1,721,051 research outputs found
Interspecific transfer of a Wolbachia infection into Aedes albopictus (diptera: culicidae) yields a novel phenotype capable of rescuing a superinfection
No full textWolbachia are maternally transmitted obligate bacteria that occur naturally in many arthropods. The phenotype observed in mosquitoes is known as cytoplasmic incompatibility (CI), which results in reduced or absent egg hatch in crosses between individuals with different infection types. Applied mosquito control strategies propose that by releasing individuals infected with a Wolbachia strain that differs from that in the natural host population, CI could be used to suppress or replace mosquito populations. Here, using tetracycline treatment and embryonic microinjection, Aedes albopictus (Skuse) was cleared of its natural Wolbachia infection and artificially infected with a Wolbachia strain originating from Aedes riversi Bohart & Ingram. Crossing experiments were carried out to determine whether CI could be observed between the artificially infected strain (UC), naturally infected (wild type), and uninfected strains of Ae. albopictus. Crosses between UC males and uninfected females resulted in no egg hatch, a classic unidirectional CI pattern. Crosses between the wild-type and UC strain also exhibited a unidirectional pattern of CI, demonstrating that the UC strain is compatible with both of the Wolbachia types that occur within Ae. albopictus and that wild-type Wolbachia infections are unable to fully rescue the UC Wolbachia type. Crosses between the UC strain and another artificially infected Ae. albopictus strain (ARwP), were bidirectionally incompatible, demonstrating that the UC strain is not compatible with all Wolbachia types. The CI patterns observed in this study were atypical and the opposite of that typically observed with superinfections
wPip Wolbachia contribution to Aedes albopictus SIT performance: Advantages under intensive rearing
No full textAs a part of a project aiming at the suppression of the mosquito vector Aedes albopictus, a specific Ae. albopictus line producing sterile males, ARwP, was tested for its suitability to intense rearing conditions compatible with mass production and field release. This line was developed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development thanks to the artificial infection with a heterologous Wolbachia strain, resulting in a bidirectional incompatibility pattern with wild-type Ae. albopictus. ARwP was reared under Standard Operating Procedures at the Centro Agricoltura Ambiente and compared with a wild-type strain in terms of time of pupation onset, production of male pupae in the following 24 h and mechanical sexing efficacy. Mating competitiveness of ARwP males was also evaluated in comparison with irradiated wild-type males in large field enclosures. ARwP males demonstrated a significantly shorter time of pupation onset, a higher rate of production of male pupae in the following 24 h and a lower percentage of residual contaminant females when applying mechanical sexing procedures. In addition, ARwP males were more efficient than wild-types in competing for wild-type females in large enclosures, thus inducing a level of sterility significantly higher than that expected for an equal mating competitiveness. These results encourage the use of this Ae. albopictus strain as suppression tool against Ae. albopictus based on considerations thoroughly discussed in the manuscript. © 2016 Elsevier B.V
Harnessing mosquito-Wolbachia symbiosis for vector and disease control
No full textMosquito species, members of the genera Aedes, Anopheles and Culex, are the major vectors of human pathogens including protozoa (Plasmodium sp.), filariae and of a variety of viruses (causing dengue, chikungunya, yellow fever, West Nile). There is lack of efficient methods and tools to treat many of the diseases caused by these major human pathogens, since no efficient vaccines or drugs are available; even in malaria where insecticide use and drug therapies have reduced incidence, 219 million cases still occurred in 2010. Therefore efforts are currently focused on the control of vector populations. Insecticides alone are insufficient to control mosquito populations since reduced susceptibility and even resistance is being observed more and more frequently. There is also increased concern about the toxic effects of insecticides on non-target (even beneficial) insect populations, on humans and the environment. During recent years, the role of symbionts in the biology, ecology and evolution of insect species has been well-documented and has led to suggestions that they could potentially be used as tools to control pests and therefore diseases. Wolbachia is perhaps the most renowned insect symbiont, mainly due to its ability to manipulate insect reproduction and to interfere with major human pathogens thus providing new avenues for pest control. We herein present recent achievements in the field of mosquito Wolbachia symbiosis with an emphasis on Aedes albopictus. We also discuss how Wolbachia symbiosis can be harnessed for vector control as well as the potential to combine the sterile insect technique and Wolbachia-based approaches for the enhancement of population suppression programs. © 2013 International Atomic Energy Agency 2013
Natural and artificial envenomation of Ceratitis capitata by Eupelmus urozonus and the search for new bioinsecticides
No full textThis study was designed to indentify novel bioactive molecules in the venom of the parasitoid Eupelmus urozonus Dalman (Hymenoptera: Eupelmidae). Parasitism by E. urozonus induces apparent paralysis in the larvae of the host Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and it arrests the development of host pupae. Parasitoid eggs were transferred from stung to unparasitized host pupae to determine whether adult female stings or bites from the first instars were responsible for the above effects. The two treatments gave the same results, indicating that both parasitoid adults and larvae produced venoms capable to compromise host development. A protocol was developed to artificially microinject E. urozonus venom into healthy host pupae and adults at known concentrations to study the effects. The microinjection of venom was found to produce the same macroscopic result as natural parasitization, indicating that host developmental arrest was caused by molecules produced by the parasitoid venom glands. One-tenth, one-twentieth, and one-hundredth of the contents of a female venom reservoir was sufficient to compromise the development of 100, 90, and 50% of the microinjected host pupae, respectively. The microinjection of 0.1 female venom equivalents into host adults always caused death within 24 h. Extraction and freezing did not affect the activity of the E. urozonus venom, which facilitates its storage, whereas denaturation treatments demonstrated that the bioactive molecules were proteins. The venom was also found to prevent the hosts from decaying for over 2 weeks and it promoted the accumulation of unknown subspherical granules in the host haemocoel. These results suggest the potential identification of novel molecules with interesting biological activity with various possible applications. © 2014 The Netherlands Entomological Society
Larvicidal activity of steroidal saponins from Dracaena arborea on Aedes albopictus
No full textIntroduction: Development of new and improved mosquito control methods, that are economically sustainable and effective, is a critical requirement in the management of vector-borne epidemic diseases. Aedes albopictus is one of the main vectors of various important pathogens in the tropics, which now have the potential to also spread in temperate regions, owing to the environmental and climate changes in act. Materials and Methods: We report about the isolation of steroidal saponins from Dracaena arborea by fractionation followed by column separation. The obtained fractions and/or pure compounds were tested by biological essays for their insecticidal activity against A. albopictus larvae. Results: Various compounds were found to exert larvicidal effects. In specific, spiroconazole A demonstrated the best insecticidal activity, showing LT50 value of 57.23 hours at 25 ppm. Discussion: We finally discuss about the value of this finding in the context of the present strategies of Integrated Mosquito Management. © 2016 Bentham Science Publishers
Male mating performance and cytoplasmic incompatibility in a wPip Wolbachia trans-infected line of Aedes albopictus (Stegomyia albopicta)
No full textWolbachia pipientis Hertig (Rickettsiales: Rickettsiaceae) is a maternally inherited endosymbiont of a large number of insects and other arthropods that induces various effects on host reproductive biology. Among these, cytoplasmic incompatibility (CI) is a form of sterility induced in eggs produced by mating between infected males and females uninfected or infected by an incompatible Wolbachia strain. This phenomenon has been proposed as a potential way to produce functionally sterile males to be used in genetic control programmes. In this paper, we report on experiments carried out to evaluate the mating performances of males of an Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae) line (ARwP), harbouring a new Wolbachia infection [the wPip strain from Culex pipiens Linnaeus (Diptera: Culicidae)], in comparison with naturally infected males (SR line). ARwP males did not differ from SR males with regard to insemination capacity. Mating competitiveness did not differ significantly between lines in either laboratory or greenhouse conditions. Moreover, crosses with SR females were characterized by a 100% CI regardless of ARwP male age. All of these findings suggest that ARwP males may represent a very efficient tool for control programmes against Ae. albopictus based on the release of functionally sterile males. © 2012 The Royal Entomological Society
Comparison of irradiation and Wolbachia based approaches for sterile-male strategies targeting Aedes albopictus
No full textThe global expansion of Aedes albopictus together with the absence of vaccines for most of the arboviruses transmitted by this mosquito has stimulated the development of sterile-male strategies aiming at controlling disease transmission through the suppression of natural vector populations. In this context, two environmentally friendly control strategies, namely the Sterile Insect Technique (SIT) and the Wolbachia-based Incompatible Insect Technique (IIT) are currently being developed in several laboratories worldwide. So far however, there is a lack of comparative assessment of these strategies under the same controlled conditions. Here, we compared the mating capacities, i.e. insemination capacity, sterilization capacity and mating competitiveness of irradiated (35 Gy) and incompatible Ae. albopictus males at different ages and ratios under laboratory controlled conditions. Our data show that there was no significant difference in insemination capacity of irradiated and incompatible males, both male types showing lower capacities than untreated males at 1 day but recovering full capacity within 5 days following emergence. Regarding mating competitiveness trials, a global observed trend is that incompatible males tend to induce a lower hatching rate than irradiated males in cage controlled confrontations. More specifically, incompatible males were found more competitive than irradiated males in 5:1 ratio regardless of age, while irradiated males were only found more competitive than incompatible males in the 1:1 ratio at 10 days old. Overall, under the tested conditions, IIT seemed to be slightly more effective than SIT. However, considering that a single strategy will likely not be adapted to all environments, our data stimulates the need for comparative assessments of distinct strategies in up-scaled conditions in order to identify the most suitable and safe sterilizing technology to be implemented in a specific environmental setting and to identify the parameters requiring fine tuning in order to reach optimal release conditions. © 2016 Atyame et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Incompatible insect technique: insights on potential outcomes of releasing contaminant females: a proof of concept under semi-field conditions
No full textReleasing large numbers of Aedes albopictus males, carrying the artificially introduced Wolbachia ‘wPip’ strain, results in a decrease in the reproductive capacity of wild females due to a phenomenon known as cytoplasmic incompatibility (CI). This vector control strategy is referred to as the incompatible insect technique (IIT). However, its widespread implementation faces various challenges, including the complexity of removing fertile females from the males intended for release. Here, we present the results of semi-field experiments comparing the impact of minimal female co-release on two IIT modes: unidirectional CI-based (UnCI IIT) and bidirectional CI-based (BiCI IIT), specifically targeting Ae. albopictus. RESULTS: The contamination of ‘wPip’ infected females (2%) during male releases significantly weakened the overall effectiveness of IIT, emphasizing the need for thorough sex separation. Specifically, with UnCI IIT, despite the low rate of co-released females, there was a gradual rise in ‘wPip’ infection frequency, resulting in more compatible mating and subsequently higher rates of egg hatching. Conversely, this pattern was effectively mitigated in BiCI IIT owing to the reciprocal sterility between the wild-type and the ‘wPip’ infected populations. CONCLUSION: Through an experimental approach, conducted in a semi-field setting, we have contributed to advancing scientific understanding regarding the potential outcomes of implementing the IIT strategy in the absence of a complete sexing system. The results suggest that safety measures for mitigating the potential impacts of co-released females can be tailored according to the specific type of IIT being utilized
A draft genome sequence of an invasive mosquito: An Italian Aedes albopictus
No full textThe draft genome sequence of Italian specimens of the Asian tiger mosquito Aedes (Stegomyia) albopictus (Diptera: Culicidae) was determined using a standard NGS (next generation sequencing) approach. The size of the assembled genome is comparable to that of Aedes aegypti; the two mosquitoes are also similar as far as the high content of repetitive DNA is concerned, most of which is made up of transposable elements. Although, based on BUSCO (Benchmarking Universal Single-Copy Orthologues) analysis, the genome assembly reported here contains more than 99% of protein-coding genes, several of those are expected to be represented in the assembly in a fragmented state. We also present here the annotation of several families of genes (tRNA genes, miRNA genes, the sialome, genes involved in chromatin condensation, sex determination genes, odorant binding proteins and odorant receptors). These analyses confirm that the assembly can be used for the study of the biology of this invasive vector of disease. © W. S. Maney & Son Ltd 2015
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