scholarly journals Molecular Detection of Insecticide Resistance Mutations in Anopheles gambiae from Sierra Leone Using Multiplex SNaPshot and Sequencing

2021 ◽  
Vol 11 ◽  
Author(s):  
Jianhai Yin ◽  
Frederick Yamba ◽  
Canjun Zheng ◽  
Shuisen Zhou ◽  
Samuel Juana Smith ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Sierra Leone ◽  
Statistical Significance ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Mosquito Vector ◽  
Resistance Mutations ◽  
African Countries

Vector control interventions including long-lasting insecticidal nets and indoor residual spraying are important for malaria control and elimination. And effectiveness of these interventions depends entirely on the high level of susceptibility of malaria vectors to insecticides. However, the insecticide resistance in majority of mosquito vector species across African countries is a serious threat to the success of vector control efforts with the extensive use of insecticides, while no data on insecticide resistance was reported from Sierra Leone in the past decade. In the present study, the polymerase chain reaction was applied for the identification of species of 757 dry adult female Anopheles gambiae mosquitoes reared from larvae collected from four districts in Sierra Leone during May and June 2018. And the mutations of kdr, rdl, ace-1 genes in An. gambiae were detected using SNaPshot and sequencing. As a result, one sample from Western Area Rural district belonged to Anopheles melas, and 748 An. gambiae were identified. Furthermore, the rdl mutations, kdr west mutations and ace-1 mutation were found. The overall frequency was 35.7%, 0.3%, 97.6% and 4.5% in A296G rdl, A296S rdl, kdrW and ace-1, respectively. The frequencies of A296G rdl mutation (P < 0.001), kdrW mutation (P = 0.001) and ace-1 mutation (P < 0.001) were unevenly distributed in four districts, respectively, while no statistical significance was found in A296S rdl mutation (P = 0.868). In addition, multiple resistance patterns were also found. In conclusion, multiple mutations involved in insecticide resistance in An. gambiae populations in Sierra Leone were detected in the kdrW, A296G rdl and ace-1 alleles in the present study. It is necessary to monitor vector susceptibility levels to insecticides used in this country, and update the insecticide resistance monitoring and management strategy.

scholarly journals Resting Behavior of Malaria Vectors in Ghana and Its Implication on Vector Control.

2022 ◽  
Author(s):  
Akua Obeng Forson ◽  
Isaac A. Hinne ◽  
Shittu B. Dhikrullahi ◽  
Isaac Kwame Sr ◽  
Abdul Rahim Mohammed ◽  
...  
Keyword(s):  
Vector Control ◽  
Anopheles Gambiae ◽  
Blood Meal ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Resistance Mutations ◽  
Sub Saharan ◽  
Outdoor Resting ◽  
Resting Behavior

Abstract Background: In Sub-Saharan Africa, there is widespread use of long-lasting insecticidal nets (LLINs) and Indoor residual spraying (IRS) to help control the density of malaria vectors and decrease the incidence of malaria in communities. An understanding of the interactions between increased insecticide use and resting behaviour patterns of malaria mosquitoes is important for an effective vector control programme. This study was carried out to investigate the resting behavior, host preference and infection with Plasmodium falciparum of malaria vectors in Ghana in the context of increasing insecticide resistance in malaria vectors in sub-saharan Africa.Methods: Indoor and outdoor resting Anopheline mosquitoes were sampled during the dry and rainy seasons in five sites that were in 3 ecological landscapes [Sahel savannah (Kpalsogou, Pagaza, Libga), Coastal savannah (Anyakpor) and Forest (Konongo) zones] using pyrethrum spray catches (PSC), mechanical aspiration (Prokopack) for indoor collections, pit shelter and Prokopack for outdoor collections. PCR based molecular diagnostics were used to determine mosquito speciation, genotype for knockdown resistance mutations (L1014S and L1014F), G119S Ace-1 mutation, specific host blood meal origins and sporozoite infection in field collected mosquitoes.Results: Anopheles gambiae s. l. was the predominant species (89.95%, n = 1,718), followed by An. rufipes (8.48%, n=162), and An. funestus s. l. (1.57%, n = 30). Sibling species of the Anopheles gambiae revealed An. coluzzii accounted for 63% (95% CI: 57.10 – 68.91), followed by An. gambiae s. s [27% (95% CI: 21.66 – 32.55)], and An. arabiensis [9% (95% CI: 6.22 – 13.57)]. The mean resting density of An. gambiae s. l. was higher outdoors (79.63%; 1,368/1,718) than indoors (20.37%; 350/1,718) (z = -4.815, p< 0.0001). The kdr west L1014F and the Ace-1 mutations were highest in indoor resting An. coluzzii and An. gambiae in the sahel-savannah sites compared to the forest and coastal savannah sites. Overall, the blood meal analyses revealed a large proportion of the malaria vectors preferred feeding on humans (70.2 %) than animals (29.8%) in all sites. The sporozoite rates was only detected in indoor resting An. coluzzii from the sahel savannah (5.0%) and forest (2.5%) zones.Conclusion: The study reports high outdoor resting densities of An. gambiae and An. coluzzii with high kdr west mutation frequencies, and persistence of malaria transmission indoors despite the use of LLINs and IRS. Continuous monitoring of changes in resting behavior of mosquitoes and implementation of complementary malaria control interventions are needed to target outdoor resting Anopheles mosquitoes in Ghana.

scholarly journals Insecticide resistance status of malaria vectors Anopheles gambiae (s.l.) of southwest Burkina Faso and residual efficacy of indoor residual spraying with microencapsulated pirimiphos-methyl insecticide

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Dieudonné Diloma Soma ◽  
Barnabas Zogo ◽  
Domonbabele François de Sales Hien ◽  
Aristide Sawdetuo Hien ◽  
Didier Alexandre Kaboré ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Burkina Faso ◽  
Anopheles Gambiae ◽  
Local Population ◽  
Residual Activity ◽  
Indoor Residual Spraying ◽  
Susceptible Strain ◽  
Malaria Vectors ◽  
Pirimiphos Methyl ◽  
Residual Efficacy

Abstract Background The rapid spread of insecticide resistance in malaria vectors and the rebound in malaria cases observed recently in some endemic areas underscore the urgent need to evaluate and deploy new effective control interventions. A randomized control trial (RCT) was conducted with the aim to investigate the benefit of deploying complementary strategies, including indoor residual spraying (IRS) with pirimiphos-methyl in addition to long-lasting insecticidal nets (LLINs) in Diébougou, southwest Burkina Faso. Methods We measured the susceptibility of the Anopheles gambiae (s.l.) population from Diébougou to conventional insecticides. We further monitored the efficacy and residual activity of pirimiphos-methyl on both cement and mud walls using a laboratory susceptible strain (Kisumu) and the local An. gambiae (s.l.) population. Results An. gambiae (s.l.) from Diébougou was resistant to DDT, pyrethroids (deltamethrin, permethrin and alphacypermethrin) and bendiocarb but showed susceptibility to organophosphates (pirimiphos-methyl and chlorpyrimiphos-methyl). A mixed-effect generalized linear model predicted that pirimiphos-methyl applied on cement or mud walls was effective for 210 days against the laboratory susceptible strain and 247 days against the local population. The residual efficacy of pirimiphos-methyl against the local population on walls made of mud was similar to that of cement (OR = 0.792, [0.55–1.12], Tukey’s test p-value = 0.19). Conclusions If data on malaria transmission and malaria cases (as measured trough the RCT) are consistent with data on residual activity of pirimiphos-methyl regardless of the type of wall, one round of IRS with pirimiphos-methyl would have the potential to control malaria in a context of multi-resistant An. gambiae (s.l.) for at least 7 months.

scholarly journals Insecticide resistance status of Anopheles arabiensis in irrigated and non-irrigated areas in western Kenya

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Pauline Winnie Orondo ◽  
Steven G. Nyanjom ◽  
Harrysone Atieli ◽  
John Githure ◽  
Benyl M. Ondeto ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Arabiensis ◽  
Crop Protection ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Western Kenya ◽  
Animal Protection ◽  
Selection Of ◽  
Selection Of Resistance

Abstract Background Malaria control in Kenya is based on case management and vector control using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). However, the development of insecticide resistance compromises the effectiveness of insecticide-based vector control programs. The use of pesticides for agricultural purposes has been implicated as one of the sources driving the selection of resistance. The current study was undertaken to assess the status and mechanism of insecticide resistance in malaria vectors in irrigated and non-irrigated areas with varying agrochemical use in western Kenya. Methods The study was carried out in 2018–2019 in Homa Bay County, western Kenya. The bioassay was performed on adults reared from larvae collected from irrigated and non-irrigated fields in order to assess the susceptibility of malaria vectors to different classes of insecticides following the standard WHO guidelines. Characterization of knockdown resistance (kdr) and acetylcholinesterase-inhibiting enzyme/angiotensin-converting enzyme (Ace-1) mutations within Anopheles gambiae s.l. species was performed using the polymerase chain reaction (PCR) method. To determine the agricultural and public health insecticide usage pattern, a questionnaire was administered to farmers, households, and veterinary officers in the study area. Results Anopheles arabiensis was the predominant species in the irrigated (100%, n = 154) area and the dominant species in the non-irrigated areas (97.5%, n = 162), the rest being An. gambiae sensu stricto. In 2018, Anopheles arabiensis in the irrigated region were susceptible to all insecticides tested, while in the non-irrigated region reduced mortality was observed (84%) against deltamethrin. In 2019, phenotypic mortality was decreased (97.8–84% to 83.3–78.2%). In contrast, high mortality from malathion (100%), DDT (98.98%), and piperonyl butoxide (PBO)-deltamethrin (100%) was observed. Molecular analysis of the vectors from the irrigated and non-irrigated areas revealed low levels of leucine-serine/phenylalanine substitution at position 1014 (L1014S/L1014F), with mutation frequencies of 1–16%, and low-frequency mutation in the Ace-1R gene (0.7%). In addition to very high coverage of LLINs impregnated with pyrethroids and IRS with organophosphate insecticides, pyrethroids were the predominant chemical class of pesticides used for crop and animal protection. Conclusion Anopheles arabiensis from irrigated areas showed increased phenotypic resistance, and the intensive use of pesticides for crop protection in this region may have contributed to the selection of resistance genes observed. The susceptibility of these malaria vectors to organophosphates and PBO synergists in pyrethroids offers a promising future for IRS and insecticide-treated net-based vector control interventions. These findings emphasize the need for integrated vector control strategies, with particular attention to agricultural practices to mitigate mosquito resistance to insecticides. Graphic abstract

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.

scholarly journals Multiple insecticide resistance target sites in adult field strains of An. gambiae s.l. from southeast Senegal.

2020 ◽  
Author(s):  
El hadji Diouf ◽  
El hadji Amadou Niang ◽  
Badara Samb ◽  
Cheikh Tidiane Diagne ◽  
Mbaye Diouf ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Control Strategies ◽  
Mosquito Species ◽  
Indoor Residual Spraying ◽  
Malaria Prevention ◽  
Mortality Rates ◽  
Malaria Vectors ◽  
Public Health Issue ◽  
Genetic Mutations ◽  
African Countries

Abstract Background: Malaria prevention strategies are based on the use of long-lasting insecticide-treated mosquito nets (LLINs), indoor residual spraying of insecticides (IRS) and seasonal malaria chemoprevention (SMC). The combination of these strategies with artemisinin-based combination therapy (ACTs) has led to a significant reduction in malaria cases. However, malaria remains a major public health issue in most sub-Saharan African countries. Indeed, the resistance of vectors to most WHO-approved insecticides could jeopardize vector-control strategies. This study examines insecticide resistance and associated genetic mutations among malaria vectors in southeast Senegal. Methods: The study was conducted in October and November 2014 in two sites in southeast Senegal. An. gambiae s.l. populations were sampled from Kedougou (Kedougou district) and Wassadou-Badi (Tambacounda district) and were evaluated for insecticide resistance according to WHO susceptibility tests. Specimens were 3 to 5-day-old adults raised from collected larvae. Eleven insecticides belonging to the four known classes of insecticides were assessed. Mosquito species were identified and mutations associated with insecticide resistance (ace-1, rdl (A296S or A296G), Vgsc-1014F and Vgsc-1014S) were determined. Results: A total of 3,742 An. gambiae s.l. were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). In both sites, mosquitoes showed high levels of resistance to all the five pyrethroids tested (mortality rates ranged from 42.8 to 81.4% in Kedougou and 52.4 to 86.4% in Wassadou-Badi) as well as to dieldrin (67.8 and 83%) and DDT (12.7 and 55%). The mosquitoes were susceptible to pirimiphos-methyl (mortality rate 100%) and malathion (mortality rates 100% and 99% in Kedougou and Wassadou-Badi respectively). An. gambiae s.l. populations from Kedougou were also resistant to bendiocarb and fenitrothion. Of the 745 An. gambiae s.l. genotyped An. gambiae s.s. (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae s.s./An. coluzzii; 0.4%). The Vgsc-1014F mutation was widely distributed and is predominant in An. gambiae s.s. and An. coluzzii in comparison to An. arabiensis. Vgsc-1014S was present in An. gambiae s.l. populations in Wassadou but not in Kedougou. The ace-1 and rdl mutations were more frequent in An. gambiae s.s. compared to An. arabiensis whereas they were detected weakly in An. coluzzii populations.Conclusions: The present study demonstrates the resistance of malaria vectors to pyrethroids and organo chlorines in southeast Senegal as well as the presence of genetic mutations associated with this resistance in An. gambiae s.l. No Vgsc-1014S mutation was detected in An. gambiae s.s. population in Kedougou. These findings are key for monitoring and managing the resistance of vectors to insecticides in this region.

scholarly journals Status of insecticide susceptibility in Anopheles arabiensis and detection of the knockdown resistance mutation (kdr) concerning agricultural practices from Northern Sudan state, Sudan

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
M. Y. Korti ◽  
T. B. Ageep ◽  
A. I. Adam ◽  
K. B. Shitta ◽  
A. A. Hassan ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Arabiensis ◽  
Resistance Mutation ◽  
Indoor Residual Spraying ◽  
Mortality Rates ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Knockdown Resistance ◽  
Insecticide Susceptibility

Abstract Background Chemical control has been the most efficient method in mosquito control, the development of insecticide resistance in target populations has a significant impact on vector control. The use of agricultural pesticides may have a profound impact on the development of resistance in the field populations of malaria vectors. Our study focused on insecticide resistance and knockdown resistance (kdr) of Anopheles arabiensis populations from Northern Sudan, related to agricultural pesticide usage. Results Anopheles arabiensis from urban and rural localities (Merowe and Al-hamadab) were fully susceptible to bendiocarb 0.1% and permethrin 0.75% insecticides while resistant to DDT 4% and malathion 5%. The population of laboratory reference colony F189 from Dongola showed a mortality of 91% to DDT (4%) and fully susceptible to others. GLM analysis indicated that insecticides, sites, site type, and their interaction were determinant factors on mortality rates (P < 0.01). Except for malathion, mortality rates of all insecticides were not significant (P > 0.05) according to sites. Mortality rates of malathion and DDT were varied significantly (P < 0.0001 and P < 0.05 respectively) by site types, while mortality rates of bendiocarb and permethrin were not significant (P >0.05). The West African kdr mutation (L1014F) was found in urban and rural sites. Even though, the low-moderate frequency of kdr (L1014F) mutation was observed. The findings presented here for An. arabiensis showed no correlation between the resistant phenotype as ascertained by bioassay and the presence of the kdr mutation, with all individuals tested except the Merowe site which showed a moderate association with DDT (OR= 6 in allelic test), suggesting that kdr genotype would be a poor indicator of phenotypic resistance. Conclusion The results provide critical pieces of information regarding the insecticide susceptibility status of An. arabiensis in northern Sudan. The usage of the same pesticides in agricultural areas seemed to affect the Anopheles susceptibility when they are exposed to those insecticides in the field. The kdr mutation might have a less role than normally expected in pyrethroids resistance; however, other resistance genes should be in focus. These pieces of information will help to improve the surveillance system and The implication of different vector control programs employing any of these insecticides either in the treatment of bed nets or for indoor residual spraying would achieve satisfactory success rates.

scholarly journals Multiple insecticide resistance target sites in adult field strains of An. gambiae s.l. from southeast Senegal.

2020 ◽  
Author(s):  
El hadji Diouf ◽  
El hadji Amadou Niang ◽  
Badara Samb ◽  
Cheikh Tidiane Diagne ◽  
Mbaye Diouf ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Control Strategies ◽  
Mosquito Species ◽  
Indoor Residual Spraying ◽  
Malaria Prevention ◽  
Mortality Rates ◽  
Malaria Vectors ◽  
Public Health Issue ◽  
Genetic Mutations ◽  
African Countries

Abstract Background: Malaria prevention strategies are based on the use of long-lasting insecticide-treated mosquito nets (LLINs), indoor residual spraying of insecticides (IRS) and seasonal malaria chemoprevention (SMC). The combination of these strategies with artemisinin-based combination therapy (ACTs) has led to a significant reduction in malaria cases. However, malaria remains a major public health issue in most sub-Saharan African countries. Indeed, the resistance of vectors to most WHO-approved insecticides could jeopardize vector-control strategies. This study examines insecticide resistance and associated genetic mutations among malaria vectors in southeast Senegal. Methods: The study was conducted in October and November 2014 in two sites in southeast Senegal. An. gambiae s.l. populations were sampled from Kedougou (Kedougou district) and Wassadou-Badi (Tambacounda district) and were evaluated for insecticide resistance according to WHO susceptibility tests. Specimens were 3 to 5-day-old adults raised from collected larvae. Eleven insecticides belonging to the four known classes of insecticides were assessed. Mosquito species were identified and mutations associated with insecticide resistance (ace-1, rdl (A296S or A296G), Vgsc-1014F and Vgsc-1014S) were determined. Results: A total of 3,742 An. gambiae s.l. were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). In both sites, mosquitoes showed high levels of resistance to all the five pyrethroids tested (mortality rates ranged from 42.8 to 81.4% in Kedougou and 52.4 to 86.4% in Wassadou-Badi) as well as to dieldrin (67.8 and 83%) and DDT (12.7 and 55%). The mosquitoes were susceptible to pirimiphos-methyl (mortality rate 100%) and malathion (mortality rates 100% and 99% in Kedougou and Wassadou-Badi respectively). An. gambiae s.l. populations from Kedougou were also resistant to bendiocarb and fenitrothion. Of the 745 An. gambiae s.l. genotyped An. gambiae s.s. (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae s.s./An. coluzzii; 0.4%). The Vgsc-1014F mutation was widely distributed and is predominant in An. gambiae s.s. and An. coluzzii in comparison to An. arabiensis. Vgsc-1014S was present in An. gambiae s.l. populations in Wassadou but not in Kedougou. The ace-1 and rdl mutations were more frequent in An. gambiae s.s. compared to An. arabiensis whereas they were detected weakly in An. coluzzii populations.Conclusions: The present study demonstrates the resistance of malaria vectors to pyrethroids and organo chlorines in southeast Senegal as well as the presence of genetic mutations associated with this resistance in An. gambiae s.l. No Vgsc-1014S mutation was detected in An. gambiae s.s. population in Kedougou. These findings are key for monitoring and managing the resistance of vectors to insecticides in this region.

scholarly journals Impact of sublethal pyrethroid exposure on resistant Anopheles gambiae mosquitoes’ fitness

2020 ◽  
Author(s):  
Alida Kropf ◽  
Behi K Fodjo ◽  
Marius G Zoh ◽  
Chistabelle G Sadia ◽  
Affoué FP Kouadio ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Indoor Residual Spraying ◽  
Laboratory Strain ◽  
Blood Feeding ◽  
Egg Laying ◽  
Bed Net ◽  
Gonotrophic Cycle ◽  
Non Parametric

Abstract Background : There is increasing evidence of insecticide resistance spreading among wild mosquito populations, which is widely believed to compromise vector control once it reaches a threshold that enables mosquitoes to survive exposure to long lasting treated bed-net (LLIN) or indoor residual spraying (IRS). However, very little is known about the long-term impact of insecticide resistance on malaria transmission, which makes the consequence of insecticide resistance spreading difficult to predict. Methods: To gain more clarity, we have assessed five life-history traits of a resistant Anopheles gambiae laboratory strain that was repeatedly exposed to a LLIN and compared with individuals issued from the same strain but exposed to an untreated bed-net. Results: The non-parametric Kruskal-Wallis test did not show any significant impact of gonotrophic cycle on the five traits. However, the Kolmogorov-Smirnov non-parametric test revealed a significant (i) drop in blood feeding mean rates (D = 0.800; P< 0.0001), (ii) increase in 24-hours post-exposure (D = 0.600; P< 0.001) and (iii) end of gonotrophic cycle mortality (D = 0.611; P <0.006), and (iv) drop in egg laying rate (D = 0.730, P< 0.0001) when mosquitoes were exposed. Surprisingly, there was rather an upward trend in the number of L3 larvae/female mosquito for the exposed group comparing to the unexposed one, although the difference was not significant (D = 0.417, P> 0.05). Conclusion: Our study shows that in a context of widespread of resistance to insecticides, current pyrethroid-based vector control tools can still confer protection against malaria.

scholarly journals Multiple Insecticide Resistance Target Sites in Adult Field Strains of An. Gambiae s.l. From Southeast Senegal.

2020 ◽  
Author(s):  
El hadji Diouf ◽  
El hadji Amadou Niang ◽  
Badara Samb ◽  
Cheikh Tidiane Diagne ◽  
Mbaye Diouf ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Control Strategies ◽  
Mosquito Species ◽  
Indoor Residual Spraying ◽  
Malaria Prevention ◽  
Mortality Rates ◽  
Malaria Vectors ◽  
Public Health Issue ◽  
Genetic Mutations ◽  
African Countries

Abstract Background: Malaria prevention strategies are based on the use of long-lasting insecticide-treated mosquito nets (LLINs), indoor residual spraying of insecticides (IRS) and seasonal malaria chemoprevention (SMC). The combination of these strategies with artemisinin-based combination therapy (ACTs) has led to a significant reduction in malaria cases. However, malaria remains a major public health issue in most sub-Saharan African countries. Indeed, the resistance of vectors to most WHO-approved insecticides could jeopardize vector-control strategies. This study examines insecticide resistance and associated genetic mutations among malaria vectors in southeast Senegal. Methods: The study was conducted in October and November 2014 in two sites in southeast Senegal. An. gambiae s.l. populations were sampled from Kedougou (Kedougou district) and Wassadou-Badi (Tambacounda district) and were evaluated for insecticide resistance according to WHO susceptibility tests. Specimens were 3 to 5-day-old adults raised from collected larvae. Eleven insecticides belonging to the four known classes of insecticides were assessed. Mosquito species were identified and mutations associated with insecticide resistance (ace-1, rdl (A296S or A296G), Vgsc-1014F and Vgsc-1014S) were determined. Results: A total of 3,742 An. gambiae s.l. were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). In both sites, mosquitoes showed high levels of resistance to all the five pyrethroids tested (mortality rates ranged from 42.8 to 81.4% in Kedougou and 52.4 to 86.4% in Wassadou-Badi) as well as to dieldrin (67.8 and 83%) and DDT (12.7 and 55%). The mosquitoes were susceptible to pirimiphos-methyl (mortality rate 100%) and malathion (mortality rates 100% and 99% in Kedougou and Wassadou-Badi respectively). An. gambiae s.l. populations from Kedougou were also resistant to bendiocarb. Of the 745 An. gambiae s.l. genotyped An. gambiae s.s. (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae s.s./An. coluzzii; 0.4%). The Vgsc-1014F kdr mutation was widely distributed and is predominant in An. gambiae s.s. and An. coluzzii in comparison to An. arabiensis. Vgsc-1014S was present in An. gambiae s.l. populations in Wassadou but not in Kedougou. The ace-1 and rdl mutations were more frequent in An. gambiae s.s. compared to An. arabiensis but were not detected in all populations of An. coluzzii.Conclusion: The present study demonstrates the resistance of malaria vectors to pyrethroids and organo chlorines in southeast Senegal as well as the presence of genetic mutations associated with this resistance in An. gambiae s.l. There was no Vgsc-1014S mutation in An. gambiae s.s. population in Kedougou. These findings are key for monitoring and managing the resistance of vectors to insecticides in this region.

scholarly journals Characterization of resistance profile (intensity and mechanisms) of Anopheles gambiae in three communes of northern Benin, West Africa

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Casimir Dossou Kpanou ◽  
Hermann W. Sagbohan ◽  
Fortuné Dagnon ◽  
Germain G. Padonou ◽  
Razaki Ossè ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
High Intensity ◽  
Mortality Rates ◽  
Detoxification Enzymes ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Biochemical Tests ◽  
Diagnostic Dose

Abstract Background The selection and the spread of insecticide resistance in malaria vectors to the main classes of insecticides used in vector control tools are a major and ongoing challenge to malaria vector control programmes. This study aimed to determine the intensity of vector resistance to insecticides in three regions of Benin with different agro-ecological characteristics. Methods Larvae of Anopheles gambiae sensu lato (s.l.) were collected from September to November 2017 in different larval sites in three northern Benin communes: Parakou, Kandi and Malanville. Two to five-day-old, non-blood-fed, female mosquitoes were exposed to papers impregnated with deltamethrin, permethrin and bendiocarb at dosages of 1 × the diagnostic dose, 5 × and 10 × to determine the intensity of resistance in these vectors. Molecular frequencies of the kdr L1014F and ace-1R G119S insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled at each study site. Results Resistance to pyrethroids (permethrin and deltamethrin) was recorded in all three communes with mortality rates below 60% using the diagnostic dose (1x). The results obtained after exposure of An. gambiae to permethrin 10 × were 99% in Kandi, 98% in Malanville and 99% in Parakou. With deltamethrin 10x, mortality rates were 100% in Kandi, 96% in Malanville and 73% in Parakou. For the diagnostic dose of bendiocarb, suspected resistance was recorded in the communes of Malanville (97%) and Kandi (94%) while sensitivity was observed in Parakou (98%).Using the 10 × dose, mortality was 98% in Kandi, 100% in Malanville and 99% in Parakou. The frequencies of the kdr L1014F allele varied between 59 and 83% depending on the sites and species of the An. gambiae complex, while the frequency of the ace-1R G119S gene varied between 0 and 5%. Biochemical tests showed high levels of oxidase and esterase activity compared to the susceptible colony strain of An. gambiae sensu stricto (Kisumu strain). Conclusion Anopheles gambiae showed a generalized loss of susceptibility to permethrin and deltamethrin but also showed moderate to high intensity of resistance in different regions of Benin. This high intensity of resistance is a potential threat to the effectiveness of vector control.

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