The long term objective is to facilitate the rational use of insecticides in malaria and filaria control campaigns based by upon a more complete understanding of resistance mechanisms.
The specific aims of this proposal are to: i) identify genes that render Anopheles gambiae s.l. mosquitoes resistant to a range of insecticides that are used for indoor residual spraying (IRS) for malaria and filariasis namely an organochloride (DDT), a carbamate (Bendiocarb) and a class II pyrethroid (?-cyhalothrin). ii) develop DNA-based insecticide resistance screening tools for use by the staff of vector control programmes in the malaria and filariasis affected countries of sub-Saharan Africa. These routine resistance screens will permit routine monitoring of mutations giving information vital for predicting the success of IRS and ITN programmes. The objective will be addressed in three specific phases: Phase 1 - The discovery of resistance-associated loci using candidate gene association mapping and whole genome microarrays. In two focal African countries, genes potentially involved in resistance to three major IRS insecticides (DDT, Bendiocarb, ?-cyhalothrin) will be identified using two complementary approaches:- i) Variation at the DNA level will be investigated using a custom candidate gene 1536plex SNP array and ii) differential gene expression between resistant and susceptible Anopheles gambiae will be investigated via whole genome microarrays. Putative resistance-associated SNPs within and around the most promising genes or gene regulators will be taken forward to phase 2 for wider field validation. Phase 2 - Candidate gene validation in the PMI and TDR network countries of sub-Saharan Africa. The putative resistance-associated SNPs identified in phase 1 will be screened for association with resistance in a much larger sample from a large section of sub-Saharan Africa via collaboration with extant World Health Organization/Tropical Disease Research (TDR) and President's Malaria Initiative (PMI) programmes.
The aim i s to screen for association of SNPs with resistance within and across populations producing a multi-site association meta-analysis to identify resistance-associated SNPs of major and/or generic effect. Phase 3 - Integrating metabolic resistance markers into a Field Applicable Screening Tool. The final phase of the programme will involve design, testing and roll-out of a field applicable screening tool (FAST), which will comprise straightforward and robust diagnostics to be used in laboratories in the disease-affected countries. The FAST diagnostics will include the most important genetic markers for resistance to the IRS insecticides, in addition to any critical pre-identified markers (e.g. for species/ molecular form identification). FAST roll-out will occur via collaboration with extant Innovative Vector Control Consortium (IVCC), TDR and PMI programmes. The development of insecticide resistance in Anopheles mosquitoes is a major threat to malaria control. Conventional means of assessing resistance are costly, insensitive and inaccurate. We propose to develop assays that will allow disease programme managers to detect resistance when it is still at a low frequency and before control failure has occurred.
The development of insecticide resistance in Anopheles mosquitoes is a major threat to malaria control. Conventional means of assessing resistance are costly, insensitive and inaccurate. We propose to develop assays that will allow disease programme managers to detect resistance when it is still at a low frequency and before control failure has occurred.
|Kabula, Bilali; Tungu, Patrick; Rippon, Emily J et al. (2016) A significant association between deltamethrin resistance, Plasmodium falciparum infection and the Vgsc-1014S resistance mutation in Anopheles gambiae highlights the epidemiological importance of resistance markers. Malar J 15:289|
|Wilding, C S; Weetman, D; Rippon, E J et al. (2015) Parallel evolution or purifying selection, not introgression, explains similarity in the pyrethroid detoxification linked GSTE4 of Anopheles gambiae and An. arabiensis. Mol Genet Genomics 290:201-15|
|Weetman, David; Mitchell, Sara N; Wilding, Craig S et al. (2015) Contemporary evolution of resistance at the major insecticide target site gene Ace-1 by mutation and copy number variation in the malaria mosquito AnophelesÂ gambiae. Mol Ecol 24:2656-72|
|Mitchell, Sara N; Rigden, Daniel J; Dowd, Andrew J et al. (2014) Metabolic and target-site mechanisms combine to confer strong DDT resistance in Anopheles gambiae. PLoS One 9:e92662|
|Edi, Constant V; DjogbÃ©nou, Luc; Jenkins, Adam M et al. (2014) CYP6 P450 enzymes and ACE-1 duplication produce extreme and multiple insecticide resistance in the malaria mosquito Anopheles gambiae. PLoS Genet 10:e1004236|
|Clarkson, Chris S; Weetman, David; Essandoh, John et al. (2014) Adaptive introgression between Anopheles sibling species eliminates a major genomic island but not reproductive isolation. Nat Commun 5:4248|
|Weetman, David; Steen, Keith; Rippon, Emily J et al. (2014) Contemporary gene flow between wild An. gambiae s.s. and An. arabiensis. Parasit Vectors 7:345|
|Essandoh, John; Yawson, Alexander E; Weetman, David (2013) Acetylcholinesterase (Ace-1) target site mutation 119S is strongly diagnostic of carbamate and organophosphate resistance in Anopheles gambiae s.s. and Anopheles coluzzii across southern Ghana. Malar J 12:404|
|Jones, Christopher M; Liyanapathirana, Milindu; Agossa, Fiacre R et al. (2012) Footprints of positive selection associated with a mutation (N1575Y) in the voltage-gated sodium channel of Anopheles gambiae. Proc Natl Acad Sci U S A 109:6614-9|
|Mitchell, Sara N; Stevenson, Bradley J; Muller, Pie et al. (2012) Identification and validation of a gene causing cross-resistance between insecticide classes in Anopheles gambiae from Ghana. Proc Natl Acad Sci U S A 109:6147-52|
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