Dissertations / Theses on the topic 'Mosquitoes as carriers of disease – Reunion'

[Truncated abstract] In March 2005, the Indian Ocean island of Reunion, a former colony and now overseas department of France, saw the first cases of what was to become a massive epidemic of the mosquito borne viral infection Chikungunya. More than 250,000 people, one third of the Island's population, were subject to high fevers, rash, and joint and muscle pains over the next 18 months, yet the public health authorities in metropolitan France were arguably slow to take the epidemic seriously. The research presented here explores attitudes underlying the management of the epidemic by examining both metropolitan and local representations of mosquito borne disease from historical, epidemiological and media perspectives. The research seeks to answer the general question Does colonial history continue to influence the representation and management of mosquito borne disease in Reunion? Three parallel approaches are taken to answering this question, using a common framework of tropicality (a Western discourse that exalts the temperate world over its tropical counterpart, and overlaps with colonialism and orientalism). ... Several factors are likely to have contributed to the persistence of tropicality in public health practice in Reunion: Othering as a universal phenomenon; the cost of administering interventions to combat tropical diseases in the remote environments of French overseas departments and territories; the denial of a serious public health risk as a cultural trait in Reunion; and the significant role of the colonies in forming and maintaining the French national identity. It has to be acknowledged that historically, tropicalism does appear to have played one positive role in the management of mosquito borne disease:

The ultimate goal of this research was to perform a domain exchange between a computer identified insect specificity region of the mosquito larvicidal protein Cry IVB and a previously identified domain in a related protein toxin which targets lepidopteran insect larvae. If the insect specificity domain has been correctly identified, an exchange of DNA in this manner transfers the toxicity of one peptide to another by an exchange of the insect specificity domains. New, chimeric peptides may be designed which will target a larger spectrum of insect larvae.In previous research a domain exchange was performed between the two genes carried on plasmid vectors in E. coli and low levels of toxicity to mosquito larvae were observed. Initial efforts of this research attempted to identify these recombinants. However, stability was not achieved by sequential colony screens. Furthermore, a recently published three-dimensional structural model for all the B. thuringiensis crystalline toxins became available and it was quickly determined that the first exchanges excluded most of the f3-sheet domain that is responsible for insect cell receptor binding, the feature that gives the toxins their specificity. Therefore, it was decided that a larger, more inclusive region of Cry IVB DNA must be exchanged between the two toxins.Extensive computer analyses of the Cry IVB sequence and retroactive comparison of these sequences to the three-dimensional model yielded a fragment of DNA that encoded more than 60% of the putative insect specificity domain. Oligonucleotide primers were subsequently designed to flank this region so that the polymerase chain reaction could be employed to amplify the region. Additionally, the primers were engineered to contain terminal restriction endonuclease sites to ease in the exchange of the domain encoding region into Cry IA(c). The region of Cry IVB DNA flanked by the oligonucleotide primers was successfully amplified by the PCR and cloned into the plasmid vector pUC 19 as a reservoir for a future domain exchange.
Department of Biology

Various strains of Bacillus thuringiensis Mt.) produce crystalline endotoxins specific for larvae of different insect classes. Two strains, B.t. subspp. israelensis and kurstaki produce similar 130 kDa toxins encoded by the CryIVB gene (toxic to Diptera) and the CryIA gene (toxic to Lepidoptera), respectively. The N-terminal region of the CryIVB gene was cloned into the Escherichia coli expression vector pKX223-3. A mosquitocidal transformant was obtained as determined by mosquito bioassays. The gene fragment, if stable, can be cloned into cyanobacteria to achieve biological control of mosquito-borne diseases. A second goal was to identify the binding specificity domain of the CryIVB gene which encodes the portion of the protein toxin that binds the insect midgut causing cell lysis and death. Two potential insect binding specificity domains identified by computer analyses were switched with a known binding specificity region of the CryIA gene. The polymerase chain reaction was utilized to obtain gene fragments of the CryIVB gene which replaced the CryIA gene binding specificity domain. The resulting recombinant clones carrying the CryIA gene containing the .000nd proposed insect binding specificity domain of the CryIVB gene were fotsd to be mosquitocidal.
Department of Biology

Bacillus sphaericus 2362 is a mosquito pathogenic bacterium. Its greatest industrial potential may be in developing countries where mosquitos are often vectors for diseases. This strain is typical of the species in that it is unable to grow using carbohydrates as a sole source of carbon. The goal of this research was to determine the metabolic deficiency(s) responsible for the inability of this organism to grow on carbohydrates. Compounds that supported light growth of this organism on an agar-solidified, defined medium included acetate, glycerol, and gluconate. Growth in a defined liquid medium with acetate as the source of carbon was much slower than growth in a complex, protein-based broth. B. sphaericus grew poorly in a defined, liquid medium with glycerol or gluconate as the carbon source. Activity of enzymes responsible for the initiation of metabolism of some substrates was not detected in cell extracts. These enzymes were: glucokinase, hexokinase, beta-galactosidase, and amylase. Growth of this bacterium on glycerol as a sole source of carbon implies the presence of the enzymes from the lower half of the Embden-Meyerhof-Parnas (EMP) pathway. Two enzymes of the upper half of the EMF pathway, phosphofructokinase and fructose diphosphate aldolase, were undetected in cell extracts. In addition, glucose dehydrogenase activity was not detected. The inability to form glucose-6-phosphate from glucose prevents the catabolism of this and related substrates via the Entner-Doudoroff (ED), hexose monophosphate (HMP), and EMF pathways. Oxygen uptake studies indicated that B. sphaericus oxidized gluconate slightly but only when the cells were grown in a complex, protein-based medium supplemented with gluconate. Although gluconokinase activity was detected in cell extracts, no activity was detected for the key enzymes of the ED (phosphogluconate dehydratase/KDPG aldolase), or HMP (6-phosphogluconate dehydrogenase) pathway. It is unclear how B. sphaericus grows on a defined medium with gluconate as the sole source of carbon. In addition to enzymatic deficiencies, whole cells were unable to accumulate [¹⁴C]glucose or [¹⁴C]sucrose.
Master of Science

Thesis (M.S.)--University of Nevada, Reno, 2006.
"December, 2006." Includes bibliographical references (leaves 29-33). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.

Anopheles species composition and relative seasonal abundance were measured in an irrigated division (low historical malaria incidence) and in a rain-fed division (high historical malaria incidence) of southern Sri Lanka. Twelve species of anophelines were represented in adult and larval collections with Anopheles vagus Donitz being the most abundant. In cattle-baited net trap collections, Anopheles adults were significantly more abundant in the irrigated division than in the rain-fed division. In pyrethrum-spray sheet collections, cattle-baited but trap collections and larval collections, Anopheles abundance was significantly greater in the rain-fed division. Houses were of poorer construction in the rain-fed division, where pyrethrum-spray sheet collections consisted mainly of Anopheles subpictus Grassi (98%) and Anopheles culicifacies Giles (2%). Hut trap collections also consisted mainly of An. subpictus (88%) and An. culicifacies (7%). Net trap collections consisted mainly of An. vagus (43%) and Anopheles peditaeniatus Leicester (31%). Larval collections also consisted of An. peditaeniatus (24%) and An. vagus (21%). Weak associations were found between species abundance and environmental factors explored in this study (e.g., vegetation, water quality, sunlight exposure). The greater malaria risk in the rain-fed division is due in part to the occurrence of potential vectors in relatively higher numbers.

Orientador: Carlos Fernando Salgueirosa de Andrade
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-05T12:43:31Z (GMT). No. of bitstreams: 1 Silva_GilciaAparecidadeCarvalho_D.pdf: 2420692 bytes, checksum: 389c3c5a059387fa98ae9be752bd8f0e (MD5) Previous issue date: 2006
Resumo: Mosquitos pertencentes aos gêneros Culex, Aedes, Anopheles, Mansonia, Psorophora e Coquillettidia são susceptíveis à infecção por Dirofilaria immitis (Leidy, 1856), podendo transmitir o filarídeo aos cães e gatos. Os vetores de D. immitis no Brasil são conhecidos apenas nos Estados do Rio de Janeiro e do Maranhão, fazendo-se necessária a investigação da susceptibilidade e da competência vetorial de espécies existentes nos demais Estados brasileiros. O presente trabalho teve por finalidade verificar a freqüência de infecção por D. immitis em cães domiciliados na Região Metropolitana do Recife, bem como avaliar a susceptibilidade e a competência vetorial de Culex quinquefasciatus Say, 1823, Aedes aegypti Linnaeus, 1762 e Ae. albopictus Skuse, 1894 provenientes de área endêmica e não endêmica para a transmissão desse filarídeo, em condições experimentais. A resposta imune humoral (melanização) apresentada pelos mosquitos expostos à infecção também foi avaliada. Para a realização do inquérito epidemiológico, 816 amostras de sangue canino foram coletadas nas áreas costeiras da Região Metropolitana do Recife e no município de Bezerros, agreste do Estado de Pernambuco. As amostras sangüíneas foram analisadas por meio de teste parasitológico para a pesquisa de microfilárias de D. immitis, utilizando-se o método modificado de Knott. Para a avaliação da competência vetorial Cx. Quinquefasciatus população RECIFE, Ae. aegypti populações RECIFE, UNICAMP e linhagem ROCKFELLER e Ae. albopictus população RECIFE foram criados em insetário sob condições controladas (28 '+ ou ¿' '1 GRAU C¿ e 80 ' + ou ¿' 5% de umidade relativa do ar). As fêmeas das espécies estudadas foram alimentadas com sangue canino contendo diferentes densidades de microfilárias de D. immitis, por meio de membrana artificial confeccionada com pele fresca de animal. Para Cx. quinquefasciatus, que é uma espécie ornitofílica, foi utilizada pele de codorna, e para Ae. aegypti e Ae. albopictus a membrana artificial foi confeccionada com pele de rato. Os resultados obtidos no estudo mostraram freqüência de 3,61%, 7,89% e 7,69% de cães infectados na Ilha de Itamaracá, Igarassu e Recife, respectivamente. Após as infecções experimentais, observou-se que a mortalidade de Cx. quinquefasciatus não foi influenciada pela exposição a diferentes densidades de microfilárias de D. immitis (F = 0,0615, p>0,05) e os índices encontrados variaram de 8,9% a 36,25%. Os índices de eficiência vetorial (IEV) apresentados por Cx. quinquefasciatus população RECIFE variaram de 7,8% a 56,5%. Em relação à razão de infecção, o maior índice foi encontrado no grupo de fêmeas expostas a densidade de 1913 microfilárias/ml, entretanto, não foi influenciado pela taxa de ingurgitamento das fêmeas (F=3,2937, p>0,05). Por meio de melanização, Cx. quinquefasciatus população RECIFE, limitou a intensidade do parasitismo, promovendo o equilíbrio da relação parasito-hospedeiro e deste modo passando a ser um excelente vetor de D. immitis na Região Metropolitana do Recife. Dentre as espécies de Aedes estudadas, verificou-se que a população RECIFE de Ae. aegypti apresentou maior mortalidade (70,7%) ao final dos experimentos, apresentando diferença estatisticamente significante (p<0,01) em relação à linhagem ROCKFELLER, população UNICAMP e Ae. albopictus população RECIFE, que não diferiram entre si (p>0,05). Em relação ao índice de eficiência vetorial (IEV) foi detectado um índice de 7,4% para a linhagem ROCKFELLER e uma variação de 20,0% a 53,8% para as populações de Ae. aegypti e 25,2% para Ae. albopictus população RECIFE. O maior número de larvas de D. immitis infectantes na probóscide foi apresentado por Ae. albopictus população RECIFE, além de uma baixa mortalidade. Desta forma, esta população mostrou-se susceptível ao filarídeo e por apresentar baixa mortalidade, foi considerada como a melhor vetora. Ae. aegypti população RECIFE não apresentou reação de melanização e apresentou mortalidade acentuada, enquanto que Ae. aegypti população UNICAMP e linhagem ROCKFELLER mostraram-se refratárias à infecção por D. immitis
Abstract: Mosquitoes belong to the genus Culex, Aedes, Anopheles, Mansonia, Psorophora and Coquillettidia are susceptible to infection of Dirofilaria immitis (Leidy, 1856) and some of them serve as vectors heartworm disease in dogs and cats. Although the potential vectors of canine heartworm in Brazil have been recorded only in Rio de Janeiro and Maranhão State and no more date are available. The objective of this study was to verify the frequency of heartworm infection in dogs in metropolitan region of Recife and also identify under experimental conditions their ability of Culex quinquefasciatus Say, 1823, Aedes aegypti Linnaeus, 1762 and Ae. albopictus Skuse,1894 from enzootic and non enzootic areas to become infected with and transmit D. immitis. After the experimental infection of mosquitoes, the melanization response to larvae of D. immitis also was evaluated. The survey study were performed on a total of 816 dogs from costal areas of Metropolitan Region of Recife and Bezerros County, located in agreste area of Pernambuco State. Whole blood samples were collected from all animals and were examined for the presence of microfilariae of D. immitis by the modified Knott test. To verify the vector competence of Cx. quinquefasciatus RECIFE population, Ae. aegypti RECIFE, UNICAMP populations and also ROCKFELLER strain and Ae. albopictus RECIFE population, the mosquitoes were reared under constant insectary conditions (28 '+ or ¿' '1 DEGREE C¿ and 80 '+ or ¿' 5% relative humidity). Females mosquitoes, were exposed to blood¿s dog with diferents density of D. immitis microfilariae by artificial feeding apparatus made by fresh animal skin. For this puporse, ornithophilic Cx. quinquefasciatus was feeding by skin quail menbrane, and for the Ae. aegypti and Ae. albopictus the artificial membrane was made by rat skin. The results of the survey study showed 3.61%, 7.89%, and 7.69% of heartworm infection frequency in dog from Itamaracá Island, Igarassu and the city of Recife respectively. The mortality of Cx. Quinquefasciatus RECIFE population observed in the vector competence study did not show influence of different density of microfilariae of D. immitis (F = 0.0615, p>0.05) and the mortality rate was 8.9% to 36.25%. The vector efficiency (VE) rates of Cx. quinquefasciatus RECIFE population were 7.8% to 56.5%. The higher infection rate was showed in females feeding with blood containing 1913 mf/ml, but no influence was observed in engorged females. The melanization response observed in Cx. quinquefasciatus was important for vector survival by limiting the number of larvae, acting as an important mechanism of parasitic-host interactions. The data indicate that the Cx. quinquefasciatus RECIFE population should is an excelent vector of D. immitis at metropolitan region of Recife. Significant difference (p<0.01) was observed in the mortality rates between the RECIFE population of Ae. aegypti, UNICAMP population, ROCKFELLER strain, and Ae. albopictus RECIFE population. Although no difference were observed between Ae. aegypti ROCKFELLER, UNICAMP and Ae. albopictus RECIFE population. The vector efficiency (VE) rates of Ae. aegypti and Ae. albopictus RECIFE population were 7.4% to 53.8% and 25.2% respectively. Not only the high number of infective third stage larvae of D. immitis in mouth of mosquitoes but also low mortality was observed in Ae. albopictus RECIFE population. This data showed that this specie is the best vector of heartworm infection in the study area. No melanization response was observed in Ae. Aegypti RECIFE population but high mortality was reported. The UNICAMP population and ROCKFELLER strain of Ae. aegypti were refractory to infection to D. immitis
Doutorado
Doutor em Parasitologia

A population survey was conducted on the mosquito species recorded in Denton, Texas for the years of 2005 to 2015. Data used in this project were obtained from an ongoing, long-term surveillance program led by the City of Denton and conducted through the University of North Texas. Research focused on the population dynamics and community structure of mosquitoes collected within urban areas of Denton, Texas in relation to certain environmental variables. A total of 80,837 female mosquitoes were captured and represented 38 species found under the following genera: Aedes, Anopheles, Coquillettidia, Culex, Culiseta, Mansonia, Orthopodomyia, Psorophora, Toxorhynchites, and Uranotaenia. Culex quinquefasciatus was the most abundant species followed by Aedes vexans. Seasonal patterns of the most abundant species revealed high variability throughout the study. Container breeders were most abundant in August and those that breed in floodwaters were most abundant in the months of May and September. Samples were tested for arbovirus presence through the Texas Department of State Health Services in Austin, Texas and multiple pools tested positive for West Nile virus throughout the study. Stepwise multiple regression and Spearman's rank correlation analyses were performed to examine the relationship between the mosquito community and environmental variables. Data revealed that temperature, precipitation, and dew point were the most important variables influencing the mosquito population in the City of Denton.

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.

[Truncated abstract] A functional ecosystem is increasingly being recognised as a requirement for health and well being of resident human populations. Clearing of native vegetation for agriculture has left 1.047 million hectares of south-west Western Australia affected by a severe form of environmental degradation, dryland salinity, characterised by secondary soil salinisation and waterlogging. This area may expand by a further 1.7-3.4 million hectares if current trends continue. Ecosystems in saline affected regions display many of the classic characteristics of Ecosystem Distress Syndrome (EDS). One outcome of EDS that has not yet been investigated in relation to dryland salinity is adverse human health implications. This thesis focuses on one such potential adverse health outcome: increased incidence of Ross River virus (RRV), the most common mosquito-borne disease in Australia. Spatial analysis of RRV notifications did not reveal a significant association with dryland salinity. To overcome inherent limitations with notification data, serological RRV antibody prevalence was also investigated, and again no significant association with dryland salinity was detected. However, the spatial scale imposed limited the sensitivity of both studies. ... This thesis represents the first attempt to prospectively investigate the influence of secondary soil salinity on mosquito-borne disease by combining entomological, environmental and epidemiological data. The evidence collected indicates that RRV disease incidence is not currently a significant population health priority in areas affected by dryland salinity despite the dominant presence of Ae. camptorhynchus. Potential limiting factors include; local climatic impact on the seasonal mosquito population dynamics; vertebrate host distribution and feeding behaviour of Ae. camptorhynchus; and the scarce and uneven human population distribution across the region. However, the potential for increased disease risk in dryland salinity affected areas to become apparent in the future cannot be discounted, particularly in light of the increasing extent predicted to develop over coming decades before any benefits of amelioration strategies are observed. Finally, it is important to note that both dryland salinity and salinity induced by irrigation are important forms of environmental degradation in arid and semi-arid worldwide, with a total population of over 400 million people. Potential health risks will of course vary widely across different regions depending on a range of factors specific to the local region and the complex interactions between them. It is therefore not possible to make broad generalisations. The need is highlighted for similar research in other regions and it is contended that an ecosystem health framework provides the necessary basis for such investigations.

Thesis (M.S.)--University of Tennessee, Knoxville, 2004.
Title from title page screen (viewed Feb. 2, 2005). Thesis advisor: Reid R. Gerhardt. Document formatted into pages (xiii, 110 p. : ill., maps). Vita. Includes bibliographical references (p. 90-109).

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Science, 1998.
This study was initiated in order to determine the identities and distribution patterns of the anopheline fauna, more especially the malaria vectors, in regions of Botswana prone to malaria epidemics. Field samples collected from Shakawe, Maun and Kasane over three consecutive years were subjected to morphological, cytogenetic, isoenzyme and PCR analyses. The results established that Anopheles arabiensis and Anopheles funestus were the predominant vector species.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2005.
Title from title page screen (viewed on July 13, 2005). Thesis advisor: Reid R. Gerhardt. Document formatted into pages (xii, 77 p. : ill. (some col.), maps (some col.)). Vita. Includes bibliographical references (p. 67-76).

Background: Mosquito-borne diseases are a growing concern for temperate regions including the northeastern US. There the two primary mosquito vectors, Cx. pipiens and Ae. albopictus are widespread, endemic circulation of West Nile virus causes sporadic outbreaks, and imported arboviruses such as dengue, chikungunya, and Zika are on the rise. With temperate mosquito-borne disease outbreaks likely to increase in frequency, it is critical to reduce mosquito populations in the northeastern US. Community-based source reduction is heralded as the most sustainable component of integrated mosquito management. Yet mosquitoes develop rapidly, requiring weekly maintenance of mosquito habitat. This is onerous and community commitment flags. The development of predictive models to inform focused vector-control efforts is therefore of great utility. Objectives and Methods: The overarching objective of this research is to make robust predictive modeling frameworks based on empirically derived relationships of the ecology and epidemiology of mosquito-borne disease systems in the northeastern US. We aim to quantify the relationships between local environmental and meteorological conditions and mosquito vectors. In Chapters 2 and 4 we use lengthy surveillance records to develop models and use model ensembles to generate predictions based on out-of-sample data. For chapter 3 we use more spatially refined data to investigate the influence of intra-urban heterogeneities and how climatic conditions influence mosquito populations across these defined differences. Results: In Chapter 2, we model and forecast WNV infection rates among mosquito vectors using meteorological and hydrological conditions. We show that real-time climate information can predict WNV Culex infection rates prior to when human risk is greatest. In Chapter 3, we link infrastructure degradation and vegetation patterns with Ae. albopictus infestation levels as well as the interactive effect of precipitation across these environmental conditions. In Chapter 4, we identify key land use characteristics and meteorological conditions associated with annual Ae. albopictus abundance. Further we use imported chikungunya cases to delineate areas of high arboviral importation and, in combination with areas of high Ae. albopictus abundance, areas at heightened risk for arboviral transmission. Conclusions: While temperate outbreaks are often self-limiting they may be increasing in frequency and severity. Due to the multitude of invasive vectors and arboviruses, vector control techniques that work for multiple mosquito species are likely more effective and sustainable. Here we build build empirical models that accurately predict mosquito dynamics before populations peak which is critical for vector control. We recommend integrating predictive modeling into mosquito management guidelines as this could focus valuable resources to when and where mosquito-borne transmission risk is greatest. Further we find social and ecological determinants of mosquito dynamics, supporting further study that combine socio-ecological processes into model frameworks.

Thesis (Ph.D.)--York University, 2006. Graduate Programme in Mathematics and Statistics.
Typescript. Includes bibliographical references (leaves 126-132). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR19847

West Nile Virus (WNV), a vector-borne disease continues to be a serious threat to public health in the United States, particularly in the Southwest region. While all the states in the U.S. experienced a decreasing trend of WNV disease in 2010, the state of Arizona experienced a sharp increase from 20 in 2009 to 166 cases the following year. This dissertation endeavored to develop forecasting models to predict future cases of disease and identify counties with increased propensity for WNV. Furthermore, this study aimed to identify environmental and economic factors that contributed to the increase in WNV cases in Maricopa County, Arizona. A spatiotemporal stochastic regression model was developed using Bayesian principles and was successful in calculating the annual mean cases of disease from 2003 to 2011 for all counties. The model was also able to predict future cases of disease by fitting historical data. The model-based inference identified counties in the southern region of Arizona as having an elevated propensity for disease compared to counties in the northern region. A Seasonal Autoregressive Integrated Moving Average (SARIMA) model was developed and effectively forecasted monthly cases of human WNV in Maricopa County, Arizona. By fitting the SARIMA model to monthly historical disease data from 2005 to 2011, the temporal model presented a decreasing trend of monthly incidence of disease for 2012. The impact of home foreclosures, climate variability, and population growth on the resurgence of human WNV disease cases in Maricopa County during the 2010 epidemic was investigated. These factors were found to have contributed to the resurgence of the disease by creating the optimal environmental conditions that allowed the amplification of mosquito populations, thus increasing the risk of disease transmission to humans. As spatiotemporal disease data become readily available, forecasting models can be an important and viable risk assessment tool for public health practitioners. Forecasting models allow the mobilization and distribution of limited resources to areas with elevated propensity for disease, and the timely deployment of intervention programs to reduce the overall risk of disease.
Graduation date: 2013

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

The irrigation farming methods on the Makhathini Flats are thought to be responsible for recent increase in malaria cases in the Mamfene area of northern KwaZulu-Natal despite ongoing malaria control activities. Their coincidence with the period of intensive fanning is an interesting one. This study was therefore carried out to determine the relationship between larval habitats and adult mosquito population in malaria transmission using Geographic Information System (GIS). Four types of breeding sites were utilised by malaria vectors in Mamfene, viz; types 1, II, III and IV. Habitat type I was tap pools, type II was irrigation spillage in agricultural land, type III was spillage outside but adjacent to the agricultural land and type IV was depression pools located both in the Balamhlanga swamp and inland. The cumulative larval density in all habitats peaked in March 1995 (20/man-hr), with irrigation spillage (type III) recording the highest density index (33/man-hr) as compared to tap pools (type I) which recorded 32.8/man-hr while other waterbodies recorded I3 .4/man-hr (type II) and O.5/man-hr (type IV) respectively. Subsamples of both larvae and adults of An. gambiae group were identified by the Polymerase Chain Reaction (PCR) technique. Of the larvae identified, 94.1 % and 5.9% (n=289) were An. arabiensis and An. quadriannulatus respectively while in the adult component, the composition was 98.7% and 1.3% (n=303) for An. arabiensis and An. quadriannulatus respectively. This confirmed An. arabiensis as the dominant malaria vector in Mamfene area while the exophilic behaviour of An. quadriannulatus was portrayed. Of the An. gambiae group dissected for parity, 51 .5%) were found parous. This is an indication that the population was old and was able to maintain transmission locally despite ongoing vector control measures. The Global Positioning System (GPS) was used to position larval and adult mosquito sampling sites. The spatial distribution of adult mosquitoes from the breeding sites were plotted using GIS soft ware (Map Info ) and the distance between the breeding sites and study houses were measured using a utility distance tool. With the aid of GIS, the adult mosquito density in houses could be used as an indicator to locate the breeding sites in the vicinity. The importance of these findings in terms of application in cost-effective malaria control cannot be over-emphasized.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Malaria is a serious and life-threatening mosquito-borne disease that every year affects over 200 million individuals and causes 400,00 deaths. An additional 0.5 billion people globally are at risk of malaria infection. The unique role of climate in influencing malaria transmission outcomes across individual communities by acting on multiple dimensions of the malaria vector and parasite ecology has been long recognized. This recognition has led to the development of explicit and implicit climate-driven models of malaria transmission designed to better understand and predict patterns of population vulnerability and uncover potential challenges to malaria control. However, existing implicitly-forced process-based models of malaria have relied on indirectly correlated predictors of malaria transmission, instead of direct relationships among climate, vector entomology and parasite ecology. The lack of biologically-motivated modulation of malaria transmission compromises meaningful interpretation of the ecological role played by climate in malaria transmission. Similarly, the specific influence of climate on vector and parasite dynamics is obscured, limiting the utility of these simple and powerful model forms. This dissertation focuses on elaborating the direct ecological relationships between climate, the malaria vector and parasite to enhance the ecological utility of lower dimensional mathematical models of malaria transmission. In the 2nd chapter of this thesis, a climate-driven entomological modeling framework is developed, consisting of a simple dynamic model that explicitly tracks malaria transmission in human populations and implicitly represents the malaria force of infection through climate-regulation of multiple aspects of the Entomological Inoculation Rate (EIR). The EIR-model construct is found to accurately capture seasonal malaria dynamics under free-simulation, when coupled to local rainfall and temperature climatology across multiple local regions in Rwanda. Furthermore, local rainfall modulation of sub-adult survivorship is found to be a more critical driver of seasonal malaria dynamics than other environmentally-regulated components of EIR. In chapter 3, the model framework is paired with data assimilation methods to dynamically simulate interannual malaria incidence in Rwanda, infer parameters of malaria transmission and validate the malaria model. Results indicate that the implicitly-forced transmission model is able to reproduce interannual and seasonal malaria incidence at regional and local scales. However, accuracy of model description of malaria incidence is more varied at the more resolved local level. Intensified malaria control efforts during the later years of the study are suspected to increase the discrepancy between the vector and parasite dynamics dictated by climate and the observed widespread decline in malaria activity in the region. Nonetheless, the parameters of transmission identified across populations in Rwanda were comparable to existing estimates of malaria, further validating the transmission model and data assimilation approach. For the 4th chapter, a state-of-the-art Bayesian inference forecasting system for the EIR-model framework is developed, as well as a multi-model forecasting system consisting of weighted-average predictions from the dynamic malaria model and historical expectance predictions. Retrospective forecasts of four years of malaria data from 42 regions in Rwanda indicate that the model-inference forecasting system predicts malaria incidence more accurately than historical expectance alone, particularly for predictions with 1-6 weeks lead times. Although slightly less skillful, the multi-model system was found to substantively enhance forecast reliability of the EIR-model system, bolstering the utility of the malaria model as a robust forecaster of malaria in the region. The concluding chapter describes areas for improving the specification of the parsimonious model construct. The need to include malaria control coverage data as exogenous forces of transmission, non-climate drivers and alternate sources of climate exposure that support transmission are highlighted. Future works on forecast calibration needed to improve model performance for real-time prediction are also detailed. In addition, areas for application within information systems for evaluating malaria risk and for advising malaria control efforts, specifically relating to local variability in malaria burden and characterization of entomological drivers of local malaria, are identified and further discussed. The model systems developed in this thesis advance the capabilities of lower dimension dynamic models to connect the ecological drivers of malaria transmission to climate variation. Such process-based formulations could provide better climate-driven descriptions of malaria, while limiting model complexity, without compromising representation of entomological relationships that are potentially valuable for improved understanding and control of malaria transmission.

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

PhD (Geography)
Department of Geography and Geo-Information Sciences
Malaria is a climate-change concatenated biological hazard that may, like any other natural hazard, can lead to a disaster if there is a failure in handling emergencies or risks. A holistic solution for malaria mitigation can be provided when indigenous knowledge is complemented with scientific knowledge. Malaria remains a challenge in South Africa and Limpopo province is the highest burdened malaria-endemic region. Specifically, Vhembe District is the highest burdened followed by Mopani District (Raman et al., 2016). This research sought to mitigate malaria transmissions in Mopani District through the integration of indigenous and scientific knowledge. The study was carried out in Mopani District of South Africa and 4 municipalities were involved. These are Ba-Phalaborwa, Greater Tzaneen, Greater Letaba, and Maruleng. A pragmatism philosophy was adopted hence the study took a mixed approach (sequential multiphase design). Data was collected from 381 selected participants through in-depth interviews, a survey and a focus group discussion. Participants for the in-depth interviews were obtained through snowballing and selected randomly for the survey, while for the focus group discussion purposive sampling was used. The study applied constructivist grounded theory to analyze qualitative data and to generate theory. Statistical Package for Social Sciences version 23.0 was used for quantitative data. Based on empirical findings, it was concluded that temperature and rainfall among other various factors exacerbate malaria transmission in the study area. Results of the study also show that people in Mopani District predict the malaria season onset by forecasting rainfall using various indigenous knowledge based indicators. The rainfall indicators mentioned by participants in the study were used in the developed early warning system. An Early warning system is an essential tool that builds the capacities of communities so that they can reduce their vulnerability to hazards or disasters. In the design of the system, Apache Cordova, JDK 1.8, Node JS, and XAMPP software were used. The study recommends malaria management and control key stakeholders to adopt the developed early warning system as a further mitigation strategy to the problem of malaria transmission in Mopani District.
NRF