Competição entre larvas de Aedes aegypti e Aedes albopictus em laboratório

Este estudo teve como objetivo avaliar os efeitos da competição larval intra e interespecífica entre Aedes aegypti e Aedes albopictus, sobre sobrevivência de larvas, tempo de desenvolvimento e comprimento de asa. O experimento foi realizado em três densidades com 5 proporções das espécies. A sobrevivência de Aedes aegypti apresentou-se superior a de Aedes albopictus em densidade intermediária e inferior em densidade alta. Somente Aedes albopictus teve seu tempo de desenvolvimento afetado. Diferenças encontradas nas comparações das combinações das espécies demonstraram que o comprimento médio de asas de Aedes aegypti, no geral, foi maior que Aedes albopictus. Nas duas espécies, a competição afetou mais o comprimento de asa e a sobrevivência que o tempo de desenvolvimento. Aedes aegypti parece apresentar maior capacidade competitiva em relação a Aedes albopictus em densidade intermediária.

Evaluation of oviposition traps as an entomological surveillance method for Aedes aegypti (Diptera, Culicidae)

This study aimed to describe the behavior of oviposition traps for Aedes aegypti over time, to compare it with the larval survey and to investigate the association with climatic variables. It was conducted in São José do Rio Preto city, São Paulo. Daily climatic data and fortnightly measurements for oviposition traps and larval infestation were collected from October 2003 to September 2004. Three different periods were identified in the behavior of oviposition traps' positivity and mean number of eggs: increase, plateau and decrease in values. These measurements followed the variation of climatic data from the first and third periods. High correlation was obtained between the positivity and the mean number of eggs. The oviposition traps showed higher capacity to detect the vector than did larval survey. It was observed that the first (October to December) and third (May to September) periods were considered to be the most suitable to use oviposition traps than larval surveys.

Estimação da infestação predial por Aedes aegypti (Díptera: Culicidae) por meio da armadilha Adultrap

Foi utilizada a armadilha Adultrap em uma amostra de domicílio preconizada pelo levantamento de índice rápido de infestação por Aedes aegypti (LIRAa) para mensuração do número de adulto de Aedes aegypti no domicílio. Foi vistoriada uma média de 555 imóveis mês: 15 unidades continham criadouros da espécie; e 53, a presença de fêmeas. O índice de infestação para larva/pupa (IPL) variou de zero ao máximo de 4,9 por cento, enquanto o índice de infestação para adulto (IPA), de 2,21 a 17,32 por cento. O teste de MacNemar mostrou diferenças significativas entre a positividade de IPL e IPA em todos os meses do ano. Além disso, detectaram-se fêmeas de Ae. Aegypti em período de baixa densidade populacional, sem o caráter invasivo e incômodo da pesquisa de recipientes para o IPL. A Adultrap mostrou-se útil para revelar situações propícias à transmissão da dengue, bem como de fácil operacionalidade

Proteção de Bromeliaceae para evitar a formação de criadouros de Aedes aegypti (Diptera: Culicidae)

As plantas da família bromeliaceae constituem criadouros de Aede aegypti. O presente estudo de campo mostrou que medidas mecânicas podem ser uma solução para o controle do mosquito nessas plantas. Na região norte do estado do Paraná, área de infestação por Ae. aegypti, q5 bromélias foram monitoradas durante um ano após receberem tratamento com palha de madeira e cascas de árvore. Nesse período não foram observadas formas imaturas de mosquitos, o que sugere que o uso deste material natural pode servir como medida complementar aos programas de controle vetorial.

Blood Meal-Derived Heme Decreases ROS Levels in the Midgut of Aedes aegypti and Allows Proliferation of Intestinal Microbiota

The presence of bacteria in the midgut of mosquitoes antagonizes infectious agents, such as Dengue and Plasmodium, acting as a negative factor in the vectorial competence of the mosquito. Therefore, knowledge of the molecular mechanisms involved in the control of midgut microbiota could help in the development of new tools to reduce transmission. We hypothesized that toxic reactive oxygen species (ROS) generated by epithelial cells control bacterial growth in the midgut of Aedes aegypti, the vector of Yellow fever and Dengue viruses. We show that ROS are continuously present in the midgut of sugar-fed (SF) mosquitoes and a blood-meal immediately decreased ROS through a mechanism involving heme-mediated activation of PKC. This event occurred in parallel with an expansion of gut bacteria. Treatment of sugar-fed mosquitoes with increased concentrations of heme led to a dose dependent decrease in ROS levels and a consequent increase in midgut endogenous bacteria. In addition, gene silencing of dual oxidase (Duox) reduced ROS levels and also increased gut flora. Using a model of bacterial oral infection in the gut, we show that the absence of ROS resulted in decreased mosquito resistance to infection, increased midgut epithelial damage, transcriptional modulation of immune-related genes and mortality. As heme is a pro-oxidant molecule released in large amounts upon hemoglobin degradation, oxidative killing of bacteria in the gut would represent a burden to the insect, thereby creating an extra oxidative challenge to the mosquito. We propose that a controlled decrease in ROS levels in the midgut of Aedes aegypti is an adaptation to compensate for the ingestion of heme.

Structure of an Odorant-Binding Protein from the Mosquito Aedes aegypti Suggests a Binding Pocket Covered by a pH-Sensitive ""Lid""

Background: The yellow fever mosquito, Aedes aegypti, is the primary vector for the viruses that cause yellow fever, mostly in tropical regions of Africa and in parts of South America, and human dengue, which infects 100 million people yearly in the tropics and subtropics. A better understanding of the structural biology of olfactory proteins may pave the way for the development of environmentally-friendly mosquito attractants and repellents, which may ultimately contribute to reduction of mosquito biting and disease transmission. Methodology: Previously, we isolated and cloned a major, female-enriched odorant-binding protein (OBP) from the yellow fever mosquito, AaegOBP1, which was later inadvertently renamed AaegOBP39. We prepared recombinant samples of AaegOBP1 by using an expression system that allows proper formation of disulfide bridges and generates functional OBPs, which are indistinguishable from native OBPs. We crystallized AaegOBP1 and determined its three-dimensional structure at 1.85 angstrom resolution by molecular replacement based on the structure of the malaria mosquito OBP, AgamOBP1, the only mosquito OBP structure known to date. Conclusion: The structure of AaegOBP1 (= AaegOBP39) shares the common fold of insect OBPs with six alpha-helices knitted by three disulfide bonds. A long molecule of polyethylene glycol (PEG) was built into the electron-density maps identified in a long tunnel formed by a crystallographic dimer of AaegOBP1. Circular dichroism analysis indicated that delipidated AaegOBP1 undergoes a pH-dependent conformational change, which may lead to release of odorant at low pH (as in the environment in the vicinity of odorant receptors). A C-terminal loop covers the binding cavity and this ""lid"" may be opened by disruption of an array of acid-labile hydrogen bonds thus explaining reduced or no binding affinity at low pH.

Effects of Plasmodium gallinaceum on hemolymph physiology of Aedes aegypti during parasite development

Insect disease vectors show diminished fecundity when infected with Plasmodium. This phenomenon has already been demonstrated in laboratory models such as Aedes aegypti, Anopheles gambiae and Anopheles stephensi. This study demonstrates several changes in physiological processes of A. aegypti occurring upon infection with Plasmodium gallinaceum, such as reduced ecdysteroid levels in hemolymph as well as altered expression patterns for genes involved in vitellogenesis, lipid transport and immune response. Furthermore, we could show that P. gallinaceum infected A. aegypti presented a reduction in reproductive fitness, accompanied by an activated innate immune response and increase in lipophorin expression, with the latter possibly representing a nutritional resource for Plasmodium sporozoites. (C) 2010 Elsevier Ltd. All rights reserved.

A novel trypsin Kazal-type inhibitor from Aedes aegypti with thrombin coagulant inhibitory activity

Kazal-type inhibitors play several important roles in invertebrates, such as anticoagulant, vasodilator and antimicrobial activities. Putative Kazal-type inhibitors were described in several insect transcriptomes. In this paper we characterized for the first time a Kazal unique domain trypsin inhibitor from the Aedes aegypti mosquito. Previously, analyses of sialotranscriptome of A. aegypti showed the potential presence of a Kazal-type serine protease inhibitor, in female salivary glands, carcass and also in whole male, which we named AaTI (A. aegypti trypsin inhibitor). AaTI sequence showed amino acid sequence similarity with insect thrombin inhibitors, serine protease inhibitor from Litopenaeus vannamei hemocytes and tryptase inhibitor from leech Hirudo medicinalis (LDTI). In this work we expressed, purified and characterized the recombinant AaTI (rAaTI). Molecular weight of purified rAaTI was 7 kDa rAaTI presented dissociation constant (K(i)) of 0.15 and 3.8 nM toward trypsin and plasmin, respectively, and it weakly inhibited thrombin amidolytic activity. The rAaTI was also able to prolong prothrombin time, activated partial thromboplastin time and thrombin time. AaTI transcription was confirmed in A. aegypti female salivary gland and gut 3 h and 24 h after blood feeding, suggesting that this molecule can act as anticoagulant during the feeding and digestive processes. Its transcription in larvae and pupae suggested that AaTI may also play other functions during the mosquito`s development. (C) 2010 Elsevier Masson SAS. All rights reserved.

The Aedes aegypti larval transcriptome: a comparative perspective with emphasis on trypsins and the domain structure of peritrophins

The genome sequence of Aedes aegypti was recently reported. A significant amount of Expressed Sequence Tags (ESTs) were sequenced to aid in the gene prediction process. In the present work we describe an integrated analysis of the genomic and EST data, focusing on genes with preferential expression in larvae (LG), adults (AG) and in both stages (SG). A total of 913 genes (5.4% of the transcript complement) are LG, including ion transporters and cuticle proteins that are important for ion homeostasis and defense. From a starting set of 245 genes encoding the trypsin domain, we identified 66 putative LG, AG, and SG trypsins by manual curation. Phylogenetic analyses showed that AG trypsins are divergent from their larval counterparts (LG), grouping with blood-induced trypsins from Anopheles gambiae and Simulium vittatum. These results support the hypothesis that blood-feeding arose only once, in the ancestral Culicomorpha. Peritrophins are proteins that interlock chitin fibrils to form the peritrophic membrane (PM) that compartmentalizes the food in the midgut. These proteins are recognized by having chitin-binding domains with 6 conserved Cys and may also present mucin-like domains (regions expected to be highly O-glycosylated). PM may be formed by a ring of cells (type 2, seen in Ae. aegypti larvae and Drosophila melanogaster) or by most midgut cells (type 1, found in Ae. aegypti adult and Tribolium castaneum). LG and D. melanogaster peritrophins have more complex domain structures than AG and T. castaneum peritrophins. Furthermore, mucin-like domains of peritrophins from T. castaneum (feeding on rough food) are lengthier than those of adult Ae. aegypti (blood-feeding). This suggests, for the first time, that type 1 and type 2 PM may have variable molecular architectures determined by different peritrophins and/or ancillary proteins, which may be partly modulated by diet.

LARVICIDAL ACTIVITY OF GRANDISIN AGAINST AEDES AEGYPTI

Dengue is a tropical disease caused by an arbovirus transmitted by the mosquito Aedes aegypti. Because no effective vaccine is available for the disease, the strategy for its prevention has focused on vector control by the use of natural insecticides. The aim of this study was to evaluate the larvicidal activity of the lignan grandisin, a leaf extract from Piper solmsianum, against Ae. aegypti.

Triagem sorológica e influência do conhecimento sobre a dengue em pacientes do ambulatório de especialidades do SUS

INTRODUÇÃO: A dengue é causa de preocupação em países como o Brasil. OBJETIVO: Verificar a soropositividade dos pacientes do ambulatório de especialidades do Sistema Único de Saúde (SUS) para anticorpos antidengue, relacionando os resultados com os dados sociodemográficos. METODOLOGIA: Foram respondidos 184 questionários de avaliação sociodemográfica e de conhecimento sobre a transmissão da dengue. Foi utilizado o método de imunoensaio enzimático (ELISA) para pesquisar imunoglobulina da classe M (IgM) e da classe G (IgG) contra os vírus. RESULTADOS: Quinze por cento dos pacientes apresentaram IgG contra o vírus, sem a presença de IgM. CONCLUSÃO: Os pacientes demonstraram conhecimento sobre a doença e sua prevenção, independentemente da classe econômica. A infecção assintomática deve ser avaliada, principalmente nos casos de doença febril.

System Identification and Prediction of Dengue Fever Incidence in Rio de Janeiro

Identification, prediction, and control of a system are engineering subjects, regardless of the nature of the system. Here, the temporal evolution of the number of individuals with dengue fever weekly recorded in the city of Rio de Janeiro, Brazil, during 2007, is used to identify SIS (susceptible-infective-susceptible) and SIR (susceptible-infective-removed) models formulated in terms of cellular automaton (CA). In the identification process, a genetic algorithm (GA) is utilized to find the probabilities of the state transition S -> I able of reproducing in the CA lattice the historical series of 2007. These probabilities depend on the number of infective neighbors. Time-varying and non-time-varying probabilities, three different sizes of lattices, and two kinds of coupling topology among the cells are taken into consideration. Then, these epidemiological models built by combining CA and GA are employed for predicting the cases of sick persons in 2008. Such models can be useful for forecasting and controlling the spreading of this infectious disease.

Spatio-Temporal Tracking and Phylodynamics of an Urban Dengue 3 Outbreak in Sao Paulo, Brazil

The dengue virus has a single-stranded positive-sense RNA genome of similar to 10.700 nucleotides with a single open reading frame that encodes three structural (C, prM, and E) and seven nonstructural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins. It possesses four antigenically distinct serotypes (DENV 1-4). Many phylogenetic studies address particularities of the different serotypes using convenience samples that are not conducive to a spatio-temporal analysis in a single urban setting. We describe the pattern of spread of distinct lineages of DENV-3 circulating in Sao Jose do Rio Preto, Brazil, during 2006. Blood samples from patients presenting dengue-like symptoms were collected for DENV testing. We performed M-N-PCR using primers based on NS5 for virus detection and identification. The fragments were purified from PCR mixtures and sequenced. The positive dengue cases were geo-coded. To type the sequenced samples, 52 reference sequences were aligned. The dataset generated was used for iterative phylogenetic reconstruction with the maximum likelihood criterion. The best demographic model, the rate of growth, rate of evolutionary change, and Time to Most Recent Common Ancestor (TMRCA) were estimated. The basic reproductive rate during the epidemics was estimated. We obtained sequences from 82 patients among 174 blood samples. We were able to geo-code 46 sequences. The alignment generated a 399-nucleotide-long dataset with 134 taxa. The phylogenetic analysis indicated that all samples were of DENV-3 and related to strains circulating on the isle of Martinique in 2000-2001. Sixty DENV-3 from Sao Jose do Rio Preto formed a monophyletic group (lineage 1), closely related to the remaining 22 isolates (lineage 2). We assumed that these lineages appeared before 2006 in different occasions. By transforming the inferred exponential growth rates into the basic reproductive rate, we obtained values for lineage 1 of R(0) = 1.53 and values for lineage 2 of R(0) = 1.13. Under the exponential model, TMRCA of lineage 1 dated 1 year and lineage 2 dated 3.4 years before the last sampling. The possibility of inferring the spatio-temporal dynamics from genetic data has been generally little explored, and it may shed light on DENV circulation. The use of both geographic and temporally structured phylogenetic data provided a detailed view on the spread of at least two dengue viral strains in a populated urban area.

The Function and Three-Dimensional Structure of a Thromboxane A(2)/Cysteinyl Leukotriene-Binding Protein from the Saliva of a Mosquito Vector of the Malaria Parasite

The highly expressed D7 protein family of mosquito saliva has previously been shown to act as an anti-inflammatory mediator by binding host biogenic amines and cysteinyl leukotrienes (CysLTs). In this study we demonstrate that AnSt-D7L1, a two-domain member of this group from Anopheles stephensi, retains the CysLT binding function seen in the homolog AeD7 from Aedes aegypti but has lost the ability to bind biogenic amines. Unlike any previously characterized members of the D7 family, AnSt-D7L1 has acquired the important function of binding thromboxane A(2) (TXA(2)) and its analogs with high affinity. When administered to tissue preparations, AnSt-D7L1 abrogated Leukotriene C(4) (LTC(4))-induced contraction of guinea pig ileum and contraction of rat aorta by the TXA(2) analog U46619. The protein also inhibited platelet aggregation induced by both collagen and U46619 when administered to stirred platelets. The crystal structure of AnSt-D7L1 contains two OBP-like domains and has a structure similar to AeD(7). In AnSt-D7L1, the binding pocket of the C-terminal domain has been rearranged relative to AeD7, making the protein unable to bind biogenic amines. Structures of the ligand complexes show that CysLTs and TXA(2) analogs both bind in the same hydrophobic pocket of the N-terminal domain. The TXA(2) analog U46619 is stabilized by hydrogen bonding interactions of the omega-5 hydroxyl group with the phenolic hydroxyl group of Tyr 52. LTC(4) and occupies a very similar position to LTE(4) in the previously determined structure of its complex with AeD7. As yet, it is not known what, if any, new function has been acquired by the rearranged C-terminal domain. This article presents, to our knowledge, the first structural characterization of a protein from mosquito saliva that inhibits collagen mediated platelet activation.

THE TEMPO AND MODE OF EVOLUTION OF TRANSPOSABLE ELEMENTS AS REVEALED BY MOLECULAR PHYLOGENIES RECONSTRUCTED FROM MOSQUITO GENOMES

Although many mathematical models exist predicting the dynamics of transposable elements (TEs), there is a lack of available empirical data to validate these models and inherent assumptions. Genomes can provide a snapshot of several TE families in a single organism, and these could have their demographics inferred by coalescent analysis, allowing for the testing of theories on TE amplification dynamics. Using the available genomes of the mosquitoes Aedes aegypti and Anopheles gambiae, we indicate that such an approach is feasible. Our analysis follows four steps: (1) mining the two mosquito genomes currently available in search of TE families; (2) fitting, to selected families found in (1), a phylogeny tree under the general time-reversible (GTR) nucleotide substitution model with an uncorrelated lognormal (UCLN) relaxed clock and a nonparametric demographic model; (3) fitting a nonparametric coalescent model to the tree generated in (2); and (4) fitting parametric models motivated by ecological theories to the curve generated in (3).