Browsing by Author "Neira Oviedo, Marco Vinicio"
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Item Unknown Assessment of the impact of potential tetracycline exposure on the phenotype of Aedes aegypti OX513A: implications for field use(2015-08-13) Neira Oviedo, Marco Vinicio; Curtis, ZoeBackground: Aedes aegypti is the primary vector of dengue fever, a viral disease which has an estimated incidence of 390 million infections annually. Conventional vector control methods have been unable to curb the transmission of the disease. We have previously reported a novel method of vector control using a tetracycline repressible self-limiting strain of Ae. aegypti OX513A which has achieved >90% suppression of wild populations. Methodology/Principal Findings: We investigated the impact of tetracycline and its analogues on the phenotype of OX513A from the perspective of possible routes and levels of environmental exposure. We determined the minimum concentration of tetracycline and its analogues that will allow an increased survivorship and found these to be greater than the maximum concentration of tetracyclines found in known Ae. aegypti breeding sites and their surrounding areas. Furthermore, we determined that OX513A parents fed tetracycline are unable to pre-load their progeny with sufficient antidote to increase their survivorship. Finally, we studied the changes in concentration of tetracycline in the mass production rearing water of OX513A and the developing insect. Conclusion/Significance: Together, these studies demonstrate that potential routes of exposure of OX513A individuals to tetracycline and its analogues in the environment are not expected to increase the survivorship of OX513A.Item Unknown Comparative study of the pathological effects of western equine encephalomyelitis virus in four strains of Culex tarsalis Coquillett (Diptera: Culicidae).(2014) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioEarly reports suggested that mosquito cells infected with arboviruses remain viable and undamaged. However, more recent experimental evidence suggests that arboviral infection of mosquito tissues might indeed result in pathological changes, with potential implications for vector survival and virus transmission. Here, we compare the pathological effects of western equine encephalomyelitis virus (WEEV) infection in four strains of Culex tarsalis previously reported to differ in their competence as WEEV vectors. Pathological effects were observed in cells of the midgut epithelium, salivary glands, and eggs. Cell rounding and sloughing of midgut epithelial cells was associated with those strains reported to be the least susceptible to WEEV infection, whereas midgut necrosis and vacuolation upon infection were associated with strains showing higher susceptibility. Although pathological effects were sporadically observed in infected salivary glands, further studies are required to evaluate their impact on vector competence. Additionally, the potential implications of observed C. tarsalis egg infection with WEEV are discussed.Item Open Access 
Developing a Novel Attractive Toxic Sugar Bait (ATSB) Device for Intra-domiciliary Control of Aedes aegypti(PUCE - Quito, 2016) Rivera Pazmiño, Galo Enrique; Neira Oviedo, Marco VinicioOn account of vector control being the most successful approach towards prevention of the major arboviral concerns worldwide and the imperative pursuit of alternatives to traditional pesticides, we developed a novel attractive toxic sugar bait (ATSB) device. The device incorporates seemingly inexpensive (cost < 1 USD) olfactory and visual cues attractive to Aedes aegypti L. We incorporated 1% boric acid in 10% sucrose solution as toxic component on the devices and this showed to be effective killing female A.aegypti in controlled laboratory conditions (0% survival probability after 48h). In addition, we evaluated the biological action of the device and concluded that boric acid acts as a stomach poison. Using transmission electron microscopy we further determined that it disrupts the continuity of the epithelial tissue of the posterior midgut. The device is effective poisoning A. aegypti females in two different physiological statuses (recently blood fed and parous). Finally, devices were effective after 180 days of being assembled. These features provide us with information that will be useful for future semi-field and field trials.Item Metadata only Ecosalud en las enfermedades transmitidas por vectores: chagas, dengue y malaria(2018-05) Neira Oviedo, Marco Vinicio; Sáenz Calderón, Fabián Ernesto; Villacis Salazar, Anita Gabriela; Arteaga, E., Aguilar, H., Breilh, J. y Campaña, M.La Medicina Ecuatoriana en el siglo XXI es una colección de tres tomos dedicados a: Clínica y diagnóstico, Cirugía e intervencionismo, y las Ciencias en la salud colectiva y terapias integrativas. La colección es un esfuerzo científico y editorial inédito en el país. Cuenta con el trabajo de 177 especialistas ecuatorianos. Los tomos recogen 450 cuadros, figuras y fotografías. Más de 1200 páginas distribuidas en 55 capítulos especializados.Item Metadata only Efecto de la temperatura y el pH del agua sobre la longevidad y resistencia a pesticidas en Aedes aegypti (Diptera: Culicidae)Neira Oviedo, Marco VinicioAedes aegypti (Diptera: Culicidae) es uno de los principales vectores de dengue, chikungunya, Zika, fiebre amarilla, entre otras. Las condiciones climáticas influyen en la biología, distribución, dinámica poblacional y capacidad vectorial de esta especie. Para investigar el potencial impacto del cambio climático futuro en A. aegypti, se estudió el efecto de las variaciones en la temperatura ambiental y el pH del agua de crianza inicial sobre la longevidad y la resistencia a pesticidas. Los mosquitos fueron criados, durante todos sus estadios, en diferentes temperaturas ambientales y pH del agua. Después de la emergencia de los adultos, se monitoreó la longevidad y la resistencia a deltametrina. Encontramos que, dentro de nuestro gradiente de temperatura, 28°C maximiza la longevidad de los mosquitos analizados. Temperaturas superiores o inferiores a esta óptima, disminuyeron significativamente la duración de vida del vector, al igual que la acidificación de los hábitats acuáticos de las etapas larvales (pH 5 y 4). En referencia a la resistencia a deltametrina, la acidificación del agua y las temperaturas de crianza no óptimas (25 y 31°C) produjeron menores niveles de resistencia que los observados en los tratamientos control. Este estudio contribuye con información novedosa sobre la biología y fisiología de A. aegypti en condiciones ambientales controladas, para así comprender los potenciales efectos de diferentes escenarios climáticos sobre la transmisión de enfermedades arbovirales en el futuro.Item Open Access Estimation of Aedes aegypti (Diptera: Culicidae) population size and adult male survival in an urban area in Panamá.(2014) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioTraditional mosquito control strategies rely heavily on the use of chemical insecticides. However, concerns about the efficiency of traditional control methods, environmental impact and emerging pesticide resistance have highlighted the necessity for developing innovative tools for mosquito control. Some novel strategies, including release of insects carrying a dominant lethal gene (RIDL®), rely on the sustained release of modified male mosquitoes and therefore benefit from a thorough understanding of the biology of the male of the species. In this report we present the results of a mark-release-recapture study aimed at: (i) establishing the survival in the field of laboratory-reared, wild-type male Aedes aegypti and (b) estimating the size of the local adult Ae. aegypti population. The study took place in Panama, a country where recent increases in the incidence and severity of dengue cases have prompted health authorities to evaluate alternative strategies for vector control. Results suggest a life expectancy of 2.3 days for released male mosquitoes (confidence interval: 1.78-2.86). Overall, the male mosquito population was estimated at 58 males/ha (range 12-81 males/ha), which can be extrapolated to an average of 0.64 pupae/person for the study area. The practical implications of these results are discussed.Item Open Access Evaluación de la actividad larvicida de extractos vegetales y nanopartículas de plata sintetizadas a partir de extractos vegetales de especies nativas del Ecuador contra Aedes aegypti L. (Diptera: Culicidae).(PUCE - Quito, 2017) Morejón Viteri, Bianca Dominique; Neira Oviedo, Marco VinicioEl gran impacto global de las enfermedades transmitidas por mosquitos representa un importante problema de salud pública que debe ser prevenido, controlado y tratado constantemente. Recientemente, la transmisión ha aumentado en áreas urbanas debido al rápido crecimiento poblacional, la globalización, el transporte moderno, los efectos del cambio climático y el aumento de la resistencia del mosquito a insecticidas. El mosquito Aedes aegypti es el vector primario de las infecciones de dengue, chikungunya y Zika a nivel mundial. Debido a que no existen vacunas o medicinas efectivas para la prevención y/o tratamiento de estas patologías, el control vectorial es la principal estrategia para reducir su transmisión. Para controlar el tamaño de las poblaciones de Aedes, la herramienta más utilizada es la aplicación de insecticidas sintéticos y a pesar de su efectividad, su uso extensivo ha producido altos costos operativos y efectos colaterales adversos. Los insecticidas derivados de plantas representan una alternativa de biocontrol ecoamigable, costo-efectiva y segura. El presente estudio evalúa la actividad larvicida de los extractos frutales de Solanum mammosum, extractos foliares de Ambrosia arborescens y nanopartículas de plata (AgNPs) sintetizadas utilizando los extractos acuosos de estas plantas contra las larvas de tercer estadío de A. aegypti. Para esto, las larvas fueron expuestas a un gradiente de concentraciones de extractos vegetales y AgNPs durante 24 horas. Los ensayos de laboratorio muestran que las AgNPs obtenidas a partir de las dos plantas fueron significativamente más tóxicas para las larvas de mosquito que los extractos vegetales, siendo las AgNPs de S. mammosum las de mayor toxicidad. Estos resultados sugieren que tanto los extractos vegetales como las AgNPs obtenidas a partir de S. mammosum y A. arborescens tienen el potencial para desarrollarse como herramientas alternativas apropiadas para el control de este insecto vector de arbovirus.Item Open Access Genetic Control of Aedes Mosquitoes.(2013) Neira Oviedo, Marco Vinicio; Luke, AlpheyAedes mosquitoes include important vector species such as Aedes aegypti, the major vector of dengue. Genetic control methods are being developed for several of these species, stimulated by an urgent need owing to the poor effectiveness of current methods combined with an increase in chemical pesticide resistance. In this review we discuss the various genetic strategies that have been proposed, their present status, and future prospects. We focus particularly on those methods that are already being tested in the field, including RIDL and Wolbachia-based approaches.Item Metadata only Green synthesis of silver nanoparticles using Solanum mammosum L. (Solanaceae) fruit extract and their larvicidal activity against Aedes aegypti L. (Diptera: Culicidae)(2019-10) Neira Oviedo, Marco Vinicio; Pilaquinga Flores, María Fernanda; Neira Oviedo, Marco VinicioThe family of mosquitoes (Diptera: Culicidae) contains several species of major public health relevance due to their role as vectors of human disease. One of these species, Aedes aegypti, is responsible for the transmission of some of the most important vector-borne viruses affecting humankind, including dengue fever, chikungunya and Zika. Traditionally, control of Ae. aegypti and other arthropod species has relied on the use of a relatively small diversity of chemical insecticides. However, widespread and intensive use of these substances has caused significant adverse environmental effects and has contributed to the appearance of pesticide-resistant populations in an increasing number of locations around the world, thereby dramatically reducing their efficiency. Therefore, it becomes urgent to develop novel alternative tools for vector control. In that context, our study aimed at evaluating the insecticidal activity against Ae. aegypti of aqueous extracts obtained from the fruits of Solanum mammosum L., as well as silver nanoparticles synthesized using aqueous extracts from this plant species (SmAgNPs). To perform the test, third instar Ae. aegypti larvae were exposed to increasing concentrations of plant extract and SmAgNPs for 24 h. Our results suggest that both the aqueous extract and SmAgNPs were toxic to the larvae, with SmAgNPs displaying a much higher level of toxicity than the extract alone, as reflected in their LC50 values (0.06 ppm vs 1631.27 ppm, respectively). These results suggest that both S. mammosum extracts and SmAgNPs exhibit noteworthy larvicidal activity, and should be further explored as potential source of alternative tools in the fight against insect vectors of human disease.Item Metadata only Household dengue prevention interventions, expenditures, and barriers to aedes aegypti control in Machala, Ecuador(2017-02) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioThe Aedes aegypti mosquito is an efficient vector for the transmission of Zika, chikungunya, and dengue viruses, causing major epidemics and a significant social and economic burden throughout the tropics and subtropics. The primary means of preventing these diseases is household-level mosquito control. However, relatively little is known about the economic burden of Ae. aegypti control in resource-limited communities. We surveyed residents from 40 households in a high-risk community at the urban periphery in the city of Machala, Ecuador, on dengue perceptions, vector control interventions, household expenditures, and factors influencing purchasing decisions. The results of this study show that households spend a monthly median of US$2.00, or 1.90% (range: 0.00%, 9.21%) of their family income on Ae. aegypti control interventions. Households reported employing, on average, five different mosquito control and dengue prevention interventions, including aerosols, liquid sprays, repellents, mosquito coils, and unimpregnated bed nets. We found that effectiveness and cost were the most important factors that influence people's decisions to purchase a mosquito control product. Our findings will inform the development and deployment of new Ae. aegypti control interventions by the public health and private sectors, and add to prior studies that have focused on the economic burden of dengue-like illness.Item Open Access Impact of rearing temperature and water pH on longevity and pesticide resistance in Aedes aegypti (Diptera: Culicidae)(PUCE - Quito, 2017) López Latorre, María de los Ángeles; Neira Oviedo, Marco VinicioBackground: Aedes aegypti (Diptera: Culicidae) is considered as one of the main arboviral disease vectors around the planet. Because A. aegypti is an ectotherm and breeds in fresh water pools, climatic conditions influence its biology, distribution, population dynamics and vectorial capacity. To investigate the potential impact of future climate change on A. aegypti´s biology, we studied the effect of variations in environmental temperature and the pH of breeding water on this species longevity and pesticide resistance. Methods: Mosquitoes of both geographic (experimental) and control strains were reared under different environmental conditions (environmental temperatures of 25°, 28°, 31°C, maintained throughout the insects´ life span; water pH values of 4, 5 and 6 set at the beginning of larval development). Upon adult emergence, we monitored the longevity and pesticide 25 resistance for each treatment. Results: Both environmental temperature and water pH seem to influence adult longevity and pesticide resistance in A. aegypti. Longevity is significantly diminished in temperatures above or below 28°C, as well as with the acidification of the initial breeding water. Similarly, pesticide resistance seems to decrease significantly in specimens reared above or below 28oC, and in specimens reared in acidic environments. Conclusions: We found that within our temperature gradient there is an optimal rearing temperature (28°C) which maximizes the longevity of our specimens. Additionally, the acidification of the aquatic habitats of larval stages diminished the lifespan of the vector. In reference to deltamethrin resistance, acidification of the breeding water as well as non-optimal rearing temperatures (25 & 31°C) produced lower levels of resistance than those observed in the control treatments, for both temperature and water pH. Although the definitive effects of climate change on A. aegypti biology and physiology in the field are hard to predict, our study contributes novel information about the biology and physiology of this vector species under controlled conditions. This information could help us understand the potential effects of putative future climate scenarios on the transmission of arboviral diseases.Item Open Access Influencia del cambio climático en la biología de Aedes Aegypti (Diptera:Culicidae) mosquito transmisor de arbovirosis humanas(2016-10) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioEn la actualidad, las enfermedades transmitidas por el mosquito Aedes aegypti, incluyendo las fiebres del dengue, chikungunya y Zika, se encuentran ntre los principales problemas de salud de los países tropicales. Si se considera que la biología de esta especie de insecto está influenciada en gran medida por las condiciones ambientales, podemos afirmar que los cambios previstos en el clima del futuro del planeta tendrán un impacto considerable en el panorama epidemológico de las enfermedades transmitidas por Aedes aegypti. En el presente trabajo revisamos el estado del conocimiento actual sobre la influencia que factores ambientales pueden tener en la biología y fisiología de Aedes aegypti. Adicionalmente, discutimos cómo los cambios climáticos previstos para el futuro pueden afectar la capacidad vectorial de esta importante especie, con especial énfasis en el ecuador y sus países vecinos.Item Metadata only Ingested insecticide to control Aedes aegypti: developing a novel dried attractive toxic sugar bait device for intra-domiciliary control(2020) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioBackground: Illnesses transmitted by Aedes aegypti (Linnaeus, 1762) such as dengue, chikungunya and Zika comprise a considerable global burden; mosquito control is the primary public health tool to reduce disease transmission. Current interventions are inadequate and insecticide resistance threatens the effectiveness of these options. Dried attractive bait stations (DABS) are a novel mechanism to deliver insecticide to Ae. aegypti. The DABS are a high-contrast 28 inch2 surface coated with dried sugar-boric acid solution. Aedes aegypti are attracted to DABS by visual cues only, and the dried sugar solution elicits an ingestion response from Ae. aegypti landing on the surface. The study presents the development of the DABS and tests of their impact on Ae. aegypti mortality in the laboratory and a series of semi-field trials. Methods: We conducted multiple series of laboratory and semi-field trials to assess the survivability of Ae. aegypti mosquitoes exposed to the DABS. In the laboratory experiments, we assessed the lethality, the killing mechanism, and the shelf life of the device through controlled experiments. In the semi-field trials, we released laboratory-reared female Ae. aegypti into experimental houses typical of peri-urban tropical communities in South America in three trial series with six replicates each. Laboratory experiments were conducted in Quito, Ecuador, and semi-field experiments were conducted in Machala, Ecuador, an area with abundant wild populations of Ae. aegypti and endemic arboviral transmission. Results: In the laboratory, complete lethality was observed after 48 hours regardless of physiological status of the mosquito. The killing mechanism was determined to be through ingestion, as the boric acid disrupted the gut of the mosquito. In experimental houses, total mosquito mortality was greater in the treatment house for all series of experiments (P < 0.0001). Conclusions: The DABS devices were effective at killing female Ae. aegypti under a variety of laboratory and semi-field conditions. DABS are a promising intervention for interdomiciliary control of Ae. aegypti and arboviral disease prevention.Item Metadata only Larvicidal activity of silver nanoparticles synthesized using extracts of Ambrosia arborescens (Asteraceae) to control Aedes aegypti L. (Diptera: Culicidae)(2018-04) Neira Oviedo, Marco Vinicio; Pilaquinga Flores, María Fernanda; Neira Oviedo, Marco VinicioThe mosquito species Aedes aegypti is the primary vector of dengue, chikungunya, and Zika infections worldwide. Since effective vaccines or drugs are not available for the prevention and/or treatment of these pathologies, vector control has been adopted as the main approach to reduce their transmission. To control Aedes populations, the most commonly used tool is the application of chemical insecticides and, despite their effectiveness, indiscriminate use of these chemicals has led to high operational costs, appearance of resistant populations, and adverse nontarget effects. Plant-derived insecticides may be an eco-friendly, cost-effective, and safe biocontrol alternative. The present study was carried out to evaluate the larvicidal activity of leaf extracts of Ambrosia arborescens and green-synthesized silver nanoparticles (AgNPs) using aqueous extracts obtained from this plant against third instar larvae of Ae. aegypti. To test this, larvae were exposed for 24 h to the aqueous plant extract at 1500, 3000, 4500, and 6000 ppm and the plant-synthesized AgNPs at 0.2, 0.3, 0.4, and 0.5 ppm. In laboratory assays, AgNPs were more toxic (LC50 = 0.28 ppm; LC90 = 0.43 ppm) than the plant extract (LC50 = 1844.61 ppm; LC90 = 6043.95 ppm). These results suggest that A. arborescens aqueous extract and green-synthesized silver nanoparticles produced from those extracts have the potential to be developed into suitable alternative tools useful for the control of Ae. aegypti populations.Item Open Access The Orthologue of the Fruitfly Sex Behaviour Gene Fruitless in the Mosquito Aedes aegypti: Evolution of Genomic Organisation and Alternative Splicing.(2013) Neira Oviedo, Marco Vinicio; Salvemini, MarcoIn Drosophila melanogaster the doublesex (dsx) and fruitless (fru) regulatory genes act at the bottom of the somatic sex determination pathway. Both are regulated via alternative splicing by an upstream female-specific TRA/TRA-2 complex, recognizing a common cis element. dsx controls somatic sexual differentiation of non-neural as well as of neural tissues. fru, on the other hand, expresses male-specific functions only in neural system where it is required to built the neural circuits underlying proper courtship behaviour. In the mosquito Aedes aegypti sex determination is different from Drosophila. The key male determiner M, which is located on one of a pair of homomorphic sex chromosomes, controls sex-specific splicing of the mosquito dsx orthologue. In this study we report the genomic organization and expression of the fru homologue in Ae. aegypti (Aeafru). We found that it is sex-specifically spliced suggesting that it is also under the control of the sex determination pathway. Comparative analyses between the Aeafru and Anopheles gambiae fru (Angfru) genomic loci revealed partial conservation of exon organization and extensive divergence of intron lengths. We find that Aeadsx and Aeafru share novel cis splicing regulatory elements conserved in the alternatively spliced regions. We propose that in Aedes aegypti sex-specific splicing of dsx and fru is most likely under the control of splicing regulatory factors which are different from TRA and TRA-2 found in other dipteran insects and discuss the potential use of fru and dsx for developing new genetic strategies in vector control.Item Open Access Rift Valley fever virus-infected mosquito ova and associated pathology: possible implications for endemic maintenance(2011) Neira Oviedo, Marco Vinicio; Romoser, William.Endemic/enzootic maintenance mechanisms like vertical transmission (pathogen passage from infected adults to their offspring) are central in the epidemiology of zoonotic pathogens. In Kenya, Rift Valley fever virus (RVFV) may be maintained by vertical transmission in ground-pool mosquitoes such as Aedes mcintoshi. RVFV can cause serious morbidity and mortality in humans and livestock. Past epidemics/epizootics have occurred in sub-Saharan Africa but, since the late 1970s. RVFV-infected eggs in Ae. mcintoshi after virus injection into the hemocoel after the first of two blood meals, justifying further study. Mosquitoes were collected from an artificially flooded water-catching depression along a stream in Kenya, shipped live to the USA, and studied using an immunocytochemical method for RVFV-antigen localization in mosquito sections. After virus injection into the hemocoel, RVFV-infected reproductive tissues were found, particularly follicular epithelia and oocyte/nurse cells. Ovarian infection from the hemocoel is a crucial step in establishing a vertically transmitting mosquito line. Ovarian follicles originate from germarial cells, primordia located distally in each ovariole, and infection of these cells is expected to be requisite for long-term vercial transmission. However, no germarial cell infection was found, so establishing a new line of vertically transmitting mosquitoes may require two generations. The findings support the hypothesis that Ae. mcintoshi is involved in the endemic maintenance of RVFV by vertical transmission. Detection of distinct pathology in infected eggs raises the possibility of virus-laden eggs being deposited among healthy eggs, thereby providing an exogenous source of infection via ingestion by mosquito larvae and other organisms. This has potentially significant epidemiological implications. Possible modes of entry of virus from the hemocoel into the ovaries and routes by which larvae might become infected by ingesting virus are discussed.Item Metadata only Seasonal and geographic variation in insecticide resistance in aedes aegypti in southern Ecuador(2019-06) Neira Oviedo, Marco Vinicio; Neira Oviedo, Marco VinicioInsecticide resistance (IR) can undermine efforts to control vectors of public health importance. Aedes aegypti is the main vector of resurging diseases in the Americas such as yellow fever and dengue, and recently emerging chikungunya and Zika fever, which have caused unprecedented epidemics in the region. Vector control remains the primary intervention to prevent outbreaks of Aedes-transmitted diseases. In many high-risk regions, like southern Ecuador, we have limited information on IR. In this study, Ae. aegypti IR was measured across four cities in southern Ecuador using phenotypic assays and genetic screening for alleles associated with pyrethroid IR. Bottle bioassays showed significant inter-seasonal variation in resistance to deltamethrin, a pyrethroid commonly used by the Ministry of Health, and alpha-cypermethrin, as well as between-city differences in deltamethrin resistance. There was also a significant difference in phenotypic response to the organophosphate, Malathion, between two cities during the second sampling season. Frequencies of the resistant V1016I genotype ranged from 0.13 to 0.68. Frequencies of the resistant F1534C genotype ranged from 0.63 to 1.0, with sampled populations in Machala and Huaquillas at fixation for the resistant genotype in all sampled seasons. In Machala and Portovelo, there were statistically significant inter-seasonal variation in genotype frequencies for V1016I. Resistance levels were highest in Machala, a city with hyperendemic dengue transmission and historically intense insecticide use. Despite evidence that resistance alleles conferred phenotypic resistance to pyrethroids, there was not a precise correspondence between these indicators. For the F1534C gene, 17.6% of homozygous mutant mosquitoes and 70.8% of heterozygotes were susceptible, while for the V1016I gene, 45.6% homozygous mutants and 55.6% of heterozygotes were susceptible. This study shows spatiotemporal variability in IR in Ae. aegypti populations in southern coastal Ecuador, and provides an initial examination of IR in this region, helping to guide vector control efforts for Ae. aegypti.Item Open Access Slc4-like anion transporters of the larval mosquito alimentary canal.(2012) Neira Oviedo, Marco Vinicio; Linser, Paul J.Mosquito larvae exhibit luminal pH extremes along the axial length of their alimentary canal that range from very alkaline (pH > 10) in the anterior midgut to slightly acid in the hindgut. The principal buffer in the system is thought to be bicarbonate and/or carbonate, because the lumen is known to contain high levels of bicarbonate/carbonate and is surrounded by various epithelial cell types which express a variety of carbonic anhydrases. However, the precise mechanisms responsible for the transport of bicarbonate/ carbonate into and out of the lumen are unclear. In the present study, we test the hypothesis that SLC4-like anion transporters play a role in bicarbonate/carbonate accumulation in the larval mosquito alimentary canal. Molecular, physiological and immnuohistochemical characterizations of Slc4-like transporters in the gut of larval mosquitoes (Aedes aegypti and Anopheles gambiae) demonstrate the pres- ence of both a Na+-independent chloride/bicarbonate anion exchanger (AE) as well as a Na+-dependent anion exchanger (NDAE). Notably, immunolocalization experiments in Malpighian tubules show that the two proteins can be located in the same tissue, but to different cell types. Immunolabeling experi- ments in the gastric caecae show that the two proteins can be found in the same cells, but on opposite sides (basal vs. apical). In summary, our results indicate that the alimentary canal of larval mosquitoes exhibits robust expression of two SLC4-like transporters in locations that are consistent with a role in the regulation of luminal pH. The precise physiological contributions of each transporter remain to be determined.Item Open Access Successful suppression of a field mosquito population by sustained release of engineered male mosquitoes.(2012) Neira Oviedo, Marco Vinicio; Luke, AlpheyOur paper published last year described the results of preliminary release experiments showing that engineered sterile male mosquitoes could mate with females in a wild population in the Cayman Islands. This trial was supported by simple simulation models indicating that sustained release of sufficient numbers of such males should substantially suppress a target population within a few weeks or months. In the following letter, we describe a field release experiment testing this proposition. The sterile insect technique is an environmentally friendly, species-specific method of pest control that is used to successfully control several agricultural pest insects. Large numbers of sterile insects are released to mate with their wild counterparts and thereby reduce their reproductive potential. However, despite its attractive features, this technique is not in operational use against mosquitoes, in part because of damaging effects of sterilizing doses of radiation on the released mosquitoes. Following a similar principle, we have proposed that engineered males carrying a dominant lethal transgene could be released to mate with wild females; the resulting progeny would die as a result of the lethal effect of the transgene. We named this system RIDL (release of insects carrying a dominant lethal gene). The Aedes aegypti RIDL strain, OX513A, has a single transgenic sequence encoding a red fluorescent marker and tetracycline-repressible late-acting dominant lethality.Item Metadata only Thermal biology of mosquito-borne disease(2019-07-08) Neira Oviedo, Marco VinicioMosquito-borne diseases cause a major burden of disease worldwide. The vital rates of these ectothermic vectors and parasites respond strongly and nonlinearly to temperature and therefore to climate change. Here, we review how trait-based approaches can synthesise and mechanistically predict the temperature dependence of transmission across vectors, pathogens, and environments. We present 11 pathogens transmitted by 15 different mosquito species – including globally important diseases like malaria, dengue, and Zika – synthesised from previously published studies. Transmission varied strongly and unimodally with temperature, peaking at 23–29ºC and declining to zero below 9–23ºC and above 32–38ºC. Different traits restricted transmission at low versus high temperatures, and temperature effects on transmission varied by both mosquito and parasite species. Temperate pathogens exhibit broader thermal ranges and cooler thermal minima and optima than tropical pathogens. Among tropical pathogens, malaria and Ross River virus had lower thermal optima (25–26ºC) while dengue and Zika viruses had the highest (29ºC) thermal optima. We expect warming to increase transmission below thermal optima but decrease transmission above optima. Key directions for future work include linking mechanistic models to field transmission, combining temperature effects with control measures, incorporating trait variation and temperature variation, and investigating climate adaptation and migration.