Time filter

Source Type

Liverpool, United Kingdom

Esu E.,University of Calabar | Lenhart A.,Vector Group | Smith L.,London School of Hygiene and Tropical Medicine | Horstick O.,World Health Organization
Tropical Medicine and International Health | Year: 2010

Objective To review the evidence on effectiveness of peridomestic space spraying of insecticides in reducing wild Aedes populations and interrupting dengue transmission. Methods Comprehensive literature search of MEDLINE, EMBASE, LILACS, Web of Science, WHOLIS, MedCarib and CENTRAL, and a manual search of reference lists from identified studies. Duplicates were removed and abstracts assessed for selection. All field evaluations of peridomestic space spraying targeting wild adult Aedes vectors in dengue endemic countries were included. Data were extracted, and the methodological quality of the studies was assessed independently by two reviewers. Results Fifteen studies met the inclusion criteria. Outcome measures were heterogeneous, foregoing the possibility of meta-analysis. Thirteen studies showed reductions in immature entomological indices that were not sustained for long periods. The remainder showed space spray interventions to be ineffective at reducing adult and/or immature entomological indices. Only one study measured human disease indicators, but its outcomes could not be directly attributed to space sprays alone. Conclusion Although peridomestic space spraying is commonly applied by national dengue control programmes, there are very few studies evaluating the effectiveness of this intervention. There is no clear evidence for recommending peridomestic space spraying as a single, effective control intervention. Thus, peridomestic space spraying is more likely best applied as part of an integrated vector management strategy. The effectiveness of this intervention should be measured in terms of impact on both adult and immature mosquito populations, as well as on disease transmission. © 2010 Blackwell Publishing Ltd.

Killeen G.F.,Ifakara Health Institute | Killeen G.F.,Vector Group | Moore S.J.,Ifakara Health Institute | Moore S.J.,London School of Hygiene and Tropical Medicine
Malaria Journal | Year: 2012

Background: Long-lasting insecticidal nets (LLINs) and indoor residual sprays (IRS) have decimated malaria transmission by killing indoor-feeding mosquitoes. However, complete elimination of malaria transmission with these proven methods is confounded by vectors that evade pesticide contact by feeding outdoors. Methods. For any assumed level of indoor coverage and personal protective efficacy with insecticidal products, process-explicit malaria transmission models suggest that insecticides that repel mosquitoes will achieve less impact upon transmission than those that kill them outright. Here such models are extended to explore how outdoor use of products containing either contact toxins or spatial repellents might augment or attenuate impact of high indoor coverage of LLINs relying primarily upon contact toxicity. Results: LLIN impact could be dramatically enhanced by high coverage with spatial repellents conferring near-complete personal protection, but only if combined indoor use of both measures can be avoided where vectors persist that prefer feeding indoors upon humans. While very high levels of coverage and efficacy will be required for spatial repellents to substantially augment the impact of LLINs or IRS, these ambitious targets may well be at least as practically achievable as the lower requirements for equivalent impact using contact insecticides. Conclusions: Vapour-phase repellents may be more acceptable, practical and effective than contact insecticides for preventing outdoor malaria transmission because they need not be applied to skin or clothing and may protect multiple occupants of spaces outside of treatable structures such as nets or houses. © 2012Killeen and Moore; licensee BioMed Central Ltd.2012.

Harris A.F.,Mosquito Research and Control Unit MRCU | Harris A.F.,Vector Group | Nimmo D.,Oxitec Ltd | McKemey A.R.,Oxitec Ltd | And 7 more authors.
Nature Biotechnology | Year: 2011

Dengue is the most medically important arthropod-borne viral disease, with 50-100 million cases reported annually worldwide. As no licensed vaccine or dedicated therapy exists for dengue, the most promising strategies to control the disease involve targeting the predominant mosquito vector, Aedes aegypti. However, the current methods to do this are inadequate. Various approaches involving genetically engineered mosquitoes have been proposed, including the release of transgenic sterile males. However, the ability of laboratory-reared, engineered male mosquitoes to effectively compete with wild males in terms of finding and mating with wild females, which is critical to the success of these strategies, has remained untested. We report data from the first open-field trial involving a strain of engineered mosquito. We demonstrated that genetically modified male mosquitoes, released across 10 hectares for a 4-week period, mated successfully with wild females and fertilized their eggs. These findings suggest the feasibility of this technology to control dengue by suppressing field populations of A. aegypti. © 2011 Nature America, Inc. All rights reserved.

Lynd A.,Vector Group | Lycett G.J.,Vector Group
PLoS ONE | Year: 2012

Functional genetic analysis in Anopheles gambiae would be greatly improved by the development of a binary expression system, which would allow the more rapid and flexible characterisation of genes influencing disease transmission, including those involved in insecticide resistance, parasite interaction, host and mate seeking behaviour. The Gal4-UAS system, widely used in Drosophila melanogaster functional genetics, has been significantly modified to achieve robust application in several different species. Towards this end, previous work generated a series of modified Gal4 constructs that were up to 20 fold more active than the native gene in An. gambiae cells. To examine the Gal4-UAS system in vivo, transgenic An. gambiae driver lines carrying a modified Gal4 gene under the control of the carboxypeptidase promoter, and responder lines carrying UAS regulated luciferase and eYFP reporter genes have been created. Crossing of the Gal4 and UAS lines resulted in progeny that expressed both reporters in the expected midgut specific pattern. Although there was minor variation in reporter gene activity between the different crosses examined, the tissue specific expression pattern was consistent regardless of the genomic location of the transgene cassettes. The results show that the modified Gal4-UAS system can be used to successfully activate expression of transgenes in a robust and tissue specific manner in Anopheles gambiae. The midgut driver and dual reporter responder constructs are the first to be developed and tested successfully in transgenic An. gambiae and provide the basis for further advancement of the system in this and other insect species. © 2012 Lynd, Lycett.

Service M.W.,Vector Group
Annual review of entomology | Year: 2010

This article describes the childhood of Mike Service, his very early interest in insects, his time at Imperial College, London University, and his career in Nigeria studying the taxonomy and biology of anopheline malaria vectors. On his return to England he became increasingly interested in the ecology and population dynamics of hematophagous insects. After almost eight years undertaking only research, he joined the Liverpool School of Tropical Medicine, where he was involved in lecturing as well as research and engaged in frequent overseas travel mainly to Africa, Central and South America, and Asia. On retirement he retains an active interest in medical entomology. Although he undertook a considerable amount of taxonomic work on mosquitoes, he believes his most important, and possibly influential, work was introducing ecological methods that were used by agricultural scientists to the study of mosquitoes. For example, the construction of life tables, calculating the percentage mortality of pre-adult mosquitoes, and the identification of predators by serological methods.

Discover hidden collaborations