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At least 19 recordsLinked to original sources
PubMed1994

DNA-based methods for the identification of insect vectors.

Many insect vectors are members of complexes composed of morphologically identical sibling species. The identification of individual species, a requirement of epidemiological studies and control programmes, has traditionally relied upon techniques such as chromosomal analysis or isoenzyme typing. Owing to the limitations of these techniques, the last few years have seen many developments in DNA-based technologies for identification. DNA-based protocols have advantages over the other techniques utilized, in that they may identify all insect stages of both sexes using alcohol-preserved, dried, fresh or frozen specimens. The methods ultimately rely upon either DNA probe hybridization or the polymerase chain reaction (PCR). This review describes a number of approaches taken towards the development of these techniques. The aim of these approaches, whether directed or random, is to produce a methodology that is cheap, accurate and easy to use. In this review, the DNA-based techniques developed for the identification of Anopheles gambiae complex mosquitoes are used to illustrate the power of these methods, although, as the review demonstrates, the technology is directly applicable to many other mosquito or insect vectors. In addition, the methods discussed may be utilized for generating additional epidemiological data, such as identification of parasites within the vector or origin of the bloodmeal. A comprehensive survey of the probe systems available for the identification of insect vectors and the disease-causing organisms they transmit to the human population is therefore included. Given further advances in this technology, it may be anticipated that DNA-based approaches to identification may eventually supersede more traditional methodologies in the fields of tropical medicine and parasitology.

Animals↗
PubMedDate not supplied

Approaches to vector control: new and trusted. 3. Prospects for genetic manipulation of insect vectors.

Insect vector control has proved an effective method of reducing the transmission of disease-causing organisms to human populations in many tropical countries. A variety of methods has been employed for suppressing vector populations, including the application of biological control agents and the elimination of breeding sites, with a continuing and heavy reliance on the use of chemical insecticides. However, the development of insecticide resistance by vector insects, the cost of developing and registering new insecticidal compounds, and the increase in legislation to combat the detrimental effects of insecticidal residues on the environment, have emphasized the need to assess a variety of alternatives to vector control. What is required is a completely novel approach either to suppress vector populations, or to alter their ability to transmit disease-causing organisms in such a way as to have a profound and long-lasting effect on disease transmission. Genetic manipulation of insect vectors may provide just such an approach. The major requirements for being able to manipulate the genomes of insects are reviewed together with the progress which has been made to create transgenic vector insects. The potential applications of this technology are then explored, emphasizing that its most immediate use will be as an analytical tool. Finally, the feasibility of creating refractory vector strains by genetic manipulation and releasing them into the environment is assessed in relation to its future use as a disease control strategy.

Animals↗
PubMed1994

Interactions between parasites and insects vectors.

This review stresses the importance of studies that will provide a basic understanding of the pathology of parasite-infected vector insects. This knowledge should be a vital component of the very focussed initiatives currently being funded in the areas of vector control. Vector fecundity reduction is discussed as an example of such pathology. Underlying mechanisms are being investigated in a model system, Hymenolepis diminuta-infected Tenebrio molitor and in Onchocerca-infected blackflies and Plasmodium-infected Anopheles stephensi. In all cases, host vitellogenesis is disrupted by the parasite and, in the tapeworm/beetle model, interaction between the parasite and the endocrine control of the insect's reproductive physiology has been demonstrated.

Aedes↗
PubMed1994

Genetic manipulation of insect vectors as a strategy for the control of vector-borne disease.

A variety of very effective methods have been employed for suppressing insect vector populations, including the application of biological control agents and the elimination of breeding sites, with a continuing and heavy reliance on the use of chemical insecticides. However, the development of insecticide resistance by vector insects, the cost of developing and registering new insecticidal compounds, and the increase in legislation to combat the detrimental effects of insecticidal residues on the environment, have emphasized the need to assess alternative strategies for vector control. What is required is a completely novel approach to either suppress vector populations, or to alter their ability to transmit disease-causing organisms in such a way as to have a profound and long-lasting effect on disease transmission. Genetic manipulation of insect vectors may provide just such an approach. The major requirements for genome manipulation in insects and the progress which has been made to create transgenic vector insects are reviewed. The potential applications of this methodology are then explored in the context of its future use for the control of vector-borne diseases.

Animals↗
PubMed2004

The plant virus Tomato Spotted Wilt Tospovirus activates the immune system of its main insect vector, Frankliniella occidentalis.

Tospoviruses have the ability to infect plants and their insect vectors. Tomato spotted wilt virus (TSWV), the type species in the Tospovirus genus, infects its most important insect vector, Frankliniella occidentalis, the western flower thrips (WFT). However, no detrimental effects on the life cycle or cytopathological changes have been reported in the WFT after TSWV infection, and relatively few viral particles can be observed even several days after infection. We hypothesized that TSWV infection triggers an immune response in the WFT. Using subtractive cDNA libraries to probe WFT DNA macroarrays, we found that the WFT's immune system is activated by TSWV infection. The activated genes included (i) those encoding antimicrobial peptides, such as defensin and cecropin; (ii) genes involved in pathogen recognition, such as those encoding lectins; (iii) those encoding receptors that activate the innate immune response, such as Toll-3; and (iv) those encoding members of signal transduction pathways activated by Toll-like receptors, such as JNK kinase. Transcriptional upregulation of these genes after TSWV infection was confirmed by Northern analysis, and the kinetics of the immune response was measured over time. Several of the detected genes were activated at the same time that viral replication was first detected by reverse transcription-PCR. To our knowledge, this is the first report of the activation of an insect vector immune response by a plant virus. The results may lead to a better understanding of insects' immune responses against viruses and may help in the future development of novel control strategies against plant viruses, as well as human and animal viruses transmitted by insect vectors.

Animals↗
PubMed1997

The loss of outer capsid protein P2 results in nontransmissibility by the insect vector of rice dwarf phytoreovirus.

A transmission-defective (TD) isolate of rice dwarf phytoreovirus lacked the ability to infect cells when derived from the virus-free insect vector Nephotettix cincticeps. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified virus showed that among six structural proteins, the P2 outer capsid protein (encoded by genome segment S2) was absent from the TD isolate, whereas all six proteins were present in the transmission-competent (TC) isolate. P2 was not detected on immunoblots of rice plants infected with the TD isolate. Genome segment S2 and its transcript were detected in both TD and TC isolates. Sequence analysis of the S2 segment of the TD isolate revealed the presence of a termination codon due to a point mutation in the open reading frame, which might explain the absence of P2 in the TD isolate. These results demonstrate that the P2 protein is one of the factors essential for infection by the virus of vector cells and, thus, influences transmissibility by vector insects.

Amino Acid Sequence↗
PubMed2003

A single gene that promotes interaction of a phytopathogenic bacterium with its insect vector, Drosophila melanogaster.

Insects are major vectors of plant and animal disease, and bacterial phytopathogens are often disseminated by flies. We have previously reported that some isolates of the phytopathogenic bacterial species Erwinia carotovora infect Drosophila and activate an immune response. Using a genetic screen, we have now identified two genes that are required by E. carotovora to infect Drosophila. One of these genes has a regulatory role whereas the other, evf, confers an infectious phenotype: its transfer to non-infectious Erwinia strains or to several enterobacteria improves survival in the gut and triggers the immune response. Overexpression of Erwinia virulence factor (evf) allowed bacteria to colonize the apical side of the gut epithelium and in some cases to spread to the body cavity. Our results demonstrate a specific interaction between plant pathogens and flies that promote their dissemination.

Animals↗
PubMed1998

The P2 protein of rice dwarf phytoreovirus is required for adsorption of the virus to cells of the insect vector.

Intact particles of rice dwarf phytoreovirus adsorbed to and entered monolayer-cultured cells of the insect vector Nephotettix cincticeps and multiplied within the cells. Particles that lacked the P2 protein neither attached to nor infected such cells. Furthermore, P2-free particles obtained from a transmission-competent isolate of the virus were unable to infect insect vectors that had been allowed to feed on these virus particles through a membrane. However, when such virus particles were injected into insects via a glass capillary tube they successfully infected the insects, which became able to transmit the virus. These results support the hypothesis that, while P2-free particles can neither interact with nor infect cells in the intestinal tract of the insect vector, they do retain the ability to infect such cells when physically introduced into the hemolymph by injection.

Adsorption↗
PubMed1996

Immunity to eukaryotic parasites in vector insects.

Mosquitoes and blackflies have been the focus of recent efforts to elucidate factors influencing the susceptibility of vector insects to metazoan and protozoan parasites of medical significance. Vector species exhibit variation in cellular and humoral immune responses, as highlighted by studies of melanotic encapsulation and components of the phenoloxidase system. Significant progress has been made in the development of genetic maps based upon molecular markers, leading to the genetic analysis of loci influencing susceptibility. The identification of specific inducible antibacterial peptides, and the cloning of genes encoding immune effector proteins as well as potential regulatory factors, open the path to fruitful studies of vector insect innate immunity and its relationship to insect-parasite interactions.

Animals↗
PubMed2000

Insecticide resistance in insect vectors of human disease.

Insecticide resistance is an increasing problem in many insect vectors of disease. Our knowledge of the basic mechanisms underlying resistance to commonly used insecticides is well established. Molecular techniques have recently allowed us to start and dissect most of these mechanisms at the DNA level. The next major challenge will be to use this molecular understanding of resistance to develop novel strategies with which we can truly manage resistance. State-of-the-art information on resistance in insect vectors of disease is reviewed in this context.

Animals↗
PubMed1987

Trypanosoma cruzi strain-specific monoclonal antibodies: identification of Colombian strain flagellates in the insect vector.

Spleen cells from mice immunized with insect-derived Trypanosoma cruzi metacyclic trypomastigotes were used to obtain Colombian strain-specific monoclonal antibodies. At least 4 different strain-specific antigens were recognized by the monoclonal antibodies on epimastigotes or metacyclic trypomastigotes. There was no reactivity with other stages of Colombian strain T. cruzi, nor with any stage of 15 other T. cruzi strains or isolates, nor with 22 other Trypanosomatidae. One of the monoclonal antibodies was used to identify, by indirect immunofluorescence, Colombian strain flagellates in cryostat sections or glass-slide smears of the insect vector's intestine.

Animals↗