as G3BP, PABP, and eIF3A, but not HuR. Arsenite-induced SG formation is still inhibited by WNV infection in these cells. eIF2a phosphorylation was observed in some infected cells that contained WNV-induced TIAR foci but viral NS3 protein accumulation was not inhibited. The data suggest that WNV-induced TIAR foci in primate cells are not canonical SGs.