scholarly journals A pyrethroïd-treated bed net increases host attractiveness for Anopheles gambiae s.s. carrying the kdr allele in a dual-choice olfactometer

2016 ◽  
Author(s):  
Angélique Porciani ◽  
Malal Diop ◽  
Nicolas Moiroux ◽  
Tatiana Kadoke-Lambi ◽  
Anna Cohuet ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Anopheles Gambiae S.S ◽  
Host Seeking ◽  
Seeking Behavior ◽  
Sub Saharan ◽  
The Impact

AbstractThe use of long lasting insecticide nets (LLINs) treated with pyrethroïd is known for its major contribution in malaria control. However, LLINs are suspected to induce behavioral changes in malaria vectors, which may in turn drastically affect their efficacy against Plasmodium sp. transmission. In sub Saharan Africa, where malaria imposes the heaviest burden, the main malaria vectors are widely resistant to pyrethroïds, the insecticide family used on LLINs, which also threatens LLIN efficiency. There is therefore a crucial need for deciphering how insecticide-impregnated materials might affect the host-seeking behavior of malaria vectors in regards to insecticide resistance. In this study, we explored the impact of permethrin-impregnated net on the host attractiveness for Anopheles gambiae mosquitoes, either susceptible to insecticides, or carrying the insecticide resistance conferring allele kdr. Groups of female mosquitoes were released in a dual-choice olfactometer and their movements towards an attractive odor source (a rabbit) protected by insecticide-treated (ITN) or untreated nets (UTN) were monitored. Kdr homozygous mosquitoes, resistant to insecticides, were more attracted by a host behind an ITN than an UTN, while the presence of insecticide on the net did not affect the choice of susceptible mosquitoes. These results suggest that permethrin-impregnated net is detectable by malaria vectors and that the kdr mutation impacts their response to a LLIN protected host. We discuss the implication of these results for malaria vector control.

scholarly journals Behavioral Responses of Pyrethroid-resistant Anopheles Gambiae Mosquitoes to Insecticide-treated Bed Net

2021 ◽  
Author(s):  
Maxwell G. Machani ◽  
Eric Ochomo ◽  
Fred Amimo ◽  
Andrew K. Githeko ◽  
Guiyun Yan ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Malaria Transmission ◽  
Malaria Vectors ◽  
Bed Net ◽  
Anopheles Gambiae S.S ◽  
Field Environment ◽  
Host Seeking ◽  
Seeking Behavior ◽  
Vector Behavior

Abstract Background: Long-lasting insecticidal nets are an effective tool in reducing malaria transmission. However, with increasing insecticide resistance little is known about how physiologically resistant malaria vectors behave around a human-occupied bed net, despite their importance in malaria transmission. We assessed the host-seeking behavior of the major malaria vector Anopheles gambiae s.s, when an intact human-occupied treated bed net is in place, with respect to their insecticide resistance status under semi-field conditions. Methods: Pyrethroid resistant and susceptible colonies of female Anopheles gambiae s.s aged 3-5 days that have been bred in our insectary, were color-marked with fluorescent powder and released inside a semi-field environment housing a hut which was occupied by a human host. Inside the hut, the occupant slept under an insecticide-treated bed net trap or untreated bed net trap. The window exit trap was installed to catch mosquitoes exiting the hut. A prokopack aspirator was used to collect indoor and outdoor resting mosquitoes in the morning. Clay pots were placed outside the hut to collect mosquitoes resting outdoors. Results: The proportion of resistant mosquitoes caught in the treated bed net trap was higher 43% (95% CI= [40.6-45.3]) compared to the susceptible mosquitoes 28.3% (OR=1.445; P<0.00019). The proportion of susceptible mosquitoes caught in the untreated bed net trap was higher 51.3% (95% CI= [48.8-53.6]) compared to the treated bed net trap 28.3% (95% CI= [26.3-30.5]) (OR=2.65; P<0.0001). Resistant mosquitoes were less likely to exit the house when a treated bed net was present (5.2%; 95% CI= [4.2-6.4]) compared to the susceptible mosquitoes (11.5%; 95% CI= [9.6-12.6]). The proportion of susceptible mosquitoes avoiding contact with the treated bed net and caught resting indoors in the hut (53.8%) and outdoors (64.5%) was higher compared to the resistant mosquitoes (indoors: 46.2%, outdoor: 35.4%). The susceptible females were 2.3 times more likely to stay outdoors away from the treated bed net (OR=2.25; 95% CI= [1.7-2.9]; P<0.0001).Conclusion: The results show that in the presence of a treated net, the host-seeking performance was not altered for the resistant mosquitoes, unlike the susceptible females that were observed to exit the house and remained outdoors when a treated net was used. However, further investigations of the behavior of resistant mosquitoes under natural conditions should be undertaken to confirm these observations and improve the current intervention which are threatened by insecticide resistance and altered vector behavior.

scholarly journals Host-seeking behavior and hourly biting rhythm of vectors in malaria endemic district of Arba Minch area, Southwest Ethiopia

2020 ◽  
Author(s):  
Melkam Abiye Zeru ◽  
Simon Shibru ◽  
Fekadu Massebo
Keyword(s):  
Malaria Vector ◽  
Negative Binomial ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Southwest Ethiopia ◽  
Anopheles Mosquitoes ◽  
Host Seeking ◽  
Human Landing ◽  
Seeking Behavior ◽  
The Impact

Abstract Background The early and outdoor biting behaviors of malaria vectors are among the key challenges in malaria control. Hence, understanding the host-seeking behavior and the peak biting time of malaria vectors is important in malaria vector control programs. This study assessed the host-seeking behavior and hourly biting activity of malaria mosquitoes in Chano Mille village in Arba Minch district, southwest Ethiopia. Methods The first trial was done by keeping cattle together with human that collects the entered mosquitoes in tent, while the other was done by keeping cattle outside a 1 m distance from human collector inside a tent. In both trials, mosquito collation was done inside tents baited by cattle and human using human landing catches (HLC) techniques. Four human volunteers’ were recruited and trained to collect mosquitoes in the four tents from 18:00-24:00 for three months. Two tents were selected randomly for human alone and two for cattle baited collections in the first night and then rotated to minimize the variation due to location of tents and collectors skill. The tent trial was done close to the shore of the Lake Abaya to minimize the interference of other animals on mosquito movement. The peak biting hour of malaria vectors was assessed within a Chano village from 18:00-6:00. Mosquito collation was done both indoor and outdoor by HLC. Morphological speciation of Anopheles mosquitoes was done. The sporozoite infectivity status of Anopheles pharoensis was examined using enzyme-linked immuno-sorbent assay technique. The data was analyzed using a Generalized Estimating Equations with a negative binomial distribution. Results An. pharoensis, An. gambiae complex and An. tenebrosus were the three species documented during the trial. Keeping cattle together with human collector inside the tent attracted 42% ( P < 0.001) more An. pharoensis compared to human alone tent. Also, keeping cattle outside near to a tent with human at 1 m distance, attracted the entering An. pharoensis into the tent inside with human by 46% ( P = 0.002) than human in a tent with no cattle outside the same tent. The impact was not significant for An. gambiae complex and An. tenebrosus. Anopheles pharoensis and An. gambiae complex showed early night biting activity with peak biting from 19.00-20:00 which was significant for both An. gambiae complex ( P < 0.001) and An. pharoensis ( P = 0.015). Anopheles gambiae complex was mainly biting humans outdoor in the village. Conclusions Finally, keeping cattle within and close to human dwellings could increase malaria vectors bite exposure particularly to the zoophilic malaria vector An. pharoensis and, hence deployment of cattle far from human residence could be recommended to reduce the human exposure. The outdoor and early hours biting behavior of the An. gambiae complex could be a threat for success of current indoor based interventions and hence, tools could be designed to reduce this threat.

scholarly journals Pyrethroid resistance in Anopheles gambiae not associated with insecticide-treated mosquito net effectiveness across sub-Saharan Africa

2020 ◽  
Author(s):  
David A. Larsen ◽  
Rachael L. Church
Keyword(s):  
Anopheles Gambiae ◽  
Malaria Vector ◽  
Malaria Infection ◽  
Pyrethroid Resistance ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Lr Test ◽  
Meta Regression ◽  
Sub Saharan ◽  
The Impact

AbstractBackgroundPyrethroid resistance is a major concern for malaria vector control programs that predominantly rely on insecticide-treated mosquito nets (ITN). Contradictory results of the impact of resistance have been observed in field studies.MethodsWe combined continent-wide estimates of pyrethroid resistance in Anopheles gambiae from 2006-2017 with continent-wide survey data to assess the effect of increasing pyrethroid resistance on the effectiveness of ITNs to prevent malaria infections in sub-Saharan Africa. We utilized both a pooled-data approach and meta-regression of survey regions to assess how pyrethroid resistance affects the association between ITN ownership and malaria outcomes in children aged 6-59 months.FindingsITN ownership reduced the risk of malaria outcomes in both pooled and meta-regression approaches. In the pooled analysis, there was no observed interaction between ITN ownership and estimated level of pyrethroid resistance (Likelihood ratio [LR] test = 1.127 for the outcome of rapid diagnostic test confirmed malaria infection, p = 0.2885; LR test = 0.161 for the outcome of microscopy confirmed malaria infection, p = 0.161; LR test = 0.646 for the outcome of moderate or severe anemia, p = 0.4215). In the meta-regression approach the level of pyrethroid resistance did not explain any of the variance in subnational estimates of ITN effectiveness for any of the outcomes.InterpretationITNs decreased risk of malaria outcomes independent of the levels of pyrethroid resistance in the malaria vector populations.FundingDAL did not receive funding and RC received a SOURCE grant from Syracuse University for this project.

scholarly journals Pyrethroid Resistance in Anopheles gambiae Not Associated with Insecticide-Treated Mosquito Net Effectiveness Across Sub-Saharan Africa

2021 ◽  
Author(s):  
David A. Larsen ◽  
Rachael L. Church
Keyword(s):  
Anopheles Gambiae ◽  
Malaria Vector ◽  
Malaria Infection ◽  
Pyrethroid Resistance ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Lr Test ◽  
Meta Regression ◽  
Sub Saharan ◽  
The Impact

Pyrethroid resistance is a major concern for malaria vector control programs that predominantly rely on insecticide-treated mosquito nets (ITNs). Contradictory results of the impact of resistance have been observed during field studies. We combined continent-wide estimates of pyrethroid resistance in Anopheles gambiae from 2006 to 2017, with continent-wide survey data to assess the effect of increasing pyrethroid resistance on the effectiveness of ITNs to prevent malaria infections in sub-Saharan Africa. We used a pooled-data approach and a meta-regression of survey regions to assess how pyrethroid resistance affects the association between ITN ownership and malaria outcomes for children 6 to 59 months of age. ITN ownership reduced the risk of malaria outcomes according to both the pooled and meta-regression approaches. According to the pooled analysis, there was no observed interaction between ITN ownership and estimated level of pyrethroid resistance (likelihood ratio [LR] test, 1.127 for malaria infection confirmed by the rapid diagnostic test, P = 0.2885; LR test = 0.161 for microscopy-confirmed malaria infection, P = 0.161; LR test = 0.646 for moderate or severe anemia, P = 0.4215). Using the meta-regression approach to determine the level of pyrethroid resistance did not explain any of the variance in subnational estimates of ITN effectiveness for any of the outcomes. ITNs decreased the risk of malaria independent of the levels of pyrethroid resistance in malaria vector populations.

scholarly journals Investigating the relationship between insecticide resistance, underlying molecular mechanisms and malaria prevalence in Anopheles gambiae s.l. from Guinea

2018 ◽  
Author(s):  
Emma Collins ◽  
Natasha M. Vaselli ◽  
Moussa Sylla ◽  
Abdoul H. Beavogui ◽  
James Orsborne ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Molecular Mechanisms ◽  
Pyrethroid Resistance ◽  
Resistance Mechanisms ◽  
Malaria Prevalence ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Partial Restoration ◽  
Sub Saharan

AbstractThe threat of insecticide resistance across sub-Saharan Africa is anticipated to severely impact the continued effectiveness of malaria vector control. We investigated the effect of carbamate and pyrethroid resistance on Anopheles gambiae s.l age, Plasmodium falciparum infection and characterized molecular resistance mechanisms in Guinea. Pyrethroid resistance was intense, with survivors of ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr allele was significantly associated with mosquito survival following deltamethrin or permethrin treatment (p=0.003 and p=0.04, respectively). N1575Y and I1527T mutations were identified in 13% and 10% of individuals, respectively, but neither conferred increased pyrethroid tolerance. Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggest a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation (p=0.001). Oocyst rates were 6.8% and 4.2% among resistant and susceptible mosquitoes, respectively; survivors of bendiocarb exposure were significantly more likely to be infected (p=0.03). Resistant mosquitoes had significantly lower parity rates; however, a subset of intensely pyrethroid-resistant vectors were more likely to be parous (p=0.042 and p=0.045, for survivors of five and ten times the diagnostic dose of insecticides, respectively). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.

scholarly journals Influence of pyrethroïd-treated bed net on host seeking behavior of Anopheles gambiae s.s. carrying the kdr allele

PLoS ONE ◽  
2017 ◽  
Vol 12 (7) ◽  
pp. e0164518 ◽  
Author(s):  
Angélique Porciani ◽  
Malal Diop ◽  
Nicolas Moiroux ◽  
Tatiana Kadoke-Lambi ◽  
Anna Cohuet ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
Bed Net ◽  
Anopheles Gambiae S.S ◽  
Host Seeking ◽  
Seeking Behavior

scholarly journals Impact of insecticide resistance in Anopheles arabiensis on malaria incidence and prevalence in Sudan and the costs of mitigation

2017 ◽  
Vol 114 (52) ◽  
pp. E11267-E11275 ◽  
Author(s):  
Hmooda Toto Kafy ◽  
Bashir Adam Ismail ◽  
Abraham Peter Mnzava ◽  
Jonathan Lines ◽  
Mogahid Shiekh Eldin Abdin ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Pyrethroid Resistance ◽  
Malaria Incidence ◽  
Disease Incidence ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Incidence And Mortality ◽  
Additional Protection ◽  
The Impact

Insecticide-based interventions have contributed to ∼78% of the reduction in the malaria burden in sub-Saharan Africa since 2000. Insecticide resistance in malaria vectors could presage a catastrophic rebound in disease incidence and mortality. A major impediment to the implementation of insecticide resistance management strategies is that evidence of the impact of resistance on malaria disease burden is limited. A cluster randomized trial was conducted in Sudan with pyrethroid-resistant and carbamate-susceptible malaria vectors. Clusters were randomly allocated to receive either long-lasting insecticidal nets (LLINs) alone or LLINs in combination with indoor residual spraying (IRS) with a pyrethroid (deltamethrin) insecticide in the first year and a carbamate (bendiocarb) insecticide in the two subsequent years. Malaria incidence was monitored for 3 y through active case detection in cohorts of children aged 1 to <10 y. When deltamethrin was used for IRS, incidence rates in the LLIN + IRS arm and the LLIN-only arm were similar, with the IRS providing no additional protection [incidence rate ratio (IRR) = 1.0 (95% confidence interval [CI]: 0.36–3.0; P = 0.96)]. When bendiocarb was used for IRS, there was some evidence of additional protection [interaction IRR = 0.55 (95% CI: 0.40–0.76; P < 0.001)]. In conclusion, pyrethroid resistance may have had an impact on pyrethroid-based IRS. The study was not designed to assess whether resistance had an impact on LLINs. These data alone should not be used as the basis for any policy change in vector control interventions.

scholarly journals Phenotypic Insecticide Resistance in Anopheles gambiae (Diptera: Culicidae): Specific Characterization of Underlying Resistance Mechanisms Still Matters

2020 ◽  
Author(s):  
Adandé A Medjigbodo ◽  
Luc S Djogbenou ◽  
Aubin A Koumba ◽  
Laurette Djossou ◽  
Athanase Badolo ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Resistance Mechanisms ◽  
Malaria Vectors ◽  
Effective Control ◽  
Anopheles Coluzzii ◽  
Anopheles Gambiae S.S ◽  
Diagnostic Dose ◽  
Pirimiphos Methyl ◽  
Old Adult

Abstract An effective control of malaria vectors requires an extensive knowledge of mechanisms underlying the resistance-phenotypes developed by these vectors against insecticides. We investigated Anopheles gambiae mosquitoes from Benin and Togo for their intensity of insecticide resistance and we discussed the involvement of genotyped mechanisms in the resistance-phenotypes observed. Three- to five-day-old adult mosquitoes emerged from field and laboratory An. gambiae larvae were assayed using WHO tube intensity tests against various doses of deltamethrin: 1× (0.05%); 2× (0.1%); 5× (0.25%); 7.5× (0.375%) and those of pirimiphos-methyl: 0.5× (0.125%); 1× (0.25%). Members of An. gambiae complex were screened in field populations using polymerase chain reaction (PCR) assays. The presence of kdrR(1014F/1014S) and ace-1R(119S) mutations was also investigated using TaqMan and PCR-RFLP techniques, respectively. Anopheles gambiae from field were very resistant to deltamethrin, whereas KisKdr and AcerKdrKis strains displayed 100% mortality rates at 2× the diagnostic dose. In contrast, the field mosquitoes displayed a low resistance-intensity against 1× the diagnostic dose of pirimiphos-methyl, whereas AcerKis and AcerKdrKis strains showed susceptibility at 0.5× the diagnostic dose. Anopheles gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis were identified. Allelic frequencies of kdrR (1014F) and ace-1R (119S) mutations in the field populations varied from 0.65 to 1 and 0 to 0.84, respectively. The field An. gambiae displayed high-resistance levels against deltamethrin and pirimiphos-methyl when compared with those of the laboratory An. gambiae-resistant strains. These results exhibit the complexity of underlying insecticide resistance mechanisms in these field malaria vectors.

scholarly journals Reduced human-biting preferences of the African malaria vectors Anopheles arabiensis and Anopheles gambiae in an urban context: controlled, competitive host-preference experiments in Tanzania

2020 ◽  
Author(s):  
Yeromin P Mlacha ◽  
Prosper P. Chaki ◽  
Athuman Muhili ◽  
Dennis J. Massue ◽  
Marcel Tanner ◽  
...  
Keyword(s):  
Vector Control ◽  
Anopheles Gambiae ◽  
Anopheles Arabiensis ◽  
Host Preference ◽  
Urban Setting ◽  
Sub Saharan Africa ◽  
Rural Setting ◽  
Malaria Vectors ◽  
Baited Traps ◽  
The Impact

Abstract BackgroundHost preference is a critical determinant of human exposure to vector-borne infections and the impact of vector control interventions. Widespread use of long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) across sub-Saharan Africa, which protect humans against mosquitoes, may select for altered host preference traits of malaria vectors over the long term. Here, the host preferences of Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) were experimentally assessed in the field, using direct host-preference assays in two distinct ecological settings in Tanzania.MethodsEight Ifakara Tent Trap (ITT), four baited with humans and four with bovine calves, were simultaneously used to catch malaria vectors in open field sites in urban and rural Tanzania. The numbers of mosquitoes collected in human-baited traps versus calf-baited traps were used to estimate human feeding preference for each site's vector species. ResultsThe estimated proportion [95% confidence interval (CI)] of mosquitoes attacking humans rather than cattle was 0.60 [0.40, 0.77] for An. arabiensis in the rural setting and 0.61 [0.32, 0.85] for An. gambiae s.s. in the urban setting, indicating no preference for either host in both cases (P=0.32 and 0.46, respectively) and no difference in preference between the two (Odds Ratio (OR) [95%] = 0.95 [0.30, 3.01], P=0.924). However, only a quarter of An. arabiensis in the urban setting attacked humans (0.25 [0.09, 0.53]), indicating a preference for cattle that approached significance (P=0.08). Indeed, urban An. arabiensis were less likely to attack humans rather than cattle when compared to the same species in the rural setting (OR [95%] = 0.21 [0.05, 0.91], P =0.037). ConclusionUrban An. arabiensis had a stronger preference for cattle than the rural population and urban An. gambiae s.s. showed no clear preference for either humans or cattle. In the urban setting, both species exhibited stronger tendencies to attack cattle than previous studies of the same species in rural contexts. Cattle keeping may, therefore, particularly limit the impact of human-targeted vector control interventions in Dar es Salaam and perhaps in other African towns and cities.

scholarly journals Monitoring of Insecticide Resistance in Anopheles culicifacies in Twelve Districts of Madhya Pradesh, Central India (2017–2019)

2022 ◽  
Vol 2022 ◽  
pp. 1-8
Author(s):  
Ashok K. Mishra ◽  
Praveen K Bharti ◽  
Gyan Chand ◽  
Aparup Das ◽  
Himanshu Jayswar ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Indoor Residual Spraying ◽  
Central India ◽  
Control Programme ◽  
Madhya Pradesh ◽  
Control Measures ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
The Impact

Background. Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are malaria vector control measures used in India, but the development of insecticide resistance poses major impediments for effective vector control strategies. As per the guidelines of the National Vector Borne Disease Control Programme (NVBDCP), the study was conducted in 12 districts of Madhya Pradesh to generate data on insecticide resistance in malaria vectors. Methods. The susceptibility tests were conducted on adult An. culicifacies as per the WHO standard technique with wild-caught mosquitoes. The blood-fed female mosquitoes were exposed in 3 to 4 replicates on each occasion to the impregnated papers with specified discriminating dosages of the insecticides (DDT: 4%, malathion: 5%, deltamethrin: 0.05%, and alphacypermethrin: 0.05%), for one hour, and mortality was recorded after 24-hour holding. Results. An. culicifacies was found resistant to DDT 4% in all the 12 districts and malathion in 11 districts. The resistance to alphacypermethrin was also observed in two districts, and possible resistance was found to alphacypermethrin in seven districts and to deltamethrin in eight districts, while the vector was found susceptible to both deltamethrin and alphacypermethrin in only 3 districts. Conclusion. An. culicifacies is resistant to DDT and malathion and has emerging resistance to pyrethroids, alphacypermethrin, and deltamethrin. Therefore, regular monitoring of insecticide susceptibility in malaria vectors is needed for implementing effective vector management strategies. However, studies to verify the impact of IRS with good coverage on the transmission of disease are required before deciding on the change of insecticide in conjunction with epidemiological data.

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