LLINs containing an insecticide plus the synergist, piperonyl butoxide (PBO) have been designed for increased efficacy against pyrethroid-resistant malaria vectors. In this study, two LLINs with PBO, PermaNet® 3.0 and Olyset® Plus, and a pyrethroid-only LLIN, Yorkool®, were evaluated in experimental huts against a free-flying, wild population of Anopheles gambiae s.l. in Kolokopé, a cotton cultivated area of Togo. WHO susceptibility tube tests and subsequent molecular assays determine the An. gambiae s.l. populations to be resistant to pyrethroids and DDT with both target site kdr and metabolic resistance mechanisms involved in the resistance observed. Anopheles gambiae s.s. and An. coluzzi were present in sympatry though the kdr (L1014F) mutation was observed at a higher frequency in An. gambiae s.s. The experimental hut results showed that both PermaNet® 3.0 and Olyset® Plus nets induced similar levels of deterrence, exophily, and reduced blood feeding rate against wild An. gambiae s.l. in contrast to the pyrethroid only LLIN, Yorkool®. The proportion of wild An. gambiae s.l. killed by unwashed PermaNet® 3.0 was significantly higher than unwashed Olyset® Plus (corrected mortality 80.5% compared to 66.6%). Similar blood feeding inhibition rates were observed for unwashed PermaNet® 3.0 and Olyset® Plus; however, PermaNet® 3.0 washed 20 times demonstrated significantly higher blood feeding inhibition rate than Olyset® Plus washed 20 times (91.1% compared with 85.6% respectively). Yorkool® performed the worst for all the parameters evaluated. In an area of pyrethroid resistance of An. gambiae s.l involving kdr target site and metabolic resistance mechanisms, LLINs with PBO can provide additional protection in terms of reduction in blood feeding and increase in mosquito mortality compared to a pyrethroid-only net, and should be considered in malaria vector control strategies.
Background: To optimize the success of insecticide-based malaria control intervention, knowledge of the distribution of Anopheles gambiae species and insecticide resistance mechanisms is necessary. This paper reported an updated data on pyrethroids/DDT resistance in the An. gambiae s.l population from Togo. Methods: From December 2013 to April 2015, females of indoor-resting An. gambiae s.l were captured in three locations belonging to three different ecological zones. Resistance to DDT, permethrin and deltamethrin was screened in F1 progeny of collected mosquitoes using WHO susceptibility tests. The identification of species of An. gambiae complex and the detection of kdr and ace.1 R allele were carried out using DNA-based molecular techniques. Results: An. gambiae from Kovié and Nangbéto were highly resistant to DDT and permethrin with mortalities rate ranging from 0.83% to 1.58% for DDT and zero to 8.54% for permethrin. Mosquitoes collected in Nangbéto displayed 81.53% mortality with deltamethrin. An. coluzzii and An. gambiae s.s were found in sympatry in Nangbéto and Mango . The allelic frequency of L1014F was high, ranging from 66 to 100% in both An. coluzzii and An. gambiae s.s. For the first time we detected the L1014S allele in both An. coluzzii and An. gambiae s.s. from Togo at the frequency ranging from 5% to 13% in all the sites. The kdr N1575Y was present at various frequencies in both species ranging from 10% to 45%. Both An. gambiae s.s. and An. coluzzii shared the ace1 R mutation in all investigated sites with allelic frequency ranging from 4% to 16%. Conclusion: These results showed that multiple mutations are involved in insecticides resistance in An. gambiae populations from Togo including the kdr L1014F, L1014S, and N1575Y and ace.1 R G119S mutations.
Background Malaria, one of the world’s greatest public health challenges, is an endemic disease with stable transmission in Togo. Combating malaria requires an effective vector control. This study provides temporal data on insecticide resistance status in the major malaria vector Anopheles gambiae sensu lato (s.l.) from Togo. Methods Two to 5 days old females of An. gambiae s.l., originating from three localities (Baguida, Kovié, Kolokopé) were subjected to insecticide-impregnated papers during 3 years (2012, 2013, 2016) as follows: organochlorides (4% DDT), pyrethroids (0.05% deltamethrin, 0.75% permethrin, 0.05% lambdacyhalothrin), carbamates (0.4% bendiocarb and 0.1% propoxur), and organophosphates (5% malathion, 0.4% chlorpyrifos methyl, 1% fenitrothion) following the WHO standard protocol. Dead and surviving mosquitoes were stored separately in Eppendorf tubes containing silica gel for DNA extraction, species identification, and kdr and ace - 1 genotyping. Results Knockdown times (KDT 50 and KDT 95 ) were high in An. gambiae s.l. The lowest KDTs were recorded at Baguida in 2013 for deltamethrin (KDT 50 = 24.7, CI [22.4–27.12] and KDT 95 = 90.78, CI [76.35–113.49]). No KDTs were recorded for DDT and in some instances for permethrin. In general, An. gambiae s.l. was resistant to most of the four classes of insecticides during the survey periods regardless of locality and year, except to chlorpyrifos methyl. In some instances, mosquitoes were fully susceptible to fenitrothion (Kolokopé: 100% and Kovié: 98.05%, CI [95.82–100.26]) and malathion (100% at both Kolokopé and Kovié) in 2013, and malathion only (Kolokopé; 100%) in 2016. Anopheles coluzzii , An. gambiae and Anopheles arabiensis were the three sibling species identified at the three localities with some hybrids at Baguida (2013), and Kovié (2012 and 2016), respectively. Anopheles gambiae was relatively dominant (61.6%). The kdr 1014F allele frequency was > 0.9 in most of the cases, except at Kolokopé (f (1014F) = 0.63, CI [0.55–0.71]) in 2013. The kdr 1014S allele frequency was below 0.02. The highest ace - 1 frequencies were identified in An. gambiae at Baguida (2012: 0.52, CI [0.34–0.69] and 2013: 0.66, CI [0.46–0.86]). Conclusion The resistance status is worrying in Togo and should be considered in future malaria vector resistance management programmes by decision-makers. Electronic supplementary materia...
The concept of a fundamental ecological niche is central to questions of geographic distribution, population demography, species conservation, and evolutionary potential. However, robust inference of genomic regions associated with evolutionary adaptation to particular environmental conditions remains difficult due to the myriad of potential confounding processes that can generate heterogeneous patterns of variation across the genome. Here, we interrogate the potential role of genome environment association (GEA) testing as an initial step in building an understanding of the genetic basis of ecological niche. We leverage publicly available genomic data from the Anopheles gambiae 1000 Genomes (Ag1000g) Consortium to test the ability of multiple analytically unique GEA methods to handle confounding patterns of genetic variation, control false positive rates, and discern associations with broadly relevant climate variables from random allele frequency patterns throughout the genome. We found evidence supporting the ability of commonly implemented GEA methods to account for confounding patterns of spatial and genetic variation, and control false positive rates. However, we fail to find evidence supporting the ability of GEA tests to reject signals of adaptation to randomly simulated environmental variables, indicating that discerning between true signals of genome environment adaptation and genome environment correlations resulting from alternative evolutionary processes, remains challenging. Because signals of environmental adaptation are so diffuse and confounded throughout the genome, we argue that genomic adaptation to ecological niche is likely best understood under an omnigenic model wherein highly interconnected, genome-wide gene regulatory networks shape genomic adaptation to key environmental conditions.
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