Home About us Contact
|
Home About us Contact | ||
|
|
||
Main Vector (main + vector)
Selected AbstractsLarvicidal Effects of Fungal Meroterpenoids in the Control of Aedes aegypti L., the Main Vector of Dengue and Yellow FeverCHEMISTRY & BIODIVERSITY, Issue 2 2008Regina Geris Abstract The mosquito Aedes aegypti is an increasing problem of public health, being the vector responsible for dengue and Yellow Fever in tropical and subtropical regions. The aim of this work was to determine the potential larvicidal activity of a series of meroterpenoids, compounds 1,7, previously obtained fungal secondary metabolites from Penicillium sp., against the third-instar larvae of A. aegypti. The lethal concentrations (LC50 and LC90) of 1,7 were evaluated 24,h after exposure. Dehydroaustin (4) was the most active meroterpenoid in the series, with an LC50 value of 2.9,ppm, making it an attractive natural insecticide. [source] Effects of crowding on populations of Aedes albifasciatus larvae under laboratory conditionsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2000Raquel M. Gleiser Abstract Aedes (Ochlerotatus) albifasciatus (Macquart 1838) (Diptera: Culicidae) is a neotropical flood water mosquito, incriminated as the main vector of the western equine encephalitis virus, and which affects beef and milk production in central Argentina. The short time required to hatch and develop from egg to adult, usually in temporary pools, suggests a strategy which allows for exploitation of transient pools, thus evading predation and interspecific competition. Under these conditions intra specific competition could represent a major density-dependent source of larval mortality, but the relative importance of density-dependent regulation of mosquito populations has generated controversy. Therefore we examined the effects of larval density on basic population characteristics of Ae. albifasciatus in the laboratory. Larvae were obtained by synchronous hatching of eggs laid by field-trapped females. Emerging larvae (L1) were used to build cohorts of different initial densities, kept in plastic trays with 400 ml of distilled water, and food supplied daily during the first 10 days (0.1 g per larvae day,1). Age-specific development time and specific and relative mortality were estimated, and their relation to initial larval density was assessed through linear and non-linear regressions and correlation analysis. First hatching was registered 3 h after flooding the eggs. Higher levels of pre-adult mortality were detected in groups with higher densities. Specific mortality and average time to enter a stage of L1 to L3 could directly be related to initial larval density, but no significant relations were found for L4 and pupae. Results suggest that crowding could be a factor capable of regulating the density of natural populations of Ae. albifasciatus. [source] Aldehyde oxidase is coamplified with the World's most common Culex mosquito insecticide resistance-associated esterasesINSECT MOLECULAR BIOLOGY, Issue 1 2000J. Hemingway Abstract The evolution and spread of insecticide resistance is an important factor in human disease prevention and crop protection. The mosquito Culex quinquefasciatus is the main vector of the disease filariasis and a member of a species complex which is a common biting nuisance worldwide. The common insecticide resistance mechanism in this species involves germline amplification of the esterases est,21 and est,21. This amplification has arisen once and rapidly spread worldwide. Less common and more variable resistance phenotypes involve coamplification of est,3 and est,1, or individual amplification of a single est,1, different alleles of the same est, and est, gene loci. Est,21 and est,21 are on the same large fragment of amplified DNA (amplicon) 2.7 kb apart. We have now shown that this amplicon contains another full-length gene immediately 5, of est,21 which codes for a molybdenum-containing hydroxylase, with highest homology to aldehyde oxidase (AO) from other organisms. The full-length putative AO gene is not present on the est,3/est,1 or est,1 amplicons, but multiple truncated 5, ends of this gene are present around the presumed est,3/est,1 amplicon breakpoint. Polymerase chain reaction (PCR) analysis of insecticide-susceptible genomic DNA demonstrated that a different allele of the putative AO gene in its non-amplified form is immediately 5, of est,. The ,AO' gene on the est,21/est,21 amplicon is expressed and resistant insects have greater AO activity. This AO activity is sensitive to inhibition by an aldehyde-containing herbicide and pesticide. This enzyme may confer a selective advantage to these insects in the presence of insecticide, as AO in mammals is believed to be important in the detoxification process of several environmental pollutants. [source] Genetic differentiation between three ecological variants (,type', ,mysorensis' and ,intermediate') of malaria vector Anopheles stephensi (Diptera: Culicidae)INSECT SCIENCE, Issue 4 2010Vipin Abstract,Anopheles stephensi is the main vector of urban malaria in South Asia. Three ecological variants (,type', ,mysorensis'and,intermediate') of An. stephensi have been reported on the basis of ecology and egg morphology. However, it is unclear if there is any genetic isolation between the three variants. We analyzed the three variants of An. stephensi using eight microsatellite loci and found that large and significant genetic differentiation exists between them (mean FST= 0.393 and mean RST= 0.422). Pairwise estimates of genetic differentiation between the variants were ,type' versus ,mysorensis' (mean FST= 0.411 and mean RST= 0.308), ,type' versus ,intermediate' (mean FST= 0.388 and mean RST= 0.518) and ,intermediate' versus ,mysorensis' (mean FST= 0.387 and mean RST= 0.398) and all were statistically significant (P < 0.05). The greater sensitivity of RST in differentiation indicated that mutations and not genetic drift had generated the differences between three variants of An. stephensi. The present study indicated large genetic differentiation and presence of non-significant low level of gene flow between the three variants (,type', ,mysorensis'and,intermediate') of An. stephensi. [source] Functional characterization of the NF-,B transcription factor gene REL2 from Anopheles gambiaeINSECT SCIENCE, Issue 3 2007NGO T. HOA Abstract The REL2 gene plays an important role in innate immunity against both Gram (+) and Gram (-) bacteria and malaria parasites in Anopheles gambiae, the main vector of malaria in Africa. Through alternative splicing, REL2 produces two protein products, REL2F (with a Rel-homology domain as well as an inhibitory ankyrin repeat region) and REL2S (without the ankyrin repeats). In the immune-competent cell line Sua1B from An. gambiae, REL2 has been shown to be a key regulator for cecropin A (or CEC1). The high level expression of CEC1 in Sua1B was postulated to be the result of constitutive activation of REL2F. Here we showed that REL2F is indeed processed, albeit at a low level, in the Sua1B cell line. The primary cleavage requires residue 678 (an aspartic acid). Proteolytic cleavage of REL2F can be enhanced by challenge with bacteria Escherichia coli and Bacillus subtilis, but not with fungus Beauveria bassiana. The inducible cleavage can be substantially reduced by RNA interference against PGRP-LC and CASPL1. Over-expression of REL2S or a constitutively active form of REL2F (REL2F380C or REL2F678) in An. gambiae cell line can further increase expression of CEC1 and other antimicrobial peptide genes. Over-expression of these constitutive active proteins in an immune naive cell line, MSQ43, from Anopheles stephensi, results in even more dramatic increased expression of antimicrobial peptides. [source] Ecology of wildlife rabies in EuropeMAMMAL REVIEW, Issue 1 2006KATJA HOLMALA ABSTRACT 1The number of wildlife rabies cases has increased in Europe in recent years. We review the epizootiology of wildlife rabies in Europe, paying special attention to recent changes to the situation of two important vector species: the red fox and the raccoon dog. Red fox Vulpes vulpes has been the main vector of rabies since 1945, but the number and proportion of raccoon dog Nyctereutes procyonoides cases has rapidly increased during the past few years, particularly in north-eastern Europe. 2The transmission rate (average number of susceptible animals infected by each rabid animal) is critical for rabies spread and is partly determined by population density. Both raccoon dogs and foxes live in pairs. Foxes also live in family groups. Pairs and groups share their territories. Home range size usually correlates negatively with population density. Fox home ranges are 50,1500 ha, those of raccoon dogs 150,700 ha. The threshold value for rabies spread among foxes is estimated to be 0.63 individuals/km2. Although fox density in eastern and northern Europe may be lower than this, the pooled density of foxes and raccoon dogs exceeds the threshold density. 3Animal movements, especially dispersal of young, pose a risk for rabies spread. Although the likelihood of an epizootic is highest where fox and raccoon dog densities are highest, rabies may spread fastest where population densities are lower, because dispersal distances tend to correlate negatively with population density. 4Oral vaccinations have been more effective in rabies control than culling foxes. Where two vector species exist, vaccination should be conducted twice a year, because most raccoon dogs disperse in autumn but some foxes do not disperse before mid- or late winter. 5New rabies models, based on two vector species and their interaction, and which take into account the hibernation period of raccoon dogs, are needed for north-eastern Europe. [source] Genetic relationships among populations of Aedes aegypti from Uruguay and northeastern Argentina inferred from ISSR-PCR dataMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2010C. SOLIANI Aedes aegypti (L.) (Diptera: Culicidae), the main vector of yellow fever and dengue viruses, was eradicated from Argentina between 1955 and 1963, but reinvaded the country in 1986. In Uruguay, the species was reintroduced in 1997. In this study we used highly polymorphic inter-simple sequence repeats (ISSR) markers to analyse the genetic structure of Ae. aegypti populations from Uruguay and northeastern Argentina to identify possible colonization patterns of the vector. Overall genetic differentiation among populations was high (FST = 0.106) and showed no correlation with geographic distance, which is consistent with the short time since the reintroduction of the species in the area. Differentiation between pairs of Argentine populations (FST 0.072 to 0.221) was on average higher than between Uruguayan populations (FST,0.044 to 0.116). Bayesian estimation of population structure defined four genetic clusters and most populations were admixtures of two of them: Mercedes and Treinta y Tres (Uruguay) were mixtures of clusters 1 and 3; Salto (Uruguay) and Paraná (Argentina) of clusters 1 and 4; Fray Bentos (Uruguay) of clusters 2 and 3, and Gualeguaychú (Argentina) of clusters 2 and 3. Posadas and Buenos Aires in Argentina were fairly genetically homogeneous. Our results suggest that Ae. aegypti recolonized Uruguay from bordering cities in Argentina via bridges over the Uruguay River and also from Brazil. [source] Analysis of the activity patterns of two sympatric sandfly siblings of the Lutzomyia longipalpis species complex from BrazilMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2008G. B. S. RIVAS AbstractLutzomyia longipalpis s.l. (Lutz & Neiva) (Diptera: Psychodidae) is the main vector of visceral leishmaniasis in Latin America. Differences in copulation songs, pheromones and molecular markers show that L. longipalpis is a species complex in Brazil. The patterns of activity of insect vectors are important in disease transmission. In addition, differences in activity rhythms have a potential role as a temporal reproductive isolation mechanism in closely related species. We compared the activity patterns of males and females of two sympatric species of the Longipalpis complex from Sobral (Ceará State, Brazil) in controlled laboratory conditions. We observed small but significant differences between the two species in the activity phase in both males and females. [source] Spatial distribution of bluetongue virus and its Culicoides vectors in SicilyMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2004A. Torina Abstract., During the recent Mediterranean epizootic of bluetongue, an extensive programme of serological and vector (Culicoides biting midges (Diptera: Ceratopogonidae)) surveillance was carried out across Sicily. This paper presents the analysis of 911 light trap catches collected at the times of peak Culicoides abundance (summer to autumn 2000,2002) in 269 sites, in order to produce detailed maps of the spatial distribution of the main European vector, Culicoides imicola Kieffer and that of potential novel vectors. Whereas C. imicola was found at only 12% of sites, potential novel vectors, Culicoides obsoletus group Meigen, Culicoides pulicaris Linnaeus and Culicoides newsteadi Austen were present at over 50% of sites. However, the spatial distribution of C. imicola showed the closest correspondence to that of the 2000 and 2001 bluetongue (BT) outbreaks and its presence and abundance were significant predictors of the probability of an outbreak, suggesting that it was the main vector during these years. Although C. imicola may have played a role in transmission in several sites near Paternó, it was absent from the majority of sites at which outbreaks occurred in 2002 and from all sites in the province of Messina. All three potential novel vectors were widespread across sites at which outbreaks occurred during 2002. Of these, C. newsteadi was an unlikely candidate, as it was significantly less prevalent in outbreak vs. non-outbreak sites in Messina. It is hypothesized that the yearly distribution and intensity of outbreaks is directly attributable to the distribution and abundance of the vectors involved in transmission during each year. When C. imicola operated as the main vector in 2000 and 2001, outbreaks were few in number and were restricted to coastal regions due to low abundance and prevalence of this species. In 2002, it is hypothesized that BTV transmission was handed over to more prevalent and abundant novel vector species, leading to numerous and widespread outbreaks and probably to overwintering of the virus between 2001 and 2002. Based on catch ranges in outbreak vs. non-outbreak sites, it is tentatively suggested that nightly catches of 400 or more C. obsoletus and 150 or more C. pulicaris allow BTV transmission at a site, and provide a strategy for a fuller examination of the relationship between BTV transmission and the abundance and distribution of different vector species. [source] Mitochondrial and Wolbachia markers for the sandfly Phlebotomus papatasi: little population differentiation between peridomestic sites and gerbil burrows in Isfahan province, IranMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2003P. Parvizi Abstract., In Iran, Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) is the main vector of Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae), the causative agent of rural zoonotic cutaneous leishmaniasis. This sandfly is abundant both in villages and in the burrows of the main reservoir host, the gerbil Rhombomys opimus (Licht.) (Rodentia: Gerbillidae). Populations of P. papatasi were sampled from the edges of villages in Isfahan province, using CDC miniature light traps in peridomestic sites and sticky papers placed at the entrances to gerbil burrows. Single peridomestic sites in two northern provinces were also sampled. Individual sandflies were characterized by PCR amplification and sequencing of fragments of their mitochondrial cytochrome b gene and of the wsp gene of endosymbiotic Wolbachia pipientis Hertig (alpha-Proteobacteria: Rickettsiaceae). The distributions of the haplotypes of these two maternally inherited genes were analysed to assess the population differentiation of P. papatasi, knowledge of which will be needed for planning control measures. For the first time these markers were used to characterize P. papatasi from gerbil burrows, and they indicated the absence not only of sympatric cryptic species but also of any long-term differentiation of lineages in different habitats. A single lineage of cytochrome b haplotypes was found, and both sexes in all populations had a high infection rate of the same A-group strain of Wolbachia (wPap). The distributions of cytochrome b haplotypes were consistent with females dispersing more than males, which has been reported for P. papatasi in other countries. The widespread distribution of wPap suggests that Wolbachia could be used to spread transgenes between populations of P. papatasi in different habitats. [source] Genetic inherence of the response to human kairomones by two allopatric members of the Lutzomyia longipalpis complexPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2006E. A. Rebollar-Téllez Abstract., The sandfly Lutzomyia longipalpis (Lutz & Neiva) is the main vector of Leishmania infantum in the New World. Several studies show that Lu. longipalpis is a species complex of at least three members. The feeding habits among the members of the complex vary from one geographical location to another. These differences in feeding habits may be related to differences between different members of the complex. The present study investigates differences in the response to human kairomones by two members of the complex, as well as the possibility that differences in the response have a genetic basis. One of the members used in this study is from Jacobina Bahia State, Brazil. Males from this population are known to produce a sex pheromone characterized by a C16 molecule identified as 3-methyl-,-himachelene. The other member is from a population originating in Marajó Island, Pará State, Brazil. Males from this location secrete a sex pheromone characterized by a C20 molecule whose structure remains to be elucidated, but is known to be a diterpene type. Our findings indicate that Jacobina females are significantly more responsive to human odours than Marajo females. When Jacobina and Marajó populations of Lu. longipalpis complex are cross-mated, the response of F1 females to the human odours is found to be genetically controlled. [source] Epidemiology of sharka disease in SpainEPPO BULLETIN, Issue 2 2006M. Cambra PPV was first detected in Spain in 1984 in Japanese plum (Prunus salicina Lindl) cv. Red Beaut and spread very quickly to other Japanese and European plums and apricot cultivars but left peach cultivars unaffected. In the years following the detection of PPV, the predominant aphid species visiting Prunus orchards in Mediterranean areas were Aphis gossypii followed by Aphis spiraecola, the latter being the main aphid species found at present. Both species are considered to be the main vectors of PPV in Spanish early Prunus growing areas. Spatial analysis of the spread of PPV-D in Japanese plum and apricot trees confirmed the lack of significant association between immediately adjacent trees. The observed spatial pattern of sharka suggests a lack of movement of PPV-viruliferous aphid vectors to immediately adjacent trees and indicates their preferential movement to trees several tree spaces away. PPV-D is the only type currently present in Spain, with the exception of a PPV-M outbreak that was detected in and successfully eradicated from Aragón in 2002. The short-distance spread of PPV-M infection occurred as far as 12 m along the rows of peach trees. However, PPV-D has not been observed to spread through peach cultivars, despite being grown in the vicinity of heavily infected plots of apricot or Japanese plum trees. [source] The feasibility of developing a risk assessment for the impact of climate change on the emergence of Crimean-Congo haemorrhagic fever in livestock in Europe: a ReviewJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2010P. Gale Summary Crimean-Congo haemorrhagic fever virus (CCHFV) is one of the most widespread of all medically important arboviruses with ticks of the Hyalomma spp. serving as the main vectors. Infection of livestock by CCHFV serves as a route of exposure to humans, as a reservoir of disease and as a route of importation. This study discusses the pathways and data requirements for a qualitative risk assessment for the emergence of CCHFV in livestock in Europe. A risk map approach is proposed based on layers that include the potential routes of release (e.g. by migrating birds carrying infected ticks) together with the main components for exposure, namely the distributions of the tick vectors, the small vertebrate host reservoirs and the livestock. A layer on landscape fragmentation serves as a surrogate for proximity of livestock to the tick cycle. Although the impact of climate change on the emergence of CCHF is not clear, comparing the distribution of risk factors in each layer currently with those predicted in the 2080s with climate change can be used to speculate how potential high-risk areas may shift. According to the risk pathway, transstadial and/or transovarial transmission in the tick vector are crucial for CCHFV spread. Vector competence and tick vector switching, however, remain critical factors for CCHFV colonization of new regions in Europe. The species of migratory bird is also an important consideration in the release assessment with greater abundance and biodiversity of ground-dwelling birds in southern Europe than in northern Europe. [source] Gene therapy for rheumatoid arthritisTHE JOURNAL OF GENE MEDICINE, Issue 6 2002Natacha Bessis Abstract Rheumatoid arthritis (RA) is a severe autoimmune systemic disease. Chronic synovial inflammation results in destruction of the joints. No conventional treatment is efficient in RA. Gene therapy of RA targets mainly the players of inflammation or articular destruction: TNF-, or IL-1 blocking agents (such as anti-TNF-, monoclonal antibodies, soluble TNF-, receptor, type II soluble receptor of IL-1, IL-1 receptor antagonist), antiinflammatory cytokines (such as IL-4, IL-10, IL-1), and growth factors. In this polyarticular disease, the vector expressing the therapeutic protein can be administered as a local (intra-articular injection) or a systemic treatment (extra-articular injection). All the main vectors have been used in experimental models, including the more recent lentivirus and adeno-associated virus. Ex vivo gene transfer was performed with synovial cells, fibroblasts, T cells, dendritic cells, and different cells from xenogeneic origin. In vivo gene therapy is simpler, although a less controlled method. Clinical trials in human RA have started with ex vivo retrovirus-expressing IL-1 receptor antagonists and have demonstrated the feasibility of the strategy of gene therapy. The best target remains to be determined and extensive research has to be conducted in preclinical studies. Copyright © 2002 John Wiley & Sons, Ltd. [source] T-Wave Morphology in Short QT SyndromeANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009Olli Anttonen M.D. Background: Short QT syndrome (SQTS) is an inherited disorder characterized by a short QT interval and vulnerability to ventricular tachyarrhythmias. The diagnostic criteria for this syndrome are not well defined, since there is uncertainty about the lowest normal limits for the corrected QT (QTc) interval. Objective: The aim of this study was to determine whether T-wave morphology parameters are abnormal in short QT subjects and whether those parameters can help in the diagnosis of SQTS. Methods and Results: We describe three families (10 patients) with short QT intervals (QTc 310 ± 32 ms). Seven subjects had suffered serious arrhythmic events and three were asymptomatic. T-wave morphology was assessed using the principal component analysis (PCA). QTc was significantly shorter and T-wave amplitude in lead V2 higher in the short QT subjects compared to healthy controls (n = 149), (P < 0.001 for both). The total cosine of the angle between the main vectors of the QRS and T-wave loops (TCRT) was markedly abnormal among the symptomatic patients with short QT syndrome (n = 7) (TCRT ,0.14 ± 0.55 vs 0.36 ± 0.51, P = 0.019). None of the three asymptomatic patients with short QT but without a history of arrhythmic events had an abnormally low TCRT. Conclusion: Our observations suggest that patients with a short QT interval and a history of arrhythmic events have abnormal T-wave loop parameters. These electrocardiogram (ECG) features may help in the diagnosis of SQTS in addition to the measurement of the duration of QT interval from the 12-lead ECG. [source] | ||||||||||