Juvenile hormone III (JH) plays a key role in regulating the reproduction of female mosquitoes. Microarray time-course analysis revealed dynamic changes in gene expression during posteclosion (PE) ...development in the fat body of female Aedes aegypti . Hierarchical clustering identified three major gene clusters: 1,843 early-PE (EPE) genes maximally expressed at 6 h PE, 457 mid-PE (MPE) genes at 24 h PE, and 1,815 late-PE (LPE) genes at 66 h PE. The RNAi microarray screen for the JH receptor Methoprene-tolerant (Met) showed that 27% of EPE and 40% of MPE genes were up-regulated whereas 36% of LPE genes were down-regulated in the absence of this receptor. Met repression of EPE and MPE and activation of LPE genes were validated by an in vitro fat-body culture experiment using Met RNAi. Sequence motif analysis revealed the consensus for a 9-mer Met-binding motif, CACG C/ TG ᴬ/ Gᵀ/ AG. Met-binding motif variants were overrepresented within the first 300 bases of the promoters of Met RNAi–down-regulated (LPE) genes but not in Met RNAi–up-regulated (EPE) genes. EMSAs using a combination of mutational and anti-Met antibody supershift analyses confirmed the binding properties of the Met consensus motif variants. There was a striking temporal separation of expression profiles among major functional gene groups, with carbohydrate, lipid, and xenobiotics metabolism belonging to the EPE and MPE clusters and transcription and translation to the LPE cluster. This study represents a significant advancement in the understanding of the regulation of gene expression by JH and its receptor Met during female mosquito reproduction.
In Europe, the air-borne accidental introduction of exotic mosquito species (EMS) has been demonstrated using mosquito surveillance schemes at Schiphol International Airport (Amsterdam, The ...Netherlands). Based upon these findings and given the increasing volume of air transport movements per year, the establishment of EMS after introduction via aircraft is being considered a potential risk. Here we present the airport surveillance results performed by the Centre for Monitoring of Vectors of the Netherlands, by the Monitoring of Exotic Mosquitoes (MEMO) project in Belgium, and by the Public Health England project on invasive mosquito surveillance. The findings of our study demonstrate the aircraft mediated transport of EMS into Europe from a wide range of possible areas in the world. Results show accidental introductions of
and
, as well as exotic
and
specimens. The findings of
at Schiphol airport are the first evidence of accidental introduction of the species using this pathway in Europe. Furthermore, our results stress the importance of the use of molecular tools to validate the morphology-based species identifications. We recommend monitoring of EMS at airports with special attention to locations with a high movement of cargo and passengers.
•In T. infestans CPR activity is crucial for P450-mediated deltamethrin detoxification.•Silencing of the CPR increased susceptibility to deltamethrin in resistant strain.•P450 detoxification is ...involved in reducing susceptibility in resistant strain.
The enzyme NADPH-cytochrome P450 reductase (CPR) plays a central role in cytochromes P450 activity. Gene expression analysis of cytochromes P450 and CPR in deltamethrin-resistant and susceptible populations revealed that P450s genes are involved in the development of insecticide resistance in Triatoma infestans. To clarify the role of cytochromes P450 in insecticide resistance, it was proposed to investigate the effect of CPR gene silencing by RNA interference (RNAi) in a pyrethroid resistant population of T. infestans. Silencing of the CPR gene showed a significant increase in susceptibility to deltamethrin in the population analysed. This result support the hypothesis that the metabolic process of detoxification mediated by cytochromes P450 contributes to the decreased deltamethrin susceptibility observed in the resistant strain of T. infestans.
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The Asian tiger mosquito Aedes albopictus (Skuse 1894), which is native to Southeast Asia, is among the top 100 invasive species worldwide and one of the most troubling vector species. It has become ...established in more than 20 European countries. Since its arrival in Italy in the 1990s, the species has colonized all the regions of the country, up to an altitude of 600 m. Nevertheless, no thorough investigation has ever been performed to confirm or extend its elevation limit (EL) in Italy.
To define the EL of Ae. albopictus and analyse its phenology along an altitudinal gradient, we carried out an investigation by means of ovitraps placed in Lazio region, central Italy. Sampling was performed on a weekly basis in 13 villages within five 200-m altitudinal ranges 0-1000 m above sea level (asl), with the addition of higher localities to the species range whenever the species was recorded in the highest range.
Aedes albopictus has colonized sites well beyond its known EL, with established populations at 900 m asl and positive ovitraps recorded at 1193 m asl. The relationship between egg abundance and elevation was described by an exponential decay regression, which predicted an EL for oviposition at 1015 m asl. In the active season, egg-laying started earlier at low altitude and ended earlier within the highest altitudinal range. Aedes albopictus abundance and activity period (number of days active) decreased, respectively, by 95% and 34% from the lowest to the highest altitudinal range.
Using data from the present study, the altitudinal limit of Ae. albopictus in central Italy was updated from 600 to 900 m asl. In addition, established populations were predicted to exist up to 1015 m asl. Considering that up to 99.5% of Lazio region's inhabitants could potentially be affected by Aedes-borne virus outbreaks, the surveillance area for Ae. albopictus should be expanded accordingly. However, our results also indicate that Ae. albopictus surveillance programs need to be revised in order to harmonize the resources earmarked for these with the altitudinal changes in the phenology of this species.
Metabolic resistance to chemical insecticides implies a greater capacity to detoxify insecticides due to an increase in the expression of genes and/or in the activity of enzymes related to ...detoxification metabolism. The insect integument is known to participate as the cuticular penetration factor of resistance, but recently this tissue was also linked with metabolic resistance due to P450-dependent detoxification in the Chagas disease vector Triatoma infestans. The objectives of this study were i) to name and classify all P450s known to date in T. infestans, ii) to characterise one of them, CYP4PR1, representing the first member of a new cytochrome P450 subfamily described in insects, and iii) to investigate the potential role of CYP4PR1 in metabolic resistance to deltamethrin in T. infestans. We found that CYP4PR1 is expressed almost exclusively in the integument tissue, and its expression was not induced by deltamethrin. Knockdown of CYP4PR1 by RNA interference in pyrethroid-resistant nymphs caused a significant increment in insect mortality after topical application of two different doses of deltamethrin. These results support the role of the integument on metabolic resistance and suggest that CYP4PR1 might contribute to resistance in integument tissue of T. infestans.
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•We identified CYP4PR1 as the first member of a new cytochrome P450 subfamily described in insects.•CYP4PR1 is highly expressed in the integument tissue of deltametrhin- resistant T. infestans nymphs.•Knockdown of CYP4PR1 resulted in increased mortality after topical application of deltamethrin.
La Crosse virus (LACV), a leading cause of arboviral encephalitis in children in the United States, is emerging in Appalachia. For local arboviral surveillance, mosquitoes were tested. LACV RNA was ...detected and isolated from Aedes japonicus mosquitoes. These invasive mosquitoes may significantly affect LACV range expansion and dynamics.
The triatomine
is the main vector of Chagas disease in countries such as Colombia and Venezuela, and the first kissing bug whose genome has been sequenced and assembled. In the repetitive genome ...fraction (repeatome) of this species, the transposable elements represented 19% of
genome, being mostly DNA transposon (Class II elements). However, scarce information has been published regarding another important repeated DNA fraction, the satellite DNA (satDNA), or satellitome. Here, we offer, for the first time, extended data about satellite DNA families in the
genome using bioinformatics pipeline based on low-coverage sequencing data. The satellitome of
represents 8% of the total genome and it is composed by 39 satDNA families, including four satDNA families that are shared with
, as well as telomeric (TTAGG)
and (GATA)
repeats, also present in the
genome. Only three of them exceed 1% of the genome. Chromosomal hybridization with these satDNA probes showed dispersed signals over the euchromatin of all chromosomes, both in autosomes and sex chromosomes. Moreover, clustering analysis revealed that most abundant satDNA families configured several superclusters, indicating that
satellitome is complex and that the four most abundant satDNA families are composed by different subfamilies. Additionally, transcription of satDNA families was analyzed in different tissues, showing that 33 out of 39 satDNA families are transcribed in four different patterns of expression across samples.
•The cat flea, Ctenocephalides felis, is an ectoparasite and a disease vector.•Studies on salivary glands enrich knowledge of vector-pathogen-host interactions.•Pictorial dissection guide facilitates ...research of flea salivary gland molecules.•We illustrated dynamic changes in salivary gland morphology upon blood feeding.•We complemented existing drawings and histology images of flea internal anatomy.
Fleas are morphologically unique ectoparasites that are hardly mistaken for any other insect. Most flea species that feed on humans and their companion animals, including the cat flea (Ctenocephalides felis), have medical and veterinary importance. Besides facilitating blood acquisition, salivary biomolecules can modulate pathogen transmission. Thus, dissection of salivary glands is essential for comprehensive studies on disease vectors like the cat flea. Herein, we present the pictorial dissection protocol assisting future research targeting individual flea organs, for revealing their roles in vector competence and physiology. We provide a comprehensive guide, allowing researchers, even with limited practical experience, to successfully perform microdissection for collecting cat flea salivary glands. Furthermore, the protocol does not require expensive, sophisticated equipment and can be accomplished with routinely available tools. We illustrated expected results with morphological changes of salivary glands upon blood feeding as well as fluorescently stained these organs.
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•Aquatic plant extracts and presence affect mosquito mortality and development.•Lagarosiphon major and Lemna minuta extracts are significantly toxic on Culex.•Floating Lemna minor and L. minuta ...caused significant mortality physically.•Larval mosquito pupation and adult emergence can be significantly reduced.•Plant extracts and presence have species-specific effects on mosquitoes.
Environmental concerns and insecticide resistance threaten the sustained efficacy of mosquito control approaches which remain reliant on synthetic chemicals. Plant-based extracts may be an environmentally sustainable and effective alternative to contemporary mosquito control approaches; however, the efficacies of many possible plant-based extracts remain untested. The present study examines the effects of extracts from three floating and three submerged aquatic plants on larval mosquito Culex pipiens mortality, and development to pupal and adult stages. Physical impacts of floating plant species on mosquito mortality and development are also examined. Extracts of Lagarosiphon major and Lemna minuta were toxic, causing significantly increased mosquito mortality compared to plant-free controls. Effects of Azolla filiculoides, Crassula helmsii, Elodea canadensis and Lemna minor were statistically unclear, yet in some cases tended to increase pupal and larval numbers at high extract concentrations. Surface coverage of all floating Lemna species drove significant mosquito mortality through mechanical processes which likely impeded surface respiration by larval mosquitoes. In particular, high-density mats of L. minuta consistently caused total larval mortality. The present study thus suggests that targeted use of specific aquatic plants could assist in mosquito control protocols. However, as the chemical composition of botanic material will differ across spatial and temporal gradients, even for a singular species, localised assessment of the efficacy of plant-based extracts from within areas experiencing problematic mosquito control is required. The application of aquatic plants that are both toxic to larvae and are effective physical control agents presents an economic and effective method of mosquito control.
As anthropogenic factors contribute to the introduction and expansion of new and established vector species, the geographic incidence of mosquito-borne disease is shifting. Computer simulations, ...informed by field data where possible, facilitate the cost-effective evaluation of available public health interventions and are a powerful tool for informing appropriate policy action. However, a variety of measurements are used in such assessments; this can complicate direct comparisons across both vector control technologies and the models used to simulate them. The expansion of biocontrol to include genetically engineered organisms is now prompting additional metrics with no analogy to traditional measurement approaches. We propose Standard Entomological Metrics (SEMs) to facilitate the model-based appraisal of both existing and novel intervention tools and define two examples: Suppression Efficacy Score and Time to Reduction Target. We formulate twelve synthetic case studies featuring two vector control technologies over three years of observed daily temperature in Cairns, Australia. After calculating Suppression Efficacy Score and Time to Reduction Target results, we apply these example outcomes to a discussion of health policy decision-making using SEMs. We submit that SEMs such as Suppression Efficacy Score and Time to Reduction Target facilitate the wholistic and environmentally appropriate simulation-based evaluation of intervention programs and invite the community to further discussion on this topic.
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